{-
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}
-}

{-# LANGUAGE CPP #-}

module SpecConstr(
        specConstrProgram,
        SpecConstrAnnotation(..)
    ) where

#include "HsVersions.h"

import GhcPrelude

import CoreSyn
import CoreSubst
import CoreUtils
import CoreUnfold       ( couldBeSmallEnoughToInline )
import CoreFVs          ( exprsFreeVarsList )
import CoreMonad
import Literal          ( litIsLifted )
import HscTypes         ( ModGuts(..) )
import WwLib            ( isWorkerSmallEnough, mkWorkerArgs )
import DataCon
import Coercion         hiding( substCo )
import Rules
import Type             hiding ( substTy )
import TyCon            ( tyConName )
import Id
import PprCore          ( pprParendExpr )
import MkCore           ( mkImpossibleExpr )
import VarEnv
import VarSet
import Name
import BasicTypes
import DynFlags         ( DynFlags(..), GeneralFlag( Opt_SpecConstrKeen )
                        , gopt, hasPprDebug )
import Maybes           ( orElse, catMaybes, isJust, isNothing )
import Demand
import GHC.Serialized   ( deserializeWithData )
import Util
import Pair
import UniqSupply
import Outputable
import FastString
import UniqFM
import MonadUtils
import Control.Monad    ( zipWithM )
import Data.List
import PrelNames        ( specTyConName )
import Module
import TyCon ( TyCon )
import GHC.Exts( SpecConstrAnnotation(..) )
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 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; Trac #4448)
  * Only specialise on recursive types a finite number of times
        (see is_too_recursive; Trac #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.)  Trac #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 Trac #5550.   Also Trac #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?)

-----------------------------------------------------
                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 guts :: 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
      UniqFM SpecConstrAnnotation
annos  <- ([Word8] -> SpecConstrAnnotation)
-> ModGuts -> CoreM (UniqFM SpecConstrAnnotation)
forall a.
Typeable a =>
([Word8] -> a) -> ModGuts -> CoreM (UniqFM 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
      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]
                    (env :: ScEnv
env, binds :: [CoreBind]
binds) <- ScEnv -> [CoreBind] -> UniqSM (ScEnv, [CoreBind])
goEnv (DynFlags -> Module -> UniqFM SpecConstrAnnotation -> ScEnv
initScEnv DynFlags
dflags Module
this_mod UniqFM 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 (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 env :: ScEnv
env []            = (ScEnv, [CoreBind]) -> UniqSM (ScEnv, [CoreBind])
forall (m :: * -> *) a. Monad m => a -> m a
return (ScEnv
env, [])
    goEnv env :: ScEnv
env (bind :: CoreBind
bind:binds :: [CoreBind]
binds)  = do (env' :: ScEnv
env', bind' :: CoreBind
bind')   <- ScEnv -> CoreBind -> UniqSM (ScEnv, CoreBind)
scTopBindEnv ScEnv
env CoreBind
bind
                                 (env'' :: ScEnv
env'', binds' :: [CoreBind]
binds') <- ScEnv -> [CoreBind] -> UniqSM (ScEnv, [CoreBind])
goEnv ScEnv
env' [CoreBind]
binds
                                 (ScEnv, [CoreBind]) -> UniqSM (ScEnv, [CoreBind])
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 _   _   []           = [CoreBind] -> UniqSM [CoreBind]
forall (m :: * -> *) a. Monad m => a -> m a
return []
    go env :: ScEnv
env usg :: ScUsage
usg (bind :: CoreBind
bind:binds :: [CoreBind]
binds) = do (usg' :: ScUsage
usg', bind' :: 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 (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 Trac #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 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 scrutinied 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 speicalise whenever
the function is applied to a data constructor.
-}

data ScEnv = SCE { ScEnv -> DynFlags
sc_dflags    :: DynFlags,
                   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 -> UniqFM SpecConstrAnnotation
sc_annotations :: UniqFM 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 con :: AltCon
con args :: [CoreArg]
args) = AltCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr AltCon
con SDoc -> SDoc -> SDoc
<+> [CoreArg] -> SDoc
forall a. Outputable a => [a] -> SDoc
interpp'SP [CoreArg]
args
   ppr LambdaVal         = String -> SDoc
text "<Lambda>"

---------------------
initScEnv :: DynFlags -> Module -> UniqFM SpecConstrAnnotation -> ScEnv
initScEnv :: DynFlags -> Module -> UniqFM SpecConstrAnnotation -> ScEnv
initScEnv dflags :: DynFlags
dflags this_mod :: Module
this_mod anns :: UniqFM SpecConstrAnnotation
anns
  = $WSCE :: DynFlags
-> Module
-> Maybe Int
-> Maybe Int
-> Int
-> Bool
-> Bool
-> Subst
-> HowBoundEnv
-> ValueEnv
-> UniqFM SpecConstrAnnotation
-> ScEnv
SCE { sc_dflags :: DynFlags
sc_dflags      = 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 :: UniqFM SpecConstrAnnotation
sc_annotations = UniqFM 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 RecFun = String -> SDoc
text "RecFun"
  ppr RecArg = String -> SDoc
text "RecArg"

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

lookupHowBound :: ScEnv -> Id -> Maybe HowBound
lookupHowBound :: ScEnv -> Id -> Maybe HowBound
lookupHowBound env :: ScEnv
env id :: 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 -> CoreArg
scSubstId env :: ScEnv
env v :: Id
v = SDoc -> Subst -> Id -> CoreArg
lookupIdSubst (String -> SDoc
text "scSubstId") (ScEnv -> Subst
sc_subst ScEnv
env) Id
v

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

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

zapScSubst :: ScEnv -> ScEnv
zapScSubst :: ScEnv -> ScEnv
zapScSubst env :: 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 env :: ScEnv
env qvars :: [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 -> CoreArg -> ScEnv
extendScSubst env :: ScEnv
env var :: Id
var expr :: CoreArg
expr = ScEnv
env { sc_subst :: Subst
sc_subst = Subst -> Id -> CoreArg -> Subst
extendSubst (ScEnv -> Subst
sc_subst ScEnv
env) Id
var CoreArg
expr }

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

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

extendBndr :: ScEnv -> Var -> (ScEnv, Var)
extendBndr :: ScEnv -> Id -> (ScEnv, Id)
extendBndr  env :: ScEnv
env bndr :: Id
bndr  = (ScEnv
env { sc_subst :: Subst
sc_subst = Subst
subst' }, Id
bndr')
                      where
                        (subst' :: Subst
subst', bndr' :: 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 env :: ScEnv
env _  Nothing   = ScEnv
env
extendValEnv env :: ScEnv
env id :: Id
id (Just cv :: Value
cv)
 | Value -> Bool
valueIsWorkFree Value
cv      -- Don't duplicate work!!  Trac #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 env :: ScEnv
env _ _ = 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 -> CoreArg -> Id -> AltCon -> [Id] -> (ScEnv, [Id])
extendCaseBndrs env :: ScEnv
env scrut :: CoreArg
scrut case_bndr :: Id
case_bndr con :: AltCon
con alt_bndrs :: [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 v :: Id
v <- (Tickish Id -> Bool) -> CoreArg -> CoreArg
forall b. (Tickish Id -> Bool) -> Expr b -> Expr b
stripTicksTopE (Bool -> Tickish Id -> Bool
forall a b. a -> b -> a
const Bool
True) CoreArg
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 CoreArg
scrut of { Var {} -> Bool
True; _ -> 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
                DEFAULT    -> Maybe Value
forall a. Maybe a
Nothing
                LitAlt {}  -> Value -> Maybe Value
forall a. a -> Maybe a
Just (AltCon -> [CoreArg] -> Value
ConVal AltCon
con [])
                DataAlt {} -> Value -> Maybe Value
forall a. a -> Maybe a
Just (AltCon -> [CoreArg] -> Value
ConVal AltCon
con [CoreArg]
forall b. [Expr b]
vanilla_args)
                      where
                        vanilla_args :: [Expr b]
vanilla_args = (Type -> Expr b) -> [Type] -> [Expr b]
forall a b. (a -> b) -> [a] -> [b]
map Type -> Expr b
forall b. Type -> Expr b
Type (Type -> [Type]
tyConAppArgs (Id -> Type
idType Id
case_bndr)) [Expr b] -> [Expr b] -> [Expr b]
forall a. [a] -> [a] -> [a]
++
                                       [Id] -> [Expr b]
forall b. [Id] -> [Expr b]
varsToCoreExprs [Id]
alt_bndrs

   zap :: Id -> Id
zap v :: 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 env :: ScEnv
env n_specs :: 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
                       Nothing -> Maybe Int
forall a. Maybe a
Nothing
                       Just n :: 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
+ 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 env :: ScEnv
env dc :: DataCon
dc = ScEnv -> TyCon -> Bool
ignoreTyCon ScEnv
env (DataCon -> TyCon
dataConTyCon DataCon
dc)

