{-
ToDo [Oct 2013]
~~~~~~~~~~~~~~~
1. Nuke ForceSpecConstr for good (it is subsumed by GHC.Types.SPEC in ghc-prim)
2. Nuke NoSpecConstr


(c) The GRASP/AQUA Project, Glasgow University, 1992-1998

\section[SpecConstr]{Specialise over constructors}
-}



{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}

module GHC.Core.Opt.SpecConstr(
        specConstrProgram,
        SpecConstrAnnotation(..)
    ) where

import GHC.Prelude

import GHC.Driver.Session ( DynFlags(..), GeneralFlag( Opt_SpecConstrKeen )
                          , gopt, hasPprDebug )

import GHC.Core
import GHC.Core.Subst
import GHC.Core.Utils
import GHC.Core.Unfold
import GHC.Core.FVs     ( exprsFreeVarsList )
import GHC.Core.Opt.Monad
import GHC.Core.Opt.WorkWrap.Utils
import GHC.Core.DataCon
import GHC.Core.Coercion hiding( substCo )
import GHC.Core.Rules
import GHC.Core.Type     hiding ( substTy )
import GHC.Core.TyCon   (TyCon, tyConUnique, tyConName )
import GHC.Core.Multiplicity
import GHC.Core.Ppr     ( pprParendExpr )
import GHC.Core.Make    ( mkImpossibleExpr )

import GHC.Unit.Module
import GHC.Unit.Module.ModGuts

import GHC.Types.Literal ( litIsLifted )
import GHC.Types.Id
import GHC.Types.Var.Env
import GHC.Types.Var.Set
import GHC.Types.Name
import GHC.Types.Tickish
import GHC.Types.Basic
import GHC.Types.Demand
import GHC.Types.Cpr
import GHC.Types.Unique.Supply
import GHC.Types.Unique.FM

import GHC.Data.Maybe     ( orElse, catMaybes, isJust, isNothing )
import GHC.Data.Pair
import GHC.Data.FastString

import GHC.Utils.Misc
import GHC.Utils.Outputable
import GHC.Utils.Panic.Plain
import GHC.Utils.Panic
import GHC.Utils.Constants (debugIsOn)
import GHC.Utils.Monad
import GHC.Utils.Trace

import GHC.Builtin.Names ( specTyConKey )

import GHC.Exts( SpecConstrAnnotation(..) )
import GHC.Serialized   ( deserializeWithData )

import Control.Monad    ( zipWithM )
import Data.List (nubBy, sortBy, partition, dropWhileEnd, mapAccumL )
import Data.Ord( comparing )

{-
-----------------------------------------------------
                        Game plan
-----------------------------------------------------

Consider
        drop n []     = []
        drop 0 xs     = []
        drop n (x:xs) = drop (n-1) xs

After the first time round, we could pass n unboxed.  This happens in
numerical code too.  Here's what it looks like in Core:

        drop n xs = case xs of
                      []     -> []
                      (y:ys) -> case n of
                                  I# n# -> case n# of
                                             0 -> []
                                             _ -> drop (I# (n# -# 1#)) xs

Notice that the recursive call has an explicit constructor as argument.
Noticing this, we can make a specialised version of drop

        RULE: drop (I# n#) xs ==> drop' n# xs

        drop' n# xs = let n = I# n# in ...orig RHS...

Now the simplifier will apply the specialisation in the rhs of drop', giving

        drop' n# xs = case xs of
                      []     -> []
                      (y:ys) -> case n# of
                                  0 -> []
                                  _ -> drop' (n# -# 1#) xs

Much better!

We'd also like to catch cases where a parameter is carried along unchanged,
but evaluated each time round the loop:

        f i n = if i>0 || i>n then i else f (i*2) n

Here f isn't strict in n, but we'd like to avoid evaluating it each iteration.
In Core, by the time we've w/wd (f is strict in i) we get

        f i# n = case i# ># 0 of
                   False -> I# i#
                   True  -> case n of { I# n# ->
                            case i# ># n# of
                                False -> I# i#
                                True  -> f (i# *# 2#) n

At the call to f, we see that the argument, n is known to be (I# n#),
and n is evaluated elsewhere in the body of f, so we can play the same
trick as above.


Note [Reboxing]
~~~~~~~~~~~~~~~
We must be careful not to allocate the same constructor twice.  Consider
        f p = (...(case p of (a,b) -> e)...p...,
               ...let t = (r,s) in ...t...(f t)...)
At the recursive call to f, we can see that t is a pair.  But we do NOT want
to make a specialised copy:
        f' a b = let p = (a,b) in (..., ...)
because now t is allocated by the caller, then r and s are passed to the
recursive call, which allocates the (r,s) pair again.

This happens if
  (a) the argument p is used in other than a case-scrutinisation way.
  (b) the argument to the call is not a 'fresh' tuple; you have to
        look into its unfolding to see that it's a tuple

Hence the "OR" part of Note [Good arguments] below.

ALTERNATIVE 2: pass both boxed and unboxed versions.  This no longer saves
allocation, but does perhaps save evals. In the RULE we'd have
something like

  f (I# x#) = f' (I# x#) x#

If at the call site the (I# x) was an unfolding, then we'd have to
rely on CSE to eliminate the duplicate allocation.... This alternative
doesn't look attractive enough to pursue.

ALTERNATIVE 3: ignore the reboxing problem.  The trouble is that
the conservative reboxing story prevents many useful functions from being
specialised.  Example:
        foo :: Maybe Int -> Int -> Int
        foo   (Just m) 0 = 0
        foo x@(Just m) n = foo x (n-m)
Here the use of 'x' will clearly not require boxing in the specialised function.

The strictness analyser has the same problem, in fact.  Example:
        f p@(a,b) = ...
If we pass just 'a' and 'b' to the worker, it might need to rebox the
pair to create (a,b).  A more sophisticated analysis might figure out
precisely the cases in which this could happen, but the strictness
analyser does no such analysis; it just passes 'a' and 'b', and hopes
for the best.

So my current choice is to make SpecConstr similarly aggressive, and
ignore the bad potential of reboxing.


Note [Good arguments]
~~~~~~~~~~~~~~~~~~~~~
So we look for

* A self-recursive function.  Ignore mutual recursion for now,
  because it's less common, and the code is simpler for self-recursion.

* EITHER

   a) At a recursive call, one or more parameters is an explicit
      constructor application
        AND
      That same parameter is scrutinised by a case somewhere in
      the RHS of the function

  OR

    b) At a recursive call, one or more parameters has an unfolding
       that is an explicit constructor application
        AND
      That same parameter is scrutinised by a case somewhere in
      the RHS of the function
        AND
      Those are the only uses of the parameter (see Note [Reboxing])


What to abstract over
~~~~~~~~~~~~~~~~~~~~~
There's a bit of a complication with type arguments.  If the call
site looks like

        f p = ...f ((:) [a] x xs)...

then our specialised function look like

        f_spec x xs = let p = (:) [a] x xs in ....as before....

This only makes sense if either
  a) the type variable 'a' is in scope at the top of f, or
  b) the type variable 'a' is an argument to f (and hence fs)

Actually, (a) may hold for value arguments too, in which case
we may not want to pass them.  Suppose 'x' is in scope at f's
defn, but xs is not.  Then we'd like

        f_spec xs = let p = (:) [a] x xs in ....as before....

Similarly (b) may hold too.  If x is already an argument at the
call, no need to pass it again.

Finally, if 'a' is not in scope at the call site, we could abstract
it as we do the term variables:

        f_spec a x xs = let p = (:) [a] x xs in ...as before...

So the grand plan is:

        * abstract the call site to a constructor-only pattern
          e.g.  C x (D (f p) (g q))  ==>  C s1 (D s2 s3)

        * Find the free variables of the abstracted pattern

        * Pass these variables, less any that are in scope at
          the fn defn.  But see Note [Shadowing] below.


NOTICE that we only abstract over variables that are not in scope,
so we're in no danger of shadowing variables used in "higher up"
in f_spec's RHS.


Note [Shadowing]
~~~~~~~~~~~~~~~~
In this pass we gather up usage information that may mention variables
that are bound between the usage site and the definition site; or (more
seriously) may be bound to something different at the definition site.
For example:

        f x = letrec g y v = let x = ...
                             in ...(g (a,b) x)...

Since 'x' is in scope at the call site, we may make a rewrite rule that
looks like
        RULE forall a,b. g (a,b) x = ...
But this rule will never match, because it's really a different 'x' at
the call site -- and that difference will be manifest by the time the
simplifier gets to it.  [A worry: the simplifier doesn't *guarantee*
no-shadowing, so perhaps it may not be distinct?]

Anyway, the rule isn't actually wrong, it's just not useful.  One possibility
is to run deShadowBinds before running SpecConstr, but instead we run the
simplifier.  That gives the simplest possible program for SpecConstr to
chew on; and it virtually guarantees no shadowing.

Note [Specialising for constant parameters]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This one is about specialising on a *constant* (but not necessarily
constructor) argument

    foo :: Int -> (Int -> Int) -> Int
    foo 0 f = 0
    foo m f = foo (f m) (+1)

It produces

    lvl_rmV :: GHC.Base.Int -> GHC.Base.Int
    lvl_rmV =
      \ (ds_dlk :: GHC.Base.Int) ->
        case ds_dlk of wild_alH { GHC.Base.I# x_alG ->
        GHC.Base.I# (GHC.Prim.+# x_alG 1)

    T.$wfoo :: GHC.Prim.Int# -> (GHC.Base.Int -> GHC.Base.Int) ->
    GHC.Prim.Int#
    T.$wfoo =
      \ (ww_sme :: GHC.Prim.Int#) (w_smg :: GHC.Base.Int -> GHC.Base.Int) ->
        case ww_sme of ds_Xlw {
          __DEFAULT ->
        case w_smg (GHC.Base.I# ds_Xlw) of w1_Xmo { GHC.Base.I# ww1_Xmz ->
        T.$wfoo ww1_Xmz lvl_rmV
        };
          0 -> 0
        }

The recursive call has lvl_rmV as its argument, so we could create a specialised copy
with that argument baked in; that is, not passed at all.   Now it can perhaps be inlined.

When is this worth it?  Call the constant 'lvl'
- If 'lvl' has an unfolding that is a constructor, see if the corresponding
  parameter is scrutinised anywhere in the body.

- If 'lvl' has an unfolding that is a inlinable function, see if the corresponding
  parameter is applied (...to enough arguments...?)

  Also do this is if the function has RULES?

Also

Note [Specialising for lambda parameters]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    foo :: Int -> (Int -> Int) -> Int
    foo 0 f = 0
    foo m f = foo (f m) (\n -> n-m)

This is subtly different from the previous one in that we get an
explicit lambda as the argument:

    T.$wfoo :: GHC.Prim.Int# -> (GHC.Base.Int -> GHC.Base.Int) ->
    GHC.Prim.Int#
    T.$wfoo =
      \ (ww_sm8 :: GHC.Prim.Int#) (w_sma :: GHC.Base.Int -> GHC.Base.Int) ->
        case ww_sm8 of ds_Xlr {
          __DEFAULT ->
        case w_sma (GHC.Base.I# ds_Xlr) of w1_Xmf { GHC.Base.I# ww1_Xmq ->
        T.$wfoo
          ww1_Xmq
          (\ (n_ad3 :: GHC.Base.Int) ->
             case n_ad3 of wild_alB { GHC.Base.I# x_alA ->
             GHC.Base.I# (GHC.Prim.-# x_alA ds_Xlr)
             })
        };
          0 -> 0
        }

I wonder if SpecConstr couldn't be extended to handle this? After all,
lambda is a sort of constructor for functions and perhaps it already
has most of the necessary machinery?

Furthermore, there's an immediate win, because you don't need to allocate the lambda
at the call site; and if perchance it's called in the recursive call, then you
may avoid allocating it altogether.  Just like for constructors.

Looks cool, but probably rare...but it might be easy to implement.


Note [SpecConstr for casts]
~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider
    data family T a :: *
    data instance T Int = T Int

    foo n = ...
       where
         go (T 0) = 0
         go (T n) = go (T (n-1))

The recursive call ends up looking like
        go (T (I# ...) `cast` g)
So we want to spot the constructor application inside the cast.
That's why we have the Cast case in argToPat

Note [Local recursive groups]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For a *local* recursive group, we can see all the calls to the
function, so we seed the specialisation loop from the calls in the
body, not from the calls in the RHS.  Consider:

  bar m n = foo n (n,n) (n,n) (n,n) (n,n)
   where
     foo n p q r s
       | n == 0    = m
       | n > 3000  = case p of { (p1,p2) -> foo (n-1) (p2,p1) q r s }
       | n > 2000  = case q of { (q1,q2) -> foo (n-1) p (q2,q1) r s }
       | n > 1000  = case r of { (r1,r2) -> foo (n-1) p q (r2,r1) s }
       | otherwise = case s of { (s1,s2) -> foo (n-1) p q r (s2,s1) }

If we start with the RHSs of 'foo', we get lots and lots of specialisations,
most of which are not needed.  But if we start with the (single) call
in the rhs of 'bar' we get exactly one fully-specialised copy, and all
the recursive calls go to this fully-specialised copy. Indeed, the original
function is later collected as dead code.  This is very important in
specialising the loops arising from stream fusion, for example in NDP where
we were getting literally hundreds of (mostly unused) specialisations of
a local function.

In a case like the above we end up never calling the original un-specialised
function.  (Although we still leave its code around just in case.)

However, if we find any boring calls in the body, including *unsaturated*
ones, such as
      letrec foo x y = ....foo...
      in map foo xs
then we will end up calling the un-specialised function, so then we *should*
use the calls in the un-specialised RHS as seeds.  We call these
"boring call patterns", and callsToPats reports if it finds any of these.

Note [Seeding top-level recursive groups]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This seeding is done in the binding for seed_calls in specRec.

1. If all the bindings in a top-level recursive group are local (not
   exported), then all the calls are in the rest of the top-level
   bindings.  This means we can specialise with those call patterns
   ONLY, and NOT with the RHSs of the recursive group (exactly like
   Note [Local recursive groups])

2. But if any of the bindings are exported, the function may be called
   with any old arguments, so (for lack of anything better) we specialise
   based on
     (a) the call patterns in the RHS
     (b) the call patterns in the rest of the top-level bindings
   NB: before Apr 15 we used (a) only, but Dimitrios had an example
       where (b) was crucial, so I added that.
       Adding (b) also improved nofib allocation results:
                  multiplier: 4%   better
                  minimax:    2.8% better

Actually in case (2), instead of using the calls from the RHS, it
would be better to specialise in the importing module.  We'd need to
add an INLINABLE pragma to the function, and then it can be
specialised in the importing scope, just as is done for type classes
in GHC.Core.Opt.Specialise.specImports. This remains to be done (#10346).

Note [Top-level recursive groups]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
To get the call usage information from "the rest of the top level
bindings" (c.f. Note [Seeding top-level recursive groups]), we work
backwards through the top-level bindings so we see the usage before we
get to the binding of the function.  Before we can collect the usage
though, we go through all the bindings and add them to the
environment. This is necessary because usage is only tracked for
functions in the environment.  These two passes are called
   'go' and 'goEnv'
in specConstrProgram.  (Looks a bit revolting to me.)

Note [Do not specialise diverging functions]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Specialising a function that just diverges is a waste of code.
Furthermore, it broke GHC (simpl014) thus:
   {-# STR Sb #-}
   f = \x. case x of (a,b) -> f x
If we specialise f we get
   f = \x. case x of (a,b) -> fspec a b
But fspec doesn't have decent strictness info.  As it happened,
(f x) :: IO t, so the state hack applied and we eta expanded fspec,
and hence f.  But now f's strictness is less than its arity, which
breaks an invariant.


Note [Forcing specialisation]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
With stream fusion and in other similar cases, we want to fully
specialise some (but not necessarily all!) loops regardless of their
size and the number of specialisations.

We allow a library to do this, in one of two ways (one which is
deprecated):

  1) Add a parameter of type GHC.Types.SPEC (from ghc-prim) to the loop body.

  2) (Deprecated) Annotate a type with ForceSpecConstr from GHC.Exts,
     and then add *that* type as a parameter to the loop body

The reason #2 is deprecated is because it requires GHCi, which isn't
available for things like a cross compiler using stage1.

Here's a (simplified) example from the `vector` package. You may bring
the special 'force specialization' type into scope by saying:

  import GHC.Types (SPEC(..))

or by defining your own type (again, deprecated):

  data SPEC = SPEC | SPEC2
  {-# ANN type SPEC ForceSpecConstr #-}

(Note this is the exact same definition of GHC.Types.SPEC, just
without the annotation.)

After that, you say:

  foldl :: (a -> b -> a) -> a -> Stream b -> a
  {-# INLINE foldl #-}
  foldl f z (Stream step s _) = foldl_loop SPEC z s
    where
      foldl_loop !sPEC z s = case step s of
                              Yield x s' -> foldl_loop sPEC (f z x) s'
                              Skip       -> foldl_loop sPEC z s'
                              Done       -> z

SpecConstr will spot the SPEC parameter and always fully specialise
foldl_loop. Note that

  * We have to prevent the SPEC argument from being removed by
    w/w which is why (a) SPEC is a sum type, and (b) we have to seq on
    the SPEC argument.

  * And lastly, the SPEC argument is ultimately eliminated by
    SpecConstr itself so there is no runtime overhead.

This is all quite ugly; we ought to come up with a better design.

ForceSpecConstr arguments are spotted in scExpr' and scTopBinds which then set
sc_force to True when calling specLoop. This flag does four things:

  * Ignore specConstrThreshold, to specialise functions of arbitrary size
        (see scTopBind)
  * Ignore specConstrCount, to make arbitrary numbers of specialisations
        (see specialise)
  * Specialise even for arguments that are not scrutinised in the loop
        (see argToPat; #4448)
  * Only specialise on recursive types a finite number of times
        (see is_too_recursive; #5550; Note [Limit recursive specialisation])

The flag holds only for specialising a single binding group, and NOT
for nested bindings.  (So really it should be passed around explicitly
and not stored in ScEnv.)  #14379 turned out to be caused by
   f SPEC x = let g1 x = ...
              in ...
We force-specialise f (because of the SPEC), but that generates a specialised
copy of g1 (as well as the original).  Alas g1 has a nested binding g2; and
in each copy of g1 we get an unspecialised and specialised copy of g2; and so
on. Result, exponential.  So the force-spec flag now only applies to one
level of bindings at a time.

Mechanism for this one-level-only thing:

 - Switch it on at the call to specRec, in scExpr and scTopBinds
 - Switch it off when doing the RHSs;
   this can be done very conveniently in decreaseSpecCount

What alternatives did I consider?

* Annotating the loop itself doesn't work because (a) it is local and
  (b) it will be w/w'ed and having w/w propagating annotations somehow
  doesn't seem like a good idea. The types of the loop arguments
  really seem to be the most persistent thing.

* Annotating the types that make up the loop state doesn't work,
  either, because (a) it would prevent us from using types like Either
  or tuples here, (b) we don't want to restrict the set of types that
  can be used in Stream states and (c) some types are fixed by the
  user (e.g., the accumulator here) but we still want to specialise as
  much as possible.

Alternatives to ForceSpecConstr
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Instead of giving the loop an extra argument of type SPEC, we
also considered *wrapping* arguments in SPEC, thus
  data SPEC a = SPEC a | SPEC2

  loop = \arg -> case arg of
                     SPEC state ->
                        case state of (x,y) -> ... loop (SPEC (x',y')) ...
                        S2 -> error ...
The idea is that a SPEC argument says "specialise this argument
regardless of whether the function case-analyses it".  But this
doesn't work well:
  * SPEC must still be a sum type, else the strictness analyser
    eliminates it
  * But that means that 'loop' won't be strict in its real payload
This loss of strictness in turn screws up specialisation, because
we may end up with calls like
   loop (SPEC (case z of (p,q) -> (q,p)))
Without the SPEC, if 'loop' were strict, the case would move out
and we'd see loop applied to a pair. But if 'loop' isn't strict
this doesn't look like a specialisable call.

Note [Limit recursive specialisation]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
It is possible for ForceSpecConstr to cause an infinite loop of specialisation.
Because there is no limit on the number of specialisations, a recursive call with
a recursive constructor as an argument (for example, list cons) will generate
a specialisation for that constructor. If the resulting specialisation also
contains a recursive call with the constructor, this could proceed indefinitely.

For example, if ForceSpecConstr is on:
  loop :: [Int] -> [Int] -> [Int]
  loop z []         = z
  loop z (x:xs)     = loop (x:z) xs
this example will create a specialisation for the pattern
  loop (a:b) c      = loop' a b c

  loop' a b []      = (a:b)
  loop' a b (x:xs)  = loop (x:(a:b)) xs
and a new pattern is found:
  loop (a:(b:c)) d  = loop'' a b c d
which can continue indefinitely.

Roman's suggestion to fix this was to stop after a couple of times on recursive types,
but still specialising on non-recursive types as much as possible.

To implement this, we count the number of times we have gone round the
"specialise recursively" loop ('go' in 'specRec').  Once have gone round
more than N times (controlled by -fspec-constr-recursive=N) we check

  - If sc_force is off, and sc_count is (Just max) then we don't
    need to do anything: trim_pats will limit the number of specs

  - Otherwise check if any function has now got more than (sc_count env)
    specialisations.  If sc_count is "no limit" then we arbitrarily
    choose 10 as the limit (ugh).

See #5550.   Also #13623, where this test had become over-aggressive,
and we lost a wonderful specialisation that we really wanted!

Note [NoSpecConstr]
~~~~~~~~~~~~~~~~~~~
The ignoreDataCon stuff allows you to say
    {-# ANN type T NoSpecConstr #-}
to mean "don't specialise on arguments of this type".  It was added
before we had ForceSpecConstr.  Lacking ForceSpecConstr we specialised
regardless of size; and then we needed a way to turn that *off*.  Now
that we have ForceSpecConstr, this NoSpecConstr is probably redundant.
(Used only for PArray, TODO: remove?)

Note [SpecConstr and strict fields]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We treat strict fields in SpecConstr the same way we do in W/W.
That is we make the specialized function strict in arguments
representing strict fields. See Note [Call-by-value for worker args]
for why we do this.

-----------------------------------------------------
                Stuff not yet handled
-----------------------------------------------------

Here are notes arising from Roman's work that I don't want to lose.

Example 1
~~~~~~~~~
    data T a = T !a

    foo :: Int -> T Int -> Int
    foo 0 t = 0
    foo x t | even x    = case t of { T n -> foo (x-n) t }
            | otherwise = foo (x-1) t

SpecConstr does no specialisation, because the second recursive call
looks like a boxed use of the argument.  A pity.

    $wfoo_sFw :: GHC.Prim.Int# -> T.T GHC.Base.Int -> GHC.Prim.Int#
    $wfoo_sFw =
      \ (ww_sFo [Just L] :: GHC.Prim.Int#) (w_sFq [Just L] :: T.T GHC.Base.Int) ->
         case ww_sFo of ds_Xw6 [Just L] {
           __DEFAULT ->
                case GHC.Prim.remInt# ds_Xw6 2 of wild1_aEF [Dead Just A] {
                  __DEFAULT -> $wfoo_sFw (GHC.Prim.-# ds_Xw6 1) w_sFq;
                  0 ->
                    case w_sFq of wild_Xy [Just L] { T.T n_ad5 [Just U(L)] ->
                    case n_ad5 of wild1_aET [Just A] { GHC.Base.I# y_aES [Just L] ->
                    $wfoo_sFw (GHC.Prim.-# ds_Xw6 y_aES) wild_Xy
                    } } };
           0 -> 0

Example 2
~~~~~~~~~
    data a :*: b = !a :*: !b
    data T a = T !a

    foo :: (Int :*: T Int) -> Int
    foo (0 :*: t) = 0
    foo (x :*: t) | even x    = case t of { T n -> foo ((x-n) :*: t) }
                  | otherwise = foo ((x-1) :*: t)

Very similar to the previous one, except that the parameters are now in
a strict tuple. Before SpecConstr, we have

    $wfoo_sG3 :: GHC.Prim.Int# -> T.T GHC.Base.Int -> GHC.Prim.Int#
    $wfoo_sG3 =
      \ (ww_sFU [Just L] :: GHC.Prim.Int#) (ww_sFW [Just L] :: T.T
    GHC.Base.Int) ->
        case ww_sFU of ds_Xws [Just L] {
          __DEFAULT ->
        case GHC.Prim.remInt# ds_Xws 2 of wild1_aEZ [Dead Just A] {
          __DEFAULT ->
            case ww_sFW of tpl_B2 [Just L] { T.T a_sFo [Just A] ->
            $wfoo_sG3 (GHC.Prim.-# ds_Xws 1) tpl_B2             -- $wfoo1
            };
          0 ->
            case ww_sFW of wild_XB [Just A] { T.T n_ad7 [Just S(L)] ->
            case n_ad7 of wild1_aFd [Just L] { GHC.Base.I# y_aFc [Just L] ->
            $wfoo_sG3 (GHC.Prim.-# ds_Xws y_aFc) wild_XB        -- $wfoo2
            } } };
          0 -> 0 }

We get two specialisations:
"SC:$wfoo1" [0] __forall {a_sFB :: GHC.Base.Int sc_sGC :: GHC.Prim.Int#}
                  Foo.$wfoo sc_sGC (Foo.T @ GHC.Base.Int a_sFB)
                  = Foo.$s$wfoo1 a_sFB sc_sGC ;
"SC:$wfoo2" [0] __forall {y_aFp :: GHC.Prim.Int# sc_sGC :: GHC.Prim.Int#}
                  Foo.$wfoo sc_sGC (Foo.T @ GHC.Base.Int (GHC.Base.I# y_aFp))
                  = Foo.$s$wfoo y_aFp sc_sGC ;

But perhaps the first one isn't good.  After all, we know that tpl_B2 is
a T (I# x) really, because T is strict and Int has one constructor.  (We can't
unbox the strict fields, because T is polymorphic!)

