{-# LANGUAGE BangPatterns #-} {-# LANGUAGE FlexibleContexts #-} {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE MultiParamTypeClasses #-} {-# LANGUAGE UndecidableInstances #-} module GHC.Cmm.Expr ( CmmExpr(..), cmmExprType, cmmExprWidth, cmmExprAlignment, maybeInvertCmmExpr , CmmReg(..), cmmRegType, cmmRegWidth , CmmLit(..), cmmLitType , LocalReg(..), localRegType , GlobalReg(..), isArgReg, globalRegType , spReg, hpReg, spLimReg, hpLimReg, nodeReg , currentTSOReg, currentNurseryReg, hpAllocReg, cccsReg , node, baseReg , VGcPtr(..) , DefinerOfRegs, UserOfRegs , foldRegsDefd, foldRegsUsed , foldLocalRegsDefd, foldLocalRegsUsed , RegSet, LocalRegSet, GlobalRegSet , emptyRegSet, elemRegSet, extendRegSet, deleteFromRegSet, mkRegSet , plusRegSet, minusRegSet, timesRegSet, sizeRegSet, nullRegSet , regSetToList , Area(..) , module GHC.Cmm.MachOp , module GHC.Cmm.Type ) where import GhcPrelude import GHC.Cmm.BlockId import GHC.Cmm.CLabel import GHC.Cmm.MachOp import GHC.Cmm.Type import GHC.Driver.Session import Outputable (panic) import Unique import Data.Set (Set) import qualified Data.Set as Set import BasicTypes (Alignment, mkAlignment, alignmentOf) ----------------------------------------------------------------------------- -- CmmExpr -- An expression. Expressions have no side effects. ----------------------------------------------------------------------------- data CmmExpr = CmmLit CmmLit -- Literal | CmmLoad !CmmExpr !CmmType -- Read memory location | CmmReg !CmmReg -- Contents of register | CmmMachOp MachOp [CmmExpr] -- Machine operation (+, -, *, etc.) | CmmStackSlot Area {-# UNPACK #-} !Int -- addressing expression of a stack slot -- See Note [CmmStackSlot aliasing] | CmmRegOff !CmmReg Int -- CmmRegOff reg i -- ** is shorthand only, meaning ** -- CmmMachOp (MO_Add rep) [x, CmmLit (CmmInt (fromIntegral i) rep)] -- where rep = typeWidth (cmmRegType reg) instance Eq CmmExpr where -- Equality ignores the types CmmLit l1 == CmmLit l2 = l1==l2 CmmLoad e1 _ == CmmLoad e2 _ = e1==e2 CmmReg r1 == CmmReg r2 = r1==r2 CmmRegOff r1 i1 == CmmRegOff r2 i2 = r1==r2 && i1==i2 CmmMachOp op1 es1 == CmmMachOp op2 es2 = op1==op2 && es1==es2 CmmStackSlot a1 i1 == CmmStackSlot a2 i2 = a1==a2 && i1==i2 _e1 == _e2 = False data CmmReg = CmmLocal {-# UNPACK #-} !LocalReg | CmmGlobal GlobalReg deriving( Eq, Ord ) -- | A stack area is either the stack slot where a variable is spilled -- or the stack space where function arguments and results are passed. data Area = Old -- See Note [Old Area] | Young {-# UNPACK #-} !BlockId -- Invariant: must be a continuation BlockId -- See Note [Continuation BlockId] in GHC.Cmm.Node. deriving (Eq, Ord) {- Note [Old Area] ~~~~~~~~~~~~~~~~~~ There is a single call area 'Old', allocated at the extreme old end of the stack frame (ie just younger than the return address) which holds: * incoming (overflow) parameters, * outgoing (overflow) parameter to tail calls, * outgoing (overflow) result values * the update frame (if any) Its size is the max of all these requirements. On entry, the stack pointer will point to the youngest incoming parameter, which is not necessarily at the young end of the Old area. End of note -} {- Note [CmmStackSlot aliasing] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ When do two CmmStackSlots alias? - T[old+N] aliases with U[young(L)+M] for all T, U, L, N and M - T[old+N] aliases