{- (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 \section[ConFold]{Constant Folder} Conceptually, constant folding should be parameterized with the kind of target machine to get identical behaviour during compilation time and runtime. We cheat a little bit here... ToDo: check boundaries before folding, e.g. we can fold the Float addition (i1 + i2) only if it results in a valid Float. -} {-# LANGUAGE CPP, RankNTypes, PatternSynonyms, ViewPatterns, RecordWildCards #-} {-# OPTIONS_GHC -optc-DNON_POSIX_SOURCE #-} module PrelRules ( primOpRules , builtinRules , caseRules ) where #include "HsVersions.h" #include "../includes/MachDeps.h" import GhcPrelude import {-# SOURCE #-} MkId ( mkPrimOpId, magicDictId ) import CoreSyn import MkCore import Id import Literal import CoreOpt ( exprIsLiteral_maybe ) import PrimOp ( PrimOp(..), tagToEnumKey ) import TysWiredIn import TysPrim import TyCon ( tyConDataCons_maybe, isAlgTyCon, isEnumerationTyCon , isNewTyCon, unwrapNewTyCon_maybe, tyConDataCons , tyConFamilySize ) import DataCon ( dataConTagZ, dataConTyCon, dataConWorkId ) import CoreUtils ( cheapEqExpr, exprIsHNF, exprType ) import CoreUnfold ( exprIsConApp_maybe ) import Type import OccName ( occNameFS ) import PrelNames import Maybes ( orElse ) import Name ( Name, nameOccName ) import Outputable import FastString import BasicTypes import DynFlags import Platform import Util import Coercion (mkUnbranchedAxInstCo,mkSymCo,Role(..)) import Control.Applicative ( Alternative(..) ) import Control.Monad import qualified Control.Monad.Fail as MonadFail import Data.Bits as Bits import qualified Data.ByteString as BS import Data.Int import Data.Ratio import Data.Word {- Note [Constant folding] ~~~~~~~~~~~~~~~~~~~~~~~ primOpRules generates a rewrite rule for each primop These rules do what is often called "constant folding" E.g. the rules for +# might say 4 +# 5 = 9 Well, of course you'd need a lot of rules if you did it like that, so we use a BuiltinRule instead, so that we can match in any two literal values. So the rule is really more like (Lit x) +# (Lit y) = Lit (x+#y) where the (+#) on the rhs is done at compile time That is why these rules are built in here. -} primOpRules :: Name -> PrimOp -> Maybe CoreRule -- ToDo: something for integer-shift ops? -- NotOp primOpRules nm TagToEnumOp = mkPrimOpRule nm 2 [ tagToEnumRule ] primOpRules nm DataToTagOp = mkPrimOpRule nm 2 [ dataToTagRule ] -- Int operations primOpRules nm IntAddOp = mkPrimOpRule nm 2 [ binaryLit (intOp2 (+)) , identityDynFlags zeroi , numFoldingRules IntAddOp intPrimOps ] primOpRules nm IntSubOp = mkPrimOpRule nm 2 [ binaryLit (intOp2 (-)) , rightIdentityDynFlags zeroi , equalArgs >> retLit zeroi , numFoldingRules IntSubOp intPrimOps ] primOpRules nm IntAddCOp = mkPrimOpRule nm 2 [ binaryLit (intOpC2 (+)) , identityCDynFlags zeroi ] primOpRules nm IntSubCOp = mkPrimOpRule nm 2 [ binaryLit (intOpC2 (-)) , rightIdentityCDynFlags zeroi , equalArgs >> retLitNoC zeroi ] primOpRules nm IntMulOp = mkPrimOpRule nm 2 [ binaryLit (intOp2 (*)) , zeroElem zeroi , identityDynFlags onei , numFoldingRules IntMulOp intPrimOps ] primOpRules nm IntQuotOp = mkPrimOpRule nm 2 [ nonZeroLit 1 >> binaryLit (intOp2 quot) , leftZero zeroi , rightIdentityDynFlags onei , equalArgs >> retLit onei ] primOpRules nm IntRemOp = mkPrimOpRule nm 2 [ nonZeroLit 1 >> binaryLit (intOp2 rem) , leftZero zeroi , do l <- getLiteral 1 dflags <- getDynFlags guard (l == onei dflags) retLit zeroi , equalArgs >> retLit zeroi , equalArgs >> retLit zeroi ] primOpRules nm AndIOp = mkPrimOpRule nm 2 [ binaryLit (intOp2 (.&.)) , idempotent , zeroElem zeroi ] primOpRules nm OrIOp = mkPrimOpRule nm 2 [ binaryLit (intOp2 (.|.)) , idempotent , identityDynFlags zeroi ] primOpRules nm XorIOp = mkPrimOpRule nm 2 [ binaryLit (intOp2 xor) , identityDynFlags zeroi , equalArgs >> retLit zeroi ] primOpRules nm NotIOp = mkPrimOpRule nm 1 [ unaryLit complementOp , inversePrimOp NotIOp ] primOpRules nm IntNegOp = mkPrimOpRule nm 1 [ unaryLit negOp , inversePrimOp IntNegOp ] primOpRules nm ISllOp = mkPrimOpRule nm 2 [ shiftRule (const Bits.shiftL) , rightIdentityDynFlags zeroi ] primOpRules nm ISraOp = mkPrimOpRule nm 2 [ shiftRule (const Bits.shiftR) , rightIdentityDynFlags zeroi ] primOpRules nm ISrlOp = mkPrimOpRule nm 2 [ shiftRule shiftRightLogical , rightIdentityDynFlags zeroi ] -- Word operations primOpRules nm WordAddOp = mkPrimOpRule nm 2 [ binaryLit (wordOp2 (+)) , identityDynFlags zerow , numFoldingRules WordAddOp wordPrimOps ] primOpRules nm WordSubOp = mkPrimOpRule nm 2 [ binaryLit (wordOp2 (-)) , rightIdentityDynFlags zerow , equalArgs >> retLit zerow , numFoldingRules WordSubOp wordPrimOps ] primOpRules nm WordAddCOp = mkPrimOpRule nm 2 [ binaryLit (wordOpC2 (+)) , identityCDynFlags zerow ] primOpRules nm WordSubCOp = mkPrimOpRule nm 2 [ binaryLit (wordOpC2 (-)) , rightIdentityCDynFlags zerow , equalArgs >> retLitNoC zerow ] primOpRules nm WordMulOp = mkPrimOpRule nm 2 [ binaryLit (wordOp2 (*)) , identityDynFlags onew , numFoldingRules WordMulOp wordPrimOps ] primOpRules nm WordQuotOp = mkPrimOpRule nm 2 [ nonZeroLit 1 >> binaryLit (wordOp2 quot) , rightIdentityDynFlags onew ] primOpRules nm WordRemOp = mkPrimOpRule nm 2 [ nonZeroLit 1 >> binaryLit (wordOp2 rem) , leftZero zerow , do l <- getLiteral 1 dflags <- getDynFlags guard (l == onew dflags) retLit zerow , equalArgs >> retLit zerow ] primOpRules nm AndOp = mkPrimOpRule nm 2 [ binaryLit (wordOp2 (.&.)) , idempotent , zeroElem zerow ] primOpRules nm OrOp = mkPrimOpRule nm 2 [ binaryLit (wordOp2 (.|.)) , idempotent , identityDynFlags zerow ] primOpRules nm XorOp = mkPrimOpRule nm 2 [ binaryLit (wordOp2 xor) , identityDynFlags zerow , equalArgs >> retLit zerow ] primOpRules nm NotOp = mkPrimOpRule nm 1 [ unaryLit complementOp , inversePrimOp NotOp ] primOpRules nm SllOp = mkPrimOpRule nm 2 [ shiftRule (const Bits.shiftL) ] primOpRules nm SrlOp = mkPrimOpRule nm 2 [ shiftRule shiftRightLogical ] -- coercions primOpRules nm Word2IntOp = mkPrimOpRule nm 1 [ liftLitDynFlags word2IntLit , inversePrimOp Int2WordOp ] primOpRules nm Int2WordOp = mkPrimOpRule nm 1 [ liftLitDynFlags int2WordLit , inversePrimOp Word2IntOp ] primOpRules nm Narrow8IntOp = mkPrimOpRule nm 1 [ liftLit narrow8IntLit , subsumedByPrimOp Narrow8IntOp , Narrow8IntOp `subsumesPrimOp` Narrow16IntOp , Narrow8IntOp `subsumesPrimOp` Narrow32IntOp ] primOpRules nm Narrow16IntOp = mkPrimOpRule nm 1 [ liftLit narrow16IntLit , subsumedByPrimOp Narrow8IntOp , subsumedByPrimOp Narrow16IntOp , Narrow16IntOp `subsumesPrimOp` Narrow32IntOp ] primOpRules nm Narrow32IntOp = mkPrimOpRule nm 1 [ liftLit narrow32IntLit , subsumedByPrimOp Narrow8IntOp , subsumedByPrimOp Narrow16IntOp , subsumedByPrimOp Narrow32IntOp , removeOp32 ] primOpRules nm Narrow8WordOp = mkPrimOpRule nm 1 [ liftLit narrow8WordLit , subsumedByPrimOp Narrow8WordOp , Narrow8WordOp `subsumesPrimOp` Narrow16WordOp , Narrow8WordOp `subsumesPrimOp` Narrow32WordOp ] primOpRules nm Narrow16WordOp = mkPrimOpRule nm 1 [ liftLit narrow16WordLit , subsumedByPrimOp Narrow8WordOp , subsumedByPrimOp Narrow16WordOp , Narrow16WordOp `subsumesPrimOp` Narrow32WordOp ] primOpRules nm Narrow32WordOp = mkPrimOpRule nm 1 [ liftLit narrow32WordLit , subsumedByPrimOp Narrow8WordOp , subsumedByPrimOp Narrow16WordOp , subsumedByPrimOp Narrow32WordOp , removeOp32 ] primOpRules nm OrdOp = mkPrimOpRule nm 1 [ liftLit char2IntLit , inversePrimOp ChrOp ] primOpRules nm ChrOp = mkPrimOpRule nm 1 [ do [Lit lit] <- getArgs guard (litFitsInChar lit) liftLit int2CharLit , inversePrimOp OrdOp ] primOpRules nm Float2IntOp = mkPrimOpRule nm 1 [ liftLit float2IntLit ] primOpRules nm Int2FloatOp = mkPrimOpRule nm 1 [ liftLit int2FloatLit ] primOpRules nm Double2IntOp = mkPrimOpRule nm 1 [ liftLit double2IntLit ] primOpRules nm Int2DoubleOp = mkPrimOpRule nm 1 [ liftLit int2DoubleLit ] -- SUP: Not sure what the standard says about precision in the following 2 cases primOpRules nm Float2DoubleOp = mkPrimOpRule nm 1 [ liftLit float2DoubleLit ] primOpRules nm Double2FloatOp = mkPrimOpRule nm 1 [ liftLit double2FloatLit ] -- Float primOpRules nm FloatAddOp = mkPrimOpRule nm 2 [ binaryLit (floatOp2 (+)) , identity zerof ] primOpRules nm FloatSubOp = mkPrimOpRule nm 2 [ binaryLit (floatOp2 (-)) , rightIdentity zerof ] primOpRules nm FloatMulOp = mkPrimOpRule nm 2 [ binaryLit (floatOp2 (*)) , identity onef , strengthReduction twof FloatAddOp ] -- zeroElem zerof doesn't hold because of NaN primOpRules nm FloatDivOp = mkPrimOpRule nm 2 [ guardFloatDiv >> binaryLit (floatOp2 (/)) , rightIdentity onef ] primOpRules nm FloatNegOp = mkPrimOpRule nm 1 [ unaryLit negOp , inversePrimOp FloatNegOp ] -- Double primOpRules nm DoubleAddOp = mkPrimOpRule nm 2 [ binaryLit (doubleOp2 (+)) , identity zerod ] primOpRules nm DoubleSubOp = mkPrimOpRule nm 2 [ binaryLit (doubleOp2 (-)) , rightIdentity zerod ] primOpRules nm DoubleMulOp = mkPrimOpRule nm 2 [ binaryLit (doubleOp2 (*)) , identity oned , strengthReduction twod DoubleAddOp ] -- zeroElem zerod doesn't hold because of NaN primOpRules nm DoubleDivOp = mkPrimOpRule nm 2 [ guardDoubleDiv >> binaryLit (doubleOp2 (/)) , rightIdentity oned ] primOpRules nm DoubleNegOp = mkPrimOpRule nm 1 [ unaryLit negOp , inversePrimOp DoubleNegOp ] -- Relational operators primOpRules nm IntEqOp = mkRelOpRule nm (==) [ litEq True ] primOpRules nm IntNeOp = mkRelOpRule nm (/=) [ litEq False ] primOpRules nm CharEqOp = mkRelOpRule nm (==) [ litEq True ] primOpRules nm CharNeOp = mkRelOpRule nm (/=) [ litEq False ] primOpRules nm IntGtOp = mkRelOpRule nm (>) [ boundsCmp Gt ] primOpRules nm IntGeOp = mkRelOpRule nm (>=) [ boundsCmp Ge ] primOpRules nm IntLeOp = mkRelOpRule nm (<=) [ boundsCmp Le ] primOpRules nm IntLtOp = mkRelOpRule nm (<) [ boundsCmp Lt ] primOpRules nm CharGtOp = mkRelOpRule nm (>) [ boundsCmp Gt ] primOpRules nm CharGeOp = mkRelOpRule nm (>=) [ boundsCmp Ge ] primOpRules nm CharLeOp = mkRelOpRule nm (<=) [ boundsCmp Le ] primOpRules nm CharLtOp = mkRelOpRule nm (<) [ boundsCmp Lt ] primOpRules nm FloatGtOp = mkFloatingRelOpRule nm (>) primOpRules nm FloatGeOp = mkFloatingRelOpRule nm (>=) primOpRules nm FloatLeOp = mkFloatingRelOpRule nm (<=) primOpRules nm FloatLtOp = mkFloatingRelOpRule nm (<) primOpRules nm FloatEqOp = mkFloatingRelOpRule nm (==) primOpRules nm FloatNeOp = mkFloatingRelOpRule nm (/=) primOpRules nm DoubleGtOp = mkFloatingRelOpRule nm (>) primOpRules nm DoubleGeOp = mkFloatingRelOpRule nm (>=) primOpRules nm DoubleLeOp = mkFloatingRelOpRule nm (<=) primOpRules nm DoubleLtOp = mkFloatingRelOpRule nm (<) primOpRules nm DoubleEqOp = mkFloatingRelOpRule nm (==) primOpRules nm DoubleNeOp = mkFloatingRelOpRule nm (/=) primOpRules nm WordGtOp = mkRelOpRule nm (>) [ boundsCmp Gt ] primOpRules nm WordGeOp = mkRelOpRule nm (>=) [ boundsCmp Ge ] primOpRules nm WordLeOp = mkRelOpRule nm (<=) [ boundsCmp Le ] primOpRules nm WordLtOp = mkRelOpRule nm (<) [ boundsCmp Lt ] primOpRules nm WordEqOp = mkRelOpRule nm (==) [ litEq True ] primOpRules nm WordNeOp = mkRelOpRule nm (/=) [ litEq False ] primOpRules nm AddrAddOp = mkPrimOpRule nm 2 [ rightIdentityDynFlags zeroi ] primOpRules nm SeqOp = mkPrimOpRule nm 4 [ seqRule ] primOpRules nm SparkOp = mkPrimOpRule nm 4 [ sparkRule ] primOpRules _ _ = Nothing {- ************************************************************************ * * \subsection{Doing the business} * * ************************************************************************ -} -- useful shorthands mkPrimOpRule :: Name -> Int -> [RuleM CoreExpr] -> Maybe CoreRule mkPrimOpRule nm arity rules = Just $ mkBasicRule nm arity (msum rules) mkRelOpRule :: Name -> (forall a . Ord a => a -> a -> Bool) -> [RuleM CoreExpr] -> Maybe CoreRule mkRelOpRule nm cmp extra = mkPrimOpRule nm 2 $ binaryCmpLit cmp : equal_rule : extra where -- x `cmp` x does not depend on x, so -- compute it for the arbitrary value 'True' -- and use that result equal_rule = do { equalArgs ; dflags <- getDynFlags ; return (if cmp True True then trueValInt dflags else falseValInt dflags) } {- Note [Rules for floating-point comparisons] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ We need different rules for floating-point values because for floats it is not true that x = x (for NaNs); so we do not want the equal_rule rule that mkRelOpRule uses. Note also that, in the case of equality/inequality, we do /not/ want to switch to a case-expression. For example, we do not want to convert case (eqFloat# x 3.8#) of True -> this False -> that to case x of 3.8#::Float# -> this _ -> that See #9238. Reason: comparing floating-point values for equality delicate, and we don't want to implement that delicacy in the code for case expressions. So we make it an invariant of Core that a case expression never scrutinises a Float# or Double#. This transformation is what the litEq rule does; see Note [The litEq rule: converting equality to case]. So we /refrain/ from using litEq for mkFloatingRelOpRule. -} mkFloatingRelOpRule :: Name -> (forall a . Ord a => a -> a -> Bool) -> Maybe CoreRule -- See Note [Rules for floating-point comparisons] mkFloatingRelOpRule nm cmp = mkPrimOpRule nm 2 [binaryCmpLit cmp] -- common constants zeroi, onei, zerow, onew :: DynFlags -> Literal zeroi dflags = mkLitInt dflags 0 onei dflags = mkLitInt dflags 1 zerow dflags = mkLitWord dflags 0 onew dflags = mkLitWord dflags 1 zerof, onef, twof, zerod, oned, twod :: Literal zerof = mkLitFloat 0.0 onef = mkLitFloat 1.0 twof = mkLitFloat 2.0 zerod = mkLitDouble 0.0 oned = mkLitDouble 1.0 twod = mkLitDouble 2.0 cmpOp :: DynFlags -> (forall a . Ord a => a -> a -> Bool) -> Literal -> Literal -> Maybe CoreExpr cmpOp dflags cmp = go where done True = Just $ trueValInt dflags done False = Just $ falseValInt dflags -- These compares are at different types go (LitChar i1) (LitChar i2) = done (i1 `cmp` i2) go (LitFloat i1) (LitFloat i2) = done (i1 `cmp` i2) go (LitDouble i1) (LitDouble i2) = done (i1 `cmp` i2) go (LitNumber nt1 i1 _) (LitNumber nt2 i2 _) | nt1 /= nt2 = Nothing | otherwise = done (i1 `cmp` i2) go _ _ = Nothing -------------------------- negOp :: DynFlags -> Literal -> Maybe CoreExpr -- Negate negOp _ (LitFloat 0.0) = Nothing -- can't represent -0.0 as a Rational negOp dflags (LitFloat f) = Just (mkFloatVal dflags (-f)) negOp _ (LitDouble 0.0) = Nothing negOp dflags (LitDouble d) = Just (mkDoubleVal dflags (-d)) negOp dflags (LitNumber nt i t) | litNumIsSigned nt = Just (Lit (mkLitNumberWrap dflags nt (-i) t)) negOp _ _ = Nothing complementOp :: DynFlags -> Literal -> Maybe CoreExpr -- Binary complement complementOp dflags (LitNumber nt i t) = Just (Lit (mkLitNumberWrap dflags nt (complement i) t)) complementOp _ _ = Nothing -------------------------- intOp2 :: (Integral a, Integral b) => (a -> b -> Integer) -> DynFlags -> Literal -> Literal -> Maybe CoreExpr intOp2 = intOp2' . const intOp2' :: (Integral a, Integral b) => (DynFlags -> a -> b -> Integer) -> DynFlags -> Literal -> Literal -> Maybe CoreExpr intOp2' op dflags (LitNumber LitNumInt i1 _) (LitNumber LitNumInt i2 _) = let o = op dflags in intResult dflags (fromInteger i1 `o` fromInteger i2) intOp2' _ _ _ _ = Nothing -- Could find LitLit intOpC2 :: (Integral a, Integral b) => (a -> b -> Integer) -> DynFlags -> Literal -> Literal -> Maybe CoreExpr intOpC2 op dflags (LitNumber LitNumInt i1 _) (LitNumber LitNumInt i2 _) = do intCResult dflags (fromInteger i1 `op` fromInteger i2) intOpC2 _ _ _ _ = Nothing -- Could find LitLit shiftRightLogical :: DynFlags -> Integer -> Int -> Integer -- Shift right, putting zeros in rather than sign-propagating as Bits.shiftR would do -- Do this by converting to Word and back. Obviously this won't work for big -- values, but its ok as we use it here shiftRightLogical dflags x n | wordSizeInBits dflags == 32 = fromIntegral (fromInteger x `shiftR` n :: Word32) | wordSizeInBits dflags == 64 = fromIntegral (fromInteger x `shiftR` n :: Word64) | otherwise = panic "shiftRightLogical: unsupported word size" -------------------------- retLit :: (DynFlags -> Literal) -> RuleM CoreExpr retLit l = do dflags <- getDynFlags return $ Lit $ l dflags retLitNoC :: (DynFlags -> Literal) -> RuleM CoreExpr retLitNoC l = do dflags <- getDynFlags let lit = l dflags let ty = literalType lit return $ mkCoreUbxTup [ty, ty] [Lit lit, Lit (zeroi dflags)] wordOp2 :: (Integral a, Integral b) => (a -> b -> Integer) -> DynFlags -> Literal -> Literal -> Maybe CoreExpr wordOp2 op dflags (LitNumber LitNumWord w1 _) (LitNumber LitNumWord w2 _) = wordResult dflags (fromInteger w1 `op` fromInteger w2) wordOp2 _ _ _ _ = Nothing -- Could find LitLit wordOpC2 :: (Integral a, Integral b) => (a -> b -> Integer) -> DynFlags -> Literal -> Literal -> Maybe CoreExpr wordOpC2 op dflags (LitNumber LitNumWord w1 _) (LitNumber LitNumWord w2 _) = wordCResult dflags (fromInteger w1 `op` fromInteger w2) wordOpC2 _ _ _ _ = Nothing -- Could find LitLit shiftRule :: (DynFlags -> Integer -> Int -> Integer) -> RuleM CoreExpr -- Shifts take an Int; hence third arg of op is Int -- Used for shift primops -- ISllOp, ISraOp, ISrlOp :: Word# -> Int# -> Word# -- SllOp, SrlOp :: Word# -> Int# -> Word# -- See Note [Guarding against silly shifts] shiftRule shift_op = do { dflags <- getDynFlags ; [e1, Lit (LitNumber LitNumInt shift_len _)] <- getArgs ; case e1 of _ | shift_len == 0 -> return e1 -- Do the shift at type Integer, but shift length is Int Lit (LitNumber nt x t) | 0 < shift_len , shift_len <= wordSizeInBits dflags -> let op = shift_op dflags y = x `op` fromInteger shift_len in liftMaybe $ Just (Lit (mkLitNumberWrap dflags nt y t)) _ -> mzero } wordSizeInBits :: DynFlags -> Integer wordSizeInBits dflags = toInteger (platformWordSize (targetPlatform dflags) `shiftL` 3) -------------------------- floatOp2 :: (Rational -> Rational -> Rational) -> DynFlags -> Literal -> Literal -> Maybe (Expr CoreBndr) floatOp2 op dflags (LitFloat f1) (LitFloat f2) = Just (mkFloatVal dflags (f1 `op` f2)) floatOp2 _ _ _ _ = Nothing -------------------------- doubleOp2 :: (Rational -> Rational -> Rational) -> DynFlags -> Literal -> Literal -> Maybe (Expr CoreBndr) doubleOp2 op dflags (LitDouble f1) (LitDouble f2) = Just (mkDoubleVal dflags (f1 `op` f2)) doubleOp2 _ _ _ _ = Nothing -------------------------- {- Note [The litEq rule: converting equality to case] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This stuff turns n ==# 3# into case n of 3# -> True m -> False This is a Good Thing, because it allows case-of case things to happen, and case-default absorption to happen. For example: if (n ==# 3#) || (n ==# 4#) then e1 else e2 will transform to case n of 3# -> e1 4# -> e1 m -> e2 (modulo the usual precautions to avoid duplicating e1) -} litEq :: Bool -- True <=> equality, False <=> inequality -> RuleM CoreExpr litEq is_eq = msum [ do [Lit lit, expr] <- getArgs dflags <- getDynFlags do_lit_eq dflags lit expr , do [expr, Lit lit] <- getArgs dflags <- getDynFlags do_lit_eq dflags lit