************************************************************************
*                                                                      *
\subsection{Top level wrapper stuff}
*                                                                      *
************************************************************************
-}

specConstrProgram :: ModGuts -> CoreM ModGuts
specConstrProgram :: ModGuts -> CoreM ModGuts
specConstrProgram ModGuts
guts
  = do
      DynFlags
dflags <- CoreM DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
      UniqSupply
us     <- CoreM UniqSupply
forall (m :: * -> *). MonadUnique m => m UniqSupply
getUniqueSupplyM
      (ModuleEnv SpecConstrAnnotation
_, NameEnv SpecConstrAnnotation
annos) <- ([Word8] -> SpecConstrAnnotation)
-> ModGuts
-> CoreM
     (ModuleEnv SpecConstrAnnotation, NameEnv SpecConstrAnnotation)
forall a.
Typeable a =>
([Word8] -> a) -> ModGuts -> CoreM (ModuleEnv a, NameEnv a)
getFirstAnnotations [Word8] -> SpecConstrAnnotation
forall a. Data a => [Word8] -> a
deserializeWithData ModGuts
guts
      Module
this_mod <- CoreM Module
forall (m :: * -> *). HasModule m => m Module
getModule
      -- pprTraceM "specConstrInput" (ppr $ mg_binds guts)
      let binds' :: [CoreBind]
binds' = [CoreBind] -> [CoreBind]
forall a. [a] -> [a]
reverse ([CoreBind] -> [CoreBind]) -> [CoreBind] -> [CoreBind]
forall a b. (a -> b) -> a -> b
$ ([CoreBind], UniqSupply) -> [CoreBind]
forall a b. (a, b) -> a
fst (([CoreBind], UniqSupply) -> [CoreBind])
-> ([CoreBind], UniqSupply) -> [CoreBind]
forall a b. (a -> b) -> a -> b
$ UniqSupply -> UniqSM [CoreBind] -> ([CoreBind], UniqSupply)
forall a. UniqSupply -> UniqSM a -> (a, UniqSupply)
initUs UniqSupply
us (UniqSM [CoreBind] -> ([CoreBind], UniqSupply))
-> UniqSM [CoreBind] -> ([CoreBind], UniqSupply)
forall a b. (a -> b) -> a -> b
$ do
                    -- Note [Top-level recursive groups]
                    (ScEnv
env, [CoreBind]
binds) <- ScEnv -> [CoreBind] -> UniqSM (ScEnv, [CoreBind])
goEnv (DynFlags -> Module -> NameEnv SpecConstrAnnotation -> ScEnv
initScEnv DynFlags
dflags Module
this_mod NameEnv SpecConstrAnnotation
annos)
                                          (ModGuts -> [CoreBind]
mg_binds ModGuts
guts)
                        -- binds is identical to (mg_binds guts), except that the
                        -- binders on the LHS have been replaced by extendBndr
                        --   (SPJ this seems like overkill; I don't think the binders
                        --    will change at all; and we don't substitute in the RHSs anyway!!)
                    ScEnv -> ScUsage -> [CoreBind] -> UniqSM [CoreBind]
go ScEnv
env ScUsage
nullUsage ([CoreBind] -> [CoreBind]
forall a. [a] -> [a]
reverse [CoreBind]
binds)

      ModGuts -> CoreM ModGuts
forall a. a -> CoreM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ModGuts
guts { mg_binds :: [CoreBind]
mg_binds = [CoreBind]
binds' })
  where
    -- See Note [Top-level recursive groups]
    goEnv :: ScEnv -> [CoreBind] -> UniqSM (ScEnv, [CoreBind])
goEnv ScEnv
env []            = (ScEnv, [CoreBind]) -> UniqSM (ScEnv, [CoreBind])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScEnv
env, [])
    goEnv ScEnv
env (CoreBind
bind:[CoreBind]
binds)  = do (ScEnv
env', CoreBind
bind')   <- ScEnv -> CoreBind -> UniqSM (ScEnv, CoreBind)
scTopBindEnv ScEnv
env CoreBind
bind
                                 (ScEnv
env'', [CoreBind]
binds') <- ScEnv -> [CoreBind] -> UniqSM (ScEnv, [CoreBind])
goEnv ScEnv
env' [CoreBind]
binds
                                 (ScEnv, [CoreBind]) -> UniqSM (ScEnv, [CoreBind])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScEnv
env'', CoreBind
bind' CoreBind -> [CoreBind] -> [CoreBind]
forall a. a -> [a] -> [a]
: [CoreBind]
binds')

    -- Arg list of bindings is in reverse order
    go :: ScEnv -> ScUsage -> [CoreBind] -> UniqSM [CoreBind]
go ScEnv
_   ScUsage
_   []           = [CoreBind] -> UniqSM [CoreBind]
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return []
    go ScEnv
env ScUsage
usg (CoreBind
bind:[CoreBind]
binds) = do (ScUsage
usg', CoreBind
bind') <- ScEnv -> ScUsage -> CoreBind -> UniqSM (ScUsage, CoreBind)
scTopBind ScEnv
env ScUsage
usg CoreBind
bind
                                 [CoreBind]
binds' <- ScEnv -> ScUsage -> [CoreBind] -> UniqSM [CoreBind]
go ScEnv
env ScUsage
usg' [CoreBind]
binds
                                 [CoreBind] -> UniqSM [CoreBind]
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (CoreBind
bind' CoreBind -> [CoreBind] -> [CoreBind]
forall a. a -> [a] -> [a]
: [CoreBind]
binds')

{-
************************************************************************
*                                                                      *
\subsection{Environment: goes downwards}
*                                                                      *
************************************************************************

Note [Work-free values only in environment]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The sc_vals field keeps track of in-scope value bindings, so
that if we come across (case x of Just y ->...) we can reduce the
case from knowing that x is bound to a pair.

But only *work-free* values are ok here. For example if the envt had
    x -> Just (expensive v)
then we do NOT want to expand to
     let y = expensive v in ...
because the x-binding still exists and we've now duplicated (expensive v).

This seldom happens because let-bound constructor applications are
ANF-ised, but it can happen as a result of on-the-fly transformations in
SpecConstr itself.  Here is #7865:

        let {
          a'_shr =
            case xs_af8 of _ {
              [] -> acc_af6;
              : ds_dgt [Dmd=<L,A>] ds_dgu [Dmd=<L,A>] ->
                (expensive x_af7, x_af7
            } } in
        let {
          ds_sht =
            case a'_shr of _ { (p'_afd, q'_afe) ->
            TSpecConstr_DoubleInline.recursive
              (GHC.Types.: @ GHC.Types.Int x_af7 wild_X6) (q'_afe, p'_afd)
            } } in

When processed knowing that xs_af8 was bound to a cons, we simplify to
   a'_shr = (expensive x_af7, x_af7)
and we do NOT want to inline that at the occurrence of a'_shr in ds_sht.
(There are other occurrences of a'_shr.)  No no no.

It would be possible to do some on-the-fly ANF-ising, so that a'_shr turned
into a work-free value again, thus
   a1 = expensive x_af7
   a'_shr = (a1, x_af7)
but that's more work, so until its shown to be important I'm going to
leave it for now.

Note [Making SpecConstr keener]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider this, in (perf/should_run/T9339)
   last (filter odd [1..1000])

After optimisation, including SpecConstr, we get:
   f :: Int# -> Int -> Int
   f x y = case remInt# x 2# of
             __DEFAULT -> case x of
                            __DEFAULT -> f (+# wild_Xp 1#) (I# x)
                            1000000# -> ...
             0# -> case x of
                     __DEFAULT -> f (+# wild_Xp 1#) y
                    1000000#   -> y

Not good!  We build an (I# x) box every time around the loop.
SpecConstr (as described in the paper) does not specialise f, despite
the call (f ... (I# x)) because 'y' is not scrutinised in the body.
But it is much better to specialise f for the case where the argument
is of form (I# x); then we build the box only when returning y, which
is on the cold path.

Another example:

   f x = ...(g x)....

Here 'x' is not scrutinised in f's body; but if we did specialise 'f'
then the call (g x) might allow 'g' to be specialised in turn.

So sc_keen controls whether or not we take account of whether argument is
scrutinised in the body.  True <=> ignore that, and specialise whenever
the function is applied to a data constructor.
-}

data ScEnv = SCE { ScEnv -> DynFlags
sc_dflags    :: DynFlags,
                   ScEnv -> UnfoldingOpts
sc_uf_opts   :: !UnfoldingOpts, -- ^ Unfolding options
                   ScEnv -> Module
sc_module    :: !Module,
                   ScEnv -> Maybe Int
sc_size      :: Maybe Int,   -- Size threshold
                                                -- Nothing => no limit

                   ScEnv -> Maybe Int
sc_count     :: Maybe Int,   -- Max # of specialisations for any one fn
                                                -- Nothing => no limit
                                                -- See Note [Avoiding exponential blowup]

                   ScEnv -> Int
sc_recursive :: Int,         -- Max # of specialisations over recursive type.
                                                -- Stops ForceSpecConstr from diverging.

                   ScEnv -> Bool
sc_keen     :: Bool,         -- Specialise on arguments that are known
                                                -- constructors, even if they are not
                                                -- scrutinised in the body.  See
                                                -- Note [Making SpecConstr keener]

                   ScEnv -> Bool
sc_force     :: Bool,        -- Force specialisation?
                                                -- See Note [Forcing specialisation]

                   ScEnv -> Subst
sc_subst     :: Subst,       -- Current substitution
                                                -- Maps InIds to OutExprs

                   ScEnv -> HowBoundEnv
sc_how_bound :: HowBoundEnv,
                        -- Binds interesting non-top-level variables
                        -- Domain is OutVars (*after* applying the substitution)

                   ScEnv -> ValueEnv
sc_vals      :: ValueEnv,
                        -- Domain is OutIds (*after* applying the substitution)
                        -- Used even for top-level bindings (but not imported ones)
                        -- The range of the ValueEnv is *work-free* values
                        -- such as (\x. blah), or (Just v)
                        -- but NOT (Just (expensive v))
                        -- See Note [Work-free values only in environment]

                   ScEnv -> NameEnv SpecConstrAnnotation
sc_annotations :: UniqFM Name SpecConstrAnnotation
             }

---------------------
type HowBoundEnv = VarEnv HowBound      -- Domain is OutVars

---------------------
type ValueEnv = IdEnv Value             -- Domain is OutIds
data Value    = ConVal AltCon [CoreArg] -- _Saturated_ constructors
                                        --   The AltCon is never DEFAULT
              | LambdaVal               -- Inlinable lambdas or PAPs

instance Outputable Value where
   ppr :: Value -> SDoc
ppr (ConVal AltCon
con [Expr Id]
args) = AltCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr AltCon
con SDoc -> SDoc -> SDoc
<+> [Expr Id] -> SDoc
forall a. Outputable a => [a] -> SDoc
interpp'SP [Expr Id]
args
   ppr Value
LambdaVal         = String -> SDoc
text String
"<Lambda>"

---------------------
initScEnv :: DynFlags -> Module -> UniqFM Name SpecConstrAnnotation -> ScEnv
initScEnv :: DynFlags -> Module -> NameEnv SpecConstrAnnotation -> ScEnv
initScEnv DynFlags
dflags Module
this_mod NameEnv SpecConstrAnnotation
anns
  = SCE { sc_dflags :: DynFlags
sc_dflags      = DynFlags
dflags,
          sc_uf_opts :: UnfoldingOpts
sc_uf_opts     = DynFlags -> UnfoldingOpts
unfoldingOpts DynFlags
dflags,
          sc_module :: Module
sc_module      = Module
this_mod,
          sc_size :: Maybe Int
sc_size        = DynFlags -> Maybe Int
specConstrThreshold DynFlags
dflags,
          sc_count :: Maybe Int
sc_count       = DynFlags -> Maybe Int
specConstrCount     DynFlags
dflags,
          sc_recursive :: Int
sc_recursive   = DynFlags -> Int
specConstrRecursive DynFlags
dflags,
          sc_keen :: Bool
sc_keen        = GeneralFlag -> DynFlags -> Bool
gopt GeneralFlag
Opt_SpecConstrKeen DynFlags
dflags,
          sc_force :: Bool
sc_force       = Bool
False,
          sc_subst :: Subst
sc_subst       = Subst
emptySubst,
          sc_how_bound :: HowBoundEnv
sc_how_bound   = HowBoundEnv
forall a. VarEnv a
emptyVarEnv,
          sc_vals :: ValueEnv
sc_vals        = ValueEnv
forall a. VarEnv a
emptyVarEnv,
          sc_annotations :: NameEnv SpecConstrAnnotation
sc_annotations = NameEnv SpecConstrAnnotation
anns }

data HowBound = RecFun  -- These are the recursive functions for which
                        -- we seek interesting call patterns

              | RecArg  -- These are those functions' arguments, or their sub-components;
                        -- we gather occurrence information for these

instance Outputable HowBound where
  ppr :: HowBound -> SDoc
ppr HowBound
RecFun = String -> SDoc
text String
"RecFun"
  ppr HowBound
RecArg = String -> SDoc
text String
"RecArg"

scForce :: ScEnv -> Bool -> ScEnv
scForce :: ScEnv -> Bool -> ScEnv
scForce ScEnv
env Bool
b = ScEnv
env { sc_force :: Bool
sc_force = Bool
b }

lookupHowBound :: ScEnv -> Id -> Maybe HowBound
lookupHowBound :: ScEnv -> Id -> Maybe HowBound
lookupHowBound ScEnv
env Id
id = HowBoundEnv -> Id -> Maybe HowBound
forall a. VarEnv a -> Id -> Maybe a
lookupVarEnv (ScEnv -> HowBoundEnv
sc_how_bound ScEnv
env) Id
id

scSubstId :: ScEnv -> Id -> CoreExpr
scSubstId :: ScEnv -> Id -> Expr Id
scSubstId ScEnv
env Id
v = (() :: Constraint) => Subst -> Id -> Expr Id
Subst -> Id -> Expr Id
lookupIdSubst (ScEnv -> Subst
sc_subst ScEnv
env) Id
v

scSubstTy :: ScEnv -> Type -> Type
scSubstTy :: ScEnv -> Type -> Type
scSubstTy ScEnv
env Type
ty = Subst -> Type -> Type
substTy (ScEnv -> Subst
sc_subst ScEnv
env) Type
ty

scSubstCo :: ScEnv -> Coercion -> Coercion
scSubstCo :: ScEnv -> Coercion -> Coercion
scSubstCo ScEnv
env Coercion
co = HasCallStack => Subst -> Coercion -> Coercion
Subst -> Coercion -> Coercion
substCo (ScEnv -> Subst
sc_subst ScEnv
env) Coercion
co

zapScSubst :: ScEnv -> ScEnv
zapScSubst :: ScEnv -> ScEnv
zapScSubst ScEnv
env = ScEnv
env { sc_subst :: Subst
sc_subst = Subst -> Subst
zapSubstEnv (ScEnv -> Subst
sc_subst ScEnv
env) }

extendScInScope :: ScEnv -> [Var] -> ScEnv
        -- Bring the quantified variables into scope
extendScInScope :: ScEnv -> [Id] -> ScEnv
extendScInScope ScEnv
env [Id]
qvars = ScEnv
env { sc_subst :: Subst
sc_subst = Subst -> [Id] -> Subst
extendInScopeList (ScEnv -> Subst
sc_subst ScEnv
env) [Id]
qvars }

        -- Extend the substitution
extendScSubst :: ScEnv -> Var -> OutExpr -> ScEnv
extendScSubst :: ScEnv -> Id -> Expr Id -> ScEnv
extendScSubst ScEnv
env Id
var Expr Id
expr = ScEnv
env { sc_subst :: Subst
sc_subst = Subst -> Id -> Expr Id -> Subst
extendSubst (ScEnv -> Subst
sc_subst ScEnv
env) Id
var Expr Id
expr }

extendScSubstList :: ScEnv -> [(Var,OutExpr)] -> ScEnv
extendScSubstList :: ScEnv -> [(Id, Expr Id)] -> ScEnv
extendScSubstList ScEnv
env [(Id, Expr Id)]
prs = ScEnv
env { sc_subst :: Subst
sc_subst = Subst -> [(Id, Expr Id)] -> Subst
extendSubstList (ScEnv -> Subst
sc_subst ScEnv
env) [(Id, Expr Id)]
prs }

extendHowBound :: ScEnv -> [Var] -> HowBound -> ScEnv
extendHowBound :: ScEnv -> [Id] -> HowBound -> ScEnv
extendHowBound ScEnv
env [Id]
bndrs HowBound
how_bound
  = ScEnv
env { sc_how_bound :: HowBoundEnv
sc_how_bound = HowBoundEnv -> [(Id, HowBound)] -> HowBoundEnv
forall a. VarEnv a -> [(Id, a)] -> VarEnv a
extendVarEnvList (ScEnv -> HowBoundEnv
sc_how_bound ScEnv
env)
                            [(Id
bndr,HowBound
how_bound) | Id
bndr <- [Id]
bndrs] }

extendBndrsWith :: HowBound -> ScEnv -> [Var] -> (ScEnv, [Var])
extendBndrsWith :: HowBound -> ScEnv -> [Id] -> (ScEnv, [Id])
extendBndrsWith HowBound
how_bound ScEnv
env [Id]
bndrs
  = (ScEnv
env { sc_subst :: Subst
sc_subst = Subst
subst', sc_how_bound :: HowBoundEnv
sc_how_bound = HowBoundEnv
hb_env' }, [Id]
bndrs')
  where
    (Subst
subst', [Id]
bndrs') = Subst -> [Id] -> (Subst, [Id])
substBndrs (ScEnv -> Subst
sc_subst ScEnv
env) [Id]
bndrs
    hb_env' :: HowBoundEnv
hb_env' = ScEnv -> HowBoundEnv
sc_how_bound ScEnv
env HowBoundEnv -> [(Id, HowBound)] -> HowBoundEnv
forall a. VarEnv a -> [(Id, a)] -> VarEnv a
`extendVarEnvList`
                    [(Id
bndr,HowBound
how_bound) | Id
bndr <- [Id]
bndrs']

extendBndrWith :: HowBound -> ScEnv -> Var -> (ScEnv, Var)
extendBndrWith :: HowBound -> ScEnv -> Id -> (ScEnv, Id)
extendBndrWith HowBound
how_bound ScEnv
env Id
bndr
  = (ScEnv
env { sc_subst :: Subst
sc_subst = Subst
subst', sc_how_bound :: HowBoundEnv
sc_how_bound = HowBoundEnv
hb_env' }, Id
bndr')
  where
    (Subst
subst', Id
bndr') = Subst -> Id -> (Subst, Id)
substBndr (ScEnv -> Subst
sc_subst ScEnv
env) Id
bndr
    hb_env' :: HowBoundEnv
hb_env' = HowBoundEnv -> Id -> HowBound -> HowBoundEnv
forall a. VarEnv a -> Id -> a -> VarEnv a
extendVarEnv (ScEnv -> HowBoundEnv
sc_how_bound ScEnv
env) Id
bndr' HowBound
how_bound

extendRecBndrs :: ScEnv -> [Var] -> (ScEnv, [Var])
extendRecBndrs :: ScEnv -> [Id] -> (ScEnv, [Id])
extendRecBndrs ScEnv
env [Id]
bndrs  = (ScEnv
env { sc_subst :: Subst
sc_subst = Subst
subst' }, [Id]
bndrs')
                      where
                        (Subst
subst', [Id]
bndrs') = Subst -> [Id] -> (Subst, [Id])
substRecBndrs (ScEnv -> Subst
sc_subst ScEnv
env) [Id]
bndrs

extendBndrs :: ScEnv -> [Var] -> (ScEnv, [Var])
extendBndrs :: ScEnv -> [Id] -> (ScEnv, [Id])
extendBndrs ScEnv
env [Id]
bndrs = (ScEnv -> Id -> (ScEnv, Id)) -> ScEnv -> [Id] -> (ScEnv, [Id])
forall (t :: * -> *) s a b.
Traversable t =>
(s -> a -> (s, b)) -> s -> t a -> (s, t b)
mapAccumL ScEnv -> Id -> (ScEnv, Id)
extendBndr ScEnv
env [Id]
bndrs

extendBndr :: ScEnv -> Var -> (ScEnv, Var)
extendBndr :: ScEnv -> Id -> (ScEnv, Id)
extendBndr ScEnv
env Id
bndr  = (ScEnv
env { sc_subst :: Subst
sc_subst = Subst
subst' }, Id
bndr')
                     where
                       (Subst
subst', Id
bndr') = Subst -> Id -> (Subst, Id)
substBndr (ScEnv -> Subst
sc_subst ScEnv
env) Id
bndr

extendValEnv :: ScEnv -> Id -> Maybe Value -> ScEnv
extendValEnv :: ScEnv -> Id -> Maybe Value -> ScEnv
extendValEnv ScEnv
env Id
_  Maybe Value
Nothing   = ScEnv
env
extendValEnv ScEnv
env Id
id (Just Value
cv)
 | Value -> Bool
valueIsWorkFree Value
cv      -- Don't duplicate work!!  #7865
 = ScEnv
env { sc_vals :: ValueEnv
sc_vals = ValueEnv -> Id -> Value -> ValueEnv
forall a. VarEnv a -> Id -> a -> VarEnv a
extendVarEnv (ScEnv -> ValueEnv
sc_vals ScEnv
env) Id
id Value
cv }
extendValEnv ScEnv
env Id
_ Maybe Value
_ = ScEnv
env

extendCaseBndrs :: ScEnv -> OutExpr -> OutId -> AltCon -> [Var] -> (ScEnv, [Var])
-- When we encounter
--      case scrut of b
--          C x y -> ...
-- we want to bind b, to (C x y)
-- NB1: Extends only the sc_vals part of the envt
-- NB2: Kill the dead-ness info on the pattern binders x,y, since
--      they are potentially made alive by the [b -> C x y] binding
extendCaseBndrs :: ScEnv -> Expr Id -> Id -> AltCon -> [Id] -> (ScEnv, [Id])
extendCaseBndrs ScEnv
env Expr Id
scrut Id
case_bndr AltCon
con [Id]
alt_bndrs
   = (ScEnv
env2, [Id]
alt_bndrs')
 where
   live_case_bndr :: Bool
live_case_bndr = Bool -> Bool
not (Id -> Bool
isDeadBinder Id
case_bndr)
   env1 :: ScEnv
env1 | Var Id
v <- (CoreTickish -> Bool) -> Expr Id -> Expr Id
forall b. (CoreTickish -> Bool) -> Expr b -> Expr b
stripTicksTopE (Bool -> CoreTickish -> Bool
forall a b. a -> b -> a
const Bool
True) Expr Id
scrut
                         = ScEnv -> Id -> Maybe Value -> ScEnv
extendValEnv ScEnv
env Id
v Maybe Value
cval
        | Bool
otherwise      = ScEnv
env  -- See Note [Add scrutinee to ValueEnv too]
   env2 :: ScEnv
env2 | Bool
live_case_bndr = ScEnv -> Id -> Maybe Value -> ScEnv
extendValEnv ScEnv
env1 Id
case_bndr Maybe Value
cval
        | Bool
otherwise      = ScEnv
env1

   alt_bndrs' :: [Id]
alt_bndrs' | case Expr Id
scrut of { Var {} -> Bool
True; Expr Id
_ -> Bool
live_case_bndr }
              = (Id -> Id) -> [Id] -> [Id]
forall a b. (a -> b) -> [a] -> [b]
map Id -> Id
zap [Id]
alt_bndrs
              | Bool
otherwise
              = [Id]
alt_bndrs

   cval :: Maybe Value
cval = case AltCon
con of
                AltCon
DEFAULT    -> Maybe Value
forall a. Maybe a
Nothing
                LitAlt {}  -> Value -> Maybe Value
forall a. a -> Maybe a
Just (AltCon -> [Expr Id] -> Value
ConVal AltCon
con [])
                DataAlt {} -> Value -> Maybe Value
forall a. a -> Maybe a
Just (AltCon -> [Expr Id] -> Value
ConVal AltCon
con [Expr Id]
vanilla_args)
                      where
                        vanilla_args :: [Expr Id]
vanilla_args = (Type -> Expr Id) -> [Type] -> [Expr Id]
forall a b. (a -> b) -> [a] -> [b]
map Type -> Expr Id
forall b. Type -> Expr b
Type (HasCallStack => Type -> [Type]
Type -> [Type]
tyConAppArgs (Id -> Type
idType Id
case_bndr)) [Expr Id] -> [Expr Id] -> [Expr Id]
forall a. [a] -> [a] -> [a]
++
                                       [Id] -> [Expr Id]
forall b. [Id] -> [Expr b]
varsToCoreExprs [Id]
alt_bndrs

   zap :: Id -> Id
zap Id
v | Id -> Bool
isTyVar Id
v = Id
v                -- See NB2 above
         | Bool
otherwise = Id -> Id
zapIdOccInfo Id
v


decreaseSpecCount :: ScEnv -> Int -> ScEnv
-- See Note [Avoiding exponential blowup]
decreaseSpecCount :: ScEnv -> Int -> ScEnv
decreaseSpecCount ScEnv
env Int
n_specs
  = ScEnv
env { sc_force :: Bool
sc_force = Bool
False   -- See Note [Forcing specialisation]
        , sc_count :: Maybe Int
sc_count = case ScEnv -> Maybe Int
sc_count ScEnv
env of
                       Maybe Int
Nothing -> Maybe Int
forall a. Maybe a
Nothing
                       Just Int
n  -> Int -> Maybe Int
forall a. a -> Maybe a
Just (Int
n Int -> Int -> Int
forall a. Integral a => a -> a -> a
`div` (Int
n_specs Int -> Int -> Int
forall a. Num a => a -> a -> a
+ Int
1)) }
        -- The "+1" takes account of the original function;
        -- See Note [Avoiding exponential blowup]

