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 )
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 )
35 import TysWiredIn ( boolTy, trueDataConId, falseDataConId )
36 import TyCon ( tyConDataCons_maybe, isEnumerationTyCon, isNewTyCon )
37 import DataCon ( dataConTag, dataConTyCon, dataConWorkId, fIRST_TAG )
38 import CoreUtils ( cheapEqExpr, exprIsConApp_maybe )
39 import Type ( tyConAppTyCon, coreEqType )
40 import OccName ( occNameUserString)
41 import PrelNames ( unpackCStringFoldrName, unpackCStringFoldrIdKey, hasKey,
42 eqStringName, unpackCStringIdKey )
43 import Maybes ( orElse )
47 import CmdLineOpts ( opt_SimplExcessPrecision )
49 import DATA_BITS ( Bits(..) )
50 #if __GLASGOW_HASKELL__ >= 500
51 import DATA_WORD ( Word )
53 import DATA_WORD ( Word64 )
59 primOpRules :: PrimOp -> [CoreRule]
60 primOpRules op = primop_rule op
62 op_name = mkFastString (occNameUserString (primOpOcc op))
63 op_name_case = op_name `appendFS` FSLIT("->case")
66 one_rule rule_fn = [BuiltinRule op_name rule_fn]
68 -- ToDo: something for integer-shift ops?
71 primop_rule TagToEnumOp = one_rule tagToEnumRule
72 primop_rule DataToTagOp = one_rule dataToTagRule
75 primop_rule IntAddOp = one_rule (twoLits (intOp2 (+)))
76 primop_rule IntSubOp = one_rule (twoLits (intOp2 (-)))
77 primop_rule IntMulOp = one_rule (twoLits (intOp2 (*)))
78 primop_rule IntQuotOp = one_rule (twoLits (intOp2Z quot))
79 primop_rule IntRemOp = one_rule (twoLits (intOp2Z rem))
80 primop_rule IntNegOp = one_rule (oneLit negOp)
83 #if __GLASGOW_HASKELL__ >= 500
84 primop_rule WordAddOp = one_rule (twoLits (wordOp2 (+)))
85 primop_rule WordSubOp = one_rule (twoLits (wordOp2 (-)))
86 primop_rule WordMulOp = one_rule (twoLits (wordOp2 (*)))
88 primop_rule WordQuotOp = one_rule (twoLits (wordOp2Z quot))
89 primop_rule WordRemOp = one_rule (twoLits (wordOp2Z rem))
90 #if __GLASGOW_HASKELL__ >= 407
91 primop_rule AndOp = one_rule (twoLits (wordBitOp2 (.&.)))
92 primop_rule OrOp = one_rule (twoLits (wordBitOp2 (.|.)))
93 primop_rule XorOp = one_rule (twoLits (wordBitOp2 xor))
97 primop_rule Word2IntOp = one_rule (oneLit (litCoerce word2IntLit))
98 primop_rule Int2WordOp = one_rule (oneLit (litCoerce int2WordLit))
99 primop_rule Narrow8IntOp = one_rule (oneLit (litCoerce narrow8IntLit))
100 primop_rule Narrow16IntOp = one_rule (oneLit (litCoerce narrow16IntLit))
101 primop_rule Narrow32IntOp = one_rule (oneLit (litCoerce narrow32IntLit))
102 primop_rule Narrow8WordOp = one_rule (oneLit (litCoerce narrow8WordLit))
103 primop_rule Narrow16WordOp = one_rule (oneLit (litCoerce narrow16WordLit))
104 primop_rule Narrow32WordOp = one_rule (oneLit (litCoerce narrow32WordLit))
105 primop_rule OrdOp = one_rule (oneLit (litCoerce char2IntLit))
106 primop_rule ChrOp = one_rule (oneLit (litCoerce int2CharLit))
107 primop_rule Float2IntOp = one_rule (oneLit (litCoerce float2IntLit))
108 primop_rule Int2FloatOp = one_rule (oneLit (litCoerce int2FloatLit))
109 primop_rule Double2IntOp = one_rule (oneLit (litCoerce double2IntLit))
110 primop_rule Int2DoubleOp = one_rule (oneLit (litCoerce int2DoubleLit))
111 -- SUP: Not sure what the standard says about precision in the following 2 cases