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

ignoreTyCon :: ScEnv -> TyCon -> Bool
ignoreTyCon :: ScEnv -> TyCon -> Bool
ignoreTyCon env :: ScEnv
env tycon :: TyCon
tycon
  = UniqFM SpecConstrAnnotation -> TyCon -> Maybe SpecConstrAnnotation
forall key elt. Uniquable key => UniqFM elt -> key -> Maybe elt
lookupUFM (ScEnv -> UniqFM SpecConstrAnnotation
sc_annotations ScEnv
env) 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 env :: ScEnv
env var :: 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)
splitForAllTys (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 env :: 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
. ([Type], Type) -> [Type]
forall a b. (a, b) -> a
fst (([Type], Type) -> [Type])
-> (Type -> ([Type], Type)) -> Type -> [Type]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Type -> ([Type], Type)
splitFunTys

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

forceSpecArgTy env :: ScEnv
env ty :: Type
ty
  | Just (tycon :: TyCon
tycon, tys :: [Type]
tys) <- HasDebugCallStack => 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 -> Name
tyConName TyCon
tycon Name -> Name -> Bool
forall a. Eq a => a -> a -> Bool
== Name
specTyConName
        Bool -> Bool -> Bool
|| UniqFM SpecConstrAnnotation -> TyCon -> Maybe SpecConstrAnnotation
forall key elt. Uniquable key => UniqFM elt -> key -> Maybe elt
lookupUFM (ScEnv -> UniqFM SpecConstrAnnotation
sc_annotations ScEnv
env) 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 _ _ = 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 Trac #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

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 "SCU" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
braces ([SDoc] -> SDoc
sep [ PtrString -> SDoc
ptext (String -> PtrString
sLit "calls =") SDoc -> SDoc -> SDoc
<+> CallEnv -> SDoc
forall a. Outputable a => a -> SDoc
ppr CallEnv
calls
                                         , String -> SDoc
text "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 fn :: Id
fn args :: [CoreArg]
args _) = Id -> SDoc
forall a. Outputable a => a -> SDoc
ppr Id
fn SDoc -> SDoc -> SDoc
<+> [SDoc] -> SDoc
fsep ((CoreArg -> SDoc) -> [CoreArg] -> [SDoc]
forall a b. (a -> b) -> [a] -> [b]
map CoreArg -> SDoc
forall b. OutputableBndr b => Expr b -> SDoc
pprParendExpr [CoreArg]
args)

nullUsage :: ScUsage
nullUsage :: ScUsage
nullUsage = $WSCU :: CallEnv -> IdEnv ArgOcc -> ScUsage
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]
(++)
  where
--    plus cs ds | length res > 1
--               = pprTrace "combineCalls" (vcat [ text "cs:" <+> ppr cs
--                                               , text "ds:" <+> ppr ds])
--                 res
--               | otherwise = res
--       where
--          res = cs ++ ds

combineUsage :: ScUsage -> ScUsage -> ScUsage
combineUsage :: ScUsage -> ScUsage -> ScUsage
combineUsage u1 :: ScUsage
u1 u2 :: ScUsage
u2 = $WSCU :: CallEnv -> IdEnv ArgOcc -> ScUsage
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 us :: [ScUsage]
us = (ScUsage -> ScUsage -> ScUsage) -> [ScUsage] -> ScUsage
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 }) bndrs :: [Id]
bndrs
  = ($WSCU :: CallEnv -> IdEnv ArgOcc -> ScUsage
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

type DataConEnv a = UniqFM a     -- Keyed by DataCon

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

evalScrutOcc :: ArgOcc
evalScrutOcc :: ArgOcc
evalScrutOcc = DataConEnv [ArgOcc] -> ArgOcc
ScrutOcc DataConEnv [ArgOcc]
forall a. VarEnv a
emptyUFM

-- Experimentally, this vesion 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 NoOcc         occ :: ArgOcc
occ           = ArgOcc
occ
combineOcc occ :: ArgOcc
occ           NoOcc         = ArgOcc
occ
combineOcc (ScrutOcc xs :: DataConEnv [ArgOcc]
xs) (ScrutOcc ys :: DataConEnv [ArgOcc]
ys) = DataConEnv [ArgOcc] -> ArgOcc
ScrutOcc (([ArgOcc] -> [ArgOcc] -> [ArgOcc])
-> DataConEnv [ArgOcc]
-> DataConEnv [ArgOcc]
-> DataConEnv [ArgOcc]
forall a. (a -> a -> a) -> VarEnv a -> VarEnv a -> VarEnv a
plusUFM_C [ArgOcc] -> [ArgOcc] -> [ArgOcc]
combineOccs DataConEnv [ArgOcc]
xs DataConEnv [ArgOcc]
ys)
combineOcc UnkOcc        (ScrutOcc ys :: DataConEnv [ArgOcc]
ys) = DataConEnv [ArgOcc] -> ArgOcc
ScrutOcc DataConEnv [ArgOcc]
ys
combineOcc (ScrutOcc xs :: DataConEnv [ArgOcc]
xs) UnkOcc        = DataConEnv [ArgOcc] -> ArgOcc
ScrutOcc DataConEnv [ArgOcc]
xs
combineOcc UnkOcc        UnkOcc        = ArgOcc
UnkOcc

combineOccs :: [ArgOcc] -> [ArgOcc] -> [ArgOcc]
combineOccs :: [ArgOcc] -> [ArgOcc] -> [ArgOcc]
combineOccs xs :: [ArgOcc]
xs ys :: [ArgOcc]
ys = String
-> (ArgOcc -> ArgOcc -> ArgOcc) -> [ArgOcc] -> [ArgOcc] -> [ArgOcc]
forall a b c. String -> (a -> b -> c) -> [a] -> [b] -> [c]
zipWithEqual "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 -> CoreArg -> ArgOcc -> ScUsage
setScrutOcc env :: ScEnv
env usg :: ScUsage
usg (Cast e :: CoreArg
e _) occ :: ArgOcc
occ      = ScEnv -> ScUsage -> CoreArg -> ArgOcc -> ScUsage
setScrutOcc ScEnv
env ScUsage
usg CoreArg
e ArgOcc
occ
setScrutOcc env :: ScEnv
env usg :: ScUsage
usg (Tick _ e :: CoreArg
e) occ :: ArgOcc
occ      = ScEnv -> ScUsage -> CoreArg -> ArgOcc -> ScUsage
setScrutOcc ScEnv
env ScUsage
usg CoreArg
e ArgOcc
occ
setScrutOcc env :: ScEnv
env usg :: ScUsage
usg (Var v :: Id
v)    occ :: ArgOcc
occ
  | Just 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 _env :: ScEnv
_env usg :: ScUsage
usg _other :: CoreArg
_other _occ :: 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 -> CoreArg -> UniqSM (ScUsage, CoreArg)
scExpr env :: ScEnv
env e :: CoreArg
e = ScEnv -> CoreArg -> UniqSM (ScUsage, CoreArg)
scExpr' ScEnv
env CoreArg
e

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

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

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

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

          ; (alt_usgs :: [ScUsage]
alt_usgs, alt_occs :: [ArgOcc]
alt_occs, alts' :: [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
-> CoreArg -> Id -> Alt Id -> UniqSM (ScUsage, ArgOcc, Alt Id)
sc_alt ScEnv
alt_env CoreArg
scrut' Id
b') [Alt Id]
alts

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

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

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

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

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

        ; (body_usg :: ScUsage
body_usg, body' :: CoreArg
body') <- ScEnv -> CoreArg -> UniqSM (ScUsage, CoreArg)
scExpr ScEnv
body_env3 CoreArg
body

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

        ; (ScUsage, CoreArg) -> UniqSM (ScUsage, CoreArg)
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]
                  [CoreBind] -> CoreArg -> CoreArg
forall b. [Bind b] -> Expr b -> Expr b
mkLets [Id -> CoreArg -> CoreBind
forall b. b -> Expr b -> Bind b
NonRec Id
b CoreArg
r | (b :: Id
b,r :: CoreArg
r) <- RhsInfo -> SpecInfo -> [(Id, CoreArg)]
ruleInfoBinds RhsInfo
rhs_info SpecInfo
specs] CoreArg
body')
        }