expr ] where do_lit_eq dflags lit expr = do guard (not (litIsLifted lit)) return (mkWildCase expr (literalType lit) intPrimTy [(DEFAULT, [], val_if_neq), (LitAlt lit, [], val_if_eq)]) where val_if_eq | is_eq = trueValInt dflags | otherwise = falseValInt dflags val_if_neq | is_eq = falseValInt dflags | otherwise = trueValInt dflags -- | Check if there is comparison with minBound or maxBound, that is -- always true or false. For instance, an Int cannot be smaller than its -- minBound, so we can replace such comparison with False. boundsCmp :: Comparison -> RuleM CoreExpr boundsCmp op = do dflags <- getDynFlags [a, b] <- getArgs liftMaybe $ mkRuleFn dflags op a b data Comparison = Gt | Ge | Lt | Le mkRuleFn :: DynFlags -> Comparison -> CoreExpr -> CoreExpr -> Maybe CoreExpr mkRuleFn dflags Gt (Lit lit) _ | isMinBound dflags lit = Just $ falseValInt dflags mkRuleFn dflags Le (Lit lit) _ | isMinBound dflags lit = Just $ trueValInt dflags mkRuleFn dflags Ge _ (Lit lit) | isMinBound dflags lit = Just $ trueValInt dflags mkRuleFn dflags Lt _ (Lit lit) | isMinBound dflags lit = Just $ falseValInt dflags mkRuleFn dflags Ge (Lit lit) _ | isMaxBound dflags lit = Just $ trueValInt dflags mkRuleFn dflags Lt (Lit lit) _ | isMaxBound dflags lit = Just $ falseValInt dflags mkRuleFn dflags Gt _ (Lit lit) | isMaxBound dflags lit = Just $ falseValInt dflags mkRuleFn dflags Le _ (Lit lit) | isMaxBound dflags lit = Just $ trueValInt dflags mkRuleFn _ _ _ _ = Nothing isMinBound :: DynFlags -> Literal -> Bool isMinBound _ (LitChar c) = c == minBound isMinBound dflags (LitNumber nt i _) = case nt of LitNumInt -> i == tARGET_MIN_INT dflags LitNumInt64 -> i == toInteger (minBound :: Int64) LitNumWord -> i == 0 LitNumWord64 -> i == 0 LitNumNatural -> i == 0 LitNumInteger -> False isMinBound _ _ = False isMaxBound :: DynFlags -> Literal -> Bool isMaxBound _ (LitChar c) = c == maxBound isMaxBound dflags (LitNumber nt i _) = case nt of LitNumInt -> i == tARGET_MAX_INT dflags LitNumInt64 -> i == toInteger (maxBound :: Int64) LitNumWord -> i == tARGET_MAX_WORD dflags LitNumWord64 -> i == toInteger (maxBound :: Word64) LitNumNatural -> False LitNumInteger -> False isMaxBound _ _ = False -- | Create an Int literal expression while ensuring the given Integer is in the -- target Int range intResult :: DynFlags -> Integer -> Maybe CoreExpr intResult dflags result = Just (intResult' dflags result) intResult' :: DynFlags -> Integer -> CoreExpr intResult' dflags result = Lit (mkLitIntWrap dflags result) -- | Create an unboxed pair of an Int literal expression, ensuring the given -- Integer is in the target Int range and the corresponding overflow flag -- (@0#@/@1#@) if it wasn't. intCResult :: DynFlags -> Integer -> Maybe CoreExpr intCResult dflags result = Just (mkPair [Lit lit, Lit c]) where mkPair = mkCoreUbxTup [intPrimTy, intPrimTy] (lit, b) = mkLitIntWrapC dflags result c = if b then onei dflags else zeroi dflags -- | Create a Word literal expression while ensuring the given Integer is in the -- target Word range wordResult :: DynFlags -> Integer -> Maybe CoreExpr wordResult dflags result = Just (wordResult' dflags result) wordResult' :: DynFlags -> Integer -> CoreExpr wordResult' dflags result = Lit (mkLitWordWrap dflags result) -- | Create an unboxed pair of a Word literal expression, ensuring the given -- Integer is in the target Word range and the corresponding carry flag -- (@0#@/@1#@) if it wasn't. wordCResult :: DynFlags -> Integer -> Maybe CoreExpr wordCResult dflags result = Just (mkPair [Lit lit, Lit c]) where mkPair = mkCoreUbxTup [wordPrimTy, intPrimTy] (lit, b) = mkLitWordWrapC dflags result c = if b then onei dflags else zeroi dflags inversePrimOp :: PrimOp -> RuleM CoreExpr inversePrimOp primop = do [Var primop_id `App` e] <- getArgs matchPrimOpId primop primop_id return e subsumesPrimOp :: PrimOp -> PrimOp -> RuleM CoreExpr this `subsumesPrimOp` that = do [Var primop_id `App` e] <- getArgs matchPrimOpId that primop_id return (Var (mkPrimOpId this) `App` e) subsumedByPrimOp :: PrimOp -> RuleM CoreExpr subsumedByPrimOp primop = do [e@(Var primop_id `App` _)] <- getArgs matchPrimOpId primop primop_id return e idempotent :: RuleM CoreExpr idempotent = do [e1, e2] <- getArgs guard $ cheapEqExpr e1 e2 return e1 {- Note [Guarding against silly shifts] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Consider this code: import Data.Bits( (.|.), shiftL ) chunkToBitmap :: [Bool] -> Word32 chunkToBitmap chunk = foldr (.|.) 0 [ 1 `shiftL` n | (True,n) <- zip chunk [0..] ] This optimises to: Shift.$wgo = \ (w_sCS :: GHC.Prim.Int#) (w1_sCT :: [GHC.Types.Bool]) -> case w1_sCT of _ { [] -> 0##; : x_aAW xs_aAX -> case x_aAW of _ { GHC.Types.False -> case w_sCS of wild2_Xh { __DEFAULT -> Shift.$wgo (GHC.Prim.+# wild2_Xh 1) xs_aAX; 9223372036854775807 -> 0## }; GHC.Types.True -> case GHC.Prim.>=# w_sCS 64 of _ { GHC.Types.False -> case w_sCS of wild3_Xh { __DEFAULT -> case Shift.$wgo (GHC.Prim.+# wild3_Xh 1) xs_aAX of ww_sCW { __DEFAULT -> GHC.Prim.or# (GHC.Prim.narrow32Word# (GHC.Prim.uncheckedShiftL# 1## wild3_Xh)) ww_sCW }; 9223372036854775807 -> GHC.Prim.narrow32Word# !!!!--> (GHC.Prim.uncheckedShiftL# 1## 9223372036854775807) }; GHC.Types.True -> case w_sCS of wild3_Xh { __DEFAULT -> Shift.$wgo (GHC.Prim.+# wild3_Xh 1) xs_aAX; 9223372036854775807 -> 0## } } } } Note the massive shift on line "!!!!". It can't happen, because we've checked that w < 64, but the optimiser didn't spot that. We DO NOT want to constant-fold this! Moreover, if the programmer writes (n `uncheckedShiftL` 9223372036854775807), we can't constant fold it, but if it gets to the assember we get Error: operand type mismatch for `shl' So the best thing to do is to rewrite the shift with a call to error, when the second arg is stupid. There are two cases: - Shifting fixed-width things: the primops ISll, Sll, etc These are handled by shiftRule. We are happy to shift by any amount up to wordSize but no more. - Shifting Integers: the function shiftLInteger, shiftRInteger from the 'integer' library. These are handled by rule_shift_op, and match_Integer_shift_op. Here we could in principle shift by any amount, but we arbitary limit the shift to 4 bits; in particualr we do not want shift by a huge amount, which can happen in code like that above. The two cases are more different in their code paths that is comfortable, but that is only a historical accident. ************************************************************************ * * \subsection{Vaguely generic functions} * * ************************************************************************ -} mkBasicRule :: Name -> Int -> RuleM CoreExpr -> CoreRule -- Gives the Rule the same name as the primop itself mkBasicRule op_name n_args rm = BuiltinRule { ru_name = occNameFS (nameOccName op_name), ru_fn = op_name, ru_nargs = n_args, ru_try = \ dflags in_scope _ -> runRuleM rm dflags in_scope } newtype RuleM r = RuleM { runRuleM :: DynFlags -> InScopeEnv -> [CoreExpr] -> Maybe r } instance Functor RuleM where fmap = liftM instance Applicative RuleM where pure x = RuleM $ \_ _ _ -> Just x (<*>) = ap instance Monad RuleM where RuleM f >>= g = RuleM $ \dflags iu e -> case f dflags iu e of Nothing -> Nothing Just r -> runRuleM (g r) dflags iu e #if !MIN_VERSION_base(4,13,0) fail = MonadFail.fail #endif instance MonadFail.MonadFail RuleM where fail _ = mzero instance Alternative RuleM where empty = RuleM $ \_ _ _ -> Nothing RuleM f1 <|> RuleM f2 = RuleM $ \dflags iu args -> f1 dflags iu args <|> f2 dflags iu args instance MonadPlus RuleM instance HasDynFlags RuleM where getDynFlags = RuleM $ \dflags _ _ -> Just dflags liftMaybe :: Maybe a -> RuleM a liftMaybe Nothing = mzero liftMaybe (Just x) = return x liftLit :: (Literal -> Literal) -> RuleM CoreExpr liftLit f = liftLitDynFlags (const f) liftLitDynFlags :: (DynFlags -> Literal -> Literal) -> RuleM CoreExpr liftLitDynFlags f = do dflags <- getDynFlags [Lit lit] <- getArgs return $ Lit (f dflags lit) removeOp32 :: RuleM CoreExpr removeOp32 = do dflags <- getDynFlags if wordSizeInBits dflags == 32 then do [e] <- getArgs return e else mzero getArgs :: RuleM [CoreExpr] getArgs = RuleM $ \_ _ args -> Just args getInScopeEnv :: RuleM InScopeEnv getInScopeEnv = RuleM $ \_ iu _ -> Just iu -- return the n-th argument of this rule, if it is a literal -- argument indices start from 0 getLiteral :: Int -> RuleM Literal getLiteral n = RuleM $ \_ _ exprs -> case drop n exprs of (Lit l:_) -> Just l _ -> Nothing unaryLit :: (DynFlags -> Literal -> Maybe CoreExpr) -> RuleM CoreExpr unaryLit op = do dflags <- getDynFlags [Lit l] <- getArgs liftMaybe $ op dflags (convFloating dflags l) binaryLit :: (DynFlags -> Literal -> Literal -> Maybe CoreExpr) -> RuleM CoreExpr binaryLit op = do dflags <- getDynFlags [Lit l1, Lit l2] <- getArgs liftMaybe $ op dflags (convFloating dflags l1) (convFloating dflags l2) binaryCmpLit :: (forall a . Ord a => a -> a -> Bool) -> RuleM CoreExpr binaryCmpLit op = do dflags <- getDynFlags binaryLit (\_ -> cmpOp dflags op) leftIdentity :: Literal -> RuleM CoreExpr leftIdentity id_lit = leftIdentityDynFlags (const id_lit) rightIdentity :: Literal -> RuleM CoreExpr rightIdentity id_lit = rightIdentityDynFlags (const id_lit) identity :: Literal -> RuleM CoreExpr identity lit = leftIdentity lit `mplus` rightIdentity lit leftIdentityDynFlags :: (DynFlags -> Literal) -> RuleM CoreExpr leftIdentityDynFlags id_lit = do dflags <- getDynFlags [Lit l1, e2] <- getArgs guard $ l1 == id_lit dflags return e2 -- | Left identity rule for PrimOps like 'IntAddC' and 'WordAddC', where, in -- addition to the result, we have to indicate that no carry/overflow occured. leftIdentityCDynFlags :: (DynFlags -> Literal) -> RuleM CoreExpr leftIdentityCDynFlags id_lit = do dflags <- getDynFlags [Lit l1, e2] <- getArgs guard $ l1 == id_lit dflags let no_c = Lit (zeroi dflags) return (mkCoreUbxTup [exprType e2, intPrimTy] [e2, no_c]) rightIdentityDynFlags :: (DynFlags -> Literal) -> RuleM CoreExpr rightIdentityDynFlags id_lit = do dflags <- getDynFlags [e1, Lit l2] <- getArgs guard $ l2 == id_lit dflags return e1 -- | Right identity rule for PrimOps like 'IntSubC' and 'WordSubC', where, in -- addition to the result, we have to indicate that no carry/overflow occured. rightIdentityCDynFlags :: (DynFlags -> Literal) -> RuleM CoreExpr rightIdentityCDynFlags id_lit = do dflags <- getDynFlags [e1, Lit l2] <- getArgs guard $ l2 == id_lit dflags let no_c = Lit (zeroi dflags) return (mkCoreUbxTup [exprType e1, intPrimTy] [e1, no_c]) identityDynFlags :: (DynFlags -> Literal) -> RuleM CoreExpr identityDynFlags lit = leftIdentityDynFlags lit `mplus` rightIdentityDynFlags lit -- | Identity rule for PrimOps like 'IntAddC' and 'WordAddC', where, in addition -- to the result, we have to indicate that no carry/overflow occured. identityCDynFlags :: (DynFlags -> Literal) -> RuleM CoreExpr identityCDynFlags lit = leftIdentityCDynFlags lit `mplus` rightIdentityCDynFlags lit leftZero :: (DynFlags -> Literal) -> RuleM CoreExpr leftZero zero = do dflags <- getDynFlags [Lit l1, _] <- getArgs guard $ l1 == zero dflags return $ Lit l1 rightZero :: (DynFlags -> Literal) -> RuleM CoreExpr rightZero zero = do dflags <- getDynFlags [_, Lit l2] <- getArgs guard $ l2 == zero dflags return $ Lit l2 zeroElem :: (DynFlags -> Literal) -> RuleM CoreExpr zeroElem lit = leftZero lit `mplus` rightZero lit equalArgs :: RuleM () equalArgs = do [e1, e2] <- getArgs guard $ e1 `cheapEqExpr` e2 nonZeroLit :: Int -> RuleM () nonZeroLit n = getLiteral n >>= guard . not . isZeroLit -- When excess precision is not requested, cut down the precision of the -- Rational value to that of Float/Double. We confuse host architecture -- and target architecture here, but it's convenient (and wrong :-). convFloating :: DynFlags -> Literal -> Literal convFloating dflags (LitFloat f) | not (gopt Opt_ExcessPrecision dflags) = LitFloat (toRational (fromRational f :: Float )) convFloating dflags (LitDouble d) | not (gopt Opt_ExcessPrecision dflags) = LitDouble (toRational (fromRational d :: Double)) convFloating _ l = l guardFloatDiv :: RuleM () guardFloatDiv = do [Lit (LitFloat f1), Lit (LitFloat f2)] <- getArgs guard $ (f1 /=0 || f2 > 0) -- see Note [negative zero] && f2 /= 0 -- avoid NaN and Infinity/-Infinity guardDoubleDiv :: RuleM () guardDoubleDiv = do [Lit (LitDouble d1), Lit (LitDouble d2)] <- getArgs guard $ (d1 /=0 || d2 > 0) -- see Note [negative zero] && d2 /= 0 -- avoid NaN and Infinity/-Infinity -- Note [negative zero] Avoid (0 / -d), otherwise 0/(-1) reduces to -- zero, but we might want to preserve the negative zero here which -- is representable in Float/Double but not in (normalised) -- Rational. (#3676) Perhaps we should generate (0 :% (-1)) instead? strengthReduction :: Literal -> PrimOp -> RuleM CoreExpr strengthReduction two_lit add_op = do -- Note [Strength reduction] arg <- msum [ do [arg, Lit mult_lit] <- getArgs guard (mult_lit == two_lit) return arg , do [Lit mult_lit, arg] <- getArgs guard (mult_lit == two_lit) return arg ] return $ Var (mkPrimOpId add_op) `App` arg `App` arg -- Note [Strength reduction] -- ~~~~~~~~~~~~~~~~~~~~~~~~~ -- -- This rule turns floating point multiplications of the form 2.0 * x and -- x * 2.0 into x + x addition, because addition costs less than multiplication. -- See #7116 -- Note [What's true and false] -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -- -- trueValInt and falseValInt represent true and false values returned by -- comparison primops for Char, Int, Word, Integer, Double, Float and Addr. -- True is represented as an unboxed 1# literal, while false is represented -- as 0# literal. -- We still need Bool data constructors (True and False) to use in a rule -- for constant folding of equal Strings trueValInt, falseValInt :: DynFlags -> Expr CoreBndr trueValInt dflags = Lit $ onei dflags -- see Note [What's true and false] falseValInt dflags = Lit $ zeroi dflags trueValBool, falseValBool :: Expr CoreBndr trueValBool = Var trueDataConId -- see Note [What's true and false] falseValBool = Var falseDataConId ltVal, eqVal, gtVal :: Expr CoreBndr ltVal = Var ordLTDataConId eqVal = Var ordEQDataConId gtVal = Var ordGTDataConId mkIntVal :: DynFlags -> Integer -> Expr CoreBndr mkIntVal dflags i = Lit (mkLitInt dflags i) mkFloatVal :: DynFlags -> Rational -> Expr CoreBndr mkFloatVal dflags f = Lit (convFloating dflags (LitFloat f)) mkDoubleVal :: DynFlags -> Rational -> Expr CoreBndr mkDoubleVal dflags d = Lit (convFloating dflags (LitDouble d)) matchPrimOpId :: PrimOp -> Id -> RuleM () matchPrimOpId op id = do op' <- liftMaybe $ isPrimOpId_maybe id guard $ op == op' {- ************************************************************************ * * \subsection{Special rules for seq, tagToEnum, dataToTag} * * ************************************************************************ Note [tagToEnum#] ~~~~~~~~~~~~~~~~~ Nasty check to ensure that tagToEnum# is applied to a type that is an enumeration TyCon. Unification may refine the type later, but this check won't see that, alas. It's crude but it works. Here's are two cases that should fail f :: forall a. a f = tagToEnum# 0 -- Can't do tagToEnum# at a type variable g :: Int g = tagToEnum# 0 -- Int is not an enumeration We used to make this check in the type inference engine, but it's quite ugly to do so, because the delayed constraint solving means that we don't really know what's going on until the end. It's very much a corner case because we don't expect the user to call tagToEnum# at all; we merely generate calls in derived instances of Enum. So we compromise: a rewrite rule rewrites a bad instance of tagToEnum# to an error call, and emits a warning. -} tagToEnumRule :: RuleM CoreExpr -- If data T a = A | B | C -- then tag2Enum# (T ty) 2# --> B ty tagToEnumRule = do [Type ty, Lit (LitNumber LitNumInt i _)] <- getArgs case splitTyConApp_maybe ty of Just (tycon, tc_args) | isEnumerationTyCon tycon -> do let tag = fromInteger i correct_tag dc = (dataConTagZ dc) == tag (dc:rest) <- return $ filter correct_tag (tyConDataCons_maybe tycon `orElse` []) ASSERT(null rest) return () return $ mkTyApps (Var (dataConWorkId dc)) tc_args -- See Note [tagToEnum#] _ -> WARN( True, text "tagToEnum# on non-enumeration type" <+> ppr ty ) return $ mkRuntimeErrorApp rUNTIME_ERROR_ID ty "tagToEnum# on non-enumeration type" ------------------------------ dataToTagRule :: RuleM CoreExpr -- See Note [dataToTag#] in primops.txt.pp dataToTagRule = a `mplus` b where -- dataToTag (tagToEnum x) ==> x a = do [Type ty1, Var tag_to_enum `App` Type ty2 `App` tag] <- getArgs guard $ tag_to_enum `hasKey` tagToEnumKey guard $ ty1 `eqType` ty2 return tag -- dataToTag (K e1 e2) ==> tag-of K -- This also works (via exprIsConApp_maybe) for -- dataToTag x -- where x's unfolding is a constructor application b = do dflags <- getDynFlags [_, val_arg] <- getArgs in_scope <- getInScopeEnv (_,floats, dc,_,_) <- liftMaybe $ exprIsConApp_maybe in_scope val_arg ASSERT( not (isNewTyCon (dataConTyCon dc)) ) return () return $ wrapFloats floats (mkIntVal dflags (toInteger (dataConTagZ dc))) {- Note [dataToTag# magic] ~~~~~~~~~~~~~~~~~~~~~~~~~~ The primop dataToTag# is unusual because it evaluates its argument. Only `SeqOp` shares that property. (Other primops do not do anything as fancy as argument evaluation.) The special handling for dataToTag# is: * CoreUtils.exprOkForSpeculation has a special case for DataToTagOp, (actually in app_ok). Most primops with lifted arguments do not evaluate those arguments, but DataToTagOp and SeqOp are two exceptions. We say that they are /never/ ok-for-speculation, regardless of the evaluated-ness of their argument. See CoreUtils Note [exprOkForSpeculation and SeqOp/DataToTagOp] * There is a special case for DataToTagOp in StgCmmExpr.cgExpr, that evaluates its argument and then extracts the tag from the returned value. * An application like (dataToTag# (Just x)) is optimised by dataToTagRule in PrelRules. * A case expression like case (dataToTag# e) of gets transformed t case e of by PrelRules.caseRules; see Note [caseRules for dataToTag] See #15696 for a long saga. ************************************************************************ * * \subsection{Rules for seq# and spark#} * * ************************************************************************ -} {- Note [seq# magic] ~~~~~~~~~~~~~~~~~~~~ The primop seq# :: forall a s . a -> State# s -> (# State# s, a #) is /not/ the same as the Prelude function seq :: a -> b -> b as you can see from its type. In fact, seq# is the implementation mechanism for 'evaluate' evaluate :: a -> IO a evaluate a = IO $ \s -> seq# a s The semantics of seq# is * evaluate its first argument * and return it Things to note * Why do we need a primop at all? That is, instead of case seq# x s of (# x, s #) -> blah why not instead say this? case x of { DEFAULT -> blah) Reason (see #5129): if we saw catch# (\s -> case x of { DEFAULT -> raiseIO# exn