---------------------------------------------------
-- See Note [Forcing specialisation]
ignoreType    :: ScEnv -> Type   -> Bool
ignoreDataCon  :: ScEnv -> DataCon -> Bool
forceSpecBndr :: ScEnv -> Var    -> Bool

ignoreDataCon :: ScEnv -> DataCon -> Bool
ignoreDataCon ScEnv
env DataCon
dc = ScEnv -> TyCon -> Bool
ignoreTyCon ScEnv
env (DataCon -> TyCon
dataConTyCon DataCon
dc)

ignoreType :: ScEnv -> Type -> Bool
ignoreType ScEnv
env Type
ty
  = case Type -> Maybe TyCon
tyConAppTyCon_maybe Type
ty of
      Just TyCon
tycon -> ScEnv -> TyCon -> Bool
ignoreTyCon ScEnv
env TyCon
tycon
      Maybe TyCon
_          -> Bool
False

ignoreTyCon :: ScEnv -> TyCon -> Bool
ignoreTyCon :: ScEnv -> TyCon -> Bool
ignoreTyCon ScEnv
env TyCon
tycon
  = NameEnv SpecConstrAnnotation -> Name -> Maybe SpecConstrAnnotation
forall key elt. Uniquable key => UniqFM key elt -> key -> Maybe elt
lookupUFM (ScEnv -> NameEnv SpecConstrAnnotation
sc_annotations ScEnv
env) (TyCon -> Name
tyConName TyCon
tycon) Maybe SpecConstrAnnotation -> Maybe SpecConstrAnnotation -> Bool
forall a. Eq a => a -> a -> Bool
== SpecConstrAnnotation -> Maybe SpecConstrAnnotation
forall a. a -> Maybe a
Just SpecConstrAnnotation
NoSpecConstr

forceSpecBndr :: ScEnv -> Id -> Bool
forceSpecBndr ScEnv
env Id
var = ScEnv -> Type -> Bool
forceSpecFunTy ScEnv
env (Type -> Bool) -> (Id -> Type) -> Id -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. ([Id], Type) -> Type
forall a b. (a, b) -> b
snd (([Id], Type) -> Type) -> (Id -> ([Id], Type)) -> Id -> Type
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Type -> ([Id], Type)
splitForAllTyCoVars (Type -> ([Id], Type)) -> (Id -> Type) -> Id -> ([Id], Type)
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Id -> Type
varType (Id -> Bool) -> Id -> Bool
forall a b. (a -> b) -> a -> b
$ Id
var

forceSpecFunTy :: ScEnv -> Type -> Bool
forceSpecFunTy :: ScEnv -> Type -> Bool
forceSpecFunTy ScEnv
env = (Type -> Bool) -> [Type] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any (ScEnv -> Type -> Bool
forceSpecArgTy ScEnv
env) ([Type] -> Bool) -> (Type -> [Type]) -> Type -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. (Scaled Type -> Type) -> [Scaled Type] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map Scaled Type -> Type
forall a. Scaled a -> a
scaledThing ([Scaled Type] -> [Type])
-> (Type -> [Scaled Type]) -> Type -> [Type]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. ([Scaled Type], Type) -> [Scaled Type]
forall a b. (a, b) -> a
fst (([Scaled Type], Type) -> [Scaled Type])
-> (Type -> ([Scaled Type], Type)) -> Type -> [Scaled Type]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Type -> ([Scaled Type], Type)
splitFunTys

forceSpecArgTy :: ScEnv -> Type -> Bool
forceSpecArgTy :: ScEnv -> Type -> Bool
forceSpecArgTy ScEnv
env Type
ty
  | Just Type
ty' <- Type -> Maybe Type
coreView Type
ty = ScEnv -> Type -> Bool
forceSpecArgTy ScEnv
env Type
ty'

forceSpecArgTy ScEnv
env Type
ty
  | Just (TyCon
tycon, [Type]
tys) <- (() :: Constraint) => Type -> Maybe (TyCon, [Type])
Type -> Maybe (TyCon, [Type])
splitTyConApp_maybe Type
ty
  , TyCon
tycon TyCon -> TyCon -> Bool
forall a. Eq a => a -> a -> Bool
/= TyCon
funTyCon
      = TyCon -> Unique
tyConUnique TyCon
tycon Unique -> Unique -> Bool
forall a. Eq a => a -> a -> Bool
== Unique
specTyConKey
        Bool -> Bool -> Bool
|| NameEnv SpecConstrAnnotation -> Name -> Maybe SpecConstrAnnotation
forall key elt. Uniquable key => UniqFM key elt -> key -> Maybe elt
lookupUFM (ScEnv -> NameEnv SpecConstrAnnotation
sc_annotations ScEnv
env) (TyCon -> Name
tyConName TyCon
tycon) Maybe SpecConstrAnnotation -> Maybe SpecConstrAnnotation -> Bool
forall a. Eq a => a -> a -> Bool
== SpecConstrAnnotation -> Maybe SpecConstrAnnotation
forall a. a -> Maybe a
Just SpecConstrAnnotation
ForceSpecConstr
        Bool -> Bool -> Bool
|| (Type -> Bool) -> [Type] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any (ScEnv -> Type -> Bool
forceSpecArgTy ScEnv
env) [Type]
tys

forceSpecArgTy ScEnv
_ Type
_ = Bool
False

{-
Note [Add scrutinee to ValueEnv too]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider this:
   case x of y
     (a,b) -> case b of c
                I# v -> ...(f y)...
By the time we get to the call (f y), the ValueEnv
will have a binding for y, and for c
    y -> (a,b)
    c -> I# v
BUT that's not enough!  Looking at the call (f y) we
see that y is pair (a,b), but we also need to know what 'b' is.
So in extendCaseBndrs we must *also* add the binding
   b -> I# v
else we lose a useful specialisation for f.  This is necessary even
though the simplifier has systematically replaced uses of 'x' with 'y'
and 'b' with 'c' in the code.  The use of 'b' in the ValueEnv came
from outside the case.  See #4908 for the live example.

Note [Avoiding exponential blowup]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The sc_count field of the ScEnv says how many times we are prepared to
duplicate a single function.  But we must take care with recursive
specialisations.  Consider

        let $j1 = let $j2 = let $j3 = ...
                            in
                            ...$j3...
                  in
                  ...$j2...
        in
        ...$j1...

If we specialise $j1 then in each specialisation (as well as the original)
we can specialise $j2, and similarly $j3.  Even if we make just *one*
specialisation of each, because we also have the original we'll get 2^n
copies of $j3, which is not good.

So when recursively specialising we divide the sc_count by the number of
copies we are making at this level, including the original.


************************************************************************
*                                                                      *
\subsection{Usage information: flows upwards}
*                                                                      *
************************************************************************
-}

data ScUsage
   = SCU {
        ScUsage -> CallEnv
scu_calls :: CallEnv,           -- Calls
                                        -- The functions are a subset of the
                                        --      RecFuns in the ScEnv

        ScUsage -> IdEnv ArgOcc
scu_occs :: !(IdEnv ArgOcc)     -- Information on argument occurrences
     }                                  -- The domain is OutIds

type CallEnv = IdEnv [Call]
data Call = Call Id [CoreArg] ValueEnv
        -- The arguments of the call, together with the
        -- env giving the constructor bindings at the call site
        -- We keep the function mainly for debug output
        --
        -- The call is not necessarily saturated; we just put
        -- in however many args are visible at the call site

instance Outputable ScUsage where
  ppr :: ScUsage -> SDoc
ppr (SCU { scu_calls :: ScUsage -> CallEnv
scu_calls = CallEnv
calls, scu_occs :: ScUsage -> IdEnv ArgOcc
scu_occs = IdEnv ArgOcc
occs })
    = String -> SDoc
text String
"SCU" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
braces ([SDoc] -> SDoc
sep [ String -> SDoc
text String
"calls =" SDoc -> SDoc -> SDoc
<+> CallEnv -> SDoc
forall a. Outputable a => a -> SDoc
ppr CallEnv
calls
                                 , String -> SDoc
text String
"occs =" SDoc -> SDoc -> SDoc
<+> IdEnv ArgOcc -> SDoc
forall a. Outputable a => a -> SDoc
ppr IdEnv ArgOcc
occs ])

instance Outputable Call where
  ppr :: Call -> SDoc
ppr (Call Id
fn [Expr Id]
args ValueEnv
_) = Id -> SDoc
forall a. Outputable a => a -> SDoc
ppr Id
fn SDoc -> SDoc -> SDoc
<+> [SDoc] -> SDoc
fsep ((Expr Id -> SDoc) -> [Expr Id] -> [SDoc]
forall a b. (a -> b) -> [a] -> [b]
map Expr Id -> SDoc
forall b. OutputableBndr b => Expr b -> SDoc
pprParendExpr [Expr Id]
args)

nullUsage :: ScUsage
nullUsage :: ScUsage
nullUsage = SCU { scu_calls :: CallEnv
scu_calls = CallEnv
forall a. VarEnv a
emptyVarEnv, scu_occs :: IdEnv ArgOcc
scu_occs = IdEnv ArgOcc
forall a. VarEnv a
emptyVarEnv }

combineCalls :: CallEnv -> CallEnv -> CallEnv
combineCalls :: CallEnv -> CallEnv -> CallEnv
combineCalls = ([Call] -> [Call] -> [Call]) -> CallEnv -> CallEnv -> CallEnv
forall a. (a -> a -> a) -> VarEnv a -> VarEnv a -> VarEnv a
plusVarEnv_C [Call] -> [Call] -> [Call]
forall a. [a] -> [a] -> [a]
(++)

combineUsage :: ScUsage -> ScUsage -> ScUsage
combineUsage :: ScUsage -> ScUsage -> ScUsage
combineUsage ScUsage
u1 ScUsage
u2 = SCU { scu_calls :: CallEnv
scu_calls = CallEnv -> CallEnv -> CallEnv
combineCalls (ScUsage -> CallEnv
scu_calls ScUsage
u1) (ScUsage -> CallEnv
scu_calls ScUsage
u2),
                           scu_occs :: IdEnv ArgOcc
scu_occs  = (ArgOcc -> ArgOcc -> ArgOcc)
-> IdEnv ArgOcc -> IdEnv ArgOcc -> IdEnv ArgOcc
forall a. (a -> a -> a) -> VarEnv a -> VarEnv a -> VarEnv a
plusVarEnv_C ArgOcc -> ArgOcc -> ArgOcc
combineOcc (ScUsage -> IdEnv ArgOcc
scu_occs ScUsage
u1) (ScUsage -> IdEnv ArgOcc
scu_occs ScUsage
u2) }

combineUsages :: [ScUsage] -> ScUsage
combineUsages :: [ScUsage] -> ScUsage
combineUsages [] = ScUsage
nullUsage
combineUsages [ScUsage]
us = (ScUsage -> ScUsage -> ScUsage) -> [ScUsage] -> ScUsage
forall a. (a -> a -> a) -> [a] -> a
forall (t :: * -> *) a. Foldable t => (a -> a -> a) -> t a -> a
foldr1 ScUsage -> ScUsage -> ScUsage
combineUsage [ScUsage]
us

lookupOccs :: ScUsage -> [OutVar] -> (ScUsage, [ArgOcc])
lookupOccs :: ScUsage -> [Id] -> (ScUsage, [ArgOcc])
lookupOccs (SCU { scu_calls :: ScUsage -> CallEnv
scu_calls = CallEnv
sc_calls, scu_occs :: ScUsage -> IdEnv ArgOcc
scu_occs = IdEnv ArgOcc
sc_occs }) [Id]
bndrs
  = (SCU {scu_calls :: CallEnv
scu_calls = CallEnv
sc_calls, scu_occs :: IdEnv ArgOcc
scu_occs = IdEnv ArgOcc -> [Id] -> IdEnv ArgOcc
forall a. VarEnv a -> [Id] -> VarEnv a
delVarEnvList IdEnv ArgOcc
sc_occs [Id]
bndrs},
     [IdEnv ArgOcc -> Id -> Maybe ArgOcc
forall a. VarEnv a -> Id -> Maybe a
lookupVarEnv IdEnv ArgOcc
sc_occs Id
b Maybe ArgOcc -> ArgOcc -> ArgOcc
forall a. Maybe a -> a -> a
`orElse` ArgOcc
NoOcc | Id
b <- [Id]
bndrs])

data ArgOcc = NoOcc     -- Doesn't occur at all; or a type argument
            | UnkOcc    -- Used in some unknown way

            | ScrutOcc  -- See Note [ScrutOcc]
                 (DataConEnv [ArgOcc])   -- How the sub-components are used