-- A *local* recursive group: see Note [Local recursive groups]
scExpr' env :: ScEnv
env (Let (Rec prs :: [(Id, CoreArg)]
prs) body :: CoreArg
body)
  = do  { let (bndrs :: [Id]
bndrs,rhss :: [CoreArg]
rhss)      = [(Id, CoreArg)] -> ([Id], [CoreArg])
forall a b. [(a, b)] -> ([a], [b])
unzip [(Id, CoreArg)]
prs
              (rhs_env1 :: ScEnv
rhs_env1,bndrs' :: [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, CoreArg) -> UniqSM RhsInfo)
-> [(Id, CoreArg)] -> UniqSM [RhsInfo]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (ScEnv -> (Id, CoreArg) -> UniqSM RhsInfo
scRecRhs ScEnv
rhs_env2) ([Id]
bndrs' [Id] -> [CoreArg] -> [(Id, CoreArg)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [CoreArg]
rhss)
        ; (body_usg :: ScUsage
body_usg, body' :: CoreArg
body')     <- ScEnv -> CoreArg -> UniqSM (ScUsage, CoreArg)
scExpr ScEnv
rhs_env2 CoreArg
body

        -- NB: start specLoop from body_usg
        ; (spec_usg :: ScUsage
spec_usg, specs :: [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, CoreArg)] -> CoreBind
forall b. [(b, Expr b)] -> Bind b
Rec ([[(Id, CoreArg)]] -> [(Id, CoreArg)]
forall (t :: * -> *) a. Foldable t => t [a] -> [a]
concat ((RhsInfo -> SpecInfo -> [(Id, CoreArg)])
-> [RhsInfo] -> [SpecInfo] -> [[(Id, CoreArg)]]
forall a b c. (a -> b -> c) -> [a] -> [b] -> [c]
zipWith RhsInfo -> SpecInfo -> [(Id, CoreArg)]
ruleInfoBinds [RhsInfo]
rhs_infos [SpecInfo]
specs))

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

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

            other_fn' :: CoreArg
other_fn' -> (ScUsage, CoreArg) -> UniqSM (ScUsage, CoreArg)
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
arg_usg, CoreArg -> [CoreArg] -> CoreArg
forall b. Expr b -> [Expr b] -> Expr b
mkApps CoreArg
other_fn' [CoreArg]
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 :: CoreArg -> [CoreArg] -> CoreArg
doBeta (Lam bndr :: Id
bndr body :: CoreArg
body) (arg :: CoreArg
arg : args :: [CoreArg]
args) = CoreBind -> CoreArg -> CoreArg
forall b. Bind b -> Expr b -> Expr b
Let (Id -> CoreArg -> CoreBind
forall b. b -> Expr b -> Bind b
NonRec Id
bndr CoreArg
arg) (CoreArg -> [CoreArg] -> CoreArg
doBeta CoreArg
body [CoreArg]
args)
    doBeta fn :: CoreArg
fn              args :: [CoreArg]
args         = CoreArg -> [CoreArg] -> CoreArg
forall b. Expr b -> [Expr b] -> Expr b
mkApps CoreArg
fn [CoreArg]
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 env :: ScEnv
env (other_fn :: CoreArg
other_fn, args :: [CoreArg]
args)
  = do  { (fn_usg :: ScUsage
fn_usg,   fn' :: CoreArg
fn')   <- ScEnv -> CoreArg -> UniqSM (ScUsage, CoreArg)
scExpr ScEnv
env CoreArg
other_fn
        ; (arg_usgs :: [ScUsage]
arg_usgs, args' :: [CoreArg]
args') <- (CoreArg -> UniqSM (ScUsage, CoreArg))
-> [CoreArg] -> UniqSM ([ScUsage], [CoreArg])
forall (m :: * -> *) a b c.
Applicative m =>
(a -> m (b, c)) -> [a] -> m ([b], [c])
mapAndUnzipM (ScEnv -> CoreArg -> UniqSM (ScUsage, CoreArg)
scExpr ScEnv
env) [CoreArg]
args
        ; (ScUsage, CoreArg) -> UniqSM (ScUsage, CoreArg)
forall (m :: * -> *) a. Monad m => a -> m a
return ([ScUsage] -> ScUsage
combineUsages [ScUsage]
arg_usgs ScUsage -> ScUsage -> ScUsage
`combineUsage` ScUsage
fn_usg, CoreArg -> [CoreArg] -> CoreArg
forall b. Expr b -> [Expr b] -> Expr b
mkApps CoreArg
fn' [CoreArg]
args') }

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

----------------------
scTopBindEnv :: ScEnv -> CoreBind -> UniqSM (ScEnv, CoreBind)
scTopBindEnv :: ScEnv -> CoreBind -> UniqSM (ScEnv, CoreBind)
scTopBindEnv env :: ScEnv
env (Rec prs :: [(Id, CoreArg)]
prs)
  = do  { let (rhs_env1 :: ScEnv
rhs_env1,bndrs' :: [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, CoreArg)]
prs'              = [Id] -> [CoreArg] -> [(Id, CoreArg)]
forall a b. [a] -> [b] -> [(a, b)]
zip [Id]
bndrs' [CoreArg]
rhss
        ; (ScEnv, CoreBind) -> UniqSM (ScEnv, CoreBind)
forall (m :: * -> *) a. Monad m => a -> m a
return (ScEnv
rhs_env2, [(Id, CoreArg)] -> CoreBind
forall b. [(b, Expr b)] -> Bind b
Rec [(Id, CoreArg)]
prs') }
  where
    (bndrs :: [Id]
bndrs,rhss :: [CoreArg]
rhss) = [(Id, CoreArg)] -> ([Id], [CoreArg])
forall a b. [(a, b)] -> ([a], [b])
unzip [(Id, CoreArg)]
prs

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

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

{-
scTopBind _ usage _
  | pprTrace "scTopBind_usage" (ppr (scu_calls usage)) False
  = error "false"
-}

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

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

        ; (spec_usage :: ScUsage
spec_usage, specs :: [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 (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
body_usage ScUsage -> ScUsage -> ScUsage
`combineUsage` ScUsage
spec_usage,
                  [(Id, CoreArg)] -> CoreBind
forall b. [(b, Expr b)] -> Bind b
Rec ([[(Id, CoreArg)]] -> [(Id, CoreArg)]
forall (t :: * -> *) a. Foldable t => t [a] -> [a]
concat ((RhsInfo -> SpecInfo -> [(Id, CoreArg)])
-> [RhsInfo] -> [SpecInfo] -> [[(Id, CoreArg)]]
forall a b c. (a -> b -> c) -> [a] -> [b] -> [c]
zipWith RhsInfo -> SpecInfo -> [(Id, CoreArg)]
ruleInfoBinds [RhsInfo]
rhs_infos [SpecInfo]
specs))) }
  where
    (bndrs :: [Id]
bndrs,rhss :: [CoreArg]
rhss) = [(Id, CoreArg)] -> ([Id], [CoreArg])
forall a b. [(a, b)] -> ([a], [b])
unzip [(Id, CoreArg)]
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 env :: ScEnv
env usage :: ScUsage
usage (NonRec bndr :: Id
bndr rhs :: CoreArg
rhs)   -- Oddly, we don't seem to specialise top-level non-rec functions
  = do  { (rhs_usg' :: ScUsage
rhs_usg', rhs' :: CoreArg
rhs') <- ScEnv -> CoreArg -> UniqSM (ScUsage, CoreArg)
scExpr ScEnv
env CoreArg
rhs
        ; (ScUsage, CoreBind) -> UniqSM (ScUsage, CoreBind)
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
usage ScUsage -> ScUsage -> ScUsage
`combineUsage` ScUsage
rhs_usg', Id -> CoreArg -> CoreBind
forall b. b -> Expr b -> Bind b
NonRec Id
bndr CoreArg
rhs') }

