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 )
24 import Literal ( Literal(..), isLitLitLit, 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 )
34 import TysWiredIn ( 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, eqType )
39 import OccName ( occNameUserString)
40 import PrelNames ( unpackCStringFoldrName, unpackCStringFoldrIdKey, hasKey,
41 eqStringName, unpackCStringIdKey )
42 import Maybes ( orElse )
46 import CmdLineOpts ( 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 -> [CoreRule]
59 primOpRules op = primop_rule op
61 op_name = mkFastString (occNameUserString (primOpOcc op))
62 op_name_case = op_name `appendFS` FSLIT("->case")
65 one_rule rule_fn = [BuiltinRule op_name rule_fn]
67 -- ToDo: something for integer-shift ops?
70 primop_rule TagToEnumOp = one_rule tagToEnumRule
71 primop_rule DataToTagOp = one_rule dataToTagRule
74 primop_rule IntAddOp = one_rule (twoLits (intOp2 (+)))
75 primop_rule IntSubOp = one_rule (twoLits (intOp2 (-)))
76 primop_rule IntMulOp = one_rule (twoLits (intOp2 (*)))
77 primop_rule IntQuotOp = one_rule (twoLits (intOp2Z quot))
78 primop_rule IntRemOp = one_rule (twoLits (intOp2Z rem))
79 primop_rule IntNegOp = one_rule (oneLit negOp)
82 #if __GLASGOW_HASKELL__ >= 500
83 primop_rule WordAddOp = one_rule (twoLits (wordOp2 (+)))
84 primop_rule WordSubOp = one_rule (twoLits (wordOp2 (-)))
85 primop_rule WordMulOp = one_rule (twoLits (wordOp2 (*)))
87 primop_rule WordQuotOp = one_rule (twoLits (wordOp2Z quot))
88 primop_rule WordRemOp = one_rule (twoLits (wordOp2Z rem))
89 #if __GLASGOW_HASKELL__ >= 407
90 primop_rule AndOp = one_rule (twoLits (wordBitOp2 (.&.)))
91 primop_rule OrOp = one_rule (twoLits (wordBitOp2 (.|.)))
92 primop_rule XorOp = one_rule (twoLits (wordBitOp2 xor))
96 primop_rule Word2IntOp = one_rule (oneLit (litCoerce word2IntLit))
97 primop_rule Int2WordOp = one_rule (oneLit (litCoerce int2WordLit))
98 primop_rule Narrow8IntOp = one_rule (oneLit (litCoerce narrow8IntLit))
99 primop_rule Narrow16IntOp = one_rule (oneLit (litCoerce narrow16IntLit))
100 primop_rule Narrow32IntOp = one_rule (oneLit (litCoerce narrow32IntLit))
101 primop_rule Narrow8WordOp = one_rule (oneLit (litCoerce narrow8WordLit))
102 primop_rule Narrow16WordOp = one_rule (oneLit (litCoerce narrow16WordLit))
103 primop_rule Narrow32WordOp = one_rule (oneLit (litCoerce narrow32WordLit))
104 primop_rule OrdOp = one_rule (oneLit (litCoerce char2IntLit))
105 primop_rule ChrOp = one_rule (oneLit (litCoerce int2CharLit))
106 primop_rule Float2IntOp = one_rule (oneLit (litCoerce float2IntLit))
107 primop_rule Int2FloatOp = one_rule (oneLit (litCoerce int2FloatLit))
108 primop_rule Double2IntOp = one_rule (oneLit (litCoerce double2IntLit))
109 primop_rule Int2DoubleOp = one_rule (oneLit (litCoerce int2DoubleLit))
110 -- SUP: Not sure what the standard says about precision in the following 2 cases
111 primop_rule Float2DoubleOp = one_rule (oneLit (litCoerce float2DoubleLit))