{- Note [ScrutOcc]
~~~~~~~~~~~~~~~~~~
An occurrence of ScrutOcc indicates that the thing, or a `cast` version of the thing,
is *only* taken apart or applied.

  Functions, literal: ScrutOcc emptyUFM
  Data constructors:  ScrutOcc subs,

where (subs :: UniqFM [ArgOcc]) gives usage of the *pattern-bound* components,
The domain of the UniqFM is the Unique of the data constructor

The [ArgOcc] is the occurrences of the *pattern-bound* components
of the data structure.  E.g.
        data T a = forall b. MkT a b (b->a)
A pattern binds b, x::a, y::b, z::b->a, but not 'a'!

-}

instance Outputable ArgOcc where
  ppr :: ArgOcc -> SDoc
ppr (ScrutOcc DataConEnv [ArgOcc]
xs) = String -> SDoc
text String
"scrut-occ" SDoc -> SDoc -> SDoc
<> DataConEnv [ArgOcc] -> SDoc
forall a. Outputable a => a -> SDoc
ppr DataConEnv [ArgOcc]
xs
  ppr ArgOcc
UnkOcc        = String -> SDoc
text String
"unk-occ"
  ppr ArgOcc
NoOcc         = String -> SDoc
text String
"no-occ"

evalScrutOcc :: ArgOcc
evalScrutOcc :: ArgOcc
evalScrutOcc = DataConEnv [ArgOcc] -> ArgOcc
ScrutOcc DataConEnv [ArgOcc]
forall key elt. UniqFM key elt
emptyUFM

-- Experimentally, this version of combineOcc makes ScrutOcc "win", so
-- that if the thing is scrutinised anywhere then we get to see that
-- in the overall result, even if it's also used in a boxed way
-- This might be too aggressive; see Note [Reboxing] Alternative 3
combineOcc :: ArgOcc -> ArgOcc -> ArgOcc
combineOcc :: ArgOcc -> ArgOcc -> ArgOcc
combineOcc ArgOcc
NoOcc         ArgOcc
occ           = ArgOcc
occ
combineOcc ArgOcc
occ           ArgOcc
NoOcc         = ArgOcc
occ
combineOcc (ScrutOcc DataConEnv [ArgOcc]
xs) (ScrutOcc DataConEnv [ArgOcc]
ys) = DataConEnv [ArgOcc] -> ArgOcc
ScrutOcc (([ArgOcc] -> [ArgOcc] -> [ArgOcc])
-> DataConEnv [ArgOcc]
-> DataConEnv [ArgOcc]
-> DataConEnv [ArgOcc]
forall elt key.
(elt -> elt -> elt)
-> UniqFM key elt -> UniqFM key elt -> UniqFM key elt
plusUFM_C [ArgOcc] -> [ArgOcc] -> [ArgOcc]
combineOccs DataConEnv [ArgOcc]
xs DataConEnv [ArgOcc]
ys)
combineOcc ArgOcc
UnkOcc        (ScrutOcc DataConEnv [ArgOcc]
ys) = DataConEnv [ArgOcc] -> ArgOcc
ScrutOcc DataConEnv [ArgOcc]
ys
combineOcc (ScrutOcc DataConEnv [ArgOcc]
xs) ArgOcc
UnkOcc        = DataConEnv [ArgOcc] -> ArgOcc
ScrutOcc DataConEnv [ArgOcc]
xs
combineOcc ArgOcc
UnkOcc        ArgOcc
UnkOcc        = ArgOcc
UnkOcc

combineOccs :: [ArgOcc] -> [ArgOcc] -> [ArgOcc]
combineOccs :: [ArgOcc] -> [ArgOcc] -> [ArgOcc]
combineOccs [ArgOcc]
xs [ArgOcc]
ys = String
-> (ArgOcc -> ArgOcc -> ArgOcc) -> [ArgOcc] -> [ArgOcc] -> [ArgOcc]
forall a b c. String -> (a -> b -> c) -> [a] -> [b] -> [c]
zipWithEqual String
"combineOccs" ArgOcc -> ArgOcc -> ArgOcc
combineOcc [ArgOcc]
xs [ArgOcc]
ys

setScrutOcc :: ScEnv -> ScUsage -> OutExpr -> ArgOcc -> ScUsage
-- _Overwrite_ the occurrence info for the scrutinee, if the scrutinee
-- is a variable, and an interesting variable
setScrutOcc :: ScEnv -> ScUsage -> Expr Id -> ArgOcc -> ScUsage
setScrutOcc ScEnv
env ScUsage
usg (Cast Expr Id
e Coercion
_) ArgOcc
occ      = ScEnv -> ScUsage -> Expr Id -> ArgOcc -> ScUsage
setScrutOcc ScEnv
env ScUsage
usg Expr Id
e ArgOcc
occ
setScrutOcc ScEnv
env ScUsage
usg (Tick CoreTickish
_ Expr Id
e) ArgOcc
occ      = ScEnv -> ScUsage -> Expr Id -> ArgOcc -> ScUsage
setScrutOcc ScEnv
env ScUsage
usg Expr Id
e ArgOcc
occ
setScrutOcc ScEnv
env ScUsage
usg (Var Id
v)    ArgOcc
occ
  | Just HowBound
RecArg <- ScEnv -> Id -> Maybe HowBound
lookupHowBound ScEnv
env Id
v = ScUsage
usg { scu_occs :: IdEnv ArgOcc
scu_occs = IdEnv ArgOcc -> Id -> ArgOcc -> IdEnv ArgOcc
forall a. VarEnv a -> Id -> a -> VarEnv a
extendVarEnv (ScUsage -> IdEnv ArgOcc
scu_occs ScUsage
usg) Id
v ArgOcc
occ }
  | Bool
otherwise                           = ScUsage
usg
setScrutOcc ScEnv
_env ScUsage
usg Expr Id
_other ArgOcc
_occ        -- Catch-all
  = ScUsage
usg

{-
************************************************************************
*                                                                      *
\subsection{The main recursive function}
*                                                                      *
************************************************************************

The main recursive function gathers up usage information, and
creates specialised versions of functions.
-}

scExpr, scExpr' :: ScEnv -> CoreExpr -> UniqSM (ScUsage, CoreExpr)
        -- The unique supply is needed when we invent
        -- a new name for the specialised function and its args

scExpr :: ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id)
scExpr ScEnv
env Expr Id
e = ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id)
scExpr' ScEnv
env Expr Id
e

scExpr' :: ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id)
scExpr' ScEnv
env (Var Id
v)      = case ScEnv -> Id -> Expr Id
scSubstId ScEnv
env Id
v of
                            Var Id
v' -> (ScUsage, Expr Id) -> UniqSM (ScUsage, Expr Id)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScEnv -> Id -> [Expr Id] -> ScUsage
mkVarUsage ScEnv
env Id
v' [], Id -> Expr Id
forall b. Id -> Expr b
Var Id
v')
                            Expr Id
e'     -> ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id)
scExpr (ScEnv -> ScEnv
zapScSubst ScEnv
env) Expr Id
e'

scExpr' ScEnv
env (Type Type
t)     = (ScUsage, Expr Id) -> UniqSM (ScUsage, Expr Id)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
nullUsage, Type -> Expr Id
forall b. Type -> Expr b
Type (ScEnv -> Type -> Type
scSubstTy ScEnv
env Type
t))
scExpr' ScEnv
env (Coercion Coercion
c) = (ScUsage, Expr Id) -> UniqSM (ScUsage, Expr Id)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
nullUsage, Coercion -> Expr Id
forall b. Coercion -> Expr b
Coercion (ScEnv -> Coercion -> Coercion
scSubstCo ScEnv
env Coercion
c))
scExpr' ScEnv
_   e :: Expr Id
e@(Lit {})   = (ScUsage, Expr Id) -> UniqSM (ScUsage, Expr Id)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
nullUsage, Expr Id
e)
scExpr' ScEnv
env (Tick CoreTickish
t Expr Id
e)   = do (ScUsage
usg, Expr Id
e') <- ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id)
scExpr ScEnv
env Expr Id
e
                              (ScUsage, Expr Id) -> UniqSM (ScUsage, Expr Id)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
usg, CoreTickish -> Expr Id -> Expr Id
forall b. CoreTickish -> Expr b -> Expr b
Tick CoreTickish
t Expr Id
e')
scExpr' ScEnv
env (Cast Expr Id
e Coercion
co)  = do (ScUsage
usg, Expr Id
e') <- ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id)
scExpr ScEnv
env Expr Id
e
                              (ScUsage, Expr Id) -> UniqSM (ScUsage, Expr Id)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
usg, Expr Id -> Coercion -> Expr Id
mkCast Expr Id
e' (ScEnv -> Coercion -> Coercion
scSubstCo ScEnv
env Coercion
co))
                              -- Important to use mkCast here
                              -- See Note [SpecConstr call patterns]
scExpr' ScEnv
env e :: Expr Id
e@(App Expr Id
_ Expr Id
_)  = ScEnv -> (Expr Id, [Expr Id]) -> UniqSM (ScUsage, Expr Id)
scApp ScEnv
env (Expr Id -> (Expr Id, [Expr Id])
forall b. Expr b -> (Expr b, [Expr b])
collectArgs Expr Id
e)
scExpr' ScEnv
env (Lam Id
b Expr Id
e)    = do let (ScEnv
env', Id
b') = ScEnv -> Id -> (ScEnv, Id)
extendBndr ScEnv
env Id
b
                              (ScUsage
usg, Expr Id
e') <- ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id)
scExpr ScEnv
env' Expr Id
e
                              (ScUsage, Expr Id) -> UniqSM (ScUsage, Expr Id)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
usg, Id -> Expr Id -> Expr Id
forall b. b -> Expr b -> Expr b
Lam Id
b' Expr Id
e')

scExpr' ScEnv
env (Case Expr Id
scrut Id
b Type
ty [Alt Id]
alts)
  = do  { (ScUsage
scrut_usg, Expr Id
scrut') <- ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id)
scExpr ScEnv
env Expr Id
scrut
        ; case ValueEnv -> Expr Id -> Maybe Value
isValue (ScEnv -> ValueEnv
sc_vals ScEnv
env) Expr Id
scrut' of
                Just (ConVal AltCon
con [Expr Id]
args) -> AltCon -> [Expr Id] -> Expr Id -> UniqSM (ScUsage, Expr Id)
sc_con_app AltCon
con [Expr Id]
args Expr Id
scrut'
                Maybe Value
_other                 -> ScUsage -> Expr Id -> UniqSM (ScUsage, Expr Id)
sc_vanilla ScUsage
scrut_usg Expr Id
scrut'
        }
  where
    sc_con_app :: AltCon -> [Expr Id] -> Expr Id -> UniqSM (ScUsage, Expr Id)
sc_con_app AltCon
con [Expr Id]
args Expr Id
scrut'  -- Known constructor; simplify
     = do { let Alt AltCon
_ [Id]
bs Expr Id
rhs = AltCon -> [Alt Id] -> Maybe (Alt Id)
forall b. AltCon -> [Alt b] -> Maybe (Alt b)
findAlt AltCon
con [Alt Id]
alts
                                  Maybe (Alt Id) -> Alt Id -> Alt Id
forall a. Maybe a -> a -> a
`orElse` AltCon -> [Id] -> Expr Id -> Alt Id
forall b. AltCon -> [b] -> Expr b -> Alt b
Alt AltCon
DEFAULT [] (Type -> Expr Id
mkImpossibleExpr Type
ty)
                alt_env' :: ScEnv
alt_env'     = ScEnv -> [(Id, Expr Id)] -> ScEnv
extendScSubstList ScEnv
env ((Id
b,Expr Id
scrut') (Id, Expr Id) -> [(Id, Expr Id)] -> [(Id, Expr Id)]
forall a. a -> [a] -> [a]
: [Id]
bs [Id] -> [Expr Id] -> [(Id, Expr Id)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` AltCon -> [Expr Id] -> [Expr Id]
trimConArgs AltCon
con [Expr Id]
args)
          ; ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id)
scExpr ScEnv
alt_env' Expr Id
rhs }

    sc_vanilla :: ScUsage -> Expr Id -> UniqSM (ScUsage, Expr Id)
sc_vanilla ScUsage
scrut_usg Expr Id
scrut' -- Normal case
     = do { let (ScEnv
alt_env,Id
b') = HowBound -> ScEnv -> Id -> (ScEnv, Id)
extendBndrWith HowBound
RecArg ScEnv
env Id
b
                        -- Record RecArg for the components

          ; ([ScUsage]
alt_usgs, [ArgOcc]
alt_occs, [Alt Id]
alts')
                <- (Alt Id -> UniqSM (ScUsage, ArgOcc, Alt Id))
-> [Alt Id] -> UniqSM ([ScUsage], [ArgOcc], [Alt Id])
forall (m :: * -> *) a b c d.
Monad m =>
(a -> m (b, c, d)) -> [a] -> m ([b], [c], [d])
mapAndUnzip3M (ScEnv
-> Expr Id -> Id -> Alt Id -> UniqSM (ScUsage, ArgOcc, Alt Id)
sc_alt ScEnv
alt_env Expr Id
scrut' Id
b') [Alt Id]
alts

          ; let scrut_occ :: ArgOcc
scrut_occ  = (ArgOcc -> ArgOcc -> ArgOcc) -> ArgOcc -> [ArgOcc] -> ArgOcc
forall a b. (a -> b -> b) -> b -> [a] -> b
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr ArgOcc -> ArgOcc -> ArgOcc
combineOcc ArgOcc
NoOcc [ArgOcc]
alt_occs
                scrut_usg' :: ScUsage
scrut_usg' = ScEnv -> ScUsage -> Expr Id -> ArgOcc -> ScUsage
setScrutOcc ScEnv
env ScUsage
scrut_usg Expr Id
scrut' ArgOcc
scrut_occ
                -- The combined usage of the scrutinee is given
                -- by scrut_occ, which is passed to scScrut, which
                -- in turn treats a bare-variable scrutinee specially

          ; (ScUsage, Expr Id) -> UniqSM (ScUsage, Expr Id)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return ((ScUsage -> ScUsage -> ScUsage) -> ScUsage -> [ScUsage] -> ScUsage
forall a b. (a -> b -> b) -> b -> [a] -> b
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr ScUsage -> ScUsage -> ScUsage
combineUsage ScUsage
scrut_usg' [ScUsage]
alt_usgs,
                    Expr Id -> Id -> Type -> [Alt Id] -> Expr Id
forall b. Expr b -> b -> Type -> [Alt b] -> Expr b
Case Expr Id
scrut' Id
b' (ScEnv -> Type -> Type
scSubstTy ScEnv
env Type
ty) [Alt Id]
alts') }

    sc_alt :: ScEnv
-> Expr Id -> Id -> Alt Id -> UniqSM (ScUsage, ArgOcc, Alt Id)
sc_alt ScEnv
env Expr Id
scrut' Id
b' (Alt AltCon
con [Id]
bs Expr Id
rhs)
     = do { let (ScEnv
env1, [Id]
bs1) = HowBound -> ScEnv -> [Id] -> (ScEnv, [Id])
extendBndrsWith HowBound
RecArg ScEnv
env [Id]
bs
                (ScEnv
env2, [Id]
bs2) = ScEnv -> Expr Id -> Id -> AltCon -> [Id] -> (ScEnv, [Id])
extendCaseBndrs ScEnv
env1 Expr Id
scrut' Id
b' AltCon
con [Id]
bs1
          ; (ScUsage
usg, Expr Id
rhs') <- ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id)
scExpr ScEnv
env2 Expr Id
rhs
          ; let (ScUsage
usg', ArgOcc
b_occ:[ArgOcc]
arg_occs) = ScUsage -> [Id] -> (ScUsage, [ArgOcc])
lookupOccs ScUsage
usg (Id
b'Id -> [Id] -> [Id]
forall a. a -> [a] -> [a]
:[Id]
bs2)
                scrut_occ :: ArgOcc
scrut_occ = case AltCon
con of
                               DataAlt DataCon
dc -> DataConEnv [ArgOcc] -> ArgOcc
ScrutOcc (DataCon -> [ArgOcc] -> DataConEnv [ArgOcc]
forall key elt. Uniquable key => key -> elt -> UniqFM key elt
unitUFM DataCon
dc [ArgOcc]
arg_occs)
                               AltCon
_          -> DataConEnv [ArgOcc] -> ArgOcc
ScrutOcc DataConEnv [ArgOcc]
forall key elt. UniqFM key elt
emptyUFM
          ; (ScUsage, ArgOcc, Alt Id) -> UniqSM (ScUsage, ArgOcc, Alt Id)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
usg', ArgOcc
b_occ ArgOcc -> ArgOcc -> ArgOcc
`combineOcc` ArgOcc
scrut_occ, AltCon -> [Id] -> Expr Id -> Alt Id
forall b. AltCon -> [b] -> Expr b -> Alt b
Alt AltCon
con [Id]
bs2 Expr Id
rhs') }

scExpr' ScEnv
env (Let (NonRec Id
bndr Expr Id
rhs) Expr Id
body)
  | Id -> Bool
isTyVar Id
bndr        -- Type-lets may be created by doBeta
  = ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id)
scExpr' (ScEnv -> Id -> Expr Id -> ScEnv
extendScSubst ScEnv
env Id
bndr Expr Id
rhs) Expr Id
body

  | Bool
otherwise
  = do  { let (ScEnv
body_env, Id
bndr') = ScEnv -> Id -> (ScEnv, Id)
extendBndr ScEnv
env Id
bndr
        ; RhsInfo
rhs_info  <- ScEnv -> (Id, Expr Id) -> UniqSM RhsInfo
scRecRhs ScEnv
env (Id
bndr',Expr Id
rhs)

        ; let body_env2 :: ScEnv
body_env2 = ScEnv -> [Id] -> HowBound -> ScEnv
extendHowBound ScEnv
body_env [Id
bndr'] HowBound
RecFun
                           -- See Note [Local let bindings]
              rhs' :: Expr Id
rhs'      = RhsInfo -> Expr Id
ri_new_rhs RhsInfo
rhs_info
              body_env3 :: ScEnv
body_env3 = ScEnv -> Id -> Maybe Value -> ScEnv
extendValEnv ScEnv
body_env2 Id
bndr' (ValueEnv -> Expr Id -> Maybe Value
isValue (ScEnv -> ValueEnv
sc_vals ScEnv
env) Expr Id
rhs')

        ; (ScUsage
body_usg, Expr Id
body') <- ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id)
scExpr ScEnv
body_env3 Expr Id
body

          -- NB: For non-recursive bindings we inherit sc_force flag from
          -- the parent function (see Note [Forcing specialisation])
        ; (ScUsage
spec_usg, SpecInfo
specs) <- ScEnv -> ScUsage -> RhsInfo -> UniqSM (ScUsage, SpecInfo)
specNonRec ScEnv
env ScUsage
body_usg RhsInfo
rhs_info

        -- Specialized + original binding
        ; let spec_bnds :: Expr Id
spec_bnds = [CoreBind] -> Expr Id -> Expr Id
forall b. [Bind b] -> Expr b -> Expr b
mkLets [Id -> Expr Id -> CoreBind
forall b. b -> Expr b -> Bind b
NonRec Id
b Expr Id
r | (Id
b,Expr Id
r) <- RhsInfo -> SpecInfo -> [(Id, Expr Id)]
ruleInfoBinds RhsInfo
rhs_info SpecInfo
specs] Expr Id
body'
        -- ; pprTraceM "spec_bnds" $ (ppr spec_bnds)

        ; (ScUsage, Expr Id) -> UniqSM (ScUsage, Expr Id)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
body_usg { scu_calls :: CallEnv
scu_calls = ScUsage -> CallEnv
scu_calls ScUsage
body_usg CallEnv -> Id -> CallEnv
forall a. VarEnv a -> Id -> VarEnv a
`delVarEnv` Id
bndr' }
                    ScUsage -> ScUsage -> ScUsage
`combineUsage` ScUsage
spec_usg,  -- Note [spec_usg includes rhs_usg]
                  Expr Id
spec_bnds
                  )
        }


-- A *local* recursive group: see Note [Local recursive groups]
scExpr' ScEnv
env (Let (Rec [(Id, Expr Id)]
prs) Expr Id
body)
  = do  { let ([Id]
bndrs,[Expr Id]
rhss)      = [(Id, Expr Id)] -> ([Id], [Expr Id])
forall a b. [(a, b)] -> ([a], [b])
unzip [(Id, Expr Id)]
prs
              (ScEnv
rhs_env1,[Id]
bndrs') = ScEnv -> [Id] -> (ScEnv, [Id])
extendRecBndrs ScEnv
env [Id]
bndrs
              rhs_env2 :: ScEnv
rhs_env2          = ScEnv -> [Id] -> HowBound -> ScEnv
extendHowBound ScEnv
rhs_env1 [Id]
bndrs' HowBound
RecFun
              force_spec :: Bool
force_spec        = (Id -> Bool) -> [Id] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any (ScEnv -> Id -> Bool
forceSpecBndr ScEnv
env) [Id]
bndrs'
                -- Note [Forcing specialisation]

        ; [RhsInfo]
rhs_infos <- ((Id, Expr Id) -> UniqSM RhsInfo)
-> [(Id, Expr Id)] -> UniqSM [RhsInfo]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
forall (m :: * -> *) a b. Monad m => (a -> m b) -> [a] -> m [b]
mapM (ScEnv -> (Id, Expr Id) -> UniqSM RhsInfo
scRecRhs ScEnv
rhs_env2) ([Id]
bndrs' [Id] -> [Expr Id] -> [(Id, Expr Id)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [Expr Id]
rhss)
        ; (ScUsage
body_usg, Expr Id
body')     <- ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id)
scExpr ScEnv
rhs_env2 Expr Id
body

        -- NB: start specLoop from body_usg
        ; (ScUsage
spec_usg, [SpecInfo]
specs) <- TopLevelFlag
-> ScEnv -> ScUsage -> [RhsInfo] -> UniqSM (ScUsage, [SpecInfo])
specRec TopLevelFlag
NotTopLevel (ScEnv -> Bool -> ScEnv
scForce ScEnv
rhs_env2 Bool
force_spec)
                                       ScUsage
body_usg [RhsInfo]
rhs_infos
                -- Do not unconditionally generate specialisations from rhs_usgs
                -- Instead use them only if we find an unspecialised call
                -- See Note [Local recursive groups]

        ; let all_usg :: ScUsage
all_usg = ScUsage
spec_usg ScUsage -> ScUsage -> ScUsage
`combineUsage` ScUsage
body_usg  -- Note [spec_usg includes rhs_usg]
              bind' :: CoreBind
bind'   = [(Id, Expr Id)] -> CoreBind
forall b. [(b, Expr b)] -> Bind b
Rec ([[(Id, Expr Id)]] -> [(Id, Expr Id)]
forall (t :: * -> *) a. Foldable t => t [a] -> [a]
concat (String
-> (RhsInfo -> SpecInfo -> [(Id, Expr Id)])
-> [RhsInfo]
-> [SpecInfo]
-> [[(Id, Expr Id)]]
forall a b c. String -> (a -> b -> c) -> [a] -> [b] -> [c]
zipWithEqual String
"scExpr'" RhsInfo -> SpecInfo -> [(Id, Expr Id)]
ruleInfoBinds [RhsInfo]
rhs_infos [SpecInfo]
specs))
                        -- zipWithEqual: length of returned [SpecInfo]
                        -- should be the same as incoming [RhsInfo]

        ; (ScUsage, Expr Id) -> UniqSM (ScUsage, Expr Id)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
all_usg { scu_calls :: CallEnv
scu_calls = ScUsage -> CallEnv
scu_calls ScUsage
all_usg CallEnv -> [Id] -> CallEnv
forall a. VarEnv a -> [Id] -> VarEnv a
`delVarEnvList` [Id]
bndrs' },
                  CoreBind -> Expr Id -> Expr Id
forall b. Bind b -> Expr b -> Expr b
Let CoreBind
bind' Expr Id
body') }

{-
Note [Local let bindings]
~~~~~~~~~~~~~~~~~~~~~~~~~
It is not uncommon to find this

   let $j = \x. <blah> in ...$j True...$j True...

Here $j is an arbitrary let-bound function, but it often comes up for
join points.  We might like to specialise $j for its call patterns.
Notice the difference from a letrec, where we look for call patterns
in the *RHS* of the function.  Here we look for call patterns in the
*body* of the let.

At one point I predicated this on the RHS mentioning the outer
recursive function, but that's not essential and might even be
harmful.  I'm not sure.
-}

scApp :: ScEnv -> (InExpr, [InExpr]) -> UniqSM (ScUsage, CoreExpr)

scApp :: ScEnv -> (Expr Id, [Expr Id]) -> UniqSM (ScUsage, Expr Id)
scApp ScEnv
env (Var Id
fn, [Expr Id]
args)        -- Function is a variable
  = Bool -> UniqSM (ScUsage, Expr Id) -> UniqSM (ScUsage, Expr Id)
forall a. HasCallStack => Bool -> a -> a
assert (Bool -> Bool
not ([Expr Id] -> Bool
forall a. [a] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [Expr Id]
args)) (UniqSM (ScUsage, Expr Id) -> UniqSM (ScUsage, Expr Id))
-> UniqSM (ScUsage, Expr Id) -> UniqSM (ScUsage, Expr Id)
forall a b. (a -> b) -> a -> b
$
    do  { [(ScUsage, Expr Id)]
args_w_usgs <- (Expr Id -> UniqSM (ScUsage, Expr Id))
-> [Expr Id] -> UniqSM [(ScUsage, Expr Id)]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
forall (m :: * -> *) a b. Monad m => (a -> m b) -> [a] -> m [b]
mapM (ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id)
scExpr ScEnv
env) [Expr Id]
args
        ; let ([ScUsage]
arg_usgs, [Expr Id]
args') = [(ScUsage, Expr Id)] -> ([ScUsage], [Expr Id])
forall a b. [(a, b)] -> ([a], [b])
unzip [(ScUsage, Expr Id)]
args_w_usgs
              arg_usg :: ScUsage
arg_usg = [ScUsage] -> ScUsage
combineUsages [ScUsage]
arg_usgs
        ; case ScEnv -> Id -> Expr Id
scSubstId ScEnv
env Id
fn of
            fn' :: Expr Id
fn'@(Lam {}) -> ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id)
scExpr (ScEnv -> ScEnv
zapScSubst ScEnv
env) (Expr Id -> [Expr Id] -> Expr Id
doBeta Expr Id
fn' [Expr Id]
args')
                        -- Do beta-reduction and try again

            Var Id
fn' -> (ScUsage, Expr Id) -> UniqSM (ScUsage, Expr Id)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
arg_usg ScUsage -> ScUsage -> ScUsage
`combineUsage` ScEnv -> Id -> [Expr Id] -> ScUsage
mkVarUsage ScEnv
env Id
fn' [Expr Id]
args',
                               Expr Id -> [Expr Id] -> Expr Id
forall b. Expr b -> [Expr b] -> Expr b
mkApps (Id -> Expr Id
forall b. Id -> Expr b
Var Id
fn') [Expr Id]
args')

            Expr Id
other_fn' -> (ScUsage, Expr Id) -> UniqSM (ScUsage, Expr Id)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
arg_usg, Expr Id -> [Expr Id] -> Expr Id
forall b. Expr b -> [Expr b] -> Expr b
mkApps Expr Id
other_fn' [Expr Id]
args') }
                -- NB: doing this ignores any usage info from the substituted
                --     function, but I don't think that matters.  If it does
                --     we can fix it.
  where
    doBeta :: OutExpr -> [OutExpr] -> OutExpr
    -- ToDo: adjust for System IF
    doBeta :: Expr Id -> [Expr Id] -> Expr Id
doBeta (Lam Id
bndr Expr Id
body) (Expr Id
arg : [Expr Id]
args) = CoreBind -> Expr Id -> Expr Id
forall b. Bind b -> Expr b -> Expr b
Let (Id -> Expr Id -> CoreBind
forall b. b -> Expr b -> Bind b
NonRec Id
bndr Expr Id
arg) (Expr Id -> [Expr Id] -> Expr Id
doBeta Expr Id
body [Expr Id]
args)
    doBeta Expr Id
fn              [Expr Id]
args         = Expr Id -> [Expr Id] -> Expr Id
forall b. Expr b -> [Expr b] -> Expr b
mkApps Expr Id
fn [Expr Id]
args

-- The function is almost always a variable, but not always.
-- In particular, if this pass follows float-in,
-- which it may, we can get
--      (let f = ...f... in f) arg1 arg2
scApp ScEnv
env (Expr Id
other_fn, [Expr Id]
args)
  = do  { (ScUsage
fn_usg,   Expr Id
fn')   <- ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id)
scExpr ScEnv
env Expr Id
other_fn
        ; ([ScUsage]
arg_usgs, [Expr Id]
args') <- (Expr Id -> UniqSM (ScUsage, Expr Id))
-> [Expr Id] -> UniqSM ([ScUsage], [Expr Id])
forall (m :: * -> *) a b c.
Applicative m =>
(a -> m (b, c)) -> [a] -> m ([b], [c])
mapAndUnzipM (ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id)
scExpr ScEnv
env) [Expr Id]
args
        ; (ScUsage, Expr Id) -> UniqSM (ScUsage, Expr Id)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return ([ScUsage] -> ScUsage
combineUsages [ScUsage]
arg_usgs ScUsage -> ScUsage -> ScUsage
`combineUsage` ScUsage
fn_usg, Expr Id -> [Expr Id] -> Expr Id
forall b. Expr b -> [Expr b] -> Expr b
mkApps Expr Id
fn' [Expr Id]
args') }

----------------------
mkVarUsage :: ScEnv -> Id -> [CoreExpr] -> ScUsage
mkVarUsage :: ScEnv -> Id -> [Expr Id] -> ScUsage
mkVarUsage ScEnv
env Id
fn [Expr Id]
args
  = case ScEnv -> Id -> Maybe HowBound
lookupHowBound ScEnv
env Id
fn of
        Just HowBound
RecFun -> SCU { scu_calls :: CallEnv
scu_calls = Id -> [Call] -> CallEnv
forall a. Id -> a -> VarEnv a
unitVarEnv Id
fn [Id -> [Expr Id] -> ValueEnv -> Call
Call Id
fn [Expr Id]
args (ScEnv -> ValueEnv
sc_vals ScEnv
env)]
                           , scu_occs :: IdEnv ArgOcc
scu_occs  = IdEnv ArgOcc
forall a. VarEnv a
emptyVarEnv }
        Just HowBound
RecArg -> SCU { scu_calls :: CallEnv
scu_calls = CallEnv
forall a. VarEnv a
emptyVarEnv
                           , scu_occs :: IdEnv ArgOcc
scu_occs  = Id -> ArgOcc -> IdEnv ArgOcc
forall a. Id -> a -> VarEnv a
unitVarEnv Id
fn ArgOcc
arg_occ }
        Maybe HowBound
Nothing     -> ScUsage
nullUsage
  where
    -- I rather think we could use UnkOcc all the time
    arg_occ :: ArgOcc
arg_occ | [Expr Id] -> Bool
forall a. [a] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [Expr Id]
args = ArgOcc
UnkOcc
            | Bool
otherwise = ArgOcc
evalScrutOcc

----------------------
scTopBindEnv :: ScEnv -> CoreBind -> UniqSM (ScEnv, CoreBind)
scTopBindEnv :: ScEnv -> CoreBind -> UniqSM (ScEnv, CoreBind)
scTopBindEnv ScEnv
env (Rec [(Id, Expr Id)]
prs)
  = do  { let (ScEnv
rhs_env1,[Id]
bndrs') = ScEnv -> [Id] -> (ScEnv, [Id])
extendRecBndrs ScEnv
env [Id]
bndrs
              rhs_env2 :: ScEnv
rhs_env2          = ScEnv -> [Id] -> HowBound -> ScEnv
extendHowBound ScEnv
rhs_env1 [Id]
bndrs HowBound
RecFun

              prs' :: [(Id, Expr Id)]
prs'              = [Id] -> [Expr Id] -> [(Id, Expr Id)]
forall a b. [a] -> [b] -> [(a, b)]
zip [Id]
bndrs' [Expr Id]
rhss
        ; (ScEnv, CoreBind) -> UniqSM (ScEnv, CoreBind)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScEnv
rhs_env2, [(Id, Expr Id)] -> CoreBind
forall b. [(b, Expr b)] -> Bind b
Rec [(Id, Expr Id)]
prs') }
  where
    ([Id]
bndrs,[Expr Id]
rhss) = [(Id, Expr Id)] -> ([Id], [Expr Id])
forall a b. [(a, b)] -> ([a], [b])
unzip [(Id, Expr Id)]
prs

scTopBindEnv ScEnv
env (NonRec Id
bndr Expr Id
rhs)
  = do  { let (ScEnv
env1, Id
bndr') = ScEnv -> Id -> (ScEnv, Id)
extendBndr ScEnv
env Id
bndr
              env2 :: ScEnv
env2          = ScEnv -> Id -> Maybe Value -> ScEnv
extendValEnv ScEnv
env1 Id
bndr' (ValueEnv -> Expr Id -> Maybe Value
isValue (ScEnv -> ValueEnv
sc_vals ScEnv
env) Expr Id
rhs)
        ; (ScEnv, CoreBind) -> UniqSM (ScEnv, CoreBind)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScEnv
env2, Id -> Expr Id -> CoreBind
forall b. b -> Expr b -> Bind b
NonRec Id
bndr' Expr Id
rhs) }

----------------------
scTopBind :: ScEnv -> ScUsage -> CoreBind -> UniqSM (ScUsage, CoreBind)

scTopBind :: ScEnv -> ScUsage -> CoreBind -> UniqSM (ScUsage, CoreBind)
scTopBind ScEnv
env ScUsage
body_usage (Rec [(Id, Expr Id)]
prs)
  | Just Int
threshold <- ScEnv -> Maybe Int
sc_size ScEnv
env
  , Bool -> Bool
not Bool
force_spec
  , Bool -> Bool
not ((Expr Id -> Bool) -> [Expr Id] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
all (UnfoldingOpts -> Int -> Expr Id -> Bool
couldBeSmallEnoughToInline (ScEnv -> UnfoldingOpts
sc_uf_opts ScEnv
env) Int
threshold) [Expr Id]
rhss)
                -- No specialisation
  = -- pprTrace "scTopBind: nospec" (ppr bndrs) $
    do  { ([ScUsage]
rhs_usgs, [Expr Id]
rhss')   <- (Expr Id -> UniqSM (ScUsage, Expr Id))
-> [Expr Id] -> UniqSM ([ScUsage], [Expr Id])
forall (m :: * -> *) a b c.
Applicative m =>
(a -> m (b, c)) -> [a] -> m ([b], [c])
mapAndUnzipM (ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id)
scExpr ScEnv
env) [Expr Id]
rhss
        ; (ScUsage, CoreBind) -> UniqSM (ScUsage, CoreBind)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
body_usage ScUsage -> ScUsage -> ScUsage
`combineUsage` [ScUsage] -> ScUsage
combineUsages [ScUsage]
rhs_usgs, [(Id, Expr Id)] -> CoreBind
forall b. [(b, Expr b)] -> Bind b
Rec ([Id]
bndrs [Id] -> [Expr Id] -> [(Id, Expr Id)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [Expr Id]
rhss')) }

  | Bool
otherwise   -- Do specialisation
  = do  { [RhsInfo]
rhs_infos <- ((Id, Expr Id) -> UniqSM RhsInfo)
-> [(Id, Expr Id)] -> UniqSM [RhsInfo]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
forall (m :: * -> *) a b. Monad m => (a -> m b) -> [a] -> m [b]
mapM (ScEnv -> (Id, Expr Id) -> UniqSM RhsInfo
scRecRhs ScEnv
env) [(Id, Expr Id)]
prs

        ; (ScUsage
spec_usage, [SpecInfo]
specs) <- TopLevelFlag
-> ScEnv -> ScUsage -> [RhsInfo] -> UniqSM (ScUsage, [SpecInfo])
specRec TopLevelFlag
TopLevel (ScEnv -> Bool -> ScEnv
scForce ScEnv
env Bool
force_spec)
                                         ScUsage
body_usage [RhsInfo]
rhs_infos