112 primop_rule Float2DoubleOp = one_rule (oneLit (litCoerce float2DoubleLit))
113 primop_rule Double2FloatOp = one_rule (oneLit (litCoerce double2FloatLit))
116 primop_rule FloatAddOp = one_rule (twoLits (floatOp2 (+)))
117 primop_rule FloatSubOp = one_rule (twoLits (floatOp2 (-)))
118 primop_rule FloatMulOp = one_rule (twoLits (floatOp2 (*)))
119 primop_rule FloatDivOp = one_rule (twoLits (floatOp2Z (/)))
120 primop_rule FloatNegOp = one_rule (oneLit negOp)
123 primop_rule DoubleAddOp = one_rule (twoLits (doubleOp2 (+)))
124 primop_rule DoubleSubOp = one_rule (twoLits (doubleOp2 (-)))
125 primop_rule DoubleMulOp = one_rule (twoLits (doubleOp2 (*)))
126 primop_rule DoubleDivOp = one_rule (twoLits (doubleOp2Z (/)))
127 primop_rule DoubleNegOp = one_rule (oneLit negOp)
129 -- Relational operators
130 primop_rule IntEqOp = [BuiltinRule op_name (relop (==)), BuiltinRule op_name_case (litEq True)]
131 primop_rule IntNeOp = [BuiltinRule op_name (relop (/=)), BuiltinRule op_name_case (litEq False)]
132 primop_rule CharEqOp = [BuiltinRule op_name (relop (==)), BuiltinRule op_name_case (litEq True)]
133 primop_rule CharNeOp = [BuiltinRule op_name (relop (/=)), BuiltinRule op_name_case (litEq False)]
135 primop_rule IntGtOp = one_rule (relop (>))
136 primop_rule IntGeOp = one_rule (relop (>=))
137 primop_rule IntLeOp = one_rule (relop (<=))
138 primop_rule IntLtOp = one_rule (relop (<))
140 primop_rule CharGtOp = one_rule (relop (>))
141 primop_rule CharGeOp = one_rule (relop (>=))
142 primop_rule CharLeOp = one_rule (relop (<=))
143 primop_rule CharLtOp = one_rule (relop (<))
145 primop_rule FloatGtOp = one_rule (relop (>))
146 primop_rule FloatGeOp = one_rule (relop (>=))
147 primop_rule FloatLeOp = one_rule (relop (<=))
148 primop_rule FloatLtOp = one_rule (relop (<))
149 primop_rule FloatEqOp = one_rule (relop (==))
150 primop_rule FloatNeOp = one_rule (relop (/=))
152 primop_rule DoubleGtOp = one_rule (relop (>))
153 primop_rule DoubleGeOp = one_rule (relop (>=))
154 primop_rule DoubleLeOp = one_rule (relop (<=))
155 primop_rule DoubleLtOp = one_rule (relop (<))
156 primop_rule DoubleEqOp = one_rule (relop (==))
157 primop_rule DoubleNeOp = one_rule (relop (/=))
159 primop_rule WordGtOp = one_rule (relop (>))
160 primop_rule WordGeOp = one_rule (relop (>=))
161 primop_rule WordLeOp = one_rule (relop (<=))
162 primop_rule WordLtOp = one_rule (relop (<))
163 primop_rule WordEqOp = one_rule (relop (==))
164 primop_rule WordNeOp = one_rule (relop (/=))
166 primop_rule other = []
169 relop cmp = twoLits (cmpOp (\ord -> ord `cmp` EQ))
170 -- Cunning. cmpOp compares the values to give an Ordering.
171 -- It applies its argument to that ordering value to turn
172 -- the ordering into a boolean value. (`cmp` EQ) is just the job.
175 %************************************************************************
177 \subsection{Doing the business}
179 %************************************************************************
181 ToDo: the reason these all return Nothing is because there used to be
182 the possibility of an argument being a litlit. Litlits are now gone,
183 so this could be cleaned up.