----------------------
scRecRhs :: ScEnv -> (OutId, InExpr) -> UniqSM RhsInfo
scRecRhs :: ScEnv -> (Id, CoreArg) -> UniqSM RhsInfo
scRecRhs env :: ScEnv
env (bndr :: Id
bndr,rhs :: CoreArg
rhs)
  = do  { let (arg_bndrs :: [Id]
arg_bndrs,body :: CoreArg
body)       = CoreArg -> ([Id], CoreArg)
forall b. Expr b -> ([b], Expr b)
collectBinders CoreArg
rhs
              (body_env :: ScEnv
body_env, arg_bndrs' :: [Id]
arg_bndrs') = HowBound -> ScEnv -> [Id] -> (ScEnv, [Id])
extendBndrsWith HowBound
RecArg ScEnv
env [Id]
arg_bndrs
        ; (body_usg :: ScUsage
body_usg, body' :: CoreArg
body')         <- ScEnv -> CoreArg -> UniqSM (ScUsage, CoreArg)
scExpr ScEnv
body_env CoreArg
body
        ; let (rhs_usg :: ScUsage
rhs_usg, arg_occs :: [ArgOcc]
arg_occs)    = ScUsage -> [Id] -> (ScUsage, [ArgOcc])
lookupOccs ScUsage
body_usg [Id]
arg_bndrs'
        ; RhsInfo -> UniqSM RhsInfo
forall (m :: * -> *) a. Monad m => a -> m a
return (RI :: Id -> CoreArg -> ScUsage -> [Id] -> CoreArg -> [ArgOcc] -> RhsInfo
RI { ri_rhs_usg :: ScUsage
ri_rhs_usg = ScUsage
rhs_usg
                     , ri_fn :: Id
ri_fn = Id
bndr, ri_new_rhs :: CoreArg
ri_new_rhs = [Id] -> CoreArg -> CoreArg
forall b. [b] -> Expr b -> Expr b
mkLams [Id]
arg_bndrs' CoreArg
body'
                     , ri_lam_bndrs :: [Id]
ri_lam_bndrs = [Id]
arg_bndrs, ri_lam_body :: CoreArg
ri_lam_body = CoreArg
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, CoreArg)]
ruleInfoBinds (RI { ri_fn :: RhsInfo -> Id
ri_fn = Id
fn, ri_new_rhs :: RhsInfo -> CoreArg
ri_new_rhs = CoreArg
new_rhs })
              (SI { si_specs :: SpecInfo -> [OneSpec]
si_specs = [OneSpec]
specs })
  = [(Id
id,CoreArg
rhs) | OS { os_id :: OneSpec -> Id
os_id = Id
id, os_rhs :: OneSpec -> CoreArg
os_rhs = CoreArg
rhs } <- [OneSpec]
specs] [(Id, CoreArg)] -> [(Id, CoreArg)] -> [(Id, CoreArg)]
forall a. [a] -> [a] -> [a]
++
              -- First the specialised bindings

    [(Id
fn Id -> [CoreRule] -> Id
`addIdSpecialisations` [CoreRule]
rules, CoreArg
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 -> CoreArg
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 -> CoreArg
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 -> ([Id], [CoreArg])
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 -> CoreArg
os_rhs  :: OutExpr }  -- Spec rhs

noSpecInfo :: SpecInfo
noSpecInfo :: SpecInfo
noSpecInfo = SI :: [OneSpec] -> Int -> Maybe ScUsage -> SpecInfo
SI { si_specs :: [OneSpec]
si_specs = [], si_n_specs :: Int
si_n_specs = 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 env :: ScEnv
env body_usg :: ScUsage
body_usg rhs_info :: 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 top_lvl :: TopLevelFlag
top_lvl env :: ScEnv
env body_usg :: ScUsage
body_usg rhs_infos :: [RhsInfo]
rhs_infos
  = Int
-> CallEnv -> ScUsage -> [SpecInfo] -> UniqSM (ScUsage, [SpecInfo])
go 1 CallEnv
seed_calls ScUsage
nullUsage [SpecInfo]
init_spec_infos
  where
    (seed_calls :: CallEnv
seed_calls, init_spec_infos :: [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 (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 n_iter :: Int
n_iter seed_calls :: CallEnv
seed_calls usg_so_far :: ScUsage
usg_so_far spec_infos :: [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 (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 (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 (extra_usg_s :: [ScUsage]
extra_usg_s, new_spec_infos :: [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
+ 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
                  Nothing  -> 10    -- Ugh!
                  Just max :: 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 env :: ScEnv
env bind_calls :: 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 -> CoreArg
ri_lam_body = CoreArg
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
isBottomingId 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 (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
nullUsage, SpecInfo
spec_info)

  | Activation -> Bool
isNeverActive (Id -> Activation
idInlineActivation Id
fn) -- See Note [Transfer activation]
    Bool -> Bool -> Bool
|| [Id] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [Id]
arg_bndrs                     -- Only specialise functions
  = -- pprTrace "specialise inactive" (ppr fn) $
    case Maybe ScUsage
mb_unspec of    -- Behave as if there was a single, boring call
      Just rhs_usg :: ScUsage
rhs_usg -> (ScUsage, SpecInfo) -> UniqSM (ScUsage, SpecInfo)
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]
      Nothing      -> (ScUsage, SpecInfo) -> UniqSM (ScUsage, SpecInfo)
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
nullUsage, SpecInfo
spec_info)

  | Just all_calls :: [Call]
all_calls <- CallEnv -> Id -> Maybe [Call]
forall a. VarEnv a -> Id -> Maybe a
lookupVarEnv CallEnv
bind_calls Id
fn
  = -- pprTrace "specialise entry {" (ppr fn <+> ppr all_calls) $
    do  { (boring_call :: Bool
boring_call, new_pats :: [([Id], [CoreArg])]
new_pats) <- ScEnv
-> Id
-> SpecInfo
-> [ArgOcc]
-> [Call]
-> UniqSM (Bool, [([Id], [CoreArg])])
callsToNewPats ScEnv
env Id
fn SpecInfo
spec_info [ArgOcc]
arg_occs [Call]
all_calls

        ; let n_pats :: Int
n_pats = [([Id], [CoreArg])] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [([Id], [CoreArg])]
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
        ; (spec_usgs :: [ScUsage]
spec_usgs, new_specs :: [OneSpec]
new_specs) <- ((([Id], [CoreArg]), Int) -> UniqSM (ScUsage, OneSpec))
-> [(([Id], [CoreArg]), Int)] -> UniqSM ([ScUsage], [OneSpec])
forall (m :: * -> *) a b c.
Applicative m =>
(a -> m (b, c)) -> [a] -> m ([b], [c])
mapAndUnzipM (ScEnv
-> Id
-> [Id]
-> CoreArg
-> (([Id], [CoreArg]), Int)
-> UniqSM (ScUsage, OneSpec)
spec_one ScEnv
spec_env Id
fn [Id]
arg_bndrs CoreArg
body)
                                                 ([([Id], [CoreArg])]
new_pats [([Id], [CoreArg])] -> [Int] -> [(([Id], [CoreArg]), 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.
              (new_usg :: ScUsage
new_usg, mb_unspec' :: Maybe ScUsage
mb_unspec')
                  = case Maybe ScUsage
mb_unspec of
                      Just rhs_usg :: ScUsage
rhs_usg | Bool
boring_call -> (ScUsage
spec_usg ScUsage -> ScUsage -> ScUsage
`combineUsage` ScUsage
rhs_usg, Maybe ScUsage
forall a. Maybe a
Nothing)
                      _                          -> (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 (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
new_usg, SI :: [OneSpec] -> Int -> Maybe ScUsage -> SpecInfo
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 new seeds, so return nullUsage
  = (ScUsage, SpecInfo) -> UniqSM (ScUsage, SpecInfo)
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]
-> CoreArg
-> (([Id], [CoreArg]), Int)
-> UniqSM (ScUsage, OneSpec)
spec_one env :: ScEnv
env fn :: Id
fn arg_bndrs :: [Id]
arg_bndrs body :: CoreArg
body (call_pat :: ([Id], [CoreArg])
call_pat@(qvars :: [Id]
qvars, pats :: [CoreArg]
pats), rule_number :: Int
rule_number)
  = do  { Unique
spec_uniq <- UniqSM Unique
forall (m :: * -> *). MonadUnique m => m Unique
getUniqueM
        ; let spec_env :: ScEnv
spec_env   = ScEnv -> [(Id, CoreArg)] -> ScEnv
extendScSubstList (ScEnv -> [Id] -> ScEnv
extendScInScope ScEnv
env [Id]
qvars)
                                             ([Id]
arg_bndrs [Id] -> [CoreArg] -> [(Id, CoreArg)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [CoreArg]
pats)
              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 ("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
--      ; pprTrace "{spec_one" (ppr (sc_count env) <+> ppr fn
--                              <+> ppr pats <+> text "-->" <+> ppr spec_name) $
--        return ()

        -- Specialise the body
        ; (spec_usg :: ScUsage
spec_usg, spec_body :: CoreArg
spec_body) <- ScEnv -> CoreArg -> UniqSM (ScUsage, CoreArg)
scExpr ScEnv
spec_env CoreArg
body