112 primop_rule Double2FloatOp = one_rule (oneLit (litCoerce double2FloatLit))
115 primop_rule FloatAddOp = one_rule (twoLits (floatOp2 (+)))
116 primop_rule FloatSubOp = one_rule (twoLits (floatOp2 (-)))
117 primop_rule FloatMulOp = one_rule (twoLits (floatOp2 (*)))
118 primop_rule FloatDivOp = one_rule (twoLits (floatOp2Z (/)))
119 primop_rule FloatNegOp = one_rule (oneLit negOp)
122 primop_rule DoubleAddOp = one_rule (twoLits (doubleOp2 (+)))
123 primop_rule DoubleSubOp = one_rule (twoLits (doubleOp2 (-)))
124 primop_rule DoubleMulOp = one_rule (twoLits (doubleOp2 (*)))
125 primop_rule DoubleDivOp = one_rule (twoLits (doubleOp2Z (/)))
126 primop_rule DoubleNegOp = one_rule (oneLit negOp)
128 -- Relational operators
129 primop_rule IntEqOp = [BuiltinRule op_name (relop (==)), BuiltinRule op_name_case (litEq True)]
130 primop_rule IntNeOp = [BuiltinRule op_name (relop (/=)), BuiltinRule op_name_case (litEq False)]
131 primop_rule CharEqOp = [BuiltinRule op_name (relop (==)), BuiltinRule op_name_case (litEq True)]
132 primop_rule CharNeOp = [BuiltinRule op_name (relop (/=)), BuiltinRule op_name_case (litEq False)]
134 primop_rule IntGtOp = one_rule (relop (>))
135 primop_rule IntGeOp = one_rule (relop (>=))
136 primop_rule IntLeOp = one_rule (relop (<=))
137 primop_rule IntLtOp = one_rule (relop (<))
139 primop_rule CharGtOp = one_rule (relop (>))
140 primop_rule CharGeOp = one_rule (relop (>=))
141 primop_rule CharLeOp = one_rule (relop (<=))
142 primop_rule CharLtOp = one_rule (relop (<))
144 primop_rule FloatGtOp = one_rule (relop (>))
145 primop_rule FloatGeOp = one_rule (relop (>=))
146 primop_rule FloatLeOp = one_rule (relop (<=))
147 primop_rule FloatLtOp = one_rule (relop (<))
148 primop_rule FloatEqOp = one_rule (relop (==))
149 primop_rule FloatNeOp = one_rule (relop (/=))
151 primop_rule DoubleGtOp = one_rule (relop (>))
152 primop_rule DoubleGeOp = one_rule (relop (>=))
153 primop_rule DoubleLeOp = one_rule (relop (<=))
154 primop_rule DoubleLtOp = one_rule (relop (<))
155 primop_rule DoubleEqOp = one_rule (relop (==))
156 primop_rule DoubleNeOp = one_rule (relop (/=))
158 primop_rule WordGtOp = one_rule (relop (>))
159 primop_rule WordGeOp = one_rule (relop (>=))
160 primop_rule WordLeOp = one_rule (relop (<=))
161 primop_rule WordLtOp = one_rule (relop (<))
162 primop_rule WordEqOp = one_rule (relop (==))
163 primop_rule WordNeOp = one_rule (relop (/=))
165 primop_rule other = []
168 relop cmp = twoLits (cmpOp (\ord -> ord `cmp` EQ))
169 -- Cunning. cmpOp compares the values to give an Ordering.
170 -- It applies its argument to that ordering value to turn
171 -- the ordering into a boolean value. (`cmp` EQ) is just the job.
174 %************************************************************************
176 \subsection{Doing the business}
178 %************************************************************************
182 In all these operations we might find a LitLit as an operand; that's
183 why we have the catch-all Nothing case.