        ; (ScUsage, CoreBind) -> UniqSM (ScUsage, CoreBind)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
body_usage ScUsage -> ScUsage -> ScUsage
`combineUsage` ScUsage
spec_usage,
                  [(Id, Expr Id)] -> CoreBind
forall b. [(b, Expr b)] -> Bind b
Rec ([[(Id, Expr Id)]] -> [(Id, Expr Id)]
forall (t :: * -> *) a. Foldable t => t [a] -> [a]
concat ((RhsInfo -> SpecInfo -> [(Id, Expr Id)])
-> [RhsInfo] -> [SpecInfo] -> [[(Id, Expr Id)]]
forall a b c. (a -> b -> c) -> [a] -> [b] -> [c]
zipWith RhsInfo -> SpecInfo -> [(Id, Expr Id)]
ruleInfoBinds [RhsInfo]
rhs_infos [SpecInfo]
specs))) }
  where
    ([Id]
bndrs,[Expr Id]
rhss) = [(Id, Expr Id)] -> ([Id], [Expr Id])
forall a b. [(a, b)] -> ([a], [b])
unzip [(Id, Expr Id)]
prs
    force_spec :: Bool
force_spec   = (Id -> Bool) -> [Id] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any (ScEnv -> Id -> Bool
forceSpecBndr ScEnv
env) [Id]
bndrs
      -- Note [Forcing specialisation]

scTopBind ScEnv
env ScUsage
usage (NonRec Id
bndr Expr Id
rhs)   -- Oddly, we don't seem to specialise top-level non-rec functions
  = do  { (ScUsage
rhs_usg', Expr Id
rhs') <- ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id)
scExpr ScEnv
env Expr Id
rhs
        ; (ScUsage, CoreBind) -> UniqSM (ScUsage, CoreBind)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
usage ScUsage -> ScUsage -> ScUsage
`combineUsage` ScUsage
rhs_usg', Id -> Expr Id -> CoreBind
forall b. b -> Expr b -> Bind b
NonRec Id
bndr Expr Id
rhs') }

----------------------
scRecRhs :: ScEnv -> (OutId, InExpr) -> UniqSM RhsInfo
scRecRhs :: ScEnv -> (Id, Expr Id) -> UniqSM RhsInfo
scRecRhs ScEnv
env (Id
bndr,Expr Id
rhs)
  = do  { let ([Id]
arg_bndrs,Expr Id
body)       = Expr Id -> ([Id], Expr Id)
forall b. Expr b -> ([b], Expr b)
collectBinders Expr Id
rhs
              (ScEnv
body_env, [Id]
arg_bndrs') = HowBound -> ScEnv -> [Id] -> (ScEnv, [Id])
extendBndrsWith HowBound
RecArg ScEnv
env [Id]
arg_bndrs
        ; (ScUsage
body_usg, Expr Id
body')         <- ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id)
scExpr ScEnv
body_env Expr Id
body
        ; let (ScUsage
rhs_usg, [ArgOcc]
arg_occs)    = ScUsage -> [Id] -> (ScUsage, [ArgOcc])
lookupOccs ScUsage
body_usg [Id]
arg_bndrs'
        ; RhsInfo -> UniqSM RhsInfo
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (RI { ri_rhs_usg :: ScUsage
ri_rhs_usg = ScUsage
rhs_usg
                     , ri_fn :: Id
ri_fn = Id
bndr, ri_new_rhs :: Expr Id
ri_new_rhs = [Id] -> Expr Id -> Expr Id
forall b. [b] -> Expr b -> Expr b
mkLams [Id]
arg_bndrs' Expr Id
body'
                     , ri_lam_bndrs :: [Id]
ri_lam_bndrs = [Id]
arg_bndrs, ri_lam_body :: Expr Id
ri_lam_body = Expr Id
body
                     , ri_arg_occs :: [ArgOcc]
ri_arg_occs = [ArgOcc]
arg_occs }) }
                -- The arg_occs says how the visible,
                -- lambda-bound binders of the RHS are used
                -- (including the TyVar binders)
                -- Two pats are the same if they match both ways

----------------------
ruleInfoBinds :: RhsInfo -> SpecInfo -> [(Id,CoreExpr)]
ruleInfoBinds :: RhsInfo -> SpecInfo -> [(Id, Expr Id)]
ruleInfoBinds (RI { ri_fn :: RhsInfo -> Id
ri_fn = Id
fn, ri_new_rhs :: RhsInfo -> Expr Id
ri_new_rhs = Expr Id
new_rhs })
              (SI { si_specs :: SpecInfo -> [OneSpec]
si_specs = [OneSpec]
specs })
  = [(Id
id,Expr Id
rhs) | OS { os_id :: OneSpec -> Id
os_id = Id
id, os_rhs :: OneSpec -> Expr Id
os_rhs = Expr Id
rhs } <- [OneSpec]
specs] [(Id, Expr Id)] -> [(Id, Expr Id)] -> [(Id, Expr Id)]
forall a. [a] -> [a] -> [a]
++
              -- First the specialised bindings

    [(Id
fn Id -> [CoreRule] -> Id
`addIdSpecialisations` [CoreRule]
rules, Expr Id
new_rhs)]
              -- And now the original binding
  where
    rules :: [CoreRule]
rules = [CoreRule
r | OS { os_rule :: OneSpec -> CoreRule
os_rule = CoreRule
r } <- [OneSpec]
specs]

{-
************************************************************************
*                                                                      *
                The specialiser itself
*                                                                      *
************************************************************************
-}

data RhsInfo
  = RI { RhsInfo -> Id
ri_fn :: OutId                 -- The binder
       , RhsInfo -> Expr Id
ri_new_rhs :: OutExpr          -- The specialised RHS (in current envt)
       , RhsInfo -> ScUsage
ri_rhs_usg :: ScUsage          -- Usage info from specialising RHS

       , RhsInfo -> [Id]
ri_lam_bndrs :: [InVar]       -- The *original* RHS (\xs.body)
       , RhsInfo -> Expr Id
ri_lam_body  :: InExpr        --   Note [Specialise original body]
       , RhsInfo -> [ArgOcc]
ri_arg_occs  :: [ArgOcc]      -- Info on how the xs occur in body
    }

data SpecInfo       -- Info about specialisations for a particular Id
  = SI { SpecInfo -> [OneSpec]
si_specs :: [OneSpec]          -- The specialisations we have generated

       , SpecInfo -> Int
si_n_specs :: Int              -- Length of si_specs; used for numbering them

       , SpecInfo -> Maybe ScUsage
si_mb_unspec :: Maybe ScUsage  -- Just cs  => we have not yet used calls in the
       }                                --             from calls in the *original* RHS as
                                        --             seeds for new specialisations;
                                        --             if you decide to do so, here is the
                                        --             RHS usage (which has not yet been
                                        --             unleashed)
                                        -- Nothing => we have
                                        -- See Note [Local recursive groups]
                                        -- See Note [spec_usg includes rhs_usg]

        -- One specialisation: Rule plus definition
data OneSpec =
  OS { OneSpec -> CallPat
os_pat  :: CallPat    -- Call pattern that generated this specialisation
     , OneSpec -> CoreRule
os_rule :: CoreRule   -- Rule connecting original id with the specialisation
     , OneSpec -> Id
os_id   :: OutId      -- Spec id
     , OneSpec -> Expr Id
os_rhs  :: OutExpr }  -- Spec rhs

noSpecInfo :: SpecInfo
noSpecInfo :: SpecInfo
noSpecInfo = SI { si_specs :: [OneSpec]
si_specs = [], si_n_specs :: Int
si_n_specs = Int
0, si_mb_unspec :: Maybe ScUsage
si_mb_unspec = Maybe ScUsage
forall a. Maybe a
Nothing }

----------------------
specNonRec :: ScEnv
           -> ScUsage         -- Body usage
           -> RhsInfo         -- Structure info usage info for un-specialised RHS
           -> UniqSM (ScUsage, SpecInfo)       -- Usage from RHSs (specialised and not)
                                               --     plus details of specialisations

specNonRec :: ScEnv -> ScUsage -> RhsInfo -> UniqSM (ScUsage, SpecInfo)
specNonRec ScEnv
env ScUsage
body_usg RhsInfo
rhs_info
  = ScEnv
-> CallEnv -> RhsInfo -> SpecInfo -> UniqSM (ScUsage, SpecInfo)
specialise ScEnv
env (ScUsage -> CallEnv
scu_calls ScUsage
body_usg) RhsInfo
rhs_info
               (SpecInfo
noSpecInfo { si_mb_unspec :: Maybe ScUsage
si_mb_unspec = ScUsage -> Maybe ScUsage
forall a. a -> Maybe a
Just (RhsInfo -> ScUsage
ri_rhs_usg RhsInfo
rhs_info) })

----------------------
specRec :: TopLevelFlag -> ScEnv
        -> ScUsage                         -- Body usage
        -> [RhsInfo]                       -- Structure info and usage info for un-specialised RHSs
        -> UniqSM (ScUsage, [SpecInfo])    -- Usage from all RHSs (specialised and not)
                                           --     plus details of specialisations

specRec :: TopLevelFlag
-> ScEnv -> ScUsage -> [RhsInfo] -> UniqSM (ScUsage, [SpecInfo])
specRec TopLevelFlag
top_lvl ScEnv
env ScUsage
body_usg [RhsInfo]
rhs_infos
  = Int
-> CallEnv -> ScUsage -> [SpecInfo] -> UniqSM (ScUsage, [SpecInfo])
go Int
1 CallEnv
seed_calls ScUsage
nullUsage [SpecInfo]
init_spec_infos
  where
    (CallEnv
seed_calls, [SpecInfo]
init_spec_infos)    -- Note [Seeding top-level recursive groups]
       | TopLevelFlag -> Bool
isTopLevel TopLevelFlag
top_lvl
       , (RhsInfo -> Bool) -> [RhsInfo] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any (Id -> Bool
isExportedId (Id -> Bool) -> (RhsInfo -> Id) -> RhsInfo -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. RhsInfo -> Id
ri_fn) [RhsInfo]
rhs_infos   -- Seed from body and RHSs
       = (CallEnv
all_calls,     [SpecInfo
noSpecInfo | RhsInfo
_ <- [RhsInfo]
rhs_infos])
       | Bool
otherwise                              -- Seed from body only
       = (CallEnv
calls_in_body, [SpecInfo
noSpecInfo { si_mb_unspec :: Maybe ScUsage
si_mb_unspec = ScUsage -> Maybe ScUsage
forall a. a -> Maybe a
Just (RhsInfo -> ScUsage
ri_rhs_usg RhsInfo
ri) }
                         | RhsInfo
ri <- [RhsInfo]
rhs_infos])

    calls_in_body :: CallEnv
calls_in_body = ScUsage -> CallEnv
scu_calls ScUsage
body_usg
    calls_in_rhss :: CallEnv
calls_in_rhss = (RhsInfo -> CallEnv -> CallEnv) -> CallEnv -> [RhsInfo] -> CallEnv
forall a b. (a -> b -> b) -> b -> [a] -> b
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr (CallEnv -> CallEnv -> CallEnv
combineCalls (CallEnv -> CallEnv -> CallEnv)
-> (RhsInfo -> CallEnv) -> RhsInfo -> CallEnv -> CallEnv
forall b c a. (b -> c) -> (a -> b) -> a -> c
. ScUsage -> CallEnv
scu_calls (ScUsage -> CallEnv) -> (RhsInfo -> ScUsage) -> RhsInfo -> CallEnv
forall b c a. (b -> c) -> (a -> b) -> a -> c
. RhsInfo -> ScUsage
ri_rhs_usg) CallEnv
forall a. VarEnv a
emptyVarEnv [RhsInfo]
rhs_infos
    all_calls :: CallEnv
all_calls = CallEnv
calls_in_rhss CallEnv -> CallEnv -> CallEnv
`combineCalls` CallEnv
calls_in_body

    -- Loop, specialising, until you get no new specialisations
    go :: Int   -- Which iteration of the "until no new specialisations"
                -- loop we are on; first iteration is 1
       -> CallEnv   -- Seed calls
                    -- Two accumulating parameters:
       -> ScUsage      -- Usage from earlier specialisations
       -> [SpecInfo]   -- Details of specialisations so far
       -> UniqSM (ScUsage, [SpecInfo])
    go :: Int
-> CallEnv -> ScUsage -> [SpecInfo] -> UniqSM (ScUsage, [SpecInfo])
go Int
n_iter CallEnv
seed_calls ScUsage
usg_so_far [SpecInfo]
spec_infos
      | CallEnv -> Bool
forall a. VarEnv a -> Bool
isEmptyVarEnv CallEnv
seed_calls
      = -- pprTrace "specRec1" (vcat [ ppr (map ri_fn rhs_infos)
        --                           , ppr seed_calls
        --                           , ppr body_usg ]) $
        (ScUsage, [SpecInfo]) -> UniqSM (ScUsage, [SpecInfo])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
usg_so_far, [SpecInfo]
spec_infos)

      -- Limit recursive specialisation
      -- See Note [Limit recursive specialisation]
      | Int
n_iter Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
> ScEnv -> Int
sc_recursive ScEnv
env  -- Too many iterations of the 'go' loop
      , ScEnv -> Bool
sc_force ScEnv
env Bool -> Bool -> Bool
|| Maybe Int -> Bool
forall a. Maybe a -> Bool
isNothing (ScEnv -> Maybe Int
sc_count ScEnv
env)
           -- If both of these are false, the sc_count
           -- threshold will prevent non-termination
      , (SpecInfo -> Bool) -> [SpecInfo] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any ((Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
> Int
the_limit) (Int -> Bool) -> (SpecInfo -> Int) -> SpecInfo -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. SpecInfo -> Int
si_n_specs) [SpecInfo]
spec_infos
      = -- pprTrace "specRec2" (ppr (map (map os_pat . si_specs) spec_infos)) $
        (ScUsage, [SpecInfo]) -> UniqSM (ScUsage, [SpecInfo])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
usg_so_far, [SpecInfo]
spec_infos)

      | Bool
otherwise
      = -- pprTrace "specRec3" (vcat [ text "bndrs" <+> ppr (map ri_fn rhs_infos)
        --                           , text "iteration" <+> int n_iter
        --                          , text "spec_infos" <+> ppr (map (map os_pat . si_specs) spec_infos)
        --                    ]) $
        do  { [(ScUsage, SpecInfo)]
specs_w_usg <- (RhsInfo -> SpecInfo -> UniqSM (ScUsage, SpecInfo))
-> [RhsInfo] -> [SpecInfo] -> UniqSM [(ScUsage, SpecInfo)]
forall (m :: * -> *) a b c.
Applicative m =>
(a -> b -> m c) -> [a] -> [b] -> m [c]
zipWithM (ScEnv
-> CallEnv -> RhsInfo -> SpecInfo -> UniqSM (ScUsage, SpecInfo)
specialise ScEnv
env CallEnv
seed_calls) [RhsInfo]
rhs_infos [SpecInfo]
spec_infos
            ; let ([ScUsage]
extra_usg_s, [SpecInfo]
new_spec_infos) = [(ScUsage, SpecInfo)] -> ([ScUsage], [SpecInfo])
forall a b. [(a, b)] -> ([a], [b])
unzip [(ScUsage, SpecInfo)]
specs_w_usg
                  extra_usg :: ScUsage
extra_usg = [ScUsage] -> ScUsage
combineUsages [ScUsage]
extra_usg_s
                  all_usg :: ScUsage
all_usg   = ScUsage
usg_so_far ScUsage -> ScUsage -> ScUsage
`combineUsage` ScUsage
extra_usg
            ; Int
-> CallEnv -> ScUsage -> [SpecInfo] -> UniqSM (ScUsage, [SpecInfo])
go (Int
n_iter Int -> Int -> Int
forall a. Num a => a -> a -> a
+ Int
1) (ScUsage -> CallEnv
scu_calls ScUsage
extra_usg) ScUsage
all_usg [SpecInfo]
new_spec_infos }

    -- See Note [Limit recursive specialisation]
    the_limit :: Int
the_limit = case ScEnv -> Maybe Int
sc_count ScEnv
env of
                  Maybe Int
Nothing  -> Int
10    -- Ugh!
                  Just Int
max -> Int
max


----------------------
specialise
   :: ScEnv
   -> CallEnv                     -- Info on newly-discovered calls to this function
   -> RhsInfo
   -> SpecInfo                    -- Original RHS plus patterns dealt with
   -> UniqSM (ScUsage, SpecInfo)  -- New specialised versions and their usage

-- See Note [spec_usg includes rhs_usg]

-- Note: this only generates *specialised* bindings
-- The original binding is added by ruleInfoBinds
--
-- Note: the rhs here is the optimised version of the original rhs
-- So when we make a specialised copy of the RHS, we're starting
-- from an RHS whose nested functions have been optimised already.

specialise :: ScEnv
-> CallEnv -> RhsInfo -> SpecInfo -> UniqSM (ScUsage, SpecInfo)
specialise ScEnv
env CallEnv
bind_calls (RI { ri_fn :: RhsInfo -> Id
ri_fn = Id
fn, ri_lam_bndrs :: RhsInfo -> [Id]
ri_lam_bndrs = [Id]
arg_bndrs
                              , ri_lam_body :: RhsInfo -> Expr Id
ri_lam_body = Expr Id
body, ri_arg_occs :: RhsInfo -> [ArgOcc]
ri_arg_occs = [ArgOcc]
arg_occs })
               spec_info :: SpecInfo
spec_info@(SI { si_specs :: SpecInfo -> [OneSpec]
si_specs = [OneSpec]
specs, si_n_specs :: SpecInfo -> Int
si_n_specs = Int
spec_count
                             , si_mb_unspec :: SpecInfo -> Maybe ScUsage
si_mb_unspec = Maybe ScUsage
mb_unspec })
  | Id -> Bool
isDeadEndId Id
fn  -- Note [Do not specialise diverging functions]
                    -- and do not generate specialisation seeds from its RHS
  = -- pprTrace "specialise bot" (ppr fn) $
    (ScUsage, SpecInfo) -> UniqSM (ScUsage, SpecInfo)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
nullUsage, SpecInfo
spec_info)

  | Bool -> Bool
not (Activation -> Bool
isNeverActive (Id -> Activation
idInlineActivation Id
fn))
      -- See Note [Transfer activation]
      --
      --
      -- Don't specialise OPAQUE things, see Note [OPAQUE pragma].
      -- Since OPAQUE things are always never-active (see
      -- GHC.Parser.PostProcess.mkOpaquePragma) this guard never fires for
      -- OPAQUE things.
  , Bool -> Bool
not ([Id] -> Bool
forall a. [a] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [Id]
arg_bndrs)                         -- Only specialise functions
  , Just [Call]
all_calls <- CallEnv -> Id -> Maybe [Call]
forall a. VarEnv a -> Id -> Maybe a
lookupVarEnv CallEnv
bind_calls Id
fn -- Some calls to it
  = -- pprTrace "specialise entry {" (ppr fn <+> ppr all_calls) $
    do  { (Bool
boring_call, [CallPat]
new_pats) <- ScEnv
-> Id -> SpecInfo -> [ArgOcc] -> [Call] -> UniqSM (Bool, [CallPat])
callsToNewPats ScEnv
env Id
fn SpecInfo
spec_info [ArgOcc]
arg_occs [Call]
all_calls

        ; let n_pats :: Int
n_pats = [CallPat] -> Int
forall a. [a] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [CallPat]
new_pats
--        ; if (not (null new_pats) || isJust mb_unspec) then
--            pprTrace "specialise" (vcat [ ppr fn <+> text "with" <+> int n_pats <+> text "good patterns"
--                                        , text "mb_unspec" <+> ppr (isJust mb_unspec)
--                                        , text "arg_occs" <+> ppr arg_occs
--                                        , text "good pats" <+> ppr new_pats])  $
--               return ()
--          else return ()

        ; let spec_env :: ScEnv
spec_env = ScEnv -> Int -> ScEnv
decreaseSpecCount ScEnv
env Int
n_pats
        ; ([ScUsage]
spec_usgs, [OneSpec]
new_specs) <- ((CallPat, Int) -> UniqSM (ScUsage, OneSpec))
-> [(CallPat, Int)] -> UniqSM ([ScUsage], [OneSpec])
forall (m :: * -> *) a b c.
Applicative m =>
(a -> m (b, c)) -> [a] -> m ([b], [c])
mapAndUnzipM (ScEnv
-> Id
-> [Id]
-> Expr Id
-> (CallPat, Int)
-> UniqSM (ScUsage, OneSpec)
spec_one ScEnv
spec_env Id
fn [Id]
arg_bndrs Expr Id
body)
                                                 ([CallPat]
new_pats [CallPat] -> [Int] -> [(CallPat, Int)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [Int
spec_count..])
                -- See Note [Specialise original body]

        ; let spec_usg :: ScUsage
spec_usg = [ScUsage] -> ScUsage
combineUsages [ScUsage]
spec_usgs

              -- If there were any boring calls among the seeds (= all_calls), then those
              -- calls will call the un-specialised function.  So we should use the seeds
              -- from the _unspecialised_ function's RHS, which are in mb_unspec, by returning
              -- then in new_usg.
              (ScUsage
new_usg, Maybe ScUsage
mb_unspec')
                  = case Maybe ScUsage
mb_unspec of
                      Just ScUsage
rhs_usg | Bool
boring_call -> (ScUsage
spec_usg ScUsage -> ScUsage -> ScUsage
`combineUsage` ScUsage
rhs_usg, Maybe ScUsage
forall a. Maybe a
Nothing)
                      Maybe ScUsage
_                          -> (ScUsage
spec_usg,                      Maybe ScUsage
mb_unspec)

--        ; pprTrace "specialise return }"
--             (vcat [ ppr fn
--                   , text "boring_call:" <+> ppr boring_call
--                   , text "new calls:" <+> ppr (scu_calls new_usg)]) $
--          return ()

          ; (ScUsage, SpecInfo) -> UniqSM (ScUsage, SpecInfo)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
new_usg, SI { si_specs :: [OneSpec]
si_specs = [OneSpec]
new_specs [OneSpec] -> [OneSpec] -> [OneSpec]
forall a. [a] -> [a] -> [a]
++ [OneSpec]
specs
                                , si_n_specs :: Int
si_n_specs = Int
spec_count Int -> Int -> Int
forall a. Num a => a -> a -> a
+ Int
n_pats
                                , si_mb_unspec :: Maybe ScUsage
si_mb_unspec = Maybe ScUsage
mb_unspec' }) }

  | Bool
otherwise  -- No calls, inactive, or not a function
               -- Behave as if there was a single, boring call
  = -- pprTrace "specialise inactive" (ppr fn $$ ppr mb_unspec) $
    case Maybe ScUsage
mb_unspec of    -- Behave as if there was a single, boring call
      Just ScUsage
rhs_usg -> (ScUsage, SpecInfo) -> UniqSM (ScUsage, SpecInfo)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
rhs_usg, SpecInfo
spec_info { si_mb_unspec :: Maybe ScUsage
si_mb_unspec = Maybe ScUsage
forall a. Maybe a
Nothing })
                         -- See Note [spec_usg includes rhs_usg]
      Maybe ScUsage
Nothing      -> (ScUsage, SpecInfo) -> UniqSM (ScUsage, SpecInfo)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
nullUsage, SpecInfo
spec_info)


---------------------
spec_one :: ScEnv
         -> OutId       -- Function
         -> [InVar]     -- Lambda-binders of RHS; should match patterns
         -> InExpr      -- Body of the original function
         -> (CallPat, Int)
         -> UniqSM (ScUsage, OneSpec)   -- Rule and binding

-- spec_one creates a specialised copy of the function, together
-- with a rule for using it.  I'm very proud of how short this
-- function is, considering what it does :-).

