2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[ConFold]{Constant Folder}
6 Conceptually, constant folding should be parameterized with the kind
7 of target machine to get identical behaviour during compilation time
8 and runtime. We cheat a little bit here...
11 check boundaries before folding, e.g. we can fold the Float addition
12 (i1 + i2) only if it results in a valid Float.
16 {-# OPTIONS -optc-DNON_POSIX_SOURCE #-}
18 module PrelRules ( primOpRules, builtinRules ) where
20 #include "HsVersions.h"
23 import Id ( mkWildId, isPrimOpId_maybe, idUnfolding )
24 import Literal ( Literal(..), mkMachInt, mkMachWord
26 , word2IntLit, int2WordLit
27 , narrow8IntLit, narrow16IntLit, narrow32IntLit
28 , narrow8WordLit, narrow16WordLit, narrow32WordLit
29 , char2IntLit, int2CharLit
30 , float2IntLit, int2FloatLit, double2IntLit, int2DoubleLit
31 , float2DoubleLit, double2FloatLit
33 import PrimOp ( PrimOp(..), primOpOcc, tagToEnumKey )
34 import TysWiredIn ( boolTy, trueDataConId, falseDataConId )
35 import TyCon ( tyConDataCons_maybe, isEnumerationTyCon, isNewTyCon )
36 import DataCon ( dataConTag, dataConTyCon, dataConWorkId, fIRST_TAG )
37 import CoreUtils ( cheapEqExpr, exprIsConApp_maybe )
38 import Type ( tyConAppTyCon, coreEqType )
39 import OccName ( occNameFS )
40 import PrelNames ( unpackCStringFoldrName, unpackCStringFoldrIdKey, hasKey,
41 eqStringName, unpackCStringIdKey, inlineIdName )
42 import Maybes ( orElse )
46 import StaticFlags ( opt_SimplExcessPrecision )
48 import DATA_BITS ( Bits(..) )
49 #if __GLASGOW_HASKELL__ >= 500
50 import DATA_WORD ( Word )
52 import DATA_WORD ( Word64 )
58 primOpRules :: PrimOp -> Name -> [CoreRule]
59 primOpRules op op_name = primop_rule op
61 rule_name = occNameFS (primOpOcc op)
62 rule_name_case = rule_name `appendFS` FSLIT("->case")
65 one_rule rule_fn = [BuiltinRule { ru_name = rule_name,
68 case_rule rule_fn = [BuiltinRule { ru_name = rule_name_case,
72 -- ToDo: something for integer-shift ops?
75 primop_rule TagToEnumOp = one_rule tagToEnumRule
76 primop_rule DataToTagOp = one_rule dataToTagRule
79 primop_rule IntAddOp = one_rule (twoLits (intOp2 (+)))
80 primop_rule IntSubOp = one_rule (twoLits (intOp2 (-)))
81 primop_rule IntMulOp = one_rule (twoLits (intOp2 (*)))
82 primop_rule IntQuotOp = one_rule (twoLits (intOp2Z quot))
83 primop_rule IntRemOp = one_rule (twoLits (intOp2Z rem))
84 primop_rule IntNegOp = one_rule (oneLit negOp)
87 #if __GLASGOW_HASKELL__ >= 500
88 primop_rule WordAddOp = one_rule (twoLits (wordOp2 (+)))
89 primop_rule WordSubOp = one_rule (twoLits (wordOp2 (-)))
90 primop_rule WordMulOp = one_rule (twoLits (wordOp2 (*)))
92 primop_rule WordQuotOp = one_rule (twoLits (wordOp2Z quot))
93 primop_rule WordRemOp = one_rule (twoLits (wordOp2Z rem))
94 #if __GLASGOW_HASKELL__ >= 407
95 primop_rule AndOp = one_rule (twoLits (wordBitOp2 (.&.)))
96 primop_rule OrOp = one_rule (twoLits (wordBitOp2 (.|.)))