with U[old+M] only if the areas actually overlap Or more informally, different Areas may overlap with each other. An alternative semantics, that we previously had, was that different Areas do not overlap. The problem that lead to redefining the semantics of stack areas is described below. e.g. if we had x = Sp[old + 8] y = Sp[old + 16] Sp[young(L) + 8] = L Sp[young(L) + 16] = y Sp[young(L) + 24] = x call f() returns to L if areas semantically do not overlap, then we might optimise this to Sp[young(L) + 8] = L Sp[young(L) + 16] = Sp[old + 8] Sp[young(L) + 24] = Sp[old + 16] call f() returns to L and now young(L) cannot be allocated at the same place as old, and we are doomed to use more stack. - old+8 conflicts with young(L)+8 - old+16 conflicts with young(L)+16 and young(L)+8 so young(L)+8 == old+24 and we get Sp[-8] = L Sp[-16] = Sp[8] Sp[-24] = Sp[0] Sp -= 24 call f() returns to L However, if areas are defined to be "possibly overlapping" in the semantics, then we cannot commute any loads/stores of old with young(L), and we will be able to re-use both old+8 and old+16 for young(L). x = Sp[8] y = Sp[0] Sp[8] = L Sp[0] = y Sp[-8] = x Sp = Sp - 8 call f() returns to L Now, the assignments of y go away, x = Sp[8] Sp[8] = L Sp[-8] = x Sp = Sp - 8 call f() returns to L -} data CmmLit = CmmInt !Integer Width -- Interpretation: the 2's complement representation of the value -- is truncated to the specified size. This is easier than trying -- to keep the value within range, because we don't know whether -- it will be used as a signed or unsigned value (the CmmType doesn't -- distinguish between signed & unsigned). | CmmFloat Rational Width | CmmVec [CmmLit] -- Vector literal | CmmLabel CLabel -- Address of label | CmmLabelOff CLabel Int -- Address of label + byte offset -- Due to limitations in the C backend, the following -- MUST ONLY be used inside the info table indicated by label2 -- (label2 must be the info label), and label1 must be an -- SRT, a slow entrypoint or a large bitmap (see the Mangler) -- Don't use it at all unless tablesNextToCode. -- It is also used inside the NCG during when generating -- position-independent code. | CmmLabelDiffOff CLabel CLabel Int Width -- label1 - label2 + offset -- In an expression, the width just has the effect of MO_SS_Conv -- from wordWidth to the desired width. -- -- In a static literal, the supported Widths depend on the -- architecture: wordWidth is supported on all -- architectures. Additionally W32 is supported on x86_64 when -- using the small memory model. | CmmBlock {-# UNPACK #-} !BlockId -- Code label -- Invariant: must be a continuation BlockId -- See Note [Continuation BlockId] in GHC.Cmm.Node. | CmmHighStackMark -- A late-bound constant that stands for the max -- #bytes of stack space used during a procedure. -- During the stack-layout pass, CmmHighStackMark -- is replaced by a CmmInt for the actual number -- of bytes used deriving Eq cmmExprType :: DynFlags -> CmmExpr -> CmmType cmmExprType dflags (CmmLit lit) = cmmLitType dflags lit cmmExprType _ (CmmLoad _ rep) = rep cmmExprType dflags (CmmReg reg) = cmmRegType dflags reg cmmExprType dflags (CmmMachOp op args) = machOpResultType dflags op (map (cmmExprType dflags) args) cmmExprType dflags (CmmRegOff reg _) = cmmRegType dflags reg cmmExprType dflags (CmmStackSlot _ _) = bWord dflags -- an address -- Careful though: what