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

                -- And build the results
        ; let (spec_lam_args :: [Id]
spec_lam_args, spec_call_args :: [Id]
spec_call_args) = DynFlags -> [Id] -> Type -> ([Id], [Id])
mkWorkerArgs (ScEnv -> DynFlags
sc_dflags ScEnv
env)
                                                             [Id]
qvars Type
body_ty
                -- Usual w/w hack to avoid generating
                -- a spec_rhs of unlifted type and no args

              spec_lam_args_str :: [Id]
spec_lam_args_str = [Demand] -> [Id] -> [Id]
handOutStrictnessInformation (([Demand], DmdResult) -> [Demand]
forall a b. (a, b) -> a
fst (StrictSig -> ([Demand], DmdResult)
splitStrictSig StrictSig
spec_str)) [Id]
spec_lam_args
                -- Annotate the variables with the strictness information from
                -- the function (see Note [Strictness information in worker binders])

              spec_join_arity :: Maybe Int
spec_join_arity | Id -> Bool
isJoinId Id
fn = Int -> Maybe Int
forall a. a -> Maybe a
Just ([Id] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [Id]
spec_lam_args)
                              | Bool
otherwise   = Maybe Int
forall a. Maybe a
Nothing
              spec_id :: Id
spec_id    = Name -> Type -> Id
mkLocalIdOrCoVar Name
spec_name
                                            ([Id] -> Type -> Type
mkLamTypes [Id]
spec_lam_args Type
body_ty)
                             -- See Note [Transfer strictness]
                             Id -> StrictSig -> Id
`setIdStrictness` StrictSig
spec_str
                             Id -> Int -> Id
`setIdArity` (Id -> Bool) -> [Id] -> Int
forall a. (a -> Bool) -> [a] -> Int
count Id -> Bool
isId [Id]
spec_lam_args
                             Id -> Maybe Int -> Id
`asJoinId_maybe` Maybe Int
spec_join_arity
              spec_str :: StrictSig
spec_str   = Id -> [Id] -> [CoreArg] -> StrictSig
calcSpecStrictness Id
fn [Id]
spec_lam_args [CoreArg]
pats


                -- Conditionally use result of new worker-wrapper transform
              spec_rhs :: CoreArg
spec_rhs   = [Id] -> CoreArg -> CoreArg
forall b. [b] -> Expr b -> Expr b
mkLams [Id]
spec_lam_args_str CoreArg
spec_body
              body_ty :: Type
body_ty    = CoreArg -> Type
exprType CoreArg
spec_body
              rule_rhs :: Expr b
rule_rhs   = Expr b -> [Id] -> Expr b
forall b. Expr b -> [Id] -> Expr b
mkVarApps (Id -> Expr b
forall b. Id -> Expr b
Var Id
spec_id) [Id]
spec_call_args
              inline_act :: Activation
inline_act = Id -> Activation
idInlineActivation Id
fn
              this_mod :: Module
this_mod   = ScEnv -> Module
sc_module ScEnv
spec_env
              rule :: CoreRule
rule       = Module
-> Bool
-> Bool
-> FastString
-> Activation
-> Name
-> [Id]
-> [CoreArg]
-> CoreArg
-> CoreRule
mkRule Module
this_mod Bool
True {- Auto -} Bool
True {- Local -}
                                  FastString
rule_name Activation
inline_act Name
fn_name [Id]
qvars [CoreArg]
pats CoreArg
forall b. Expr b
rule_rhs
                           -- See Note [Transfer activation]
        ; (ScUsage, OneSpec) -> UniqSM (ScUsage, OneSpec)
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
spec_usg, OS :: ([Id], [CoreArg]) -> CoreRule -> Id -> CoreArg -> OneSpec
OS { os_pat :: ([Id], [CoreArg])
os_pat = ([Id], [CoreArg])
call_pat, os_rule :: CoreRule
os_rule = CoreRule
rule
                               , os_id :: Id
os_id = Id
spec_id
                               , os_rhs :: CoreArg
os_rhs = CoreArg
spec_rhs }) }


-- See Note [Strictness information in worker binders]
handOutStrictnessInformation :: [Demand] -> [Var] -> [Var]
handOutStrictnessInformation :: [Demand] -> [Id] -> [Id]
handOutStrictnessInformation = [Demand] -> [Id] -> [Id]
go
  where
    go :: [Demand] -> [Id] -> [Id]
go _ [] = []
    go [] vs :: [Id]
vs = [Id]
vs
    go (d :: Demand
d:dmds :: [Demand]
dmds) (v :: Id
v:vs :: [Id]
vs) | Id -> Bool
isId Id
v = Id -> Demand -> Id
setIdDemandInfo Id
v Demand
d Id -> [Id] -> [Id]
forall a. a -> [a] -> [a]
: [Demand] -> [Id] -> [Id]
go [Demand]
dmds [Id]
vs
    go dmds :: [Demand]
dmds (v :: Id
v:vs :: [Id]
vs) = Id
v Id -> [Id] -> [Id]
forall a. a -> [a] -> [a]
: [Demand] -> [Id] -> [Id]
go [Demand]
dmds [Id]
vs

calcSpecStrictness :: Id                     -- The original function
                   -> [Var] -> [CoreExpr]    -- Call pattern
                   -> StrictSig              -- Strictness of specialised thing
-- See Note [Transfer strictness]
calcSpecStrictness :: Id -> [Id] -> [CoreArg] -> StrictSig
calcSpecStrictness fn :: Id
fn qvars :: [Id]
qvars pats :: [CoreArg]
pats
  = [Demand] -> DmdResult -> StrictSig
mkClosedStrictSig [Demand]
spec_dmds DmdResult
topRes
  where
    spec_dmds :: [Demand]
spec_dmds = [ VarEnv Demand -> Id -> Maybe Demand
forall a. VarEnv a -> Id -> Maybe a
lookupVarEnv VarEnv Demand
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 ]
    StrictSig (DmdType _ dmds :: [Demand]
dmds _) = Id -> StrictSig
idStrictness Id
fn

    dmd_env :: VarEnv Demand
dmd_env = VarEnv Demand -> [Demand] -> [CoreArg] -> VarEnv Demand
go VarEnv Demand
forall a. VarEnv a
emptyVarEnv [Demand]
dmds [CoreArg]
pats

    go :: DmdEnv -> [Demand] -> [CoreExpr] -> DmdEnv
    go :: VarEnv Demand -> [Demand] -> [CoreArg] -> VarEnv Demand
go env :: VarEnv Demand
env ds :: [Demand]
ds (Type {} : pats :: [CoreArg]
pats)     = VarEnv Demand -> [Demand] -> [CoreArg] -> VarEnv Demand
go VarEnv Demand
env [Demand]
ds [CoreArg]
pats
    go env :: VarEnv Demand
env ds :: [Demand]
ds (Coercion {} : pats :: [CoreArg]
pats) = VarEnv Demand -> [Demand] -> [CoreArg] -> VarEnv Demand
go VarEnv Demand
env [Demand]
ds [CoreArg]
pats
    go env :: VarEnv Demand
env (d :: Demand
d:ds :: [Demand]
ds) (pat :: CoreArg
pat : pats :: [CoreArg]
pats)     = VarEnv Demand -> [Demand] -> [CoreArg] -> VarEnv Demand
go (VarEnv Demand -> Demand -> CoreArg -> VarEnv Demand
go_one VarEnv Demand
env Demand
d CoreArg
pat) [Demand]
ds [CoreArg]
pats
    go env :: VarEnv Demand
env _      _                = VarEnv Demand
env

    go_one :: DmdEnv -> Demand -> CoreExpr -> DmdEnv
    go_one :: VarEnv Demand -> Demand -> CoreArg -> VarEnv Demand
go_one env :: VarEnv Demand
env d :: Demand
d   (Var v :: Id
v) = (Demand -> Demand -> Demand)
-> VarEnv Demand -> Id -> Demand -> VarEnv Demand
forall a. (a -> a -> a) -> VarEnv a -> Id -> a -> VarEnv a
extendVarEnv_C Demand -> Demand -> Demand
bothDmd VarEnv Demand
env Id
v Demand
d
    go_one env :: VarEnv Demand
env d :: Demand
d e :: CoreArg
e
           | Just ds :: [Demand]
ds <- Demand -> Maybe [Demand]
splitProdDmd_maybe Demand
d  -- NB: d does not have to be strict
           , (Var _, args :: [CoreArg]
args) <- CoreArg -> (CoreArg, [CoreArg])
forall b. Expr b -> (Expr b, [Expr b])
collectArgs CoreArg
e = VarEnv Demand -> [Demand] -> [CoreArg] -> VarEnv Demand
go VarEnv Demand
env [Demand]
ds [CoreArg]
args
    go_one env :: VarEnv Demand
env _         _ = VarEnv Demand
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.  He should not combine in rhs_usg
himself, or he'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 Trac #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 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 Phase 0; after all, currently, the specConstr transformation is
only run after the simplifier has reached Phase 0, 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     SS
        and a RULE     f (a:as) b = f_spec a as b

Now we want f_spec to have strictness  LLS, 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 Trac #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 Trac # 5458.  Yuk.