97 primop_rule XorOp = one_rule (twoLits (wordBitOp2 xor))
101 primop_rule Word2IntOp = one_rule (oneLit (litCoerce word2IntLit))
102 primop_rule Int2WordOp = one_rule (oneLit (litCoerce int2WordLit))
103 primop_rule Narrow8IntOp = one_rule (oneLit (litCoerce narrow8IntLit))
104 primop_rule Narrow16IntOp = one_rule (oneLit (litCoerce narrow16IntLit))
105 primop_rule Narrow32IntOp = one_rule (oneLit (litCoerce narrow32IntLit))
106 primop_rule Narrow8WordOp = one_rule (oneLit (litCoerce narrow8WordLit))
107 primop_rule Narrow16WordOp = one_rule (oneLit (litCoerce narrow16WordLit))
108 primop_rule Narrow32WordOp = one_rule (oneLit (litCoerce narrow32WordLit))
109 primop_rule OrdOp = one_rule (oneLit (litCoerce char2IntLit))
110 primop_rule ChrOp = one_rule (oneLit (litCoerce int2CharLit))
111 primop_rule Float2IntOp = one_rule (oneLit (litCoerce float2IntLit))
112 primop_rule Int2FloatOp = one_rule (oneLit (litCoerce int2FloatLit))
113 primop_rule Double2IntOp = one_rule (oneLit (litCoerce double2IntLit))
114 primop_rule Int2DoubleOp = one_rule (oneLit (litCoerce int2DoubleLit))
115 -- SUP: Not sure what the standard says about precision in the following 2 cases
116 primop_rule Float2DoubleOp = one_rule (oneLit (litCoerce float2DoubleLit))
117 primop_rule Double2FloatOp = one_rule (oneLit (litCoerce double2FloatLit))
120 primop_rule FloatAddOp = one_rule (twoLits (floatOp2 (+)))
121 primop_rule FloatSubOp = one_rule (twoLits (floatOp2 (-)))
122 primop_rule FloatMulOp = one_rule (twoLits (floatOp2 (*)))
123 primop_rule FloatDivOp = one_rule (twoLits (floatOp2Z (/)))
124 primop_rule FloatNegOp = one_rule (oneLit negOp)
127 primop_rule DoubleAddOp = one_rule (twoLits (doubleOp2 (+)))
128 primop_rule DoubleSubOp = one_rule (twoLits (doubleOp2 (-)))
129 primop_rule DoubleMulOp = one_rule (twoLits (doubleOp2 (*)))
130 primop_rule DoubleDivOp = one_rule (twoLits (doubleOp2Z (/)))
131 primop_rule DoubleNegOp = one_rule (oneLit negOp)
133 -- Relational operators
134 primop_rule IntEqOp = one_rule (relop (==)) ++ case_rule (litEq True)
135 primop_rule IntNeOp = one_rule (relop (/=)) ++ case_rule (litEq False)
136 primop_rule CharEqOp = one_rule (relop (==)) ++ case_rule (litEq True)
137 primop_rule CharNeOp = one_rule (relop (/=)) ++ case_rule (litEq False)
139 primop_rule IntGtOp = one_rule (relop (>))
140 primop_rule IntGeOp = one_rule (relop (>=))
141 primop_rule IntLeOp = one_rule (relop (<=))
142 primop_rule IntLtOp = one_rule (relop (<))
144 primop_rule CharGtOp = one_rule (relop (>))
145 primop_rule CharGeOp = one_rule (relop (>=))
146 primop_rule CharLeOp = one_rule (relop (<=))
147 primop_rule CharLtOp = one_rule (relop (<))
149 primop_rule FloatGtOp = one_rule (relop (>))
150 primop_rule FloatGeOp = one_rule (relop (>=))
151 primop_rule FloatLeOp = one_rule (relop (<=))
152 primop_rule FloatLtOp = one_rule (relop (<))
153 primop_rule FloatEqOp = one_rule (relop (==))
154 primop_rule FloatNeOp = one_rule (relop (/=))
156 primop_rule DoubleGtOp = one_rule (relop (>))
157 primop_rule DoubleGeOp = one_rule (relop (>=))
158 primop_rule DoubleLeOp = one_rule (relop (<=))
159 primop_rule DoubleLtOp = one_rule (relop (<))
160 primop_rule DoubleEqOp = one_rule (relop (==))
161 primop_rule DoubleNeOp = one_rule (relop (/=))
163 primop_rule WordGtOp = one_rule (relop (>))
164 primop_rule WordGeOp = one_rule (relop (>=))
165 primop_rule WordLeOp = one_rule (relop (<=))
166 primop_rule WordLtOp = one_rule (relop (<))
167 primop_rule WordEqOp = one_rule (relop (==))
168 primop_rule WordNeOp = one_rule (relop (/=))
170 primop_rule other = []
173 relop cmp = twoLits (cmpOp (\ord -> ord `cmp` EQ))
174 -- Cunning. cmpOp compares the values to give an Ordering.