is stored at the stack slot may be bigger than -- an address cmmLitType :: DynFlags -> CmmLit -> CmmType cmmLitType _ (CmmInt _ width) = cmmBits width cmmLitType _ (CmmFloat _ width) = cmmFloat width cmmLitType _ (CmmVec []) = panic "cmmLitType: CmmVec []" cmmLitType cflags (CmmVec (l:ls)) = let ty = cmmLitType cflags l in if all (`cmmEqType` ty) (map (cmmLitType cflags) ls) then cmmVec (1+length ls) ty else panic "cmmLitType: CmmVec" cmmLitType dflags (CmmLabel lbl) = cmmLabelType dflags lbl cmmLitType dflags (CmmLabelOff lbl _) = cmmLabelType dflags lbl cmmLitType _ (CmmLabelDiffOff _ _ _ width) = cmmBits width cmmLitType dflags (CmmBlock _) = bWord dflags cmmLitType dflags (CmmHighStackMark) = bWord dflags cmmLabelType :: DynFlags -> CLabel -> CmmType cmmLabelType dflags lbl | isGcPtrLabel lbl = gcWord dflags | otherwise = bWord dflags cmmExprWidth :: DynFlags -> CmmExpr -> Width cmmExprWidth dflags e = typeWidth (cmmExprType dflags e) -- | Returns an alignment in bytes of a CmmExpr when it's a statically -- known integer constant, otherwise returns an alignment of 1 byte. -- The caller is responsible for using with a sensible CmmExpr -- argument. cmmExprAlignment :: CmmExpr -> Alignment cmmExprAlignment (CmmLit (CmmInt intOff _)) = alignmentOf (fromInteger intOff) cmmExprAlignment _ = mkAlignment 1 -------- --- Negation for conditional branches maybeInvertCmmExpr :: CmmExpr -> Maybe CmmExpr maybeInvertCmmExpr (CmmMachOp op args) = do op' <- maybeInvertComparison op return (CmmMachOp op' args) maybeInvertCmmExpr _ = Nothing ----------------------------------------------------------------------------- -- Local registers ----------------------------------------------------------------------------- data LocalReg = LocalReg {-# UNPACK #-} !Unique CmmType -- ^ Parameters: -- 1. Identifier -- 2. Type instance Eq LocalReg where (LocalReg u1 _) == (LocalReg u2 _) = u1 == u2 -- This is non-deterministic but we do not currently support deterministic -- code-generation. See Note [Unique Determinism and code generation] -- See Note [No Ord for Unique] instance Ord LocalReg where compare (LocalReg u1 _) (LocalReg u2 _) = nonDetCmpUnique u1 u2 instance Uniquable LocalReg where getUnique (LocalReg uniq _) = uniq cmmRegType :: DynFlags -> CmmReg -> CmmType cmmRegType _ (CmmLocal reg) = localRegType reg cmmRegType dflags (CmmGlobal reg) = globalRegType dflags reg cmmRegWidth :: DynFlags -> CmmReg -> Width cmmRegWidth dflags = typeWidth . cmmRegType dflags localRegType :: LocalReg -> CmmType localRegType (LocalReg _ rep) = rep ----------------------------------------------------------------------------- -- Register-use information for expressions and other types ----------------------------------------------------------------------------- -- | Sets of registers -- These are used for dataflow facts, and a common operation is taking -- the union of two RegSets and then asking whether the union is the -- same as one of the inputs. UniqSet isn't good here, because -- sizeUniqSet is O(n) whereas Set.size is O(1), so we use ordinary -- Sets. type RegSet r = Set r type LocalRegSet = RegSet LocalReg type GlobalRegSet = RegSet GlobalReg emptyRegSet :: RegSet r nullRegSet :: RegSet r -> Bool elemRegSet :: Ord r => r -> RegSet r -> Bool extendRegSet :: Ord r => RegSet r -> r -> RegSet r deleteFromRegSet :: Ord r => RegSet r -> r -> RegSet r mkRegSet :: Ord r => [r] -> RegSet r minusRegSet, plusRegSet, timesRegSet :: Ord r => RegSet r -> RegSet r -> RegSet r sizeRegSet :: RegSet r -> Int regSetToList :: RegSet r -> [r] emptyRegSet = Set.empty nullRegSet = Set.null elemRegSet = Set.member extendRegSet = flip Set.insert deleteFromRegSet = flip Set.delete mkRegSet = Set.fromList minusRegSet = Set.difference plusRegSet = Set.union timesRegSet = Set.intersection sizeRegSet = Set.size regSetToList = Set.toList class Ord r => UserOfRegs r a where foldRegsUsed :: DynFlags -> (b -> r -> b) -> b -> a -> b foldLocalRegsUsed :: UserOfRegs LocalReg a => DynFlags -> (b -> LocalReg -> b) -> b -> a -> b foldLocalRegsUsed = foldRegsUsed class Ord r => DefinerOfRegs r a where foldRegsDefd :: DynFlags -> (b -> r -> b) -> b -> a -> b foldLocalRegsDefd :: DefinerOfRegs LocalReg a => DynFlags -> (b -> LocalReg -> b) -> b -> a -> b foldLocalRegsDefd = foldRegsDefd instance UserOfRegs LocalReg CmmReg where foldRegsUsed _ f z (CmmLocal reg) = f z reg foldRegsUsed _ _ z (CmmGlobal _) = z instance DefinerOfRegs LocalReg CmmReg where foldRegsDefd _ f z (CmmLocal reg) = f z reg foldRegsDefd _ _ z (CmmGlobal _) = z instance UserOfRegs GlobalReg CmmReg where foldRegsUsed _ _ z (CmmLocal _) = z foldRegsUsed _ f z (CmmGlobal reg) = f z reg instance DefinerOfRegs GlobalReg CmmReg where foldRegsDefd _ _ z (CmmLocal _) = z foldRegsDefd _ f z (CmmGlobal reg) = f z reg instance Ord r => UserOfRegs r r where foldRegsUsed _ f z r = f z r instance Ord r => DefinerOfRegs r r where foldRegsDefd _ f z r = f z r instance (Ord r, UserOfRegs r CmmReg) => UserOfRegs r CmmExpr where -- The (Ord r) in the context is necessary here -- See Note [Recursive superclasses] in TcInstDcls foldRegsUsed dflags f !z e = expr z e where expr z (CmmLit _) = z expr z (CmmLoad addr _) = foldRegsUsed dflags f z addr expr z (CmmReg r) = foldRegsUsed dflags f z r expr z (CmmMachOp _ exprs) = foldRegsUsed dflags f z exprs expr z (CmmRegOff r _) = foldRegsUsed dflags f z r expr z (CmmStackSlot _ _) = z instance UserOfRegs r a => UserOfRegs r [a] where foldRegsUsed dflags f set as = foldl' (foldRegsUsed dflags f) set as {-# INLINABLE foldRegsUsed #-} instance DefinerOfRegs r a => DefinerOfRegs r [a] where foldRegsDefd dflags f set as = foldl' (foldRegsDefd dflags f) set as {-# INLINABLE foldRegsDefd #-} ----------------------------------------------------------------------------- -- Global STG registers ----------------------------------------------------------------------------- data VGcPtr = VGcPtr | VNonGcPtr deriving( Eq, Show ) ----------------------------------------------------------------------------- -- Global STG registers ----------------------------------------------------------------------------- {- Note [Overlapping global registers] The backend might not faithfully implement the abstraction of the STG machine with independent registers for different values of type GlobalReg. Specifically, certain pairs of registers (r1, r2) may overlap in the sense that a store to r1 invalidates the value in r2, and vice versa. Currently this occurs only on the x86_64 architecture where FloatReg n and DoubleReg n are assigned the same microarchitectural register, in order to allow functions to receive more Float# or Double# arguments in registers (as opposed to on the stack). There are no specific rules about which registers might overlap with