Note [SpecConstr call patterns]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A "call patterns" that we collect is going to become the LHS of a RULE.
It's important that it doesn't have
     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
(Trac #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 (Trac #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 caereful 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. Trac #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 structre 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.
-}

type CallPat = ([Var], [CoreExpr])      -- Quantified variables and arguments
                                        -- See Note [SpecConstr call patterns]

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, [([Id], [CoreArg])])
callsToNewPats env :: ScEnv
env fn :: Id
fn spec_info :: SpecInfo
spec_info@(SI { si_specs :: SpecInfo -> [OneSpec]
si_specs = [OneSpec]
done_specs }) bndr_occs :: [ArgOcc]
bndr_occs calls :: [Call]
calls
  = do  { [Maybe ([Id], [CoreArg])]
mb_pats <- (Call -> UniqSM (Maybe ([Id], [CoreArg])))
-> [Call] -> UniqSM [Maybe ([Id], [CoreArg])]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (ScEnv -> [ArgOcc] -> Call -> UniqSM (Maybe ([Id], [CoreArg]))
callToPats ScEnv
env [ArgOcc]
bndr_occs) [Call]
calls

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

              good_pats :: [CallPat]
              good_pats :: [([Id], [CoreArg])]
good_pats = [Maybe ([Id], [CoreArg])] -> [([Id], [CoreArg])]
forall a. [Maybe a] -> [a]
catMaybes [Maybe ([Id], [CoreArg])]
mb_pats

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

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

              -- Remove ones that have too many worker variables
              small_pats :: [([Id], [CoreArg])]
small_pats = (([Id], [CoreArg]) -> Bool)
-> [([Id], [CoreArg])] -> [([Id], [CoreArg])]
forall a. (a -> Bool) -> [a] -> [a]
filterOut ([Id], [CoreArg]) -> Bool
forall b. ([Id], b) -> Bool
too_big [([Id], [CoreArg])]
non_dups
              too_big :: ([Id], b) -> Bool
too_big (vars :: [Id]
vars,_) = Bool -> Bool
not (DynFlags -> [Id] -> Bool
isWorkerSmallEnough (ScEnv -> DynFlags
sc_dflags ScEnv
env) [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 WwLib

                -- Discard specialisations if there are too many of them
              trimmed_pats :: [([Id], [CoreArg])]
trimmed_pats = ScEnv
-> Id -> SpecInfo -> [([Id], [CoreArg])] -> [([Id], [CoreArg])]
trim_pats ScEnv
env Id
fn SpecInfo
spec_info [([Id], [CoreArg])]
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, [([Id], [CoreArg])]) -> UniqSM (Bool, [([Id], [CoreArg])])
forall (m :: * -> *) a. Monad m => a -> m a
return (Bool
have_boring_call, [([Id], [CoreArg])]
trimmed_pats) }


trim_pats :: ScEnv -> Id -> SpecInfo -> [CallPat] -> [CallPat]
-- See Note [Choosing patterns]
trim_pats :: ScEnv
-> Id -> SpecInfo -> [([Id], [CoreArg])] -> [([Id], [CoreArg])]
trim_pats env :: ScEnv
env fn :: Id
fn (SI { si_n_specs :: SpecInfo -> Int
si_n_specs = Int
done_spec_count }) pats :: [([Id], [CoreArg])]
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)
    [([Id], [CoreArg])]
pats          -- No need to trim

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

  where
    n_pats :: Int
n_pats         = [([Id], [CoreArg])] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [([Id], [CoreArg])]
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 max_specs :: Int
max_specs = Maybe Int
mb_scc

    sorted_pats :: [([Id], [CoreArg])]
sorted_pats = ((([Id], [CoreArg]), Int) -> ([Id], [CoreArg]))
-> [(([Id], [CoreArg]), Int)] -> [([Id], [CoreArg])]
forall a b. (a -> b) -> [a] -> [b]
map (([Id], [CoreArg]), Int) -> ([Id], [CoreArg])
forall a b. (a, b) -> a
fst ([(([Id], [CoreArg]), Int)] -> [([Id], [CoreArg])])
-> [(([Id], [CoreArg]), Int)] -> [([Id], [CoreArg])]
forall a b. (a -> b) -> a -> b
$
                  ((([Id], [CoreArg]), Int) -> (([Id], [CoreArg]), Int) -> Ordering)
-> [(([Id], [CoreArg]), Int)] -> [(([Id], [CoreArg]), Int)]
forall a. (a -> a -> Ordering) -> [a] -> [a]
sortBy (((([Id], [CoreArg]), Int) -> Int)
-> (([Id], [CoreArg]), Int) -> (([Id], [CoreArg]), Int) -> Ordering
forall a b. Ord a => (b -> a) -> b -> b -> Ordering
comparing (([Id], [CoreArg]), Int) -> Int
forall a b. (a, b) -> b
snd) ([(([Id], [CoreArg]), Int)] -> [(([Id], [CoreArg]), Int)])
-> [(([Id], [CoreArg]), Int)] -> [(([Id], [CoreArg]), Int)]
forall a b. (a -> b) -> a -> b
$
                  [(([Id], [CoreArg])
pat, ([Id], [CoreArg]) -> Int
pat_cons ([Id], [CoreArg])
pat) | ([Id], [CoreArg])
pat <- [([Id], [CoreArg])]
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 :: ([Id], [CoreArg]) -> Int
pat_cons (qs :: [Id]
qs, ps :: [CoreArg]
ps) = (CoreArg -> Int -> Int) -> Int -> [CoreArg] -> Int
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) -> (CoreArg -> Int) -> CoreArg -> Int -> Int
forall b c a. (b -> c) -> (a -> b) -> a -> c
. CoreArg -> Int
forall a b. Num a => Expr b -> a
n_cons) 0 [CoreArg]
ps
       where
          q_set :: VarSet
q_set = [Id] -> VarSet
mkVarSet [Id]
qs
          n_cons :: Expr b -> a
n_cons (Var v :: Id
v) | Id
v Id -> VarSet -> Bool
`elemVarSet` VarSet
q_set = 0
                         | Bool
otherwise            = 1
          n_cons (Cast e :: Expr b
e _)  = Expr b -> a
n_cons Expr b
e
          n_cons (App e1 :: Expr b
e1 e2 :: Expr b
e2) = Expr b -> a
n_cons Expr b
e1 a -> a -> a
forall a. Num a => a -> a -> a
+ Expr b -> a
n_cons Expr b
e2
          n_cons (Lit {})    = 1
          n_cons _           = 0