175 -- It applies its argument to that ordering value to turn
176 -- the ordering into a boolean value. (`cmp` EQ) is just the job.
179 %************************************************************************
181 \subsection{Doing the business}
183 %************************************************************************
185 ToDo: the reason these all return Nothing is because there used to be
186 the possibility of an argument being a litlit. Litlits are now gone,
187 so this could be cleaned up.
190 --------------------------
191 litCoerce :: (Literal -> Literal) -> Literal -> Maybe CoreExpr
192 litCoerce fn lit = Just (Lit (fn lit))
194 --------------------------
195 cmpOp :: (Ordering -> Bool) -> Literal -> Literal -> Maybe CoreExpr
199 done res | cmp res = Just trueVal
200 | otherwise = Just falseVal
202 -- These compares are at different types
203 go (MachChar i1) (MachChar i2) = done (i1 `compare` i2)
204 go (MachInt i1) (MachInt i2) = done (i1 `compare` i2)
205 go (MachInt64 i1) (MachInt64 i2) = done (i1 `compare` i2)
206 go (MachWord i1) (MachWord i2) = done (i1 `compare` i2)
207 go (MachWord64 i1) (MachWord64 i2) = done (i1 `compare` i2)
208 go (MachFloat i1) (MachFloat i2) = done (i1 `compare` i2)
209 go (MachDouble i1) (MachDouble i2) = done (i1 `compare` i2)
212 --------------------------
214 negOp (MachFloat 0.0) = Nothing -- can't represent -0.0 as a Rational
215 negOp (MachFloat f) = Just (mkFloatVal (-f))
216 negOp (MachDouble 0.0) = Nothing
217 negOp (MachDouble d) = Just (mkDoubleVal (-d))
218 negOp (MachInt i) = intResult (-i)
221 --------------------------
222 intOp2 op (MachInt i1) (MachInt i2) = intResult (i1 `op` i2)
223 intOp2 op l1 l2 = Nothing -- Could find LitLit
225 intOp2Z op (MachInt i1) (MachInt i2)
226 | i2 /= 0 = Just (mkIntVal (i1 `op` i2))
227 intOp2Z op l1 l2 = Nothing -- LitLit or zero dividend
229 --------------------------
230 #if __GLASGOW_HASKELL__ >= 500
231 wordOp2 op (MachWord w1) (MachWord w2)
232 = wordResult (w1 `op` w2)
233 wordOp2 op l1 l2 = Nothing -- Could find LitLit
236 wordOp2Z op (MachWord w1) (MachWord w2)
237 | w2 /= 0 = Just (mkWordVal (w1 `op` w2))
238 wordOp2Z op l1 l2 = Nothing -- LitLit or zero dividend
240 #if __GLASGOW_HASKELL__ >= 500
241 wordBitOp2 op l1@(MachWord w1) l2@(MachWord w2)
242 = Just (mkWordVal (w1 `op` w2))
244 -- Integer is not an instance of Bits, so we operate on Word64
245 wordBitOp2 op l1@(MachWord w1) l2@(MachWord w2)
246 = Just (mkWordVal ((fromIntegral::Word64->Integer) (fromIntegral w1 `op` fromIntegral w2)))
248 wordBitOp2 op l1 l2 = Nothing -- Could find LitLit
250 --------------------------