{-
  Example

     In-scope: a, x::a
     f = /\b \y::[(a,b)] -> ....f (b,c) ((:) (a,(b,c)) (x,v) (h w))...
          [c::*, v::(b,c) are presumably bound by the (...) part]
  ==>
     f_spec = /\ b c \ v::(b,c) hw::[(a,(b,c))] ->
                  (...entire body of f...) [b -> (b,c),
                                            y -> ((:) (a,(b,c)) (x,v) hw)]

     RULE:  forall b::* c::*,           -- Note, *not* forall a, x
                   v::(b,c),
                   hw::[(a,(b,c))] .

            f (b,c) ((:) (a,(b,c)) (x,v) hw) = f_spec b c v hw
-}

spec_one :: ScEnv
-> Id
-> [Id]
-> Expr Id
-> (CallPat, Int)
-> UniqSM (ScUsage, OneSpec)
spec_one ScEnv
env Id
fn [Id]
arg_bndrs Expr Id
body (CallPat
call_pat, Int
rule_number)
  | CP { cp_qvars :: CallPat -> [Id]
cp_qvars = [Id]
qvars, cp_args :: CallPat -> [Expr Id]
cp_args = [Expr Id]
pats, cp_strict_args :: CallPat -> [Id]
cp_strict_args = [Id]
cbv_args } <- CallPat
call_pat
  = do  { Unique
spec_uniq <- UniqSM Unique
forall (m :: * -> *). MonadUnique m => m Unique
getUniqueM
        ; let env1 :: ScEnv
env1 = ScEnv -> [(Id, Expr Id)] -> ScEnv
extendScSubstList (ScEnv -> [Id] -> ScEnv
extendScInScope ScEnv
env [Id]
qvars)
                                       ([Id]
arg_bndrs [Id] -> [Expr Id] -> [(Id, Expr Id)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [Expr Id]
pats)
              (ScEnv
body_env, [Id]
extra_bndrs) = ScEnv -> [Id] -> (ScEnv, [Id])
extendBndrs ScEnv
env1 ([Expr Id] -> [Id] -> [Id]
forall b a. [b] -> [a] -> [a]
dropList [Expr Id]
pats [Id]
arg_bndrs)
              -- Remember, there may be fewer pats than arg_bndrs
              -- See Note [SpecConstr call patterns]
              -- extra_bndrs will then be arguments in the specialized version
              -- which are *not* applied to arguments immediately at the call sites.
              -- e.g. let f x y = ... in map (f True) xs
              -- will result in y becoming an extra_bndr

              fn_name :: Name
fn_name  = Id -> Name
idName Id
fn
              fn_loc :: SrcSpan
fn_loc   = Name -> SrcSpan
nameSrcSpan Name
fn_name
              fn_occ :: OccName
fn_occ   = Name -> OccName
nameOccName Name
fn_name
              spec_occ :: OccName
spec_occ = OccName -> OccName
mkSpecOcc OccName
fn_occ
              -- We use fn_occ rather than fn in the rule_name string
              -- as we don't want the uniq to end up in the rule, and
              -- hence in the ABI, as that can cause spurious ABI
              -- changes (#4012).
              rule_name :: FastString
rule_name  = String -> FastString
mkFastString (String
"SC:" String -> String -> String
forall a. [a] -> [a] -> [a]
++ OccName -> String
occNameString OccName
fn_occ String -> String -> String
forall a. [a] -> [a] -> [a]
++ Int -> String
forall a. Show a => a -> String
show Int
rule_number)
              spec_name :: Name
spec_name  = Unique -> OccName -> SrcSpan -> Name
mkInternalName Unique
spec_uniq OccName
spec_occ SrcSpan
fn_loc

        -- Specialise the body
        -- ; pprTraceM "body_subst_for" $ ppr (spec_occ) $$ ppr (sc_subst body_env)
        ; (ScUsage
spec_usg, Expr Id
spec_body) <- ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id)
scExpr ScEnv
body_env Expr Id
body

--      ; pprTrace "done spec_one }" (ppr fn $$ ppr (scu_calls spec_usg)) $
--        return ()

                -- And build the results
        ; let spec_body_ty :: Type
spec_body_ty   = (() :: Constraint) => Expr Id -> Type
Expr Id -> Type
exprType Expr Id
spec_body
              ([Id]
spec_lam_args1, DmdSig
spec_sig, Int
spec_arity1, Maybe Int
spec_join_arity1)
                  = Id -> CallPat -> [Id] -> ([Id], DmdSig, Int, Maybe Int)
calcSpecInfo Id
fn CallPat
call_pat [Id]
extra_bndrs
                  -- Annotate the variables with the strictness information from
                  -- the function (see Note [Strictness information in worker binders])
              add_void_arg :: Bool
add_void_arg = Id -> [Id] -> [Id] -> Bool
needsVoidWorkerArg Id
fn [Id]
arg_bndrs [Id]
spec_lam_args1
              ([Id]
spec_lam_args, [Id]
spec_call_args, Int
spec_arity, Maybe Int
spec_join_arity)
                  | Bool
add_void_arg
                  -- See Note [SpecConst needs to add void args first]
                  , ([Id]
spec_lam_args, [Id]
spec_call_args, [StrictnessMark]
_) <- [Id] -> [StrictnessMark] -> ([Id], [Id], [StrictnessMark])
addVoidWorkerArg [Id]
spec_lam_args1 []
                      -- needsVoidWorkerArg: usual w/w hack to avoid generating
                      -- a spec_rhs of unlifted type and no args.
                  , !Int
spec_arity      <- Int
spec_arity1 Int -> Int -> Int
forall a. Num a => a -> a -> a
+ Int
1
                  , !Maybe Int
spec_join_arity <- (Int -> Int) -> Maybe Int -> Maybe Int
forall a b. (a -> b) -> Maybe a -> Maybe b
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap (Int -> Int -> Int
forall a. Num a => a -> a -> a
+ Int
1) Maybe Int
spec_join_arity1
                  = ([Id]
spec_lam_args,  [Id]
spec_call_args, Int
spec_arity,  Maybe Int
spec_join_arity)
                  | Bool
otherwise
                  = ([Id]
spec_lam_args1, [Id]
spec_lam_args1, Int
spec_arity1, Maybe Int
spec_join_arity1)

              spec_id :: Id
spec_id    = Id -> Id
asWorkerLikeId (Id -> Id) -> Id -> Id
forall a b. (a -> b) -> a -> b
$
                           (() :: Constraint) => Name -> Type -> Type -> Id
Name -> Type -> Type -> Id
mkLocalId Name
spec_name Type
Many
                                     ([Id] -> Type -> Type
mkLamTypes [Id]
spec_lam_args Type
spec_body_ty)
                             -- See Note [Transfer strictness]
                             Id -> DmdSig -> Id
`setIdDmdSig`    DmdSig
spec_sig
                             Id -> CprSig -> Id
`setIdCprSig`    CprSig
topCprSig
                             Id -> Int -> Id
`setIdArity`     Int
spec_arity
                             Id -> Maybe Int -> Id
`asJoinId_maybe` Maybe Int
spec_join_arity

                -- Conditionally use result of new worker-wrapper transform
              spec_rhs :: Expr Id
spec_rhs   = [Id] -> Expr Id -> Expr Id
forall b. [b] -> Expr b -> Expr b
mkLams [Id]
spec_lam_args ([Id] -> Type -> Expr Id -> Expr Id
mkSeqs [Id]
cbv_args Type
spec_body_ty Expr Id
spec_body)
              rule_rhs :: Expr Id
rule_rhs = Expr Id -> [Id] -> Expr Id
forall b. Expr b -> [Id] -> Expr b
mkVarApps (Id -> Expr Id
forall b. Id -> Expr b
Var Id
spec_id) ([Id] -> Expr Id) -> [Id] -> Expr Id
forall a b. (a -> b) -> a -> b
$
                              -- This will give us all the arguments we quantify over
                              -- in the rule plus the void argument if present
                              -- since `length(qvars) + void + length(extra_bndrs) = length spec_call_args`
                              Int -> [Id] -> [Id]
forall a. Int -> [a] -> [a]
dropTail ([Id] -> Int
forall a. [a] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [Id]
extra_bndrs) [Id]
spec_call_args
              inline_act :: Activation
inline_act = Id -> Activation
idInlineActivation Id
fn
              this_mod :: Module
this_mod   = ScEnv -> Module
sc_module ScEnv
env
              rule :: CoreRule
rule       = Module
-> Bool
-> Bool
-> FastString
-> Activation
-> Name
-> [Id]
-> [Expr Id]
-> Expr Id
-> CoreRule
mkRule Module
this_mod Bool
True {- Auto -} Bool
True {- Local -}
                                  FastString
rule_name Activation
inline_act Name
fn_name [Id]
qvars [Expr Id]
pats Expr Id
rule_rhs
                           -- See Note [Transfer activation]

        -- ; pprTrace "spec_one {" (vcat [ text "function:" <+> ppr fn <+> ppr (idUnique fn)
        --                               , text "sc_count:" <+> ppr (sc_count env)
        --                               , text "pats:" <+> ppr pats
        --                               , text "call_pat:" <+> ppr call_pat
        --                               , text "-->" <+> ppr spec_name
        --                               , text "bndrs" <+> ppr arg_bndrs
        --                               , text "extra_bndrs" <+> ppr extra_bndrs
        --                               , text "spec_lam_args" <+> ppr spec_lam_args
        --                               , text "spec_call_args" <+> ppr spec_call_args
        --                               , text "rule_rhs" <+> ppr rule_rhs
        --                               , text "adds_void_worker_arg" <+> ppr adds_void_worker_arg
        --                               , text "body" <+> ppr body
        --                               , text "spec_rhs" <+> ppr spec_rhs
        --                               , text "how_bound" <+> ppr (sc_how_bound env) ]) $
        --   return ()
        ; (ScUsage, OneSpec) -> UniqSM (ScUsage, OneSpec)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
spec_usg, OS { os_pat :: CallPat
os_pat = CallPat
call_pat, os_rule :: CoreRule
os_rule = CoreRule
rule
                               , os_id :: Id
os_id = Id
spec_id
                               , os_rhs :: Expr Id
os_rhs = Expr Id
spec_rhs }) }

-- See Note [SpecConstr and strict fields]
mkSeqs :: [Var] -> Type -> CoreExpr -> CoreExpr
mkSeqs :: [Id] -> Type -> Expr Id -> Expr Id
mkSeqs [Id]
seqees Type
res_ty Expr Id
rhs =
  (Id -> Expr Id -> Expr Id) -> Expr Id -> [Id] -> Expr Id
forall a b. (a -> b -> b) -> b -> [a] -> b
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr Id -> Expr Id -> Expr Id
addEval Expr Id
rhs [Id]
seqees
    where
      addEval :: Var -> CoreExpr -> CoreExpr
      addEval :: Id -> Expr Id -> Expr Id
addEval Id
arg_id Expr Id
rhs
        -- Argument representing strict field and it's worth passing via cbv
        | Id -> Bool
shouldStrictifyIdForCbv Id
arg_id
        = Expr Id -> Id -> Type -> [Alt Id] -> Expr Id
forall b. Expr b -> b -> Type -> [Alt b] -> Expr b
Case (Id -> Expr Id
forall b. Id -> Expr b
Var Id
arg_id) Id
arg_id Type
res_ty ([AltCon -> [Id] -> Expr Id -> Alt Id
forall b. AltCon -> [b] -> Expr b -> Alt b
Alt AltCon
DEFAULT [] Expr Id
rhs])
        | Bool
otherwise
        = Expr Id
rhs


{- Note [SpecConst needs to add void args first]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider a function
    f start @t = e
We want to specialize for a partially applied call `f True`.
See also Note [SpecConstr call patterns], second Wrinkle.
Naively we would expect to get
    $sf @t = $se
    RULE: f True = $sf
The specialized function only takes a single type argument
so we add a void argument to prevent it from turning into
a thunk. See Note [Protecting the last value argument] for details
why. Normally we would add the void argument after the
type argument giving us:
    $sf :: forall t. Void# -> bla
    $sf @t void = $se
    RULE: f True = $sf void# (wrong)
But if you look closely this wouldn't typecheck!
If we substitute `f True` with `$sf void#` we expect the type argument to be applied first
but we apply void# first.
The easist fix seems to be just to add the void argument to the front of the arguments.
Now we get:
    $sf :: Void# -> forall t. bla
    $sf void @t = $se
    RULE: f True = $sf void#
And now we can substitute `f True` with `$sf void#` with everything working out nicely!
-}

calcSpecInfo :: Id                     -- The original function
             -> CallPat                -- Call pattern
             -> [Var]                  -- Extra bndrs
             -> ( [Var]                     -- Demand-decorated binders
                , DmdSig                    -- Strictness of specialised thing
                , Arity, Maybe JoinArity )  -- Arities of specialised thing
-- Calcuate bits of IdInfo for the specialised function
-- See Note [Transfer strictness]
-- See Note [Strictness information in worker binders]
calcSpecInfo :: Id -> CallPat -> [Id] -> ([Id], DmdSig, Int, Maybe Int)
calcSpecInfo Id
fn (CP { cp_qvars :: CallPat -> [Id]
cp_qvars = [Id]
qvars, cp_args :: CallPat -> [Expr Id]
cp_args = [Expr Id]
pats }) [Id]
extra_bndrs
  | Id -> Bool
isJoinId Id
fn    -- Join points have strictness and arity for LHS only
  = ( [Id]
bndrs_w_dmds
    , [Demand] -> Divergence -> DmdSig
mkClosedDmdSig [Demand]
qvar_dmds Divergence
div
    , (Id -> Bool) -> [Id] -> Int
forall a. (a -> Bool) -> [a] -> Int
count Id -> Bool
isId [Id]
qvars
    , Int -> Maybe Int
forall a. a -> Maybe a
Just ([Id] -> Int
forall a. [a] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [Id]
qvars) )
  | Bool
otherwise
  = ( [Id]
bndrs_w_dmds
    , [Demand] -> Divergence -> DmdSig
mkClosedDmdSig ([Demand]
qvar_dmds [Demand] -> [Demand] -> [Demand]
forall a. [a] -> [a] -> [a]
++ [Demand]
extra_dmds) Divergence
div
    , (Id -> Bool) -> [Id] -> Int
forall a. (a -> Bool) -> [a] -> Int
count Id -> Bool
isId [Id]
qvars Int -> Int -> Int
forall a. Num a => a -> a -> a
+ (Id -> Bool) -> [Id] -> Int
forall a. (a -> Bool) -> [a] -> Int
count Id -> Bool
isId [Id]
extra_bndrs
    , Maybe Int
forall a. Maybe a
Nothing )
  where
    DmdSig (DmdType DmdEnv
_ [Demand]
fn_dmds Divergence
div) = Id -> DmdSig
idDmdSig Id
fn

    val_pats :: [Expr Id]
val_pats   = (Expr Id -> Bool) -> [Expr Id] -> [Expr Id]
forall a. (a -> Bool) -> [a] -> [a]
filterOut Expr Id -> Bool
forall b. Expr b -> Bool
isTypeArg [Expr Id]
pats -- value args at call sites, used to determine how many demands to drop
                                          -- from the original functions demand and for setting up dmd_env.
    qvar_dmds :: [Demand]
qvar_dmds  = [ DmdEnv -> Id -> Maybe Demand
forall a. VarEnv a -> Id -> Maybe a
lookupVarEnv DmdEnv
dmd_env Id
qv Maybe Demand -> Demand -> Demand
forall a. Maybe a -> a -> a
`orElse` Demand
topDmd | Id
qv <- [Id]
qvars, Id -> Bool
isId Id
qv ]
    extra_dmds :: [Demand]
extra_dmds = [Expr Id] -> [Demand] -> [Demand]
forall b a. [b] -> [a] -> [a]
dropList [Expr Id]
val_pats [Demand]
fn_dmds

    bndrs_w_dmds :: [Id]
bndrs_w_dmds =  [Id] -> [Demand] -> [Id]
set_dmds [Id]
qvars       [Demand]
qvar_dmds
                 [Id] -> [Id] -> [Id]
forall a. [a] -> [a] -> [a]
++ [Id] -> [Demand] -> [Id]
set_dmds [Id]
extra_bndrs [Demand]
extra_dmds

    set_dmds :: [Var] -> [Demand] -> [Var]
    set_dmds :: [Id] -> [Demand] -> [Id]
set_dmds [] [Demand]
_   = []
    set_dmds [Id]
vs  [] = [Id]
vs  -- Run out of demands
    set_dmds (Id
v:[Id]
vs) ds :: [Demand]
ds@(Demand
d:[Demand]
ds') | Id -> Bool
isTyVar Id
v = Id
v                   Id -> [Id] -> [Id]
forall a. a -> [a] -> [a]
: [Id] -> [Demand] -> [Id]
set_dmds [Id]
vs [Demand]
ds
                               | Bool
otherwise = Id -> Demand -> Id
setIdDemandInfo Id
v Demand
d Id -> [Id] -> [Id]
forall a. a -> [a] -> [a]
: [Id] -> [Demand] -> [Id]
set_dmds [Id]
vs [Demand]
ds'

    dmd_env :: DmdEnv
dmd_env = DmdEnv -> [Demand] -> [Expr Id] -> DmdEnv
go DmdEnv
forall a. VarEnv a
emptyVarEnv [Demand]
fn_dmds [Expr Id]
val_pats

    go :: DmdEnv -> [Demand] -> [CoreExpr] -> DmdEnv
    -- We've filtered out all the type patterns already
    go :: DmdEnv -> [Demand] -> [Expr Id] -> DmdEnv
go DmdEnv
env (Demand
d:[Demand]
ds) (Expr Id
pat : [Expr Id]
pats)     = DmdEnv -> [Demand] -> [Expr Id] -> DmdEnv
go (DmdEnv -> Demand -> Expr Id -> DmdEnv
go_one DmdEnv
env Demand
d Expr Id
pat) [Demand]
ds [Expr Id]
pats
    go DmdEnv
env [Demand]
_      [Expr Id]
_                = DmdEnv
env

    go_one :: DmdEnv -> Demand -> CoreExpr -> DmdEnv
    go_one :: DmdEnv -> Demand -> Expr Id -> DmdEnv
go_one DmdEnv
env Demand
d          (Var Id
v) = (Demand -> Demand -> Demand) -> DmdEnv -> Id -> Demand -> DmdEnv
forall a. (a -> a -> a) -> VarEnv a -> Id -> a -> VarEnv a
extendVarEnv_C Demand -> Demand -> Demand
plusDmd DmdEnv
env Id
v Demand
d
    go_one DmdEnv
env (Card
_n :* SubDemand
cd) Expr Id
e -- NB: _n does not have to be strict
      | (Var Id
_, [Expr Id]
args) <- Expr Id -> (Expr Id, [Expr Id])
forall b. Expr b -> (Expr b, [Expr b])
collectArgs Expr Id
e
      , Just (Boxity
_b, [Demand]
ds) <- Int -> SubDemand -> Maybe (Boxity, [Demand])
viewProd ([Expr Id] -> Int
forall a. [a] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [Expr Id]
args) SubDemand
cd -- TODO: We may want to look at boxity _b, though...
      = DmdEnv -> [Demand] -> [Expr Id] -> DmdEnv
go DmdEnv
env [Demand]
ds [Expr Id]
args
    go_one DmdEnv
env Demand
_  Expr Id
_ = DmdEnv
env


{-
Note [spec_usg includes rhs_usg]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In calls to 'specialise', the returned ScUsage must include the rhs_usg in
the passed-in SpecInfo, unless there are no calls at all to the function.

The caller can, indeed must, assume this.  They should not combine in rhs_usg
themselves, or they'll get rhs_usg twice -- and that can lead to an exponential
blowup of duplicates in the CallEnv.  This is what gave rise to the massive
performance loss in #8852.

Note [Specialise original body]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The RhsInfo for a binding keeps the *original* body of the binding.  We
must specialise that, *not* the result of applying specExpr to the RHS
(which is also kept in RhsInfo). Otherwise we end up specialising a
specialised RHS, and that can lead directly to exponential behaviour.

Note [Transfer activation]
~~~~~~~~~~~~~~~~~~~~~~~~~~
  This note is for SpecConstr, but exactly the same thing
  happens in the overloading specialiser; see
  Note [Auto-specialisation and RULES] in GHC.Core.Opt.Specialise.

In which phase should the specialise-constructor rules be active?
Originally I made them always-active, but Manuel found that this
defeated some clever user-written rules.  Then I made them active only
in FinalPhase; after all, currently, the specConstr transformation is
only run after the simplifier has reached FinalPhase, but that meant
that specialisations didn't fire inside wrappers; see test
simplCore/should_compile/spec-inline.

So now I just use the inline-activation of the parent Id, as the
activation for the specialisation RULE, just like the main specialiser;

This in turn means there is no point in specialising NOINLINE things,
so we test for that.

Note [Transfer strictness]
~~~~~~~~~~~~~~~~~~~~~~~~~~
We must transfer strictness information from the original function to
the specialised one.  Suppose, for example

  f has strictness     SSx
        and a RULE     f (a:as) b = f_spec a as b

Now we want f_spec to have strictness  LLSx, otherwise we'll use call-by-need
when calling f_spec instead of call-by-value.  And that can result in
unbounded worsening in space (cf the classic foldl vs foldl')

See #3437 for a good example.

The function calcSpecStrictness performs the calculation.

Note [Strictness information in worker binders]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
After having calculated the strictness annotation for the worker (see Note
[Transfer strictness] above), we also want to have this information attached to
the worker’s arguments, for the benefit of later passes. The function
handOutStrictnessInformation decomposes the strictness annotation calculated by
calcSpecStrictness and attaches them to the variables.


************************************************************************
*                                                                      *
\subsection{Argument analysis}
*                                                                      *
************************************************************************

This code deals with analysing call-site arguments to see whether
they are constructor applications.

Note [Free type variables of the qvar types]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In a call (f @a x True), that we want to specialise, what variables should
we quantify over.  Clearly over 'a' and 'x', but what about any type variables
free in x's type?  In fact we don't need to worry about them because (f @a)
can only be a well-typed application if its type is compatible with x, so any
variables free in x's type must be free in (f @a), and hence either be gathered
via 'a' itself, or be in scope at f's defn.  Hence we just take
  (exprsFreeVars pats).

BUT phantom type synonyms can mess this reasoning up,
  eg   x::T b   with  type T b = Int
So we apply expandTypeSynonyms to the bound Ids.
See # 5458.  Yuk.

Note [SpecConstr call patterns]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A "call patterns" that we collect is going to become the LHS of a RULE.

Wrinkles:

* The list of argument patterns, cp_args, is no longer than the
  visible lambdas of the binding, ri_arg_occs.  This is done via
  the zipWithM in callToPats.

* The list of argument patterns can certainly be shorter than the
  lambdas in the function definition (under-saturated).  For example
      f x y = case x of { True -> e1; False -> e2 }
      ....map (f True) e...
  We want to specialise `f` for `f True`.

* In fact we deliberately shrink the list of argument patterns,
  cp_args, by trimming off all the boring ones at the end (see
  `dropWhileEnd is_boring` in callToPats).  Since the RULE only
  applies when it is saturated, this shrinking makes the RULE more
  applicable.  But it does mean that the argument patterns do not
  necessarily saturate the lambdas of the function.

* It's important that the pattern arguments do not look like
     e |> Refl
  or
    e |> g1 |> g2
  because both of these will be optimised by Simplify.simplRule. In the
  former case such optimisation benign, because the rule will match more
  terms; but in the latter we may lose a binding of 'g1' or 'g2', and
  end up with a rule LHS that doesn't bind the template variables
  (#10602).

  The simplifier eliminates such things, but SpecConstr itself constructs
  new terms by substituting.  So the 'mkCast' in the Cast case of scExpr
  is very important!