    emit_trace :: p -> p
emit_trace result :: p
result
       | Bool
debugIsOn Bool -> Bool -> Bool
|| DynFlags -> Bool
hasPprDebug (ScEnv -> DynFlags
sc_dflags ScEnv
env)
         -- Suppress this scary message for ordinary users!  Trac #5125
       = String -> SDoc -> p -> p
forall a. String -> SDoc -> a -> a
pprTrace "SpecConstr" SDoc
msg p
result
       | Bool
otherwise
       = p
result
    msg :: SDoc
msg = [SDoc] -> SDoc
vcat [ [SDoc] -> SDoc
sep [ String -> SDoc
text "Function" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (Id -> SDoc
forall a. Outputable a => a -> SDoc
ppr Id
fn)
                     , Int -> SDoc -> SDoc
nest 2 (String -> SDoc
text "has" SDoc -> SDoc -> SDoc
<+>
                               Int -> SDoc -> SDoc
speakNOf Int
spec_count' (String -> SDoc
text "call pattern") SDoc -> SDoc -> SDoc
<> SDoc
comma SDoc -> SDoc -> SDoc
<+>
                               String -> SDoc
text "but the limit is" SDoc -> SDoc -> SDoc
<+> Int -> SDoc
int Int
max_specs) ]
               , String -> SDoc
text "Use -fspec-constr-count=n to set the bound"
               , String -> SDoc
text "done_spec_count =" SDoc -> SDoc -> SDoc
<+> Int -> SDoc
int Int
done_spec_count
               , String -> SDoc
text "Keeping " SDoc -> SDoc -> SDoc
<+> Int -> SDoc
int Int
n_remaining SDoc -> SDoc -> SDoc
<> String -> SDoc
text ", out of" SDoc -> SDoc -> SDoc
<+> Int -> SDoc
int Int
n_pats
               , String -> SDoc
text "Discarding:" SDoc -> SDoc -> SDoc
<+> [([Id], [CoreArg])] -> SDoc
forall a. Outputable a => a -> SDoc
ppr (Int -> [([Id], [CoreArg])] -> [([Id], [CoreArg])]
forall a. Int -> [a] -> [a]
drop Int
n_remaining [([Id], [CoreArg])]
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 ([Id], [CoreArg]))
callToPats env :: ScEnv
env bndr_occs :: [ArgOcc]
bndr_occs call :: Call
call@(Call _ args :: [CoreArg]
args con_env :: ValueEnv
con_env)
  | [CoreArg]
args [CoreArg] -> [ArgOcc] -> Bool
forall a b. [a] -> [b] -> Bool
`ltLength` [ArgOcc]
bndr_occs      -- Check saturated
  = Maybe ([Id], [CoreArg]) -> UniqSM (Maybe ([Id], [CoreArg]))
forall (m :: * -> *) a. Monad m => a -> m a
return Maybe ([Id], [CoreArg])
forall a. Maybe a
Nothing
  | Bool
otherwise
  = do  { let in_scope :: InScopeSet
in_scope = Subst -> InScopeSet
substInScope (ScEnv -> Subst
sc_subst ScEnv
env)
        ; (interesting :: Bool
interesting, pats :: [CoreArg]
pats) <- ScEnv
-> InScopeSet
-> ValueEnv
-> [CoreArg]
-> [ArgOcc]
-> UniqSM (Bool, [CoreArg])
argsToPats ScEnv
env InScopeSet
in_scope ValueEnv
con_env [CoreArg]
args [ArgOcc]
bndr_occs
        ; let pat_fvs :: [Id]
pat_fvs = [CoreArg] -> [Id]
exprsFreeVarsList [CoreArg]
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 Unique.

              in_scope_vars :: VarSet
in_scope_vars = InScopeSet -> VarSet
getInScopeVars InScopeSet
in_scope
              is_in_scope :: Id -> Bool
is_in_scope v :: Id
v = Id
v Id -> VarSet -> Bool
`elemVarSet` VarSet
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

              (ktvs :: [Id]
ktvs, ids :: [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
id   = Id
id Id -> Type -> Id
`setIdType` Type -> Type
expandTypeSynonyms (Id -> Type
idType Id
id)
                -- See Note [Free type variables of the qvar types]

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

        ; -- pprTrace "callToPats"  (ppr args $$ ppr bndr_occs) $
          WARN( not (isEmptyVarSet bad_covars)
              , text "SpecConstr: bad covars:" <+> ppr bad_covars
                $$ ppr call )
          if Bool
interesting Bool -> Bool -> Bool
&& VarSet -> Bool
isEmptyVarSet VarSet
bad_covars
          then Maybe ([Id], [CoreArg]) -> UniqSM (Maybe ([Id], [CoreArg]))
forall (m :: * -> *) a. Monad m => a -> m a
return (([Id], [CoreArg]) -> Maybe ([Id], [CoreArg])
forall a. a -> Maybe a
Just ([Id]
qvars', [CoreArg]
pats))
          else Maybe ([Id], [CoreArg]) -> UniqSM (Maybe ([Id], [CoreArg]))
forall (m :: * -> *) a. Monad m => a -> m a
return Maybe ([Id], [CoreArg])
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
         -> UniqSM (Bool, CoreArg)

-- 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
-> CoreArg
-> ArgOcc
-> UniqSM (Bool, CoreArg)
argToPat _env :: ScEnv
_env _in_scope :: InScopeSet
_in_scope _val_env :: ValueEnv
_val_env arg :: CoreArg
arg@(Type {}) _arg_occ :: ArgOcc
_arg_occ
  = (Bool, CoreArg) -> UniqSM (Bool, CoreArg)
forall (m :: * -> *) a. Monad m => a -> m a
return (Bool
False, CoreArg
arg)

argToPat env :: ScEnv
env in_scope :: InScopeSet
in_scope val_env :: ValueEnv
val_env (Tick _ arg :: CoreArg
arg) arg_occ :: ArgOcc
arg_occ
  = ScEnv
-> InScopeSet
-> ValueEnv
-> CoreArg
-> ArgOcc
-> UniqSM (Bool, CoreArg)
argToPat ScEnv
env InScopeSet
in_scope ValueEnv
val_env CoreArg
arg ArgOcc
arg_occ
        -- Note [Notes 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 [Notes in RULE matching] in Rules

argToPat env :: ScEnv
env in_scope :: InScopeSet
in_scope val_env :: ValueEnv
val_env (Let _ arg :: CoreArg
arg) arg_occ :: ArgOcc
arg_occ
  = ScEnv
-> InScopeSet
-> ValueEnv
-> CoreArg
-> ArgOcc
-> UniqSM (Bool, CoreArg)
argToPat ScEnv
env InScopeSet
in_scope ValueEnv
val_env CoreArg
arg ArgOcc
arg_occ
        -- See Note [Matching lets] in Rule.hs
        -- 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 Rule.hs
argToPat env in_scope val_env (Case scrut _ _ [(_, _, rhs)]) arg_occ
  | exprOkForSpeculation scrut  -- See Note [Matching cases] in Rule.hhs
  = argToPat env in_scope val_env rhs arg_occ
-}

argToPat env :: ScEnv
env in_scope :: InScopeSet
in_scope val_env :: ValueEnv
val_env (Cast arg :: CoreArg
arg co :: Coercion
co) arg_occ :: ArgOcc
arg_occ
  | Bool -> Bool
not (ScEnv -> Type -> Bool
ignoreType ScEnv
env Type
ty2)
  = do  { (interesting :: Bool
interesting, arg' :: CoreArg
arg') <- ScEnv
-> InScopeSet
-> ValueEnv
-> CoreArg
-> ArgOcc
-> UniqSM (Bool, CoreArg)
argToPat ScEnv
env InScopeSet
in_scope ValueEnv
val_env CoreArg
arg ArgOcc
arg_occ
        ; if Bool -> Bool
not Bool
interesting then
                Type -> UniqSM (Bool, CoreArg)
wildCardPat Type
ty2
          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 "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, CoreArg) -> UniqSM (Bool, CoreArg)
forall (m :: * -> *) a. Monad m => a -> m a
return (Bool
interesting, CoreArg -> Coercion -> CoreArg
forall b. Expr b -> Coercion -> Expr b
Cast CoreArg
arg' (Id -> Coercion
mkCoVarCo Id
co_var)) } }
  where
    Pair ty1 :: Type
ty1 ty2 :: 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
argToPat env :: ScEnv
env in_scope :: InScopeSet
in_scope val_env :: ValueEnv
val_env arg :: CoreArg
arg arg_occ :: ArgOcc
arg_occ
  | Just (ConVal (DataAlt dc :: DataCon
dc) args :: [CoreArg]
args) <- ValueEnv -> CoreArg -> Maybe Value
isValue ValueEnv
val_env CoreArg
arg
  , Bool -> Bool
not (ScEnv -> DataCon -> Bool
ignoreDataCon ScEnv
env DataCon
dc)        -- See Note [NoSpecConstr]
  , Just arg_occs :: [ArgOcc]
arg_occs <- DataCon -> Maybe [ArgOcc]
forall key. Uniquable key => key -> Maybe [ArgOcc]
mb_scrut DataCon
dc
  = do  { let (ty_args :: [CoreArg]
ty_args, rest_args :: [CoreArg]
rest_args) = [Id] -> [CoreArg] -> ([CoreArg], [CoreArg])
forall b a. [b] -> [a] -> ([a], [a])
splitAtList (DataCon -> [Id]
dataConUnivTyVars DataCon
dc) [CoreArg]
args
        ; (_, args' :: [CoreArg]
args') <- ScEnv
-> InScopeSet
-> ValueEnv
-> [CoreArg]
-> [ArgOcc]
-> UniqSM (Bool, [CoreArg])
argsToPats ScEnv
env InScopeSet
in_scope ValueEnv
val_env [CoreArg]
rest_args [ArgOcc]
arg_occs
        ; (Bool, CoreArg) -> UniqSM (Bool, CoreArg)
forall (m :: * -> *) a. Monad m => a -> m a
return (Bool
True,
                  DataCon -> [CoreArg] -> CoreArg
forall b. DataCon -> [Arg b] -> Arg b
mkConApp DataCon
dc ([CoreArg]
ty_args [CoreArg] -> [CoreArg] -> [CoreArg]
forall a. [a] -> [a] -> [a]
++ [CoreArg]
args')) }
  where
    mb_scrut :: key -> Maybe [ArgOcc]
mb_scrut dc :: key
dc = case ArgOcc
arg_occ of
                    ScrutOcc bs :: DataConEnv [ArgOcc]
bs | Just occs :: [ArgOcc]
occs <- DataConEnv [ArgOcc] -> key -> Maybe [ArgOcc]
forall key elt. Uniquable key => UniqFM elt -> key -> Maybe elt
lookupUFM DataConEnv [ArgOcc]
bs key
dc
                                -> [ArgOcc] -> Maybe [ArgOcc]
forall a. a -> Maybe a
Just ([ArgOcc]
occs)  -- See Note [Reboxing]
                    _other :: 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