186 --------------------------
187 litCoerce :: (Literal -> Literal) -> Literal -> Maybe CoreExpr
188 litCoerce fn lit = Just (Lit (fn lit))
190 --------------------------
191 cmpOp :: (Ordering -> Bool) -> Literal -> Literal -> Maybe CoreExpr
195 done res | cmp res = Just trueVal
196 | otherwise = Just falseVal
198 -- These compares are at different types
199 go (MachChar i1) (MachChar i2) = done (i1 `compare` i2)
200 go (MachInt i1) (MachInt i2) = done (i1 `compare` i2)
201 go (MachInt64 i1) (MachInt64 i2) = done (i1 `compare` i2)
202 go (MachWord i1) (MachWord i2) = done (i1 `compare` i2)
203 go (MachWord64 i1) (MachWord64 i2) = done (i1 `compare` i2)
204 go (MachFloat i1) (MachFloat i2) = done (i1 `compare` i2)
205 go (MachDouble i1) (MachDouble i2) = done (i1 `compare` i2)
208 --------------------------
210 negOp (MachFloat 0.0) = Nothing -- can't represent -0.0 as a Rational
211 negOp (MachFloat f) = Just (mkFloatVal (-f))
212 negOp (MachDouble 0.0) = Nothing
213 negOp (MachDouble d) = Just (mkDoubleVal (-d))
214 negOp (MachInt i) = intResult (-i)
217 --------------------------
218 intOp2 op (MachInt i1) (MachInt i2) = intResult (i1 `op` i2)
219 intOp2 op l1 l2 = Nothing -- Could find LitLit
221 intOp2Z op (MachInt i1) (MachInt i2)
222 | i2 /= 0 = Just (mkIntVal (i1 `op` i2))
223 intOp2Z op l1 l2 = Nothing -- LitLit or zero dividend
225 --------------------------
226 #if __GLASGOW_HASKELL__ >= 500
227 wordOp2 op (MachWord w1) (MachWord w2)
228 = wordResult (w1 `op` w2)
229 wordOp2 op l1 l2 = Nothing -- Could find LitLit
232 wordOp2Z op (MachWord w1) (MachWord w2)
233 | w2 /= 0 = Just (mkWordVal (w1 `op` w2))
234 wordOp2Z op l1 l2 = Nothing -- LitLit or zero dividend
236 #if __GLASGOW_HASKELL__ >= 500
237 wordBitOp2 op l1@(MachWord w1) l2@(MachWord w2)
238 = Just (mkWordVal (w1 `op` w2))
240 -- Integer is not an instance of Bits, so we operate on Word64
241 wordBitOp2 op l1@(MachWord w1) l2@(MachWord w2)
242 = Just (mkWordVal ((fromIntegral::Word64->Integer) (fromIntegral w1 `op` fromIntegral w2)))
244 wordBitOp2 op l1 l2 = Nothing -- Could find LitLit
246 --------------------------
247 floatOp2 op (MachFloat f1) (MachFloat f2)
248 = Just (mkFloatVal (f1 `op` f2))
249 floatOp2 op l1 l2 = Nothing
251 floatOp2Z op (MachFloat f1) (MachFloat f2)
252 | f2 /= 0 = Just (mkFloatVal (f1 `op` f2))
253 floatOp2Z op l1 l2 = Nothing
255 --------------------------
256 doubleOp2 op (MachDouble f1) (MachDouble f2)
257 = Just (mkDoubleVal (f1 `op` f2))
258 doubleOp2 op l1 l2 = Nothing
260 doubleOp2Z op (MachDouble f1) (MachDouble f2)
261 | f2 /= 0 = Just (mkDoubleVal (f1 `op` f2))
262 doubleOp2Z op l1 l2 = Nothing
265 --------------------------
273 -- This is a Good Thing, because it allows case-of case things
274 -- to happen, and case-default absorption to happen. For
277 -- if (n ==# 3#) || (n ==# 4#) then e1 else e2
283 -- (modulo the usual precautions to avoid duplicating e1)
285 litEq :: Bool -- True <=> equality, False <=> inequality
287 litEq is_eq [Lit lit, expr] = do_lit_eq is_eq lit expr
288 litEq is_eq [expr, Lit lit] = do_lit_eq is_eq lit expr
289 litEq is_eq other = Nothing
291 do_lit_eq is_eq lit expr
292 = Just (Case expr (mkWildId (literalType lit)) boolTy
293 [(DEFAULT, [], val_if_neq),
294 (LitAlt lit, [], val_if_eq)])
296 val_if_eq | is_eq = trueVal
297 | otherwise = falseVal
298 val_if_neq | is_eq = falseVal
299 | otherwise = trueVal
301 -- Note that we *don't* warn the user about overflow. It's not done at
302 -- runtime either, and compilation of completely harmless things like
303 -- ((124076834 :: Word32) + (2147483647 :: Word32))
304 -- would yield a warning. Instead we simply squash the value into the
305 -- Int range, but not in a way suitable for cross-compiling... :-(
306 intResult :: Integer -> Maybe CoreExpr
308 = Just (mkIntVal (toInteger (fromInteger result :: Int)))
310 #if __GLASGOW_HASKELL__ >= 500
311 wordResult :: Integer -> Maybe CoreExpr
313 = Just (mkWordVal (toInteger (fromInteger result :: Word)))
318 %************************************************************************
320 \subsection{Vaguely generic functions
322 %************************************************************************
325 type RuleFun = [CoreExpr] -> Maybe CoreExpr
327 twoLits :: (Literal -> Literal -> Maybe CoreExpr) -> RuleFun
328 twoLits rule [Lit l1, Lit l2] = rule (convFloating l1) (convFloating l2)
329 twoLits rule _ = Nothing
331 oneLit :: (Literal -> Maybe CoreExpr) -> RuleFun
332 oneLit rule [Lit l1] = rule (convFloating l1)
333 oneLit rule _ = Nothing
335 -- When excess precision is not requested, cut down the precision of the
336 -- Rational value to that of Float/Double. We confuse host architecture
337 -- and target architecture here, but it's convenient (and wrong :-).