Note [Choosing patterns]
~~~~~~~~~~~~~~~~~~~~~~~~
If we get lots of patterns we may not want to make a specialisation
for each of them (code bloat), so we choose as follows, implemented
by trim_pats.

* The flag -fspec-constr-count-N sets the sc_count field
  of the ScEnv to (Just n).  This limits the total number
  of specialisations for a given function to N.

* -fno-spec-constr-count sets the sc_count field to Nothing,
  which switches of the limit.

* The ghastly ForceSpecConstr trick also switches of the limit
  for a particular function

* Otherwise we sort the patterns to choose the most general
  ones first; more general => more widely applicable.

Note [SpecConstr and casts]
~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider (#14270) a call like

    let f = e
    in ... f (K @(a |> co)) ...

where 'co' is a coercion variable not in scope at f's definition site.
If we aren't careful we'll get

    let $sf a co = e (K @(a |> co))
        RULE "SC:f" forall a co.  f (K @(a |> co)) = $sf a co
        f = e
    in ...

But alas, when we match the call we won't bind 'co', because type-matching
(for good reasons) discards casts).

I don't know how to solve this, so for now I'm just discarding any
call patterns that
  * Mentions a coercion variable in a type argument
  * That is not in scope at the binding of the function

I think this is very rare.

It is important (e.g. #14936) that this /only/ applies to
coercions mentioned in casts.  We don't want to be discombobulated
by casts in terms!  For example, consider
   f ((e1,e2) |> sym co)
where, say,
   f  :: Foo -> blah
   co :: Foo ~R (Int,Int)

Here we definitely do want to specialise for that pair!  We do not
match on the structure of the coercion; instead we just match on a
coercion variable, so the RULE looks like

   forall (x::Int, y::Int, co :: (Int,Int) ~R Foo)
     f ((x,y) |> co) = $sf x y co

Often the body of f looks like
   f arg = ...(case arg |> co' of
                (x,y) -> blah)...

so that the specialised f will turn into
   $sf x y co = let arg = (x,y) |> co
                in ...(case arg>| co' of
                         (x,y) -> blah)....

which will simplify to not use 'co' at all.  But we can't guarantee
that co will end up unused, so we still pass it.  Absence analysis
may remove it later.

Note that this /also/ discards the call pattern if we have a cast in a
/term/, although in fact Rules.match does make a very flaky and
fragile attempt to match coercions.  e.g. a call like
    f (Maybe Age) (Nothing |> co) blah
    where co :: Maybe Int ~ Maybe Age
will be discarded.  It's extremely fragile to match on the form of a
coercion, so I think it's better just not to try.  A more complicated
alternative would be to discard calls that mention coercion variables
only in kind-casts, but I'm doing the simple thing for now.
-}

data CallPat = CP { CallPat -> [Id]
cp_qvars :: [Var]           -- Quantified variables
                  , CallPat -> [Expr Id]
cp_args  :: [CoreExpr]      -- Arguments
                  , CallPat -> [Id]
cp_strict_args :: [Var] }   -- Arguments we want to pass unlifted even if they are boxed
     -- See Note [SpecConstr call patterns]

instance Outputable CallPat where
  ppr :: CallPat -> SDoc
ppr (CP { cp_qvars :: CallPat -> [Id]
cp_qvars = [Id]
qvars, cp_args :: CallPat -> [Expr Id]
cp_args = [Expr Id]
args, cp_strict_args :: CallPat -> [Id]
cp_strict_args =  [Id]
strict })
    = String -> SDoc
text String
"CP" SDoc -> SDoc -> SDoc
<> SDoc -> SDoc
braces ([SDoc] -> SDoc
sep [ String -> SDoc
text String
"cp_qvars =" SDoc -> SDoc -> SDoc
<+> [Id] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Id]
qvars SDoc -> SDoc -> SDoc
<> SDoc
comma
                               , String -> SDoc
text String
"cp_args =" SDoc -> SDoc -> SDoc
<+> [Expr Id] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Expr Id]
args
                               , String -> SDoc
text String
"cp_strict_args = " SDoc -> SDoc -> SDoc
<> [Id] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Id]
strict ])

callsToNewPats :: ScEnv -> Id
               -> SpecInfo
               -> [ArgOcc] -> [Call]
               -> UniqSM (Bool, [CallPat])
        -- Result has no duplicate patterns,
        -- nor ones mentioned in done_pats
        -- Bool indicates that there was at least one boring pattern
callsToNewPats :: ScEnv
-> Id -> SpecInfo -> [ArgOcc] -> [Call] -> UniqSM (Bool, [CallPat])
callsToNewPats ScEnv
env Id
fn spec_info :: SpecInfo
spec_info@(SI { si_specs :: SpecInfo -> [OneSpec]
si_specs = [OneSpec]
done_specs }) [ArgOcc]
bndr_occs [Call]
calls
  = do  { [Maybe CallPat]
mb_pats <- (Call -> UniqSM (Maybe CallPat))
-> [Call] -> UniqSM [Maybe CallPat]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
forall (m :: * -> *) a b. Monad m => (a -> m b) -> [a] -> m [b]
mapM (ScEnv -> [ArgOcc] -> Call -> UniqSM (Maybe CallPat)
callToPats ScEnv
env [ArgOcc]
bndr_occs) [Call]
calls

        ; let have_boring_call :: Bool
have_boring_call = (Maybe CallPat -> Bool) -> [Maybe CallPat] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any Maybe CallPat -> Bool
forall a. Maybe a -> Bool
isNothing [Maybe CallPat]
mb_pats

              good_pats :: [CallPat]
              good_pats :: [CallPat]
good_pats = [Maybe CallPat] -> [CallPat]
forall a. [Maybe a] -> [a]
catMaybes [Maybe CallPat]
mb_pats

              -- Remove patterns we have already done
              new_pats :: [CallPat]
new_pats = (CallPat -> Bool) -> [CallPat] -> [CallPat]
forall a. (a -> Bool) -> [a] -> [a]
filterOut CallPat -> Bool
is_done [CallPat]
good_pats
              is_done :: CallPat -> Bool
is_done CallPat
p = (OneSpec -> Bool) -> [OneSpec] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any (CallPat -> CallPat -> Bool
samePat CallPat
p (CallPat -> Bool) -> (OneSpec -> CallPat) -> OneSpec -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. OneSpec -> CallPat
os_pat) [OneSpec]
done_specs

              -- Remove duplicates
              non_dups :: [CallPat]
non_dups = (CallPat -> CallPat -> Bool) -> [CallPat] -> [CallPat]
forall a. (a -> a -> Bool) -> [a] -> [a]
nubBy CallPat -> CallPat -> Bool
samePat [CallPat]
new_pats

              -- Remove ones that have too many worker variables
              small_pats :: [CallPat]
small_pats = (CallPat -> Bool) -> [CallPat] -> [CallPat]
forall a. (a -> Bool) -> [a] -> [a]
filterOut CallPat -> Bool
too_big [CallPat]
non_dups
              max_args :: Int
max_args = DynFlags -> Int
maxWorkerArgs (ScEnv -> DynFlags
sc_dflags ScEnv
env)
              too_big :: CallPat -> Bool
too_big (CP { cp_qvars :: CallPat -> [Id]
cp_qvars = [Id]
vars, cp_args :: CallPat -> [Expr Id]
cp_args = [Expr Id]
args })
                = Bool -> Bool
not (Int -> Int -> [Id] -> Bool
isWorkerSmallEnough Int
max_args ([Expr Id] -> Int
forall b. [Arg b] -> Int
valArgCount [Expr Id]
args) [Id]
vars)
                  -- We are about to construct w/w pair in 'spec_one'.
                  -- Omit specialisation leading to high arity workers.
                  -- See Note [Limit w/w arity] in GHC.Core.Opt.WorkWrap.Utils

                -- Discard specialisations if there are too many of them
              (Bool
pats_were_discarded, [CallPat]
trimmed_pats) = ScEnv -> Id -> SpecInfo -> [CallPat] -> (Bool, [CallPat])
trim_pats ScEnv
env Id
fn SpecInfo
spec_info [CallPat]
small_pats

--        ; pprTrace "callsToPats" (vcat [ text "calls to" <+> ppr fn <> colon <+> ppr calls
--                                       , text "done_specs:" <+> ppr (map os_pat done_specs)
--                                       , text "good_pats:" <+> ppr good_pats ]) $
--          return ()

        ; (Bool, [CallPat]) -> UniqSM (Bool, [CallPat])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (Bool
have_boring_call Bool -> Bool -> Bool
|| Bool
pats_were_discarded, [CallPat]
trimmed_pats) }
          -- If any of the calls does not give rise to a specialisation, either
          -- because it is boring, or because there are too many specialisations,
          -- return a flag to say so, so that we know to keep the original function.


trim_pats :: ScEnv -> Id -> SpecInfo -> [CallPat] -> (Bool, [CallPat])
-- True <=> some patterns were discarded
-- See Note [Choosing patterns]
trim_pats :: ScEnv -> Id -> SpecInfo -> [CallPat] -> (Bool, [CallPat])
trim_pats ScEnv
env Id
fn (SI { si_n_specs :: SpecInfo -> Int
si_n_specs = Int
done_spec_count }) [CallPat]
pats
  | ScEnv -> Bool
sc_force ScEnv
env
    Bool -> Bool -> Bool
|| Maybe Int -> Bool
forall a. Maybe a -> Bool
isNothing Maybe Int
mb_scc
    Bool -> Bool -> Bool
|| Int
n_remaining Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
>= Int
n_pats
  = -- pprTrace "trim_pats: no-trim" (ppr (sc_force env) $$ ppr mb_scc $$ ppr n_remaining $$ ppr n_pats)
    (Bool
False, [CallPat]
pats)          -- No need to trim

  | Bool
otherwise
  = (Bool, [CallPat]) -> (Bool, [CallPat])
emit_trace ((Bool, [CallPat]) -> (Bool, [CallPat]))
-> (Bool, [CallPat]) -> (Bool, [CallPat])
forall a b. (a -> b) -> a -> b
$  -- Need to trim, so keep the best ones
    (Bool
True, Int -> [CallPat] -> [CallPat]
forall a. Int -> [a] -> [a]
take Int
n_remaining [CallPat]
sorted_pats)

  where
    n_pats :: Int
n_pats         = [CallPat] -> Int
forall a. [a] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [CallPat]
pats
    spec_count' :: Int
spec_count'    = Int
n_pats Int -> Int -> Int
forall a. Num a => a -> a -> a
+ Int
done_spec_count
    n_remaining :: Int
n_remaining    = Int
max_specs Int -> Int -> Int
forall a. Num a => a -> a -> a
- Int
done_spec_count
    mb_scc :: Maybe Int
mb_scc         = ScEnv -> Maybe Int
sc_count ScEnv
env
    Just Int
max_specs = Maybe Int
mb_scc

    sorted_pats :: [CallPat]
sorted_pats = ((CallPat, Int) -> CallPat) -> [(CallPat, Int)] -> [CallPat]
forall a b. (a -> b) -> [a] -> [b]
map (CallPat, Int) -> CallPat
forall a b. (a, b) -> a
fst ([(CallPat, Int)] -> [CallPat]) -> [(CallPat, Int)] -> [CallPat]
forall a b. (a -> b) -> a -> b
$
                  ((CallPat, Int) -> (CallPat, Int) -> Ordering)
-> [(CallPat, Int)] -> [(CallPat, Int)]
forall a. (a -> a -> Ordering) -> [a] -> [a]
sortBy (((CallPat, Int) -> Int)
-> (CallPat, Int) -> (CallPat, Int) -> Ordering
forall a b. Ord a => (b -> a) -> b -> b -> Ordering
comparing (CallPat, Int) -> Int
forall a b. (a, b) -> b
snd) ([(CallPat, Int)] -> [(CallPat, Int)])
-> [(CallPat, Int)] -> [(CallPat, Int)]
forall a b. (a -> b) -> a -> b
$
                  [(CallPat
pat, CallPat -> Int
pat_cons CallPat
pat) | CallPat
pat <- [CallPat]
pats]
     -- Sort in order of increasing number of constructors
     -- (i.e. decreasing generality) and pick the initial
     -- segment of this list

    pat_cons :: CallPat -> Int
    -- How many data constructors of literals are in
    -- the pattern.  More data-cons => less general
    pat_cons :: CallPat -> Int
pat_cons (CP { cp_qvars :: CallPat -> [Id]
cp_qvars = [Id]
qs, cp_args :: CallPat -> [Expr Id]
cp_args = [Expr Id]
ps })
       = (Expr Id -> Int -> Int) -> Int -> [Expr Id] -> Int
forall a b. (a -> b -> b) -> b -> [a] -> b
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr (Int -> Int -> Int
forall a. Num a => a -> a -> a
(+) (Int -> Int -> Int) -> (Expr Id -> Int) -> Expr Id -> Int -> Int
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Expr Id -> Int
n_cons) Int
0 [Expr Id]
ps
       where
          q_set :: CoVarSet
q_set = [Id] -> CoVarSet
mkVarSet [Id]
qs
          n_cons :: Expr Id -> Int
n_cons (Var Id
v) | Id
v Id -> CoVarSet -> Bool
`elemVarSet` CoVarSet
q_set = Int
0
                         | Bool
otherwise            = Int
1
          n_cons (Cast Expr Id
e Coercion
_)  = Expr Id -> Int
n_cons Expr Id
e
          n_cons (App Expr Id
e1 Expr Id
e2) = Expr Id -> Int
n_cons Expr Id
e1 Int -> Int -> Int
forall a. Num a => a -> a -> a
+ Expr Id -> Int
n_cons Expr Id
e2
          n_cons (Lit {})    = Int
1
          n_cons Expr Id
_           = Int
0

    emit_trace :: (Bool, [CallPat]) -> (Bool, [CallPat])
emit_trace (Bool, [CallPat])
result
       | Bool
debugIsOn Bool -> Bool -> Bool
|| DynFlags -> Bool
hasPprDebug (ScEnv -> DynFlags
sc_dflags ScEnv
env)
         -- Suppress this scary message for ordinary users!  #5125
       = String -> SDoc -> (Bool, [CallPat]) -> (Bool, [CallPat])
forall a. String -> SDoc -> a -> a
pprTrace String
"SpecConstr" SDoc
msg (Bool, [CallPat])
result
       | Bool
otherwise
       = (Bool, [CallPat])
result
    msg :: SDoc
msg = [SDoc] -> SDoc
vcat [ [SDoc] -> SDoc
sep [ String -> SDoc
text String
"Function" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (Id -> SDoc
forall a. Outputable a => a -> SDoc
ppr Id
fn)
                     , Int -> SDoc -> SDoc
nest Int
2 (String -> SDoc
text String
"has" SDoc -> SDoc -> SDoc
<+>
                               Int -> SDoc -> SDoc
speakNOf Int
spec_count' (String -> SDoc
text String
"call pattern") SDoc -> SDoc -> SDoc
<> SDoc
comma SDoc -> SDoc -> SDoc
<+>
                               String -> SDoc
text String
"but the limit is" SDoc -> SDoc -> SDoc
<+> Int -> SDoc
int Int
max_specs) ]
               , String -> SDoc
text String
"Use -fspec-constr-count=n to set the bound"
               , String -> SDoc
text String
"done_spec_count =" SDoc -> SDoc -> SDoc
<+> Int -> SDoc
int Int
done_spec_count
               , String -> SDoc
text String
"Keeping " SDoc -> SDoc -> SDoc
<+> Int -> SDoc
int Int
n_remaining SDoc -> SDoc -> SDoc
<> String -> SDoc
text String
", out of" SDoc -> SDoc -> SDoc
<+> Int -> SDoc
int Int
n_pats
               , String -> SDoc
text String
"Discarding:" SDoc -> SDoc -> SDoc
<+> [CallPat] -> SDoc
forall a. Outputable a => a -> SDoc
ppr (Int -> [CallPat] -> [CallPat]
forall a. Int -> [a] -> [a]
drop Int
n_remaining [CallPat]
sorted_pats) ]


callToPats :: ScEnv -> [ArgOcc] -> Call -> UniqSM (Maybe CallPat)
        -- The [Var] is the variables to quantify over in the rule
        --      Type variables come first, since they may scope
        --      over the following term variables
        -- The [CoreExpr] are the argument patterns for the rule
callToPats :: ScEnv -> [ArgOcc] -> Call -> UniqSM (Maybe CallPat)
callToPats ScEnv
env [ArgOcc]
bndr_occs call :: Call
call@(Call Id
fn [Expr Id]
args ValueEnv
con_env)
  = do  { let in_scope :: InScopeSet
in_scope = Subst -> InScopeSet
substInScope (ScEnv -> Subst
sc_subst ScEnv
env)

        ; [(Bool, Expr Id, [Id])]
arg_tripples <- (Expr Id
 -> ArgOcc -> StrictnessMark -> UniqSM (Bool, Expr Id, [Id]))
-> [Expr Id]
-> [ArgOcc]
-> [StrictnessMark]
-> UniqSM [(Bool, Expr Id, [Id])]
forall (m :: * -> *) a b c d.
Monad m =>
(a -> b -> c -> m d) -> [a] -> [b] -> [c] -> m [d]
zipWith3M (ScEnv
-> InScopeSet
-> ValueEnv
-> Expr Id
-> ArgOcc
-> StrictnessMark
-> UniqSM (Bool, Expr Id, [Id])
argToPat ScEnv
env InScopeSet
in_scope ValueEnv
con_env) [Expr Id]
args [ArgOcc]
bndr_occs ((Expr Id -> StrictnessMark) -> [Expr Id] -> [StrictnessMark]
forall a b. (a -> b) -> [a] -> [b]
map (StrictnessMark -> Expr Id -> StrictnessMark
forall a b. a -> b -> a
const StrictnessMark
NotMarkedStrict) [Expr Id]
args)
                   -- This zip trims the args to be no longer than
                   -- the lambdas in the function definition (bndr_occs)

          -- Drop boring patterns from the end
          -- See Note [SpecConstr call patterns]
        ; let arg_tripples' :: [(Bool, Expr Id, [Id])]
arg_tripples' | Id -> Bool
isJoinId Id
fn = [(Bool, Expr Id, [Id])]
arg_tripples
                            | Bool
otherwise   = ((Bool, Expr Id, [Id]) -> Bool)
-> [(Bool, Expr Id, [Id])] -> [(Bool, Expr Id, [Id])]
forall a. (a -> Bool) -> [a] -> [a]
dropWhileEnd (Bool, Expr Id, [Id]) -> Bool
forall {b} {c}. (Bool, b, c) -> Bool
is_boring [(Bool, Expr Id, [Id])]
arg_tripples
              is_boring :: (Bool, b, c) -> Bool
is_boring (Bool
interesting, b
_,c
_) = Bool -> Bool
not Bool
interesting
              ([Bool]
interesting_s, [Expr Id]
pats, [[Id]]
cbv_ids) = [(Bool, Expr Id, [Id])] -> ([Bool], [Expr Id], [[Id]])
forall a b c. [(a, b, c)] -> ([a], [b], [c])
unzip3 [(Bool, Expr Id, [Id])]
arg_tripples'
              interesting :: Bool
interesting           = [Bool] -> Bool
forall (t :: * -> *). Foldable t => t Bool -> Bool
or [Bool]
interesting_s

        ; let pat_fvs :: [Id]
pat_fvs = [Expr Id] -> [Id]
exprsFreeVarsList [Expr Id]
pats
                -- To get determinism we need the list of free variables in
                -- deterministic order. Otherwise we end up creating
                -- lambdas with different argument orders. See
                -- determinism/simplCore/should_compile/spec-inline-determ.hs
                -- for an example. For explanation of determinism
                -- considerations See Note [Unique Determinism] in GHC.Types.Unique.

              in_scope_vars :: CoVarSet
in_scope_vars = InScopeSet -> CoVarSet
getInScopeVars InScopeSet
in_scope
              is_in_scope :: Id -> Bool
is_in_scope Id
v = Id
v Id -> CoVarSet -> Bool
`elemVarSet` CoVarSet
in_scope_vars
              qvars :: [Id]
qvars         = (Id -> Bool) -> [Id] -> [Id]
forall a. (a -> Bool) -> [a] -> [a]
filterOut Id -> Bool
is_in_scope [Id]
pat_fvs
                -- Quantify over variables that are not in scope
                -- at the call site
                -- See Note [Free type variables of the qvar types]
                -- See Note [Shadowing] at the top

              ([Id]
ktvs, [Id]
ids)   = (Id -> Bool) -> [Id] -> ([Id], [Id])
forall a. (a -> Bool) -> [a] -> ([a], [a])
partition Id -> Bool
isTyVar [Id]
qvars
              qvars' :: [Id]
qvars'        = [Id] -> [Id]
scopedSort [Id]
ktvs [Id] -> [Id] -> [Id]
forall a. [a] -> [a] -> [a]
++ (Id -> Id) -> [Id] -> [Id]
forall a b. (a -> b) -> [a] -> [b]
map Id -> Id
sanitise [Id]
ids
                -- Order into kind variables, type variables, term variables
                -- The kind of a type variable may mention a kind variable
                -- and the type of a term variable may mention a type variable

              sanitise :: Id -> Id
sanitise Id
id   = (Type -> Type) -> Id -> Id
updateIdTypeAndMult Type -> Type
expandTypeSynonyms Id
id
                -- See Note [Free type variables of the qvar types]

              -- Bad coercion variables: see Note [SpecConstr and casts]
              bad_covars :: CoVarSet
              bad_covars :: CoVarSet
bad_covars = (Expr Id -> CoVarSet) -> [Expr Id] -> CoVarSet
forall a. (a -> CoVarSet) -> [a] -> CoVarSet
mapUnionVarSet Expr Id -> CoVarSet
get_bad_covars [Expr Id]
pats
              get_bad_covars :: CoreArg -> CoVarSet
              get_bad_covars :: Expr Id -> CoVarSet
get_bad_covars (Type Type
ty) = (Id -> Bool) -> CoVarSet -> CoVarSet
filterVarSet Id -> Bool
bad_covar (Type -> CoVarSet
tyCoVarsOfType Type
ty)
              get_bad_covars Expr Id
_         = CoVarSet
emptyVarSet
              bad_covar :: Id -> Bool
bad_covar Id
v = Id -> Bool
isId Id
v Bool -> Bool -> Bool
&& Bool -> Bool
not (Id -> Bool
is_in_scope Id
v)

        ; -- pprTrace "callToPats"  (ppr args $$ ppr bndr_occs) $
          Bool
-> String
-> SDoc
-> UniqSM (Maybe CallPat)
-> UniqSM (Maybe CallPat)
forall a. HasCallStack => Bool -> String -> SDoc -> a -> a
warnPprTrace (Bool -> Bool
not (CoVarSet -> Bool
isEmptyVarSet CoVarSet
bad_covars))
              String
"SpecConstr: bad covars"
              (CoVarSet -> SDoc
forall a. Outputable a => a -> SDoc
ppr CoVarSet
bad_covars SDoc -> SDoc -> SDoc
$$ Call -> SDoc
forall a. Outputable a => a -> SDoc
ppr Call
call) (UniqSM (Maybe CallPat) -> UniqSM (Maybe CallPat))
-> UniqSM (Maybe CallPat) -> UniqSM (Maybe CallPat)
forall a b. (a -> b) -> a -> b
$
          if Bool
interesting Bool -> Bool -> Bool
&& CoVarSet -> Bool
isEmptyVarSet CoVarSet
bad_covars
          then do
              -- pprTraceM "callToPatsOut" (
              --         text "fn:" <+> ppr fn $$
              --         text "args:" <+> ppr args $$
              --         text "in_scope:" <+> ppr in_scope $$
              --         -- text "in_scope:" <+> ppr in_scope $$
              --         text "pat_fvs:" <+> ppr pat_fvs
              --       )
              --   ppr (CP { cp_qvars = qvars', cp_args = pats })) >>
              Maybe CallPat -> UniqSM (Maybe CallPat)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (CallPat -> Maybe CallPat
forall a. a -> Maybe a
Just (CP { cp_qvars :: [Id]
cp_qvars = [Id]
qvars', cp_args :: [Expr Id]
cp_args = [Expr Id]
pats, cp_strict_args :: [Id]
cp_strict_args = [[Id]] -> [Id]
forall (t :: * -> *) a. Foldable t => t [a] -> [a]
concat [[Id]]
cbv_ids }))
          else Maybe CallPat -> UniqSM (Maybe CallPat)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return Maybe CallPat
forall a. Maybe a
Nothing }

    -- argToPat takes an actual argument, and returns an abstracted
    -- version, consisting of just the "constructor skeleton" of the
    -- argument, with non-constructor sub-expression replaced by new
    -- placeholder variables.  For example:
    --    C a (D (f x) (g y))  ==>  C p1 (D p2 p3)

argToPat :: ScEnv
         -> InScopeSet                  -- What's in scope at the fn defn site
         -> ValueEnv                    -- ValueEnv at the call site
         -> CoreArg                     -- A call arg (or component thereof)
         -> ArgOcc
         -> StrictnessMark              -- Tells us if this argument is a strict field of a data constructor
                                        -- See Note [SpecConstr and strict fields]
         -> UniqSM (Bool, CoreArg, [Id])

-- Returns (interesting, pat),
-- where pat is the pattern derived from the argument
--            interesting=True if the pattern is non-trivial (not a variable or type)
-- E.g.         x:xs         --> (True, x:xs)
--              f xs         --> (False, w)        where w is a fresh wildcard
--              (f xs, 'c')  --> (True, (w, 'c'))  where w is a fresh wildcard
--              \x. x+y      --> (True, \x. x+y)
--              lvl7         --> (True, lvl7)      if lvl7 is bound