  -- Check if the argument is a variable that
  --    (a) is used in an interesting way in the function body
  --    (b) we know what its value is
  -- In that case it counts as "interesting"
argToPat env :: ScEnv
env in_scope :: InScopeSet
in_scope val_env :: ValueEnv
val_env (Var v :: Id
v) arg_occ :: ArgOcc
arg_occ
  | ScEnv -> Bool
sc_force ScEnv
env Bool -> Bool -> Bool
|| case ArgOcc
arg_occ of { UnkOcc -> Bool
False; _other :: ArgOcc
_other -> Bool
True }, -- (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))
  = (Bool, CoreArg) -> UniqSM (Bool, CoreArg)
forall (m :: * -> *) a. Monad m => a -> m a
return (Bool
True, Id -> CoreArg
forall b. Id -> Expr b
Var Id
v)
  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 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
argToPat _env :: ScEnv
_env _in_scope :: InScopeSet
_in_scope _val_env :: ValueEnv
_val_env arg :: CoreArg
arg _arg_occ :: ArgOcc
_arg_occ
  = Type -> UniqSM (Bool, CoreArg)
wildCardPat (CoreArg -> Type
exprType CoreArg
arg)

wildCardPat :: Type -> UniqSM (Bool, CoreArg)
wildCardPat :: Type -> UniqSM (Bool, CoreArg)
wildCardPat ty :: Type
ty
  = do { Unique
uniq <- UniqSM Unique
forall (m :: * -> *). MonadUnique m => m Unique
getUniqueM
       ; let id :: Id
id = FastString -> Unique -> Type -> Id
mkSysLocalOrCoVar (String -> FastString
fsLit "sc") Unique
uniq Type
ty
       ; (Bool, CoreArg) -> UniqSM (Bool, CoreArg)
forall (m :: * -> *) a. Monad m => a -> m a
return (Bool
False, Id -> CoreArg
forall b. Id -> Expr b
varToCoreExpr Id
id) }

argsToPats :: ScEnv -> InScopeSet -> ValueEnv
           -> [CoreArg] -> [ArgOcc]  -- Should be same length
           -> UniqSM (Bool, [CoreArg])
argsToPats :: ScEnv
-> InScopeSet
-> ValueEnv
-> [CoreArg]
-> [ArgOcc]
-> UniqSM (Bool, [CoreArg])
argsToPats env :: ScEnv
env in_scope :: InScopeSet
in_scope val_env :: ValueEnv
val_env args :: [CoreArg]
args occs :: [ArgOcc]
occs
  = do { [(Bool, CoreArg)]
stuff <- (CoreArg -> ArgOcc -> UniqSM (Bool, CoreArg))
-> [CoreArg] -> [ArgOcc] -> UniqSM [(Bool, CoreArg)]
forall (m :: * -> *) a b c.
Applicative m =>
(a -> b -> m c) -> [a] -> [b] -> m [c]
zipWithM (ScEnv
-> InScopeSet
-> ValueEnv
-> CoreArg
-> ArgOcc
-> UniqSM (Bool, CoreArg)
argToPat ScEnv
env InScopeSet
in_scope ValueEnv
val_env) [CoreArg]
args [ArgOcc]
occs
       ; let (interesting_s :: [Bool]
interesting_s, args' :: [CoreArg]
args') = [(Bool, CoreArg)] -> ([Bool], [CoreArg])
forall a b. [(a, b)] -> ([a], [b])
unzip [(Bool, CoreArg)]
stuff
       ; (Bool, [CoreArg]) -> UniqSM (Bool, [CoreArg])
forall (m :: * -> *) a. Monad m => a -> m a
return ([Bool] -> Bool
forall (t :: * -> *). Foldable t => t Bool -> Bool
or [Bool]
interesting_s, [CoreArg]
args') }

isValue :: ValueEnv -> CoreExpr -> Maybe Value
isValue :: ValueEnv -> CoreArg -> Maybe Value
isValue _env :: ValueEnv
_env (Lit 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 -> [CoreArg] -> Value
ConVal (Literal -> AltCon
LitAlt Literal
lit) [])

isValue env :: ValueEnv
env (Var v :: Id
v)
  | Just cval :: 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 -> CoreArg -> Maybe Value
isValue ValueEnv
env (Unfolding -> CoreArg
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 env :: ValueEnv
env (Lam b :: Id
b e :: CoreArg
e)
  | Id -> Bool
isTyVar Id
b = case ValueEnv -> CoreArg -> Maybe Value
isValue ValueEnv
env CoreArg
e of
                  Just _  -> Value -> Maybe Value
forall a. a -> Maybe a
Just Value
LambdaVal
                  Nothing -> Maybe Value
forall a. Maybe a
Nothing
  | Bool
otherwise = Value -> Maybe Value
forall a. a -> Maybe a
Just Value
LambdaVal

isValue env :: ValueEnv
env (Tick t :: Tickish Id
t e :: CoreArg
e)
  | Bool -> Bool
not (Tickish Id -> Bool
forall id. Tickish id -> Bool
tickishIsCode Tickish Id
t)
  = ValueEnv -> CoreArg -> Maybe Value
isValue ValueEnv
env CoreArg
e

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

        Just con :: DataCon
con | [CoreArg]
args [CoreArg] -> 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 -> [CoreArg] -> Value
ConVal (DataCon -> AltCon
DataAlt DataCon
con) [CoreArg]
args)

        _other :: Maybe DataCon
_other | [CoreArg] -> Int
forall b. [Arg b] -> Int
valArgCount [CoreArg]
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

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

isValue _env :: ValueEnv
_env _expr :: CoreArg
_expr = Maybe Value
forall a. Maybe a
Nothing

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

samePat :: CallPat -> CallPat -> Bool
samePat :: ([Id], [CoreArg]) -> ([Id], [CoreArg]) -> Bool
samePat (vs1 :: [Id]
vs1, as1 :: [CoreArg]
as1) (vs2 :: [Id]
vs2, as2 :: [CoreArg]
as2)
  = (CoreArg -> CoreArg -> Bool) -> [CoreArg] -> [CoreArg] -> Bool
forall a b. (a -> b -> Bool) -> [a] -> [b] -> Bool
all2 CoreArg -> CoreArg -> Bool
forall b b.
(OutputableBndr b, OutputableBndr b) =>
Expr b -> Expr b -> Bool
same [CoreArg]
as1 [CoreArg]
as2
  where
    same :: Expr b -> Expr b -> Bool
same (Var v1 :: Id
v1) (Var v2 :: Id
v2)
        | Id
v1 Id -> [Id] -> Bool
forall (t :: * -> *) a. (Foldable t, Eq a) => a -> t a -> Bool
`elem` [Id]
vs1 = Id
v2 Id -> [Id] -> Bool
forall (t :: * -> *) a. (Foldable t, Eq a) => a -> t a -> Bool
`elem` [Id]
vs2
        | Id
v2 Id -> [Id] -> 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 l1 :: Literal
l1)    (Lit l2 :: Literal
l2)    = Literal
l1Literal -> Literal -> Bool
forall a. Eq a => a -> a -> Bool
==Literal
l2
    same (App f1 :: Expr b
f1 a1 :: Expr b
a1) (App f2 :: Expr b
f2 a2 :: Expr b
a2) = Expr b -> Expr b -> Bool
same Expr b
f1 Expr b
f2 Bool -> Bool -> Bool
&& Expr b -> Expr b -> Bool
same Expr b
a1 Expr b
a2

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

    same e1 :: Expr b
e1 e2 :: Expr b
e2 = WARN( bad e1 || bad e2, ppr e1 $$ ppr e2)
                 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 _other :: 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.
-}