338 convFloating :: Literal -> Literal
339 convFloating (MachFloat f) | not opt_SimplExcessPrecision =
340 MachFloat (toRational ((fromRational f) :: Float ))
341 convFloating (MachDouble d) | not opt_SimplExcessPrecision =
342 MachDouble (toRational ((fromRational d) :: Double))
346 trueVal = Var trueDataConId
347 falseVal = Var falseDataConId
348 mkIntVal i = Lit (mkMachInt i)
349 mkWordVal w = Lit (mkMachWord w)
350 mkFloatVal f = Lit (convFloating (MachFloat f))
351 mkDoubleVal d = Lit (convFloating (MachDouble d))
355 %************************************************************************
357 \subsection{Special rules for seq, tagToEnum, dataToTag}
359 %************************************************************************
362 tagToEnumRule [Type ty, Lit (MachInt i)]
363 = ASSERT( isEnumerationTyCon tycon )
364 case filter correct_tag (tyConDataCons_maybe tycon `orElse` []) of
367 [] -> Nothing -- Abstract type
368 (dc:rest) -> ASSERT( null rest )
369 Just (Var (dataConWorkId dc))
371 correct_tag dc = (dataConTag dc - fIRST_TAG) == tag
373 tycon = tyConAppTyCon ty
375 tagToEnumRule other = Nothing
378 For dataToTag#, we can reduce if either
380 (a) the argument is a constructor
381 (b) the argument is a variable whose unfolding is a known constructor
384 dataToTagRule [Type ty1, Var tag_to_enum `App` Type ty2 `App` tag]
385 | Just TagToEnumOp <- isPrimOpId_maybe tag_to_enum
386 , ty1 `coreEqType` ty2
387 = Just tag -- dataToTag (tagToEnum x) ==> x
389 dataToTagRule [_, val_arg]
390 | Just (dc,_) <- exprIsConApp_maybe val_arg
391 = ASSERT( not (isNewTyCon (dataConTyCon dc)) )
392 Just (mkIntVal (toInteger (dataConTag dc - fIRST_TAG)))
394 dataToTagRule other = Nothing
397 %************************************************************************
399 \subsection{Built in rules}
401 %************************************************************************
404 builtinRules :: [(Name, CoreRule)]
405 -- Rules for non-primops that can't be expressed using a RULE pragma
407 = [ (unpackCStringFoldrName, BuiltinRule FSLIT("AppendLitString") match_append_lit),
408 (eqStringName, BuiltinRule FSLIT("EqString") match_eq_string)
413 -- unpackFoldrCString# "foo" c (unpackFoldrCString# "baz" c n) = unpackFoldrCString# "foobaz" c n
415 match_append_lit [Type ty1,
418 Var unpk `App` Type ty2
419 `App` Lit (MachStr s2)
423 | unpk `hasKey` unpackCStringFoldrIdKey &&
425 = ASSERT( ty1 `coreEqType` ty2 )
426 Just (Var unpk `App` Type ty1
427 `App` Lit (MachStr (s1 `appendFS` s2))
431 match_append_lit other = Nothing
434 -- eqString (unpackCString# (Lit s1)) (unpackCString# (Lit s2) = s1==s2
436 match_eq_string [Var unpk1 `App` Lit (MachStr s1),
437 Var unpk2 `App` Lit (MachStr s2)]
438 | unpk1 `hasKey` unpackCStringIdKey,
439 unpk2 `hasKey` unpackCStringIdKey
440 = Just (if s1 == s2 then trueVal else falseVal)
442 match_eq_string other = Nothing