--                                                 somewhere further out

argToPat :: ScEnv
-> InScopeSet
-> ValueEnv
-> Expr Id
-> ArgOcc
-> StrictnessMark
-> UniqSM (Bool, Expr Id, [Id])
argToPat ScEnv
env InScopeSet
in_scope ValueEnv
val_env Expr Id
arg ArgOcc
arg_occ StrictnessMark
arg_str
  = do
    -- pprTraceM "argToPatIn" (ppr arg)
    !(Bool, Expr Id, [Id])
res <- ScEnv
-> InScopeSet
-> ValueEnv
-> Expr Id
-> ArgOcc
-> StrictnessMark
-> UniqSM (Bool, Expr Id, [Id])
argToPat1 ScEnv
env InScopeSet
in_scope ValueEnv
val_env Expr Id
arg ArgOcc
arg_occ StrictnessMark
arg_str
    -- pprTraceM "argToPatOut" (ppr res)
    (Bool, Expr Id, [Id]) -> UniqSM (Bool, Expr Id, [Id])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (Bool, Expr Id, [Id])
res

argToPat1 :: ScEnv
  -> InScopeSet
  -> ValueEnv
  -> Expr CoreBndr
  -> ArgOcc
  -> StrictnessMark
  -> UniqSM (Bool, Expr CoreBndr, [Id])
argToPat1 :: ScEnv
-> InScopeSet
-> ValueEnv
-> Expr Id
-> ArgOcc
-> StrictnessMark
-> UniqSM (Bool, Expr Id, [Id])
argToPat1 ScEnv
_env InScopeSet
_in_scope ValueEnv
_val_env arg :: Expr Id
arg@(Type {}) ArgOcc
_arg_occ StrictnessMark
_arg_str
  = (Bool, Expr Id, [Id]) -> UniqSM (Bool, Expr Id, [Id])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (Bool
False, Expr Id
arg, [])

argToPat1 ScEnv
env InScopeSet
in_scope ValueEnv
val_env (Tick CoreTickish
_ Expr Id
arg) ArgOcc
arg_occ StrictnessMark
arg_str
  = ScEnv
-> InScopeSet
-> ValueEnv
-> Expr Id
-> ArgOcc
-> StrictnessMark
-> UniqSM (Bool, Expr Id, [Id])
argToPat ScEnv
env InScopeSet
in_scope ValueEnv
val_env Expr Id
arg ArgOcc
arg_occ StrictnessMark
arg_str
        -- Note [Tick annotations in call patterns]
        -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        -- Ignore Notes.  In particular, we want to ignore any InlineMe notes
        -- Perhaps we should not ignore profiling notes, but I'm going to
        -- ride roughshod over them all for now.
        --- See Note [Tick annotations in RULE matching] in GHC.Core.Rules

argToPat1 ScEnv
env InScopeSet
in_scope ValueEnv
val_env (Let CoreBind
_ Expr Id
arg) ArgOcc
arg_occ StrictnessMark
arg_str
  = ScEnv
-> InScopeSet
-> ValueEnv
-> Expr Id
-> ArgOcc
-> StrictnessMark
-> UniqSM (Bool, Expr Id, [Id])
argToPat ScEnv
env InScopeSet
in_scope ValueEnv
val_env Expr Id
arg ArgOcc
arg_occ StrictnessMark
arg_str
        -- See Note [Matching lets] in "GHC.Core.Rules"
        -- Look through let expressions
        -- e.g.         f (let v = rhs in (v,w))
        -- Here we can specialise for f (v,w)
        -- because the rule-matcher will look through the let.

{- Disabled; see Note [Matching cases] in "GHC.Core.Rules"
argToPat env in_scope val_env (Case scrut _ _ [(_, _, rhs)]) arg_occ
  | exprOkForSpeculation scrut  -- See Note [Matching cases] in "GHC.Core.Rules"
  = argToPat env in_scope val_env rhs arg_occ
-}

argToPat1 ScEnv
env InScopeSet
in_scope ValueEnv
val_env (Cast Expr Id
arg Coercion
co) ArgOcc
arg_occ StrictnessMark
arg_str
  | Bool -> Bool
not (ScEnv -> Type -> Bool
ignoreType ScEnv
env Type
ty2)
  = do  { (Bool
interesting, Expr Id
arg', [Id]
strict_args) <- ScEnv
-> InScopeSet
-> ValueEnv
-> Expr Id
-> ArgOcc
-> StrictnessMark
-> UniqSM (Bool, Expr Id, [Id])
argToPat ScEnv
env InScopeSet
in_scope ValueEnv
val_env Expr Id
arg ArgOcc
arg_occ StrictnessMark
arg_str
        ; if Bool -> Bool
not Bool
interesting then
                Type -> StrictnessMark -> UniqSM (Bool, Expr Id, [Id])
wildCardPat Type
ty2 StrictnessMark
arg_str
          else do
        { -- Make a wild-card pattern for the coercion
          Unique
uniq <- UniqSM Unique
forall (m :: * -> *). MonadUnique m => m Unique
getUniqueM
        ; let co_name :: Name
co_name = Unique -> FastString -> Name
mkSysTvName Unique
uniq (String -> FastString
fsLit String
"sg")
              co_var :: Id
co_var  = Name -> Type -> Id
mkCoVar Name
co_name (Role -> Type -> Type -> Type
mkCoercionType Role
Representational Type
ty1 Type
ty2)
        ; (Bool, Expr Id, [Id]) -> UniqSM (Bool, Expr Id, [Id])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (Bool
interesting, Expr Id -> Coercion -> Expr Id
forall b. Expr b -> Coercion -> Expr b
Cast Expr Id
arg' (Id -> Coercion
mkCoVarCo Id
co_var), [Id]
strict_args) } }
  where
    Pair Type
ty1 Type
ty2 = Coercion -> Pair Type
coercionKind Coercion
co



{-      Disabling lambda specialisation for now
        It's fragile, and the spec_loop can be infinite
argToPat in_scope val_env arg arg_occ
  | is_value_lam arg
  = return (True, arg)
  where
    is_value_lam (Lam v e)         -- Spot a value lambda, even if
        | isId v       = True      -- it is inside a type lambda
        | otherwise    = is_value_lam e
    is_value_lam other = False
-}

  -- Check for a constructor application
  -- NB: this *precedes* the Var case, so that we catch nullary constrs
argToPat1 ScEnv
env InScopeSet
in_scope ValueEnv
val_env Expr Id
arg ArgOcc
arg_occ StrictnessMark
_arg_str
  | Just (ConVal (DataAlt DataCon
dc) [Expr Id]
args) <- ValueEnv -> Expr Id -> Maybe Value
isValue ValueEnv
val_env Expr Id
arg
  , Bool -> Bool
not (ScEnv -> DataCon -> Bool
ignoreDataCon ScEnv
env DataCon
dc)        -- See Note [NoSpecConstr]
  , Just [ArgOcc]
arg_occs <- DataCon -> Maybe [ArgOcc]
mb_scrut DataCon
dc
  = do { let ([Expr Id]
ty_args, [Expr Id]
rest_args) = [Id] -> [Expr Id] -> ([Expr Id], [Expr Id])
forall b a. [b] -> [a] -> ([a], [a])
splitAtList (DataCon -> [Id]
dataConUnivTyVars DataCon
dc) [Expr Id]
args
             con_str, matched_str :: [StrictnessMark]
             -- con_str corrresponds 1-1 with the /value/ arguments
             -- matched_str corresponds 1-1 with /all/ arguments
             con_str :: [StrictnessMark]
con_str = DataCon -> [StrictnessMark]
dataConRepStrictness DataCon
dc
             matched_str :: [StrictnessMark]
matched_str = [StrictnessMark] -> [Expr Id] -> [StrictnessMark]
match_vals [StrictnessMark]
con_str [Expr Id]
rest_args
      --  ; pprTraceM "bangs" (ppr (length rest_args == length con_str) $$
      --       ppr dc $$
      --       ppr con_str $$
      --       ppr rest_args $$
      --       ppr (map isTypeArg rest_args))
       ; [(Bool, Expr Id, [Id])]
prs <- (Expr Id
 -> ArgOcc -> StrictnessMark -> UniqSM (Bool, Expr Id, [Id]))
-> [Expr Id]
-> [ArgOcc]
-> [StrictnessMark]
-> UniqSM [(Bool, Expr Id, [Id])]
forall (m :: * -> *) a b c d.
Monad m =>
(a -> b -> c -> m d) -> [a] -> [b] -> [c] -> m [d]
zipWith3M (ScEnv
-> InScopeSet
-> ValueEnv
-> Expr Id
-> ArgOcc
-> StrictnessMark
-> UniqSM (Bool, Expr Id, [Id])
argToPat ScEnv
env InScopeSet
in_scope ValueEnv
val_env) [Expr Id]
rest_args [ArgOcc]
arg_occs [StrictnessMark]
matched_str
       ; let args' :: [Expr Id]
args' = ((Bool, Expr Id, [Id]) -> Expr Id)
-> [(Bool, Expr Id, [Id])] -> [Expr Id]
forall a b. (a -> b) -> [a] -> [b]
map (Bool, Expr Id, [Id]) -> Expr Id
forall a b c. (a, b, c) -> b
sndOf3 [(Bool, Expr Id, [Id])]
prs :: [CoreArg]
       ; Bool -> SDoc -> UniqSM () -> UniqSM ()
forall a. HasCallStack => Bool -> SDoc -> a -> a
assertPpr ([StrictnessMark] -> Int
forall a. [a] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [StrictnessMark]
con_str Int -> Int -> Bool
forall a. Eq a => a -> a -> Bool
== [Expr Id] -> Int
forall a. [a] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length ((Expr Id -> Bool) -> [Expr Id] -> [Expr Id]
forall a. (a -> Bool) -> [a] -> [a]
filter Expr Id -> Bool
isRuntimeArg [Expr Id]
rest_args))
            ( [StrictnessMark] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [StrictnessMark]
con_str SDoc -> SDoc -> SDoc
$$ [Expr Id] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Expr Id]
rest_args SDoc -> SDoc -> SDoc
$$
              Int -> SDoc
forall a. Outputable a => a -> SDoc
ppr ([StrictnessMark] -> Int
forall a. [a] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [StrictnessMark]
con_str) SDoc -> SDoc -> SDoc
$$ Int -> SDoc
forall a. Outputable a => a -> SDoc
ppr ([Expr Id] -> Int
forall a. [a] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [Expr Id]
rest_args)
            ) (UniqSM () -> UniqSM ()) -> UniqSM () -> UniqSM ()
forall a b. (a -> b) -> a -> b
$ () -> UniqSM ()
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return ()
       ; (Bool, Expr Id, [Id]) -> UniqSM (Bool, Expr Id, [Id])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (Bool
True, DataCon -> [Expr Id] -> Expr Id
forall b. DataCon -> [Arg b] -> Arg b
mkConApp DataCon
dc ([Expr Id]
ty_args [Expr Id] -> [Expr Id] -> [Expr Id]
forall a. [a] -> [a] -> [a]
++ [Expr Id]
args'), [[Id]] -> [Id]
forall (t :: * -> *) a. Foldable t => t [a] -> [a]
concat (((Bool, Expr Id, [Id]) -> [Id])
-> [(Bool, Expr Id, [Id])] -> [[Id]]
forall a b. (a -> b) -> [a] -> [b]
map (Bool, Expr Id, [Id]) -> [Id]
forall a b c. (a, b, c) -> c
thdOf3 [(Bool, Expr Id, [Id])]
prs)) }
  where
    mb_scrut :: DataCon -> Maybe [ArgOcc]
mb_scrut DataCon
dc = case ArgOcc
arg_occ of
                ScrutOcc DataConEnv [ArgOcc]
bs | Just [ArgOcc]
occs <- DataConEnv [ArgOcc] -> DataCon -> Maybe [ArgOcc]
forall key elt. Uniquable key => UniqFM key elt -> key -> Maybe elt
lookupUFM DataConEnv [ArgOcc]
bs DataCon
dc
                            -> [ArgOcc] -> Maybe [ArgOcc]
forall a. a -> Maybe a
Just ([ArgOcc]
occs)  -- See Note [Reboxing]
                ArgOcc
_other      | ScEnv -> Bool
sc_force ScEnv
env Bool -> Bool -> Bool
|| ScEnv -> Bool
sc_keen ScEnv
env
                            -> [ArgOcc] -> Maybe [ArgOcc]
forall a. a -> Maybe a
Just (ArgOcc -> [ArgOcc]
forall a. a -> [a]
repeat ArgOcc
UnkOcc)
                            | Bool
otherwise
                            -> Maybe [ArgOcc]
forall a. Maybe a
Nothing
    match_vals :: [StrictnessMark] -> [Expr Id] -> [StrictnessMark]
match_vals [StrictnessMark]
bangs (Expr Id
arg:[Expr Id]
args)
      | Expr Id -> Bool
forall b. Expr b -> Bool
isTypeArg Expr Id
arg
      = StrictnessMark
NotMarkedStrict StrictnessMark -> [StrictnessMark] -> [StrictnessMark]
forall a. a -> [a] -> [a]
: [StrictnessMark] -> [Expr Id] -> [StrictnessMark]
match_vals [StrictnessMark]
bangs [Expr Id]
args
      | (StrictnessMark
b:[StrictnessMark]
bs) <- [StrictnessMark]
bangs
      = StrictnessMark
b StrictnessMark -> [StrictnessMark] -> [StrictnessMark]
forall a. a -> [a] -> [a]
: [StrictnessMark] -> [Expr Id] -> [StrictnessMark]
match_vals [StrictnessMark]
bs [Expr Id]
args
    match_vals [] [] = []
    match_vals [StrictnessMark]
as [Expr Id]
bs =
        String -> SDoc -> [StrictnessMark]
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"spec-constr:argToPat - Bangs don't match value arguments"
            (String -> SDoc
text String
"arg:" SDoc -> SDoc -> SDoc
<> Expr Id -> SDoc
forall a. Outputable a => a -> SDoc
ppr Expr Id
arg SDoc -> SDoc -> SDoc
$$
             String -> SDoc
text String
"remaining args:" SDoc -> SDoc -> SDoc
<> [StrictnessMark] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [StrictnessMark]
as SDoc -> SDoc -> SDoc
$$
             String -> SDoc
text String
"remaining bangs:" SDoc -> SDoc -> SDoc
<> [Expr Id] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Expr Id]
bs)

  -- Check if the argument is a variable that
  --    (a) is used in an interesting way in the function body
  ---       i.e. ScrutOcc. UnkOcc and NoOcc are not interesting
  --        (NoOcc means we could drop the argument, but that's the
  --         business of absence analysis, not SpecConstr.)
  --    (b) we know what its value is
  -- In that case it counts as "interesting"
argToPat1 ScEnv
env InScopeSet
in_scope ValueEnv
val_env (Var Id
v) ArgOcc
arg_occ StrictnessMark
arg_str
  | ScEnv -> Bool
sc_force ScEnv
env Bool -> Bool -> Bool
|| case ArgOcc
arg_occ of { ScrutOcc {} -> Bool
True
                                    ; ArgOcc
UnkOcc      -> Bool
False
                                    ; ArgOcc
NoOcc       -> Bool
False } -- (a)
  , Bool
is_value                                                 -- (b)
       -- Ignoring sc_keen here to avoid gratuitously incurring Note [Reboxing]
       -- So sc_keen focused just on f (I# x), where we have freshly-allocated
       -- box that we can eliminate in the caller
  , Bool -> Bool
not (ScEnv -> Type -> Bool
ignoreType ScEnv
env (Id -> Type
varType Id
v))
  -- See Note [SpecConstr and strict fields]
  = (Bool, Expr Id, [Id]) -> UniqSM (Bool, Expr Id, [Id])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (Bool
True, Id -> Expr Id
forall b. Id -> Expr b
Var Id
v, if StrictnessMark -> Bool
isMarkedStrict StrictnessMark
arg_str then [Id
v] else [Id]
forall a. Monoid a => a
mempty)
  where
    is_value :: Bool
is_value
        | Id -> Bool
isLocalId Id
v = Id
v Id -> InScopeSet -> Bool
`elemInScopeSet` InScopeSet
in_scope
                        Bool -> Bool -> Bool
&& Maybe Value -> Bool
forall a. Maybe a -> Bool
isJust (ValueEnv -> Id -> Maybe Value
forall a. VarEnv a -> Id -> Maybe a
lookupVarEnv ValueEnv
val_env Id
v)
                -- Local variables have values in val_env
        | Bool
otherwise   = Unfolding -> Bool
isValueUnfolding (Id -> Unfolding
idUnfolding Id
v)
                -- Imports have unfoldings

--      I'm really not sure what this comment means
--      And by not wild-carding we tend to get forall'd
--      variables that are in scope, which in turn can
--      expose the weakness in let-matching
--      See Note [Matching lets] in GHC.Core.Rules

  -- Check for a variable bound inside the function.
  -- Don't make a wild-card, because we may usefully share
  --    e.g.  f a = let x = ... in f (x,x)
  -- NB: this case follows the lambda and con-app cases!!
-- argToPat _in_scope _val_env (Var v) _arg_occ
--   = return (False, Var v)
        -- SLPJ : disabling this to avoid proliferation of versions
        -- also works badly when thinking about seeding the loop
        -- from the body of the let
        --       f x y = letrec g z = ... in g (x,y)
        -- We don't want to specialise for that *particular* x,y

  -- The default case: make a wild-card
  -- We use this for coercions too
argToPat1 ScEnv
_env InScopeSet
_in_scope ValueEnv
_val_env Expr Id
arg ArgOcc
_arg_occ StrictnessMark
arg_str
  = Type -> StrictnessMark -> UniqSM (Bool, Expr Id, [Id])
wildCardPat ((() :: Constraint) => Expr Id -> Type
Expr Id -> Type
exprType Expr Id
arg) StrictnessMark
arg_str

-- | wildCardPats are always boring
wildCardPat :: Type -> StrictnessMark -> UniqSM (Bool, CoreArg, [Id])
wildCardPat :: Type -> StrictnessMark -> UniqSM (Bool, Expr Id, [Id])
wildCardPat Type
ty StrictnessMark
str
  = do { Id
id <- FastString -> Type -> Type -> UniqSM Id
forall (m :: * -> *).
MonadUnique m =>
FastString -> Type -> Type -> m Id
mkSysLocalOrCoVarM (String -> FastString
fsLit String
"sc") Type
Many Type
ty
       -- ; pprTraceM "wildCardPat" (ppr id' <+> ppr (idUnfolding id'))
       ; (Bool, Expr Id, [Id]) -> UniqSM (Bool, Expr Id, [Id])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (Bool
False, Id -> Expr Id
forall b. Id -> Expr b
varToCoreExpr Id
id, if StrictnessMark -> Bool
isMarkedStrict StrictnessMark
str then [Id
id] else []) }

isValue :: ValueEnv -> CoreExpr -> Maybe Value
isValue :: ValueEnv -> Expr Id -> Maybe Value
isValue ValueEnv
_env (Lit Literal
lit)
  | Literal -> Bool
litIsLifted Literal
lit = Maybe Value
forall a. Maybe a
Nothing
  | Bool
otherwise       = Value -> Maybe Value
forall a. a -> Maybe a
Just (AltCon -> [Expr Id] -> Value
ConVal (Literal -> AltCon
LitAlt Literal
lit) [])

isValue ValueEnv
env (Var Id
v)
  | Just Value
cval <- ValueEnv -> Id -> Maybe Value
forall a. VarEnv a -> Id -> Maybe a
lookupVarEnv ValueEnv
env Id
v
  = Value -> Maybe Value
forall a. a -> Maybe a
Just Value
cval  -- You might think we could look in the idUnfolding here
               -- but that doesn't take account of which branch of a
               -- case we are in, which is the whole point

  | Bool -> Bool
not (Id -> Bool
isLocalId Id
v) Bool -> Bool -> Bool
&& Unfolding -> Bool
isCheapUnfolding Unfolding
unf
  = ValueEnv -> Expr Id -> Maybe Value
isValue ValueEnv
env (Unfolding -> Expr Id
unfoldingTemplate Unfolding
unf)
  where
    unf :: Unfolding
unf = Id -> Unfolding
idUnfolding Id
v
        -- However we do want to consult the unfolding
        -- as well, for let-bound constructors!

isValue ValueEnv
env (Lam Id
b Expr Id
e)
  | Id -> Bool
isTyVar Id
b = case ValueEnv -> Expr Id -> Maybe Value
isValue ValueEnv
env Expr Id
e of
                  Just Value
_  -> Value -> Maybe Value
forall a. a -> Maybe a
Just Value
LambdaVal
                  Maybe Value
Nothing -> Maybe Value
forall a. Maybe a
Nothing
  | Bool
otherwise = Value -> Maybe Value
forall a. a -> Maybe a
Just Value
LambdaVal

isValue ValueEnv
env (Tick CoreTickish
t Expr Id
e)
  | Bool -> Bool
not (CoreTickish -> Bool
forall (pass :: TickishPass). GenTickish pass -> Bool
tickishIsCode CoreTickish
t)
  = ValueEnv -> Expr Id -> Maybe Value
isValue ValueEnv
env Expr Id
e

isValue ValueEnv
_env Expr Id
expr       -- Maybe it's a constructor application
  | (Var Id
fun, [Expr Id]
args, [CoreTickish]
_) <- (CoreTickish -> Bool)
-> Expr Id -> (Expr Id, [Expr Id], [CoreTickish])
forall b.
(CoreTickish -> Bool)
-> Expr b -> (Expr b, [Expr b], [CoreTickish])
collectArgsTicks (Bool -> Bool
not (Bool -> Bool) -> (CoreTickish -> Bool) -> CoreTickish -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. CoreTickish -> Bool
forall (pass :: TickishPass). GenTickish pass -> Bool
tickishIsCode) Expr Id
expr
  = case Id -> Maybe DataCon
isDataConWorkId_maybe Id
fun of

        Just DataCon
con | [Expr Id]
args [Expr Id] -> Int -> Bool
forall a. [a] -> Int -> Bool
`lengthAtLeast` DataCon -> Int
dataConRepArity DataCon
con
                -- Check saturated; might be > because the
                --                  arity excludes type args
                -> Value -> Maybe Value
forall a. a -> Maybe a
Just (AltCon -> [Expr Id] -> Value
ConVal (DataCon -> AltCon
DataAlt DataCon
con) [Expr Id]
args)

        Maybe DataCon
_other | [Expr Id] -> Int
forall b. [Arg b] -> Int
valArgCount [Expr Id]
args Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
< Id -> Int
idArity Id
fun
                -- Under-applied function
               -> Value -> Maybe Value
forall a. a -> Maybe a
Just Value
LambdaVal        -- Partial application

        Maybe DataCon
_other -> Maybe Value
forall a. Maybe a
Nothing

isValue ValueEnv
_env Expr Id
_expr = Maybe Value
forall a. Maybe a
Nothing

valueIsWorkFree :: Value -> Bool
valueIsWorkFree :: Value -> Bool
valueIsWorkFree Value
LambdaVal       = Bool
True
valueIsWorkFree (ConVal AltCon
_ [Expr Id]
args) = (Expr Id -> Bool) -> [Expr Id] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
all Expr Id -> Bool
exprIsWorkFree [Expr Id]
args

samePat :: CallPat -> CallPat -> Bool
samePat :: CallPat -> CallPat -> Bool
samePat (CP { cp_qvars :: CallPat -> [Id]
cp_qvars = [Id]
vs1, cp_args :: CallPat -> [Expr Id]
cp_args = [Expr Id]
as1 })
        (CP { cp_qvars :: CallPat -> [Id]
cp_qvars = [Id]
vs2, cp_args :: CallPat -> [Expr Id]
cp_args = [Expr Id]
as2 })
  = (Expr Id -> Expr Id -> Bool) -> [Expr Id] -> [Expr Id] -> Bool
forall a b. (a -> b -> Bool) -> [a] -> [b] -> Bool
all2 Expr Id -> Expr Id -> Bool
same [Expr Id]
as1 [Expr Id]
as2
  where
    -- If the args are the same, their strictness marks will be too so we don't compare those.
    same :: Expr Id -> Expr Id -> Bool
same (Var Id
v1) (Var Id
v2)
        | Id
v1 Id -> [Id] -> Bool
forall a. Eq a => a -> [a] -> Bool
forall (t :: * -> *) a. (Foldable t, Eq a) => a -> t a -> Bool
`elem` [Id]
vs1 = Id
v2 Id -> [Id] -> Bool
forall a. Eq a => a -> [a] -> Bool
forall (t :: * -> *) a. (Foldable t, Eq a) => a -> t a -> Bool
`elem` [Id]
vs2
        | Id
v2 Id -> [Id] -> Bool
forall a. Eq a => a -> [a] -> Bool
forall (t :: * -> *) a. (Foldable t, Eq a) => a -> t a -> Bool
`elem` [Id]
vs2 = Bool
False
        | Bool
otherwise     = Id
v1 Id -> Id -> Bool
forall a. Eq a => a -> a -> Bool
== Id
v2

    same (Lit Literal
l1)    (Lit Literal
l2)    = Literal
l1Literal -> Literal -> Bool
forall a. Eq a => a -> a -> Bool
==Literal
l2
    same (App Expr Id
f1 Expr Id
a1) (App Expr Id
f2 Expr Id
a2) = Expr Id -> Expr Id -> Bool
same Expr Id
f1 Expr Id
f2 Bool -> Bool -> Bool
&& Expr Id -> Expr Id -> Bool
same Expr Id
a1 Expr Id
a2

    same (Type {}) (Type {}) = Bool
True     -- Note [Ignore type differences]
    same (Coercion {}) (Coercion {}) = Bool
True
    same (Tick CoreTickish
_ Expr Id
e1) Expr Id
e2 = Expr Id -> Expr Id -> Bool
same Expr Id
e1 Expr Id
e2  -- Ignore casts and notes
    same (Cast Expr Id
e1 Coercion
_) Expr Id
e2 = Expr Id -> Expr Id -> Bool
same Expr Id
e1 Expr Id
e2
    same Expr Id
e1 (Tick CoreTickish
_ Expr Id
e2) = Expr Id -> Expr Id -> Bool
same Expr Id
e1 Expr Id
e2
    same Expr Id
e1 (Cast Expr Id
e2 Coercion
_) = Expr Id -> Expr Id -> Bool
same Expr Id
e1 Expr Id
e2

    same Expr Id
e1 Expr Id
e2 = Bool -> String -> SDoc -> Bool -> Bool
forall a. HasCallStack => Bool -> String -> SDoc -> a -> a
warnPprTrace (Expr Id -> Bool
forall b. Expr b -> Bool
bad Expr Id
e1 Bool -> Bool -> Bool
|| Expr Id -> Bool
forall b. Expr b -> Bool
bad Expr Id
e2) String
"samePat" (Expr Id -> SDoc
forall a. Outputable a => a -> SDoc
ppr Expr Id
e1 SDoc -> SDoc -> SDoc
$$ Expr Id -> SDoc
forall a. Outputable a => a -> SDoc
ppr Expr Id
e2) (Bool -> Bool) -> Bool -> Bool
forall a b. (a -> b) -> a -> b
$
                 Bool
False  -- Let, lambda, case should not occur
    bad :: Expr b -> Bool
bad (Case {}) = Bool
True
    bad (Let {})  = Bool
True
    bad (Lam {})  = Bool
True
    bad Expr b
_other    = Bool
False

{-
Note [Ignore type differences]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We do not want to generate specialisations where the call patterns
differ only in their type arguments!  Not only is it utterly useless,
but it also means that (with polymorphic recursion) we can generate
an infinite number of specialisations. Example is Data.Sequence.adjustTree,
I think.
-}