251 floatOp2 op (MachFloat f1) (MachFloat f2)
252 = Just (mkFloatVal (f1 `op` f2))
253 floatOp2 op l1 l2 = Nothing
255 floatOp2Z op (MachFloat f1) (MachFloat f2)
256 | f2 /= 0 = Just (mkFloatVal (f1 `op` f2))
257 floatOp2Z op l1 l2 = Nothing
259 --------------------------
260 doubleOp2 op (MachDouble f1) (MachDouble f2)
261 = Just (mkDoubleVal (f1 `op` f2))
262 doubleOp2 op l1 l2 = Nothing
264 doubleOp2Z op (MachDouble f1) (MachDouble f2)
265 | f2 /= 0 = Just (mkDoubleVal (f1 `op` f2))
266 doubleOp2Z op l1 l2 = Nothing
269 --------------------------
277 -- This is a Good Thing, because it allows case-of case things
278 -- to happen, and case-default absorption to happen. For
281 -- if (n ==# 3#) || (n ==# 4#) then e1 else e2
287 -- (modulo the usual precautions to avoid duplicating e1)
289 litEq :: Bool -- True <=> equality, False <=> inequality
291 litEq is_eq [Lit lit, expr] = do_lit_eq is_eq lit expr
292 litEq is_eq [expr, Lit lit] = do_lit_eq is_eq lit expr
293 litEq is_eq other = Nothing
295 do_lit_eq is_eq lit expr
296 = Just (Case expr (mkWildId (literalType lit)) boolTy
297 [(DEFAULT, [], val_if_neq),
298 (LitAlt lit, [], val_if_eq)])
300 val_if_eq | is_eq = trueVal
301 | otherwise = falseVal
302 val_if_neq | is_eq = falseVal
303 | otherwise = trueVal
305 -- Note that we *don't* warn the user about overflow. It's not done at
306 -- runtime either, and compilation of completely harmless things like
307 -- ((124076834 :: Word32) + (2147483647 :: Word32))
308 -- would yield a warning. Instead we simply squash the value into the
309 -- Int range, but not in a way suitable for cross-compiling... :-(
310 intResult :: Integer -> Maybe CoreExpr
312 = Just (mkIntVal (toInteger (fromInteger result :: Int)))
314 #if __GLASGOW_HASKELL__ >= 500
315 wordResult :: Integer -> Maybe CoreExpr
317 = Just (mkWordVal (toInteger (fromInteger result :: Word)))
322 %************************************************************************
324 \subsection{Vaguely generic functions
326 %************************************************************************
329 type RuleFun = [CoreExpr] -> Maybe CoreExpr
331 twoLits :: (Literal -> Literal -> Maybe CoreExpr) -> RuleFun
332 twoLits rule [Lit l1, Lit l2] = rule (convFloating l1) (convFloating l2)
333 twoLits rule _ = Nothing
335 oneLit :: (Literal -> Maybe CoreExpr) -> RuleFun
336 oneLit rule [Lit l1] = rule (convFloating l1)
337 oneLit rule _ = Nothing
339 -- When excess precision is not requested, cut down the precision of the
340 -- Rational value to that of Float/Double. We confuse host architecture
341 -- and target architecture here, but it's convenient (and wrong :-).