186 --------------------------
187 litCoerce :: (Literal -> Literal) -> Literal -> Maybe CoreExpr
188 litCoerce fn lit | isLitLitLit lit = Nothing
189 | otherwise = Just (Lit (fn lit))
191 --------------------------
192 cmpOp :: (Ordering -> Bool) -> Literal -> Literal -> Maybe CoreExpr
196 done res | cmp res = Just trueVal
197 | otherwise = Just falseVal
199 -- These compares are at different types
200 go (MachChar i1) (MachChar i2) = done (i1 `compare` i2)
201 go (MachInt i1) (MachInt i2) = done (i1 `compare` i2)
202 go (MachInt64 i1) (MachInt64 i2) = done (i1 `compare` i2)
203 go (MachWord i1) (MachWord i2) = done (i1 `compare` i2)
204 go (MachWord64 i1) (MachWord64 i2) = done (i1 `compare` i2)
205 go (MachFloat i1) (MachFloat i2) = done (i1 `compare` i2)
206 go (MachDouble i1) (MachDouble i2) = done (i1 `compare` i2)
209 --------------------------
211 negOp (MachFloat f) = Just (mkFloatVal (-f))
212 negOp (MachDouble d) = Just (mkDoubleVal (-d))
213 negOp (MachInt i) = intResult (-i)
216 --------------------------
217 intOp2 op (MachInt i1) (MachInt i2) = intResult (i1 `op` i2)
218 intOp2 op l1 l2 = Nothing -- Could find LitLit
220 intOp2Z op (MachInt i1) (MachInt i2)
221 | i2 /= 0 = Just (mkIntVal (i1 `op` i2))
222 intOp2Z op l1 l2 = Nothing -- LitLit or zero dividend
224 --------------------------
225 #if __GLASGOW_HASKELL__ >= 500
226 wordOp2 op (MachWord w1) (MachWord w2)
227 = wordResult (w1 `op` w2)
228 wordOp2 op l1 l2 = Nothing -- Could find LitLit
231 wordOp2Z op (MachWord w1) (MachWord w2)
232 | w2 /= 0 = Just (mkWordVal (w1 `op` w2))
233 wordOp2Z op l1 l2 = Nothing -- LitLit or zero dividend
235 #if __GLASGOW_HASKELL__ >= 500
236 wordBitOp2 op l1@(MachWord w1) l2@(MachWord w2)
237 = Just (mkWordVal (w1 `op` w2))
239 -- Integer is not an instance of Bits, so we operate on Word64
240 wordBitOp2 op l1@(MachWord w1) l2@(MachWord w2)
241 = Just (mkWordVal ((fromIntegral::Word64->Integer) (fromIntegral w1 `op` fromIntegral w2)))
243 wordBitOp2 op l1 l2 = Nothing -- Could find LitLit
245 --------------------------
246 floatOp2 op (MachFloat f1) (MachFloat f2)
247 = Just (mkFloatVal (f1 `op` f2))
248 floatOp2 op l1 l2 = Nothing
250 floatOp2Z op (MachFloat f1) (MachFloat f2)
251 | f2 /= 0 = Just (mkFloatVal (f1 `op` f2))
252 floatOp2Z op l1 l2 = Nothing
254 --------------------------
255 doubleOp2 op (MachDouble f1) (MachDouble f2)
256 = Just (mkDoubleVal (f1 `op` f2))
257 doubleOp2 op l1 l2 = Nothing
259 doubleOp2Z op (MachDouble f1) (MachDouble f2)
260 | f2 /= 0 = Just (mkDoubleVal (f1 `op` f2))
261 doubleOp2Z op l1 l2 = Nothing
264 --------------------------
272 -- This is a Good Thing, because it allows case-of case things
273 -- to happen, and case-default absorption to happen. For
276 -- if (n ==# 3#) || (n ==# 4#) then e1 else e2
282 -- (modulo the usual precautions to avoid duplicating e1)
284 litEq :: Bool -- True <=> equality, False <=> inequality
286 litEq is_eq [Lit lit, expr] = do_lit_eq is_eq lit expr
287 litEq is_eq [expr, Lit lit] = do_lit_eq is_eq lit expr
288 litEq is_eq other = Nothing
290 do_lit_eq is_eq lit expr
291 = Just (Case expr (mkWildId (literalType lit))
292 [(DEFAULT, [], val_if_neq),
293 (LitAlt lit, [], val_if_eq)])
295 val_if_eq | is_eq = trueVal
296 | otherwise = falseVal
297 val_if_neq | is_eq = falseVal
298 | otherwise = trueVal
300 -- Note that we *don't* warn the user about overflow. It's not done at
301 -- runtime either, and compilation of completely harmless things like
302 -- ((124076834 :: Word32) + (2147483647 :: Word32))
303 -- would yield a warning. Instead we simply squash the value into the
304 -- Int range, but not in a way suitable for cross-compiling... :-(
305 intResult :: Integer -> Maybe CoreExpr
307 = Just (mkIntVal (toInteger (fromInteger result :: Int)))
309 #if __GLASGOW_HASKELL__ >= 500
310 wordResult :: Integer -> Maybe CoreExpr
312 = Just (mkWordVal (toInteger (fromInteger result :: Word)))
317 %************************************************************************
319 \subsection{Vaguely generic functions
321 %************************************************************************
324 type RuleFun = [CoreExpr] -> Maybe CoreExpr
326 twoLits :: (Literal -> Literal -> Maybe CoreExpr) -> RuleFun
327 twoLits rule [Lit l1, Lit l2] = rule (convFloating l1) (convFloating l2)
328 twoLits rule _ = Nothing
330 oneLit :: (Literal -> Maybe CoreExpr) -> RuleFun
331 oneLit rule [Lit l1] = rule (convFloating l1)
332 oneLit rule _ = Nothing
334 -- When excess precision is not requested, cut down the precision of the
335 -- Rational value to that of Float/Double. We confuse host architecture
336 -- and target architecture here, but it's convenient (and wrong :-).