s }) handler then we'd drop the 'case x' because the body of the case is bottom anyway. But we don't want to do that; the whole /point/ of seq#/evaluate is to evaluate 'x' first in the IO monad. In short, we /always/ evaluate the first argument and never just discard it. * Why return the value? So that we can control sharing of seq'd values: in let x = e in x `seq` ... x ... We don't want to inline x, so better to represent it as let x = e in case seq# x RW of (# _, x' #) -> ... x' ... also it matches the type of rseq in the Eval monad. Implementing seq#. The compiler has magic for SeqOp in - PrelRules.seqRule: eliminate (seq# s) - StgCmmExpr.cgExpr, and cgCase: special case for seq# - CoreUtils.exprOkForSpeculation; see Note [exprOkForSpeculation and SeqOp/DataToTagOp] in CoreUtils - Simplify.addEvals records evaluated-ness for the result; see Note [Adding evaluatedness info to pattern-bound variables] in Simplify -} seqRule :: RuleM CoreExpr seqRule = do [Type ty_a, Type _ty_s, a, s] <- getArgs guard $ exprIsHNF a return $ mkCoreUbxTup [exprType s, ty_a] [s, a] -- spark# :: forall a s . a -> State# s -> (# State# s, a #) sparkRule :: RuleM CoreExpr sparkRule = seqRule -- reduce on HNF, just the same -- XXX perhaps we shouldn't do this, because a spark eliminated by -- this rule won't be counted as a dud at runtime? {- ************************************************************************ * * \subsection{Built in rules} * * ************************************************************************ Note [Scoping for Builtin rules] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ When compiling a (base-package) module that defines one of the functions mentioned in the RHS of a built-in rule, there's a danger that we'll see f = ...(eq String x).... ....and lower down... eqString = ... Then a rewrite would give f = ...(eqString x)... ....and lower down... eqString = ... and lo, eqString is not in scope. This only really matters when we get to code generation. With -O we do a GlomBinds step that does a new SCC analysis on the whole set of bindings, which sorts out the dependency. Without -O we don't do any rule rewriting so again we are fine. (This whole thing doesn't show up for non-built-in rules because their dependencies are explicit.) -} builtinRules :: [CoreRule] -- Rules for non-primops that can't be expressed using a RULE pragma builtinRules = [BuiltinRule { ru_name = fsLit "AppendLitString", ru_fn = unpackCStringFoldrName, ru_nargs = 4, ru_try = match_append_lit }, BuiltinRule { ru_name = fsLit "EqString", ru_fn = eqStringName, ru_nargs = 2, ru_try = match_eq_string }, BuiltinRule { ru_name = fsLit "Inline", ru_fn = inlineIdName, ru_nargs = 2, ru_try = \_ _ _ -> match_inline }, BuiltinRule { ru_name = fsLit "MagicDict", ru_fn = idName magicDictId, ru_nargs = 4, ru_try = \_ _ _ -> match_magicDict }, mkBasicRule divIntName 2 $ msum [ nonZeroLit 1 >> binaryLit (intOp2 div) , leftZero zeroi , do [arg, Lit (LitNumber LitNumInt d _)] <- getArgs Just n <- return $ exactLog2 d dflags <- getDynFlags return $ Var (mkPrimOpId ISraOp) `App` arg `App` mkIntVal dflags n ], mkBasicRule modIntName 2 $ msum [ nonZeroLit 1 >> binaryLit (intOp2 mod) , leftZero zeroi , do [arg, Lit (LitNumber LitNumInt d _)] <- getArgs Just _ <- return $ exactLog2 d dflags <- getDynFlags return $ Var (mkPrimOpId AndIOp) `App` arg `App` mkIntVal dflags (d - 1) ] ] ++ builtinIntegerRules ++ builtinNaturalRules {-# NOINLINE builtinRules #-} -- there is no benefit to inlining these yet, despite this, GHC produces -- unfoldings for this regardless since the floated list entries look small. builtinIntegerRules :: [CoreRule] builtinIntegerRules = [rule_IntToInteger "smallInteger" smallIntegerName, rule_WordToInteger "wordToInteger" wordToIntegerName, rule_Int64ToInteger "int64ToInteger" int64ToIntegerName, rule_Word64ToInteger "word64ToInteger" word64ToIntegerName, rule_convert "integerToWord" integerToWordName mkWordLitWord, rule_convert "integerToInt" integerToIntName mkIntLitInt, rule_convert "integerToWord64" integerToWord64Name (\_ -> mkWord64LitWord64), rule_convert "integerToInt64" integerToInt64Name (\_ -> mkInt64LitInt64), rule_binop "plusInteger" plusIntegerName (+), rule_binop "minusInteger" minusIntegerName (-), rule_binop "timesInteger" timesIntegerName (*), rule_unop "negateInteger" negateIntegerName negate, rule_binop_Prim "eqInteger#" eqIntegerPrimName (==), rule_binop_Prim "neqInteger#" neqIntegerPrimName (/=), rule_unop "absInteger" absIntegerName abs, rule_unop "signumInteger" signumIntegerName signum, rule_binop_Prim "leInteger#" leIntegerPrimName (<=), rule_binop_Prim "gtInteger#" gtIntegerPrimName (>), rule_binop_Prim "ltInteger#" ltIntegerPrimName (<), rule_binop_Prim "geInteger#" geIntegerPrimName (>=), rule_binop_Ordering "compareInteger" compareIntegerName compare, rule_encodeFloat "encodeFloatInteger" encodeFloatIntegerName mkFloatLitFloat, rule_convert "floatFromInteger" floatFromIntegerName (\_ -> mkFloatLitFloat), rule_encodeFloat "encodeDoubleInteger" encodeDoubleIntegerName mkDoubleLitDouble, rule_decodeDouble "decodeDoubleInteger" decodeDoubleIntegerName, rule_convert "doubleFromInteger" doubleFromIntegerName (\_ -> mkDoubleLitDouble), rule_rationalTo "rationalToFloat" rationalToFloatName mkFloatExpr, rule_rationalTo "rationalToDouble" rationalToDoubleName mkDoubleExpr, rule_binop "gcdInteger" gcdIntegerName gcd, rule_binop "lcmInteger" lcmIntegerName lcm, rule_binop "andInteger" andIntegerName (.&.), rule_binop "orInteger" orIntegerName (.|.), rule_binop "xorInteger" xorIntegerName xor, rule_unop "complementInteger" complementIntegerName complement, rule_shift_op "shiftLInteger" shiftLIntegerName shiftL, rule_shift_op "shiftRInteger" shiftRIntegerName shiftR, rule_bitInteger "bitInteger" bitIntegerName, -- See Note [Integer division constant folding] in libraries/base/GHC/Real.hs rule_divop_one "quotInteger" quotIntegerName quot, rule_divop_one "remInteger" remIntegerName rem, rule_divop_one "divInteger" divIntegerName div, rule_divop_one "modInteger" modIntegerName mod, rule_divop_both "divModInteger" divModIntegerName divMod, rule_divop_both "quotRemInteger" quotRemIntegerName quotRem, -- These rules below don't actually have to be built in, but if we -- put them in the Haskell source then we'd have to duplicate them -- between all Integer implementations rule_XToIntegerToX "smallIntegerToInt" integerToIntName smallIntegerName, rule_XToIntegerToX "wordToIntegerToWord" integerToWordName wordToIntegerName, rule_XToIntegerToX "int64ToIntegerToInt64" integerToInt64Name int64ToIntegerName, rule_XToIntegerToX "word64ToIntegerToWord64" integerToWord64Name word64ToIntegerName, rule_smallIntegerTo "smallIntegerToWord" integerToWordName Int2WordOp, rule_smallIntegerTo "smallIntegerToFloat" floatFromIntegerName Int2FloatOp, rule_smallIntegerTo "smallIntegerToDouble" doubleFromIntegerName Int2DoubleOp ] where rule_convert str name convert = BuiltinRule { ru_name = fsLit str, ru_fn = name, ru_nargs = 1, ru_try = match_Integer_convert convert } rule_IntToInteger str name = BuiltinRule { ru_name = fsLit str, ru_fn = name, ru_nargs = 1, ru_try = match_IntToInteger } rule_WordToInteger str name = BuiltinRule { ru_name = fsLit str, ru_fn = name, ru_nargs = 1, ru_try = match_WordToInteger } rule_Int64ToInteger str name = BuiltinRule { ru_name = fsLit str, ru_fn = name, ru_nargs = 1, ru_try = match_Int64ToInteger } rule_Word64ToInteger str name = BuiltinRule { ru_name = fsLit str, ru_fn = name, ru_nargs = 1, ru_try = match_Word64ToInteger } rule_unop str name op = BuiltinRule { ru_name = fsLit str, ru_fn = name, ru_nargs = 1, ru_try = match_Integer_unop op } rule_bitInteger str name = BuiltinRule { ru_name = fsLit str, ru_fn = name, ru_nargs = 1, ru_try = match_bitInteger } rule_binop str name op = BuiltinRule { ru_name = fsLit str, ru_fn = name, ru_nargs = 2, ru_try = match_Integer_binop op } rule_divop_both str name op = BuiltinRule { ru_name = fsLit str, ru_fn = name, ru_nargs = 2, ru_try = match_Integer_divop_both op } rule_divop_one str name op = BuiltinRule { ru_name = fsLit str, ru_fn = name, ru_nargs = 2, ru_try = match_Integer_divop_one op } rule_shift_op str name op = BuiltinRule { ru_name = fsLit str, ru_fn = name, ru_nargs = 2, ru_try = match_Integer_shift_op op } rule_binop_Prim str name op = BuiltinRule { ru_name = fsLit str, ru_fn = name, ru_nargs = 2, ru_try = match_Integer_binop_Prim op } rule_binop_Ordering str name op = BuiltinRule { ru_name = fsLit str, ru_fn = name, ru_nargs = 2, ru_try = match_Integer_binop_Ordering op } rule_encodeFloat str name op = BuiltinRule { ru_name = fsLit str, ru_fn = name, ru_nargs = 2, ru_try = match_Integer_Int_encodeFloat op } rule_decodeDouble str name = BuiltinRule { ru_name = fsLit str, ru_fn = name, ru_nargs = 1, ru_try = match_decodeDouble } rule_XToIntegerToX str name toIntegerName = BuiltinRule { ru_name = fsLit str, ru_fn = name, ru_nargs = 1, ru_try = match_XToIntegerToX toIntegerName } rule_smallIntegerTo str name primOp = BuiltinRule { ru_name = fsLit str, ru_fn = name, ru_nargs = 1, ru_try = match_smallIntegerTo primOp } rule_rationalTo str name mkLit = BuiltinRule { ru_name = fsLit str, ru_fn = name, ru_nargs = 2, ru_try = match_rationalTo mkLit } builtinNaturalRules :: [CoreRule] builtinNaturalRules = [rule_binop "plusNatural" plusNaturalName (+) ,rule_partial_binop "minusNatural" minusNaturalName (\a b -> if a >= b then Just (a - b) else Nothing) ,rule_binop "timesNatural" timesNaturalName (*) ,rule_NaturalFromInteger "naturalFromInteger" naturalFromIntegerName ,rule_NaturalToInteger "naturalToInteger" naturalToIntegerName ,rule_WordToNatural "wordToNatural" wordToNaturalName ] where rule_binop str name op = BuiltinRule { ru_name = fsLit str, ru_fn = name, ru_nargs = 2, ru_try = match_Natural_binop op } rule_partial_binop str name op = BuiltinRule { ru_name = fsLit str, ru_fn = name, ru_nargs = 2, ru_try = match_Natural_partial_binop op } rule_NaturalToInteger str name = BuiltinRule { ru_name = fsLit str, ru_fn = name, ru_nargs = 1, ru_try = match_NaturalToInteger } rule_NaturalFromInteger str name = BuiltinRule { ru_name = fsLit str, ru_fn = name, ru_nargs = 1, ru_try = match_NaturalFromInteger } rule_WordToNatural str name = BuiltinRule { ru_name = fsLit str, ru_fn = name, ru_nargs = 1, ru_try = match_WordToNatural } --------------------------------------------------- -- The rule is this: -- unpackFoldrCString# "foo" c (unpackFoldrCString# "baz" c n) -- = unpackFoldrCString# "foobaz" c n match_append_lit :: RuleFun match_append_lit _ id_unf _ [ Type ty1 , lit1 , c1 , Var unpk `App` Type ty2 `App` lit2 `App` c2 `App` n ] | unpk `hasKey` unpackCStringFoldrIdKey && c1 `cheapEqExpr` c2 , Just (LitString s1) <- exprIsLiteral_maybe id_unf lit1 , Just (LitString s2) <- exprIsLiteral_maybe id_unf lit2 = ASSERT( ty1 `eqType` ty2 ) Just (Var unpk `App` Type ty1 `App` Lit (LitString (s1 `BS.append` s2)) `App` c1 `App` n) match_append_lit _ _ _ _ = Nothing --------------------------------------------------- -- The rule is this: -- eqString (unpackCString# (Lit s1)) (unpackCString# (Lit s2)) = s1==s2 match_eq_string :: RuleFun match_eq_string _ id_unf _ [Var unpk1 `App` lit1, Var unpk2 `App` lit2] | unpk1 `hasKey` unpackCStringIdKey , unpk2 `hasKey` unpackCStringIdKey , Just (LitString s1) <- exprIsLiteral_maybe id_unf lit1 , Just (LitString s2) <- exprIsLiteral_maybe id_unf lit2 = Just (if s1 == s2 then trueValBool else falseValBool) match_eq_string _ _ _ _ = Nothing --------------------------------------------------- -- The rule is this: -- inline f_ty (f a b c) = a b c -- (if f has an unfolding, EVEN if it's a loop breaker) -- -- It's important to allow the argument to 'inline' to have args itself -- (a) because its more forgiving to allow the programmer to write -- inline f a b c -- or inline (f a b c) -- (b) because a polymorphic f wll get a type argument that the -- programmer can't avoid -- -- Also, don't forget about 'inline's type argument! match_inline :: [Expr CoreBndr] -> Maybe (Expr CoreBndr) match_inline (Type _ : e : _) | (Var f, args1) <- collectArgs e, Just unf <- maybeUnfoldingTemplate (realIdUnfolding f) -- Ignore the IdUnfoldingFun here! = Just (mkApps unf args1) match_inline _ = Nothing -- See Note [magicDictId magic] in `basicTypes/MkId.hs` -- for a description of what is going on here. match_magicDict :: [Expr CoreBndr] -> Maybe (Expr CoreBndr) match_magicDict [Type _, Var wrap `App` Type a `App` Type _ `App` f, x, y ] | Just (fieldTy, _) <- splitFunTy_maybe $ dropForAlls $ idType wrap , Just (dictTy, _) <- splitFunTy_maybe fieldTy , Just dictTc <- tyConAppTyCon_maybe dictTy , Just (_,_,co) <- unwrapNewTyCon_maybe dictTc = Just $ f `App` Cast x (mkSymCo (mkUnbranchedAxInstCo Representational co [a] [])) `App` y match_magicDict _ = Nothing ------------------------------------------------- -- Integer rules -- smallInteger (79::Int#) = 79::Integer -- wordToInteger (79::Word#) = 79::Integer -- Similarly Int64, Word64 match_IntToInteger :: RuleFun match_IntToInteger = match_IntToInteger_unop id match_WordToInteger :: RuleFun match_WordToInteger _ id_unf id [xl] | Just (LitNumber LitNumWord x _) <- exprIsLiteral_maybe id_unf xl = case splitFunTy_maybe (idType id) of Just (_, integerTy) -> Just (Lit (mkLitInteger x integerTy)) _ -> panic "match_WordToInteger: Id has the wrong type" match_WordToInteger _ _ _ _ = Nothing match_Int64ToInteger :: RuleFun match_Int64ToInteger _ id_unf id [xl] | Just (LitNumber LitNumInt64 x _) <- exprIsLiteral_maybe id_unf xl = case splitFunTy_maybe (idType id) of Just (_, integerTy) -> Just (Lit (mkLitInteger x integerTy)) _ -> panic "match_Int64ToInteger: Id has the wrong type" match_Int64ToInteger _ _ _ _ = Nothing match_Word64ToInteger :: RuleFun match_Word64ToInteger _ id_unf id [xl] | Just (LitNumber LitNumWord64 x _) <- exprIsLiteral_maybe id_unf xl = case splitFunTy_maybe (idType id) of Just (_, integerTy) -> Just (Lit (mkLitInteger x integerTy)) _ -> panic "match_Word64ToInteger: Id has the wrong type" match_Word64ToInteger _ _ _ _ = Nothing match_NaturalToInteger :: RuleFun match_NaturalToInteger _ id_unf id [xl] | Just (LitNumber LitNumNatural x _) <- exprIsLiteral_maybe id_unf xl = case splitFunTy_maybe (idType id) of Just (_, naturalTy) -> Just (Lit (LitNumber LitNumInteger x naturalTy)) _ -> panic "match_NaturalToInteger: Id has the wrong type" match_NaturalToInteger _ _ _ _ = Nothing match_NaturalFromInteger :: RuleFun match_NaturalFromInteger _ id_unf id [xl] | Just (LitNumber LitNumInteger x _) <- exprIsLiteral_maybe id_unf xl , x >= 0 = case splitFunTy_maybe (idType id) of Just (_, naturalTy) -> Just (Lit (LitNumber LitNumNatural x naturalTy)) _ -> panic "match_NaturalFromInteger: Id has the wrong type" match_NaturalFromInteger _ _ _ _ = Nothing match_WordToNatural :: RuleFun match_WordToNatural _ id_unf id [xl] | Just (LitNumber LitNumWord x _) <- exprIsLiteral_maybe id_unf xl = case splitFunTy_maybe (idType id) of Just (_, naturalTy) -> Just (Lit (LitNumber LitNumNatural x naturalTy)) _ -> panic "match_WordToNatural: Id has the wrong type" match_WordToNatural _ _ _ _ = Nothing ------------------------------------------------- {- Note [Rewriting bitInteger] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ For most types the bitInteger operation can be implemented in terms of shifts. The integer-gmp package, however, can do substantially better than this if allowed to provide its own implementation. However, in so doing it previously lost constant-folding (see #8832). The bitInteger rule above provides constant folding specifically for this function. There is, however, a bit of trickiness here when it comes to ranges. While the AST encodes all integers as Integers, `bit` expects the bit index to be given as an Int. Hence we coerce to an Int in the rule definition. This will behave a bit funny for constants larger than the word size, but the user should expect some funniness given that they will have at very least ignored a warning in this case. -} match_bitInteger :: RuleFun -- Just for GHC.Integer.Type.bitInteger :: Int# -> Integer match_bitInteger dflags id_unf fn [arg] | Just (LitNumber LitNumInt x _) <- exprIsLiteral_maybe id_unf arg , x >= 0 , x <= (wordSizeInBits dflags - 1) -- Make sure x is small enough to yield a decently small iteger -- Attempting to construct the Integer for -- (bitInteger 9223372036854775807#) -- would be a bad idea (#14959) , let x_int = fromIntegral x :: Int = case splitFunTy_maybe (idType fn) of Just (_, integerTy) -> Just (Lit (LitNumber LitNumInteger (bit x_int) integerTy)) _ -> panic "match_IntToInteger_unop: Id has the wrong type" match_bitInteger _ _ _ _ = Nothing ------------------------------------------------- match_Integer_convert :: Num a => (DynFlags -> a -> Expr CoreBndr) -> RuleFun match_Integer_convert convert dflags id_unf _ [xl] | Just (LitNumber LitNumInteger x _) <- exprIsLiteral_maybe id_unf xl = Just (convert dflags (fromInteger x)) match_Integer_convert _ _ _ _ _ = Nothing match_Integer_unop :: (Integer -> Integer) -> RuleFun match_Integer_unop unop _ id_unf _ [xl] | Just (LitNumber LitNumInteger x i) <- exprIsLiteral_maybe id_unf xl = Just (Lit (LitNumber LitNumInteger (unop x) i)) match_Integer_unop _ _ _ _ _ = Nothing match_IntToInteger_unop :: (Integer -> Integer) -> RuleFun match_IntToInteger_unop unop _ id_unf fn [xl] | Just (LitNumber LitNumInt x _) <- exprIsLiteral_maybe id_unf xl = case splitFunTy_maybe (idType fn) of Just (_, integerTy) -> Just (Lit (LitNumber LitNumInteger (unop x) integerTy)) _ -> panic "match_IntToInteger_unop: Id has the wrong type" match_IntToInteger_unop _ _ _ _ _ = Nothing match_Integer_binop :: (Integer -> Integer -> Integer) -> RuleFun match_Integer_binop binop _ id_unf _ [xl,yl] | Just (LitNumber LitNumInteger x i) <- exprIsLiteral_maybe id_unf xl , Just (LitNumber LitNumInteger y _) <- exprIsLiteral_maybe id_unf yl = Just (Lit (mkLitInteger (x `binop` y) i)) match_Integer_binop _ _ _ _ _ = Nothing match_Natural_binop :: (Integer -> Integer -> Integer) -> RuleFun match_Natural_binop binop _ id_unf _ [xl,yl] | Just (LitNumber LitNumNatural x i) <- exprIsLiteral_maybe id_unf xl , Just (LitNumber LitNumNatural y _) <- exprIsLiteral_maybe id_unf yl = Just (Lit (mkLitNatural (x `binop` y) i)) match_Natural_binop _ _ _ _ _ = Nothing match_Natural_partial_binop :: (Integer -> Integer -> Maybe Integer) -> RuleFun match_Natural_partial_binop binop _ id_unf _ [xl,yl] | Just (LitNumber LitNumNatural x i) <- exprIsLiteral_maybe id_unf xl , Just (LitNumber LitNumNatural y _) <- exprIsLiteral_maybe id_unf yl , Just z <- x `binop` y = Just (Lit (mkLitNatural z i)) match_Natural_partial_binop _ _ _ _ _ = Nothing -- This helper is used for the quotRem and divMod functions match_Integer_divop_both :: (Integer -> Integer -> (Integer, Integer)) -> RuleFun match_Integer_divop_both divop _ id_unf _ [xl,yl] | Just (LitNumber