342 convFloating :: Literal -> Literal
343 convFloating (MachFloat f) | not opt_SimplExcessPrecision =
344 MachFloat (toRational ((fromRational f) :: Float ))
345 convFloating (MachDouble d) | not opt_SimplExcessPrecision =
346 MachDouble (toRational ((fromRational d) :: Double))
350 trueVal = Var trueDataConId
351 falseVal = Var falseDataConId
352 mkIntVal i = Lit (mkMachInt i)
353 mkWordVal w = Lit (mkMachWord w)
354 mkFloatVal f = Lit (convFloating (MachFloat f))
355 mkDoubleVal d = Lit (convFloating (MachDouble d))
359 %************************************************************************
361 \subsection{Special rules for seq, tagToEnum, dataToTag}
363 %************************************************************************
366 tagToEnumRule [Type ty, Lit (MachInt i)]
367 = ASSERT( isEnumerationTyCon tycon )
368 case filter correct_tag (tyConDataCons_maybe tycon `orElse` []) of
371 [] -> Nothing -- Abstract type
372 (dc:rest) -> ASSERT( null rest )
373 Just (Var (dataConWorkId dc))
375 correct_tag dc = (dataConTag dc - fIRST_TAG) == tag
377 tycon = tyConAppTyCon ty
379 tagToEnumRule other = Nothing
382 For dataToTag#, we can reduce if either
384 (a) the argument is a constructor
385 (b) the argument is a variable whose unfolding is a known constructor
388 dataToTagRule [Type ty1, Var tag_to_enum `App` Type ty2 `App` tag]
389 | tag_to_enum `hasKey` tagToEnumKey
390 , ty1 `coreEqType` ty2
391 = Just tag -- dataToTag (tagToEnum x) ==> x
393 dataToTagRule [_, val_arg]
394 | Just (dc,_) <- exprIsConApp_maybe val_arg
395 = ASSERT( not (isNewTyCon (dataConTyCon dc)) )
396 Just (mkIntVal (toInteger (dataConTag dc - fIRST_TAG)))
398 dataToTagRule other = Nothing
401 %************************************************************************
403 \subsection{Built in rules}
405 %************************************************************************
408 builtinRules :: [CoreRule]
409 -- Rules for non-primops that can't be expressed using a RULE pragma
411 = [ BuiltinRule FSLIT("AppendLitString") unpackCStringFoldrName match_append_lit,
412 BuiltinRule FSLIT("EqString") eqStringName match_eq_string,
413 BuiltinRule FSLIT("Inline") inlineIdName match_inline
417 ---------------------------------------------------
419 -- unpackFoldrCString# "foo" c (unpackFoldrCString# "baz" c n) = unpackFoldrCString# "foobaz" c n
421 match_append_lit [Type ty1,
424 Var unpk `App` Type ty2
425 `App` Lit (MachStr s2)
429 | unpk `hasKey` unpackCStringFoldrIdKey &&
431 = ASSERT( ty1 `coreEqType` ty2 )
432 Just (Var unpk `App` Type ty1
433 `App` Lit (MachStr (s1 `appendFS` s2))
437 match_append_lit other = Nothing
439 ---------------------------------------------------
441 -- eqString (unpackCString# (Lit s1)) (unpackCString# (Lit s2) = s1==s2
443 match_eq_string [Var unpk1 `App` Lit (MachStr s1),
444 Var unpk2 `App` Lit (MachStr s2)]
445 | unpk1 `hasKey` unpackCStringIdKey,
446 unpk2 `hasKey` unpackCStringIdKey
447 = Just (if s1 == s2 then trueVal else falseVal)
449 match_eq_string other = Nothing
452 ---------------------------------------------------
454 -- inline (f a b c) = <f's unfolding> a b c
455 -- (if f has an unfolding)
456 match_inline (e:args2)
457 | (Var f, args1) <- collectArgs e,
458 Just unf <- maybeUnfoldingTemplate (idUnfolding f)
459 = Just (mkApps (mkApps unf args1) args2)
461 match_inline other = Nothing