which other registers, but presumably it's safe to assume that nothing will overlap with special registers like Sp or BaseReg. Use GHC.Cmm.Utils.regsOverlap to determine whether two GlobalRegs overlap on a particular platform. The instance Eq GlobalReg is syntactic equality of STG registers and does not take overlap into account. However it is still used in UserOfRegs/DefinerOfRegs and there are likely still bugs there, beware! -} data GlobalReg -- Argument and return registers = VanillaReg -- pointers, unboxed ints and chars {-# UNPACK #-} !Int -- its number VGcPtr | FloatReg -- single-precision floating-point registers {-# UNPACK #-} !Int -- its number | DoubleReg -- double-precision floating-point registers {-# UNPACK #-} !Int -- its number | LongReg -- long int registers (64-bit, really) {-# UNPACK #-} !Int -- its number | XmmReg -- 128-bit SIMD vector register {-# UNPACK #-} !Int -- its number | YmmReg -- 256-bit SIMD vector register {-# UNPACK #-} !Int -- its number | ZmmReg -- 512-bit SIMD vector register {-# UNPACK #-} !Int -- its number -- STG registers | Sp -- Stack ptr; points to last occupied stack location. | SpLim -- Stack limit | Hp -- Heap ptr; points to last occupied heap location. | HpLim -- Heap limit register | CCCS -- Current cost-centre stack | CurrentTSO -- pointer to current thread's TSO | CurrentNursery -- pointer to allocation area | HpAlloc -- allocation count for heap check failure -- We keep the address of some commonly-called -- functions in the register table, to keep code -- size down: | EagerBlackholeInfo -- stg_EAGER_BLACKHOLE_info | GCEnter1 -- stg_gc_enter_1 | GCFun -- stg_gc_fun -- Base offset for the register table, used for accessing registers -- which do not have real registers assigned to them. This register -- will only appear after we have expanded GlobalReg into memory accesses -- (where necessary) in the native code generator. | BaseReg -- The register used by the platform for the C stack pointer. This is -- a break in the STG abstraction used exclusively to setup stack unwinding -- information. | MachSp -- The is a dummy register used to indicate to the stack unwinder where -- a routine would return to. | UnwindReturnReg -- Base Register for PIC (position-independent code) calculations -- Only used inside the native code generator. It's exact meaning differs -- from platform to platform (see module PositionIndependentCode). | PicBaseReg deriving( Show ) instance Eq GlobalReg where VanillaReg i _ == VanillaReg j _ = i==j -- Ignore type when seeking clashes FloatReg i == FloatReg j = i==j DoubleReg i == DoubleReg j = i==j LongReg i == LongReg j = i==j -- NOTE: XMM, YMM, ZMM registers actually are the same registers -- at least with respect to store at YMM i and then read from XMM i -- and similarly for ZMM etc. XmmReg i == XmmReg j = i==j YmmReg i == YmmReg j = i==j ZmmReg i == ZmmReg j = i==j Sp == Sp = True SpLim == SpLim = True Hp == Hp = True HpLim == HpLim = True CCCS == CCCS = True CurrentTSO == CurrentTSO = True CurrentNursery == CurrentNursery = True HpAlloc == HpAlloc = True EagerBlackholeInfo == EagerBlackholeInfo = True GCEnter1 == GCEnter1 = True GCFun == GCFun = True BaseReg == BaseReg = True MachSp == MachSp = True UnwindReturnReg == UnwindReturnReg = True PicBaseReg == PicBaseReg = True _r1 == _r2 = False instance Ord GlobalReg where compare (VanillaReg i _) (VanillaReg