LitNumInteger x t) <- exprIsLiteral_maybe id_unf xl , Just (LitNumber LitNumInteger y _) <- exprIsLiteral_maybe id_unf yl , y /= 0 , (r,s) <- x `divop` y = Just $ mkCoreUbxTup [t,t] [Lit (mkLitInteger r t), Lit (mkLitInteger s t)] match_Integer_divop_both _ _ _ _ _ = Nothing -- This helper is used for the quot and rem functions match_Integer_divop_one :: (Integer -> Integer -> Integer) -> RuleFun match_Integer_divop_one divop _ id_unf _ [xl,yl] | Just (LitNumber LitNumInteger x i) <- exprIsLiteral_maybe id_unf xl , Just (LitNumber LitNumInteger y _) <- exprIsLiteral_maybe id_unf yl , y /= 0 = Just (Lit (mkLitInteger (x `divop` y) i)) match_Integer_divop_one _ _ _ _ _ = Nothing match_Integer_shift_op :: (Integer -> Int -> Integer) -> RuleFun -- Used for shiftLInteger, shiftRInteger :: Integer -> Int# -> Integer -- See Note [Guarding against silly shifts] match_Integer_shift_op binop _ id_unf _ [xl,yl] | Just (LitNumber LitNumInteger x i) <- exprIsLiteral_maybe id_unf xl , Just (LitNumber LitNumInt y _) <- exprIsLiteral_maybe id_unf yl , y >= 0 , y <= 4 -- Restrict constant-folding of shifts on Integers, somewhat -- arbitrary. We can get huge shifts in inaccessible code -- (#15673) = Just (Lit (mkLitInteger (x `binop` fromIntegral y) i)) match_Integer_shift_op _ _ _ _ _ = Nothing match_Integer_binop_Prim :: (Integer -> Integer -> Bool) -> RuleFun match_Integer_binop_Prim binop dflags id_unf _ [xl, yl] | Just (LitNumber LitNumInteger x _) <- exprIsLiteral_maybe id_unf xl , Just (LitNumber LitNumInteger y _) <- exprIsLiteral_maybe id_unf yl = Just (if x `binop` y then trueValInt dflags else falseValInt dflags) match_Integer_binop_Prim _ _ _ _ _ = Nothing match_Integer_binop_Ordering :: (Integer -> Integer -> Ordering) -> RuleFun match_Integer_binop_Ordering binop _ id_unf _ [xl, yl] | Just (LitNumber LitNumInteger x _) <- exprIsLiteral_maybe id_unf xl , Just (LitNumber LitNumInteger y _) <- exprIsLiteral_maybe id_unf yl = Just $ case x `binop` y of LT -> ltVal EQ -> eqVal GT -> gtVal match_Integer_binop_Ordering _ _ _ _ _ = Nothing match_Integer_Int_encodeFloat :: RealFloat a => (a -> Expr CoreBndr) -> RuleFun match_Integer_Int_encodeFloat mkLit _ id_unf _ [xl,yl] | Just (LitNumber LitNumInteger x _) <- exprIsLiteral_maybe id_unf xl , Just (LitNumber LitNumInt y _) <- exprIsLiteral_maybe id_unf yl = Just (mkLit $ encodeFloat x (fromInteger y)) match_Integer_Int_encodeFloat _ _ _ _ _ = Nothing --------------------------------------------------- -- constant folding for Float/Double -- -- This turns -- rationalToFloat n d -- into a literal Float, and similarly for Doubles. -- -- it's important to not match d == 0, because that may represent a -- literal "0/0" or similar, and we can't produce a literal value for -- NaN or +-Inf match_rationalTo :: RealFloat a => (a -> Expr CoreBndr) -> RuleFun match_rationalTo mkLit _ id_unf _ [xl, yl] | Just (LitNumber LitNumInteger x _) <- exprIsLiteral_maybe id_unf xl , Just (LitNumber LitNumInteger y _) <- exprIsLiteral_maybe id_unf yl , y /= 0 = Just (mkLit (fromRational (x % y))) match_rationalTo _ _ _ _ _ = Nothing match_decodeDouble :: RuleFun match_decodeDouble dflags id_unf fn [xl] | Just (LitDouble x) <- exprIsLiteral_maybe id_unf xl = case splitFunTy_maybe (idType fn) of Just (_, res) | Just [_lev1, _lev2, integerTy, intHashTy] <- tyConAppArgs_maybe res -> case decodeFloat (fromRational x :: Double) of (y, z) -> Just $ mkCoreUbxTup [integerTy, intHashTy] [Lit (mkLitInteger y integerTy), Lit (mkLitInt dflags (toInteger z))] _ -> pprPanic "match_decodeDouble: Id has the wrong type" (ppr fn <+> dcolon <+> ppr (idType fn)) match_decodeDouble _ _ _ _ = Nothing match_XToIntegerToX :: Name -> RuleFun match_XToIntegerToX n _ _ _ [App (Var x) y] | idName x == n = Just y match_XToIntegerToX _ _ _ _ _ = Nothing match_smallIntegerTo :: PrimOp -> RuleFun match_smallIntegerTo primOp _ _ _ [App (Var x) y] | idName x == smallIntegerName = Just $ App (Var (mkPrimOpId primOp)) y match_smallIntegerTo _ _ _ _ _ = Nothing -------------------------------------------------------- -- Note [Constant folding through nested expressions] -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -- -- We use rewrites rules to perform constant folding. It means that we don't -- have a global view of the expression we are trying to optimise. As a -- consequence we only perform local (small-step) transformations that either: -- 1) reduce the number of operations -- 2) rearrange the expression to increase the odds that other rules will -- match -- -- We don't try to handle more complex expression optimisation cases that would -- require a global view. For example, rewriting expressions to increase -- sharing (e.g., Horner's method); optimisations that require local -- transformations increasing the number of operations; rearrangements to -- cancel/factorize terms (e.g., (a+b-a-b) isn't rearranged to reduce to 0). -- -- We already have rules to perform constant folding on expressions with the -- following shape (where a and/or b are literals): -- -- D) op -- /\ -- / \ -- / \ -- a b -- -- To support nested expressions, we match three other shapes of expression -- trees: -- -- A) op1 B) op1 C) op1 -- /\ /\ /\ -- / \ / \ / \ -- / \ / \ / \ -- a op2 op2 c op2 op3 -- /\ /\ /\ /\ -- / \ / \ / \ / \ -- b c a b a b c d -- -- -- R1) +/- simplification: -- ops = + or -, two literals (not siblings) -- -- Examples: -- A: 5 + (10-x) ==> 15-x -- B: (10+x) + 5 ==> 15+x -- C: (5+a)-(5-b) ==> 0+(a+b) -- -- R2) * simplification -- ops = *, two literals (not siblings) -- -- Examples: -- A: 5 * (10*x) ==> 50*x -- B: (10*x) * 5 ==> 50*x -- C: (5*a)*(5*b) ==> 25*(a*b) -- -- R3) * distribution over +/- -- op1 = *, op2 = + or -, two literals (not siblings) -- -- This transformation doesn't reduce the number of operations but switches -- the outer and the inner operations so that the outer is (+) or (-) instead -- of (*). It increases the odds that other rules will match after this one. -- -- Examples: -- A: 5 * (10-x) ==> 50 - (5*x) -- B: (10+x) * 5 ==> 50 + (5*x) -- C: Not supported as it would increase the number of operations: -- (5+a)*(5-b) ==> 25 - 5*b + 5*a - a*b -- -- R4) Simple factorization -- -- op1 = + or -, op2/op3 = *, -- one literal for each innermost * operation (except in the D case), -- the two other terms are equals -- -- Examples: -- A: x - (10*x) ==> (-9)*x -- B: (10*x) + x ==> 11*x -- C: (5*x)-(x*3) ==> 2*x -- D: x+x ==> 2*x -- -- R5) +/- propagation -- -- ops = + or -, one literal -- -- This transformation doesn't reduce the number of operations but propagates -- the constant to the outer level. It increases the odds that other rules -- will match after this one. -- -- Examples: -- A: x - (10-y) ==> (x+y) - 10 -- B: (10+x) - y ==> 10 + (x-y) -- C: N/A (caught by the A and B cases) -- -------------------------------------------------------- -- | Rules to perform constant folding into nested expressions -- --See Note [Constant folding through nested expressions] numFoldingRules :: PrimOp -> (DynFlags -> PrimOps) -> RuleM CoreExpr numFoldingRules op dict = do [e1,e2] <- getArgs dflags <- getDynFlags let PrimOps{..} = dict dflags if not (gopt Opt_NumConstantFolding dflags) then mzero else case BinOpApp e1 op e2 of -- R1) +/- simplification x :++: (y :++: v) -> return $ mkL (x+y) `add` v x :++: (L y :-: v) -> return $ mkL (x+y) `sub` v x :++: (v :-: L y) -> return $ mkL (x-y) `add` v L x :-: (y :++: v) -> return $ mkL (x-y) `sub` v L x :-: (L y :-: v) -> return $ mkL (x-y) `add` v L x :-: (v :-: L y) -> return $ mkL (x+y) `sub` v (y :++: v) :-: L x -> return $ mkL (y-x) `add` v (L y :-: v) :-: L x -> return $ mkL (y-x) `sub` v (v :-: L y) :-: L x -> return $ mkL (0-y-x) `add` v (x :++: w) :+: (y :++: v) -> return $ mkL (x+y) `add` (w `add` v) (w :-: L x) :+: (L y :-: v) -> return $ mkL (y-x) `add` (w `sub` v) (w :-: L x) :+: (v :-: L y) -> return $ mkL (0-x-y) `add` (w `add` v) (L x :-: w) :+: (L y :-: v) -> return $ mkL (x+y) `sub` (w `add` v) (L x :-: w) :+: (v :-: L y) -> return $ mkL (x-y) `add` (v `sub` w) (w :-: L x) :+: (y :++: v) -> return $ mkL (y-x) `add` (w `add` v) (L x :-: w) :+: (y :++: v) -> return $ mkL (x+y) `add` (v `sub` w) (y :++: v) :+: (w :-: L x) -> return $ mkL (y-x) `add` (w `add` v) (y :++: v) :+: (L x :-: w) -> return $ mkL (x+y) `add` (v `sub` w) (v :-: L y) :-: (w :-: L x) -> return $ mkL (x-y) `add` (v `sub` w) (v :-: L y) :-: (L x :-: w) -> return $ mkL (0-x-y) `add` (v `add` w) (L y :-: v) :-: (w :-: L x) -> return $ mkL (x+y) `sub` (v `add` w) (L y :-: v) :-: (L x :-: w) -> return $ mkL (y-x) `add` (w `sub` v) (x :++: w) :-: (y :++: v) -> return $ mkL (x-y) `add` (w `sub` v) (w :-: L x) :-: (y :++: v) -> return $ mkL (0-y-x) `add` (w `sub` v) (L x :-: w) :-: (y :++: v) -> return $ mkL (x-y) `sub` (v `add` w) (y :++: v) :-: (w :-: L x) -> return $ mkL (y+x) `add` (v `sub` w) (y :++: v) :-: (L x :-: w) -> return $ mkL (y-x) `add` (v `add` w) -- R2) * simplification x :**: (y :**: v) -> return $ mkL (x*y) `mul` v (x :**: w) :*: (y :**: v) -> return $ mkL (x*y) `mul` (w `mul` v) -- R3) * distribution over +/- x :**: (y :++: v) -> return $ mkL (x*y) `add` (mkL x `mul` v) x :**: (L y :-: v) -> return $ mkL (x*y) `sub` (mkL x `mul` v) x :**: (v :-: L y) -> return $ (mkL x `mul` v) `sub` mkL (x*y) -- R4) Simple factorization v :+: w | w `cheapEqExpr` v -> return $ mkL 2 `mul` v w :+: (y :**: v) | w `cheapEqExpr` v -> return $ mkL (1+y) `mul` v w :-: (y :**: v) | w `cheapEqExpr` v -> return $ mkL (1-y) `mul` v (y :**: v) :+: w | w `cheapEqExpr` v -> return $ mkL (y+1) `mul` v (y :**: v) :-: w | w `cheapEqExpr` v -> return $ mkL (y-1) `mul` v (x :**: w) :+: (y :**: v) | w `cheapEqExpr` v -> return $ mkL (x+y) `mul` v (x :**: w) :-: (y :**: v) | w `cheapEqExpr` v -> return $ mkL (x-y) `mul` v -- R5) +/- propagation w :+: (y :++: v) -> return $ mkL y `add` (w `add` v) (y :++: v) :+: w -> return $ mkL y `add` (w `add` v) w :-: (y :++: v) -> return $ (w `sub` v) `sub` mkL y (y :++: v) :-: w -> return $ mkL y `add` (v `sub` w) w :-: (L y :-: v) -> return $ (w `add` v) `sub` mkL y (L y :-: v) :-: w -> return $ mkL y `sub` (w `add` v) w :+: (L y :-: v) -> return $ mkL y `add` (w `sub` v) w :+: (v :-: L y) -> return $ (w `add` v) `sub` mkL y (L y :-: v) :+: w -> return $ mkL y `add` (w `sub` v) (v :-: L y) :+: w -> return $ (w `add` v) `sub` mkL y _ -> mzero -- | Match the application of a binary primop pattern BinOpApp :: Arg CoreBndr -> PrimOp -> Arg CoreBndr -> CoreExpr pattern BinOpApp x op y = OpVal op `App` x `App` y -- | Match a primop pattern OpVal :: PrimOp -> Arg CoreBndr pattern OpVal op <- Var (isPrimOpId_maybe -> Just op) where OpVal op = Var (mkPrimOpId op) -- | Match a literal pattern L :: Integer -> Arg CoreBndr pattern L l <- Lit (isLitValue_maybe -> Just l) -- | Match an addition pattern (:+:) :: Arg CoreBndr -> Arg CoreBndr -> CoreExpr pattern x :+: y <- BinOpApp x (isAddOp -> True) y -- | Match an addition with a literal (handle commutativity) pattern (:++:) :: Integer -> Arg CoreBndr -> CoreExpr pattern l :++: x <- (isAdd -> Just (l,x)) isAdd :: CoreExpr -> Maybe (Integer,CoreExpr) isAdd e = case e of L l :+: x -> Just (l,x) x :+: L l -> Just (l,x) _ -> Nothing -- | Match a multiplication pattern (:*:) :: Arg CoreBndr -> Arg CoreBndr -> CoreExpr pattern x :*: y <- BinOpApp x (isMulOp -> True) y -- | Match a multiplication with a literal (handle commutativity) pattern (:**:) :: Integer -> Arg CoreBndr -> CoreExpr pattern l :**: x <- (isMul -> Just (l,x)) isMul :: CoreExpr -> Maybe (Integer,CoreExpr) isMul e = case e of L l :*: x -> Just (l,x) x :*: L l -> Just (l,x) _ -> Nothing -- | Match a subtraction pattern (:-:) :: Arg CoreBndr -> Arg CoreBndr -> CoreExpr pattern x :-: y <- BinOpApp x (isSubOp -> True) y isSubOp :: PrimOp -> Bool isSubOp IntSubOp = True isSubOp WordSubOp = True isSubOp _ = False isAddOp :: PrimOp -> Bool isAddOp IntAddOp = True isAddOp WordAddOp = True isAddOp _ = False isMulOp :: PrimOp -> Bool isMulOp IntMulOp = True isMulOp WordMulOp = True isMulOp _ = False -- | Explicit "type-class"-like dictionary for numeric primops -- -- Depends on DynFlags because creating a literal value depends on DynFlags data PrimOps = PrimOps { add :: CoreExpr -> CoreExpr -> CoreExpr -- ^ Add two numbers , sub :: CoreExpr -> CoreExpr -> CoreExpr -- ^ Sub two numbers , mul :: CoreExpr -> CoreExpr -> CoreExpr -- ^ Multiply two numbers , mkL :: Integer -> CoreExpr -- ^ Create a literal value } intPrimOps :: DynFlags -> PrimOps intPrimOps dflags = PrimOps { add = \x y -> BinOpApp x IntAddOp y , sub = \x y -> BinOpApp x IntSubOp y , mul = \x y -> BinOpApp x IntMulOp y , mkL = intResult' dflags } wordPrimOps :: DynFlags -> PrimOps wordPrimOps dflags = PrimOps { add = \x y -> BinOpApp x WordAddOp y , sub = \x y -> BinOpApp x WordSubOp y , mul = \x y -> BinOpApp x WordMulOp y , mkL = wordResult' dflags } -------------------------------------------------------- -- Constant folding through case-expressions -- -- cf Scrutinee Constant Folding in simplCore/SimplUtils -------------------------------------------------------- -- | Match the scrutinee of a case and potentially return a new scrutinee and a -- function to apply to each literal alternative. caseRules :: DynFlags -> CoreExpr -- Scrutinee -> Maybe ( CoreExpr -- New scrutinee , AltCon -> Maybe AltCon -- How to fix up the alt pattern -- Nothing <=> Unreachable -- See Note [Unreachable caseRules alternatives] , Id -> CoreExpr) -- How to reconstruct the original scrutinee -- from the new case-binder -- e.g case e of b { -- ...; -- con bs -> rhs; -- ... } -- ==> -- case e' of b' { -- ...; -- fixup_altcon[con] bs -> let b = mk_orig[b] in rhs; -- ... } caseRules dflags (App (App (Var f) v) (Lit l)) -- v `op` x# | Just op <- isPrimOpId_maybe f , Just x <- isLitValue_maybe l , Just adjust_lit <- adjustDyadicRight op x = Just (v, tx_lit_con dflags adjust_lit , \v -> (App (App (Var f) (Var v)) (Lit l))) caseRules dflags (App (App (Var f) (Lit l)) v) -- x# `op` v | Just op <- isPrimOpId_maybe f , Just x <- isLitValue_maybe l , Just adjust_lit <- adjustDyadicLeft x op = Just (v, tx_lit_con dflags adjust_lit , \v -> (App (App (Var f) (Lit l)) (Var v))) caseRules dflags (App (Var f) v ) -- op v | Just op <- isPrimOpId_maybe f , Just adjust_lit <- adjustUnary op = Just (v, tx_lit_con dflags adjust_lit , \v -> App (Var f) (Var v)) -- See Note [caseRules for tagToEnum] caseRules dflags (App (App (Var f) type_arg) v) | Just TagToEnumOp <- isPrimOpId_maybe f = Just (v, tx_con_tte dflags , \v -> (App (App (Var f) type_arg) (Var v))) -- See Note [caseRules for dataToTag] caseRules _ (App (App (Var f) (Type ty)) v) -- dataToTag x | Just DataToTagOp <- isPrimOpId_maybe f , Just (tc, _) <- tcSplitTyConApp_maybe ty , isAlgTyCon tc = Just (v, tx_con_dtt ty , \v -> App (App (Var f) (Type ty)) (Var v)) caseRules _ _ = Nothing tx_lit_con :: DynFlags -> (Integer -> Integer) -> AltCon -> Maybe AltCon tx_lit_con _ _ DEFAULT = Just DEFAULT tx_lit_con dflags adjust (LitAlt l) = Just $ LitAlt (mapLitValue dflags adjust l) tx_lit_con _ _ alt = pprPanic "caseRules" (ppr alt) -- NB: mapLitValue uses mkLitIntWrap etc, to ensure that the -- literal alternatives remain in Word/Int target ranges -- (See Note [Word/Int underflow/overflow] in Literal and #13172). adjustDyadicRight :: PrimOp -> Integer -> Maybe (Integer -> Integer) -- Given (x `op` lit) return a function 'f' s.t. f (x `op` lit) = x adjustDyadicRight op lit = case op of WordAddOp -> Just (\y -> y-lit ) IntAddOp -> Just (\y -> y-lit ) WordSubOp -> Just (\y -> y+lit ) IntSubOp -> Just (\y -> y+lit ) XorOp -> Just (\y -> y `xor` lit) XorIOp -> Just (\y -> y `xor` lit) _ -> Nothing adjustDyadicLeft :: Integer -> PrimOp -> Maybe (Integer -> Integer) -- Given (lit `op` x) return a function 'f' s.t. f (lit `op` x) = x adjustDyadicLeft lit op = case op of WordAddOp -> Just (\y -> y-lit ) IntAddOp -> Just (\y -> y-lit ) WordSubOp -> Just (\y -> lit-y ) IntSubOp -> Just (\y -> lit-y ) XorOp -> Just (\y -> y `xor` lit) XorIOp -> Just (\y -> y `xor` lit) _ -> Nothing adjustUnary :: PrimOp -> Maybe (Integer -> Integer) -- Given (op x) return a function 'f' s.t. f (op x) = x adjustUnary op = case op of NotOp -> Just (\y -> complement y) NotIOp -> Just (\y -> complement y) IntNegOp -> Just (\y -> negate y ) _ -> Nothing tx_con_tte :: DynFlags -> AltCon -> Maybe AltCon tx_con_tte _ DEFAULT = Just DEFAULT tx_con_tte _ alt@(LitAlt {}) = pprPanic "caseRules" (ppr alt) tx_con_tte dflags (DataAlt dc) -- See Note [caseRules for tagToEnum] = Just $ LitAlt $ mkLitInt dflags $ toInteger $ dataConTagZ dc tx_con_dtt :: Type -> AltCon -> Maybe AltCon tx_con_dtt _ DEFAULT = Just DEFAULT tx_con_dtt ty (LitAlt (LitNumber LitNumInt i _)) | tag >= 0 , tag < n_data_cons = Just (DataAlt (data_cons !! tag)) -- tag is zero-indexed, as is (!!) | otherwise = Nothing where tag = fromInteger i :: ConTagZ tc = tyConAppTyCon ty n_data_cons = tyConFamilySize tc data_cons = tyConDataCons tc tx_con_dtt _ alt = pprPanic "caseRules" (ppr alt) {- Note [caseRules for tagToEnum] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ We want to transform case tagToEnum x of False -> e1 True -> e2 into case x of 0# -> e1 1# -> e2 This rule eliminates a lot of boilerplate. For if (x>y) then e2 else e1 we generate case tagToEnum (x ># y) of False -> e1 True -> e2 and it is nice to then get rid of the tagToEnum. Beware (#14768): avoid the temptation to map constructor 0 to DEFAULT, in the hope of getting this case (x ># y) of DEFAULT -> e1 1# -> e2 That fails utterly in the case of data Colour = Red | Green | Blue case tagToEnum x of DEFAULT -> e1 Red -> e2 We don't want to get this! case x of DEFAULT -> e1 DEFAULT -> e2 Instead, we deal with turning one branch into DEFAULT in SimplUtils (add_default in mkCase3). Note [caseRules for dataToTag] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ See also Note [dataToTag#] in primpops.txt.pp We want to transform case dataToTag x of DEFAULT -> e1 1# -> e2 into case x of DEFAULT -> e1 (:) _ _ -> e2 Note the need for some wildcard binders in the 'cons' case. For the time, we only apply this transformation when the type of `x` is a type headed by a normal tycon. In particular, we do not apply this in the case of a data family tycon, since that would require carefully applying coercion(s) between the data family and the data family instance's representation type, which caseRules isn't currently engineered to handle (#14680). Note [Unreachable caseRules alternatives] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Take care if we see something like case dataToTag x of DEFAULT -> e1 -1# -> e2 100 -> e3 because there isn't a data constructor with tag -1 or 100. In this case the out-of-range alterantive is dead code -- we know the range of tags for x. Hence caseRules returns (AltCon -> Maybe AltCon), with Nothing indicating an alternative that is unreachable. You may wonder how this can happen: check out #15436. -}