337 convFloating :: Literal -> Literal
338 convFloating (MachFloat f) | not opt_SimplExcessPrecision =
339 MachFloat (toRational ((fromRational f) :: Float ))
340 convFloating (MachDouble d) | not opt_SimplExcessPrecision =
341 MachDouble (toRational ((fromRational d) :: Double))
345 trueVal = Var trueDataConId
346 falseVal = Var falseDataConId
347 mkIntVal i = Lit (mkMachInt i)
348 mkWordVal w = Lit (mkMachWord w)
349 mkFloatVal f = Lit (convFloating (MachFloat f))
350 mkDoubleVal d = Lit (convFloating (MachDouble d))
354 %************************************************************************
356 \subsection{Special rules for seq, tagToEnum, dataToTag}
358 %************************************************************************
361 tagToEnumRule [Type ty, Lit (MachInt i)]
362 = ASSERT( isEnumerationTyCon tycon )
363 case filter correct_tag (tyConDataCons_maybe tycon `orElse` []) of
366 [] -> Nothing -- Abstract type
367 (dc:rest) -> ASSERT( null rest )
368 Just (Var (dataConWorkId dc))
370 correct_tag dc = (dataConTag dc - fIRST_TAG) == tag
372 tycon = tyConAppTyCon ty
374 tagToEnumRule other = Nothing
377 For dataToTag#, we can reduce if either
379 (a) the argument is a constructor
380 (b) the argument is a variable whose unfolding is a known constructor
383 dataToTagRule [_, val_arg]
384 = case exprIsConApp_maybe val_arg of
385 Just (dc,_) -> ASSERT( not (isNewTyCon (dataConTyCon dc)) )
386 Just (mkIntVal (toInteger (dataConTag dc - fIRST_TAG)))
390 dataToTagRule other = Nothing
393 %************************************************************************
395 \subsection{Built in rules}
397 %************************************************************************
400 builtinRules :: [(Name, CoreRule)]
401 -- Rules for non-primops that can't be expressed using a RULE pragma
403 = [ (unpackCStringFoldrName, BuiltinRule FSLIT("AppendLitString") match_append_lit),
404 (eqStringName, BuiltinRule FSLIT("EqString") match_eq_string)
409 -- unpackFoldrCString# "foo" c (unpackFoldrCString# "baz" c n) = unpackFoldrCString# "foobaz" c n
411 match_append_lit [Type ty1,
414 Var unpk `App` Type ty2
415 `App` Lit (MachStr s2)
419 | unpk `hasKey` unpackCStringFoldrIdKey &&
421 = ASSERT( ty1 `eqType` ty2 )
422 Just (Var unpk `App` Type ty1
423 `App` Lit (MachStr (s1 `appendFS` s2))
427 match_append_lit other = Nothing
430 -- eqString (unpackCString# (Lit s1)) (unpackCString# (Lit s2) = s1==s2
432 match_eq_string [Var unpk1 `App` Lit (MachStr s1),
433 Var unpk2 `App` Lit (MachStr s2)]
434 | unpk1 `hasKey` unpackCStringIdKey,
435 unpk2 `hasKey` unpackCStringIdKey
436 = Just (if s1 == s2 then trueVal else falseVal)
438 match_eq_string other = Nothing