j _) = compare i j -- Ignore type when seeking clashes compare (FloatReg i) (FloatReg j) = compare i j compare (DoubleReg i) (DoubleReg j) = compare i j compare (LongReg i) (LongReg j) = compare i j compare (XmmReg i) (XmmReg j) = compare i j compare (YmmReg i) (YmmReg j) = compare i j compare (ZmmReg i) (ZmmReg j) = compare i j compare Sp Sp = EQ compare SpLim SpLim = EQ compare Hp Hp = EQ compare HpLim HpLim = EQ compare CCCS CCCS = EQ compare CurrentTSO CurrentTSO = EQ compare CurrentNursery CurrentNursery = EQ compare HpAlloc HpAlloc = EQ compare EagerBlackholeInfo EagerBlackholeInfo = EQ compare GCEnter1 GCEnter1 = EQ compare GCFun GCFun = EQ compare BaseReg BaseReg = EQ compare MachSp MachSp = EQ compare UnwindReturnReg UnwindReturnReg = EQ compare PicBaseReg PicBaseReg = EQ compare (VanillaReg _ _) _ = LT compare _ (VanillaReg _ _) = GT compare (FloatReg _) _ = LT compare _ (FloatReg _) = GT compare (DoubleReg _) _ = LT compare _ (DoubleReg _) = GT compare (LongReg _) _ = LT compare _ (LongReg _) = GT compare (XmmReg _) _ = LT compare _ (XmmReg _) = GT compare (YmmReg _) _ = LT compare _ (YmmReg _) = GT compare (ZmmReg _) _ = LT compare _ (ZmmReg _) = GT compare Sp _ = LT compare _ Sp = GT compare SpLim _ = LT compare _ SpLim = GT compare Hp _ = LT compare _ Hp = GT compare HpLim _ = LT compare _ HpLim = GT compare CCCS _ = LT compare _ CCCS = GT compare CurrentTSO _ = LT compare _ CurrentTSO = GT compare CurrentNursery _ = LT compare _ CurrentNursery = GT compare HpAlloc _ = LT compare _ HpAlloc = GT compare GCEnter1 _ = LT compare _ GCEnter1 = GT compare GCFun _ = LT compare _ GCFun = GT compare BaseReg _ = LT compare _ BaseReg = GT compare MachSp _ = LT compare _ MachSp = GT compare UnwindReturnReg _ = LT compare _ UnwindReturnReg = GT compare EagerBlackholeInfo _ = LT compare _ EagerBlackholeInfo = GT -- convenient aliases baseReg, spReg, hpReg, spLimReg, hpLimReg, nodeReg, currentTSOReg, currentNurseryReg, hpAllocReg, cccsReg :: CmmReg baseReg = CmmGlobal BaseReg spReg = CmmGlobal Sp hpReg = CmmGlobal Hp hpLimReg = CmmGlobal HpLim spLimReg = CmmGlobal SpLim nodeReg = CmmGlobal node currentTSOReg = CmmGlobal CurrentTSO currentNurseryReg = CmmGlobal CurrentNursery hpAllocReg = CmmGlobal HpAlloc cccsReg = CmmGlobal CCCS node :: GlobalReg node = VanillaReg 1 VGcPtr globalRegType :: DynFlags -> GlobalReg -> CmmType globalRegType dflags (VanillaReg _ VGcPtr) = gcWord dflags globalRegType dflags (VanillaReg _ VNonGcPtr) = bWord dflags globalRegType _ (FloatReg _) = cmmFloat W32 globalRegType _ (DoubleReg _) = cmmFloat W64 globalRegType _ (LongReg _) = cmmBits W64 -- TODO: improve the internal model of SIMD/vectorized registers -- the right design SHOULd improve handling of float and double code too. -- see remarks in "NOTE [SIMD Design for the future]"" in GHC.StgToCmm.Prim globalRegType _ (XmmReg _) = cmmVec 4 (cmmBits W32) globalRegType _ (YmmReg _) = cmmVec 8 (cmmBits W32) globalRegType _ (ZmmReg _) = cmmVec 16 (cmmBits W32) globalRegType dflags Hp = gcWord dflags -- The initialiser for all -- dynamically allocated closures globalRegType dflags _ = bWord dflags isArgReg :: GlobalReg -> Bool isArgReg (VanillaReg {}) = True isArgReg (FloatReg {}) = True isArgReg (DoubleReg {}) = True isArgReg (LongReg {}) = True isArgReg (XmmReg {}) = True isArgReg (YmmReg {}) = True isArgReg (ZmmReg {}) = True isArgReg _ = False