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, dataConId, fIRST_TAG )
37 import CoreUtils ( exprIsValue, 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 )
44 import Bits ( Bits(..) )
45 #if __GLASGOW_HASKELL__ >= 500
48 import Word ( Word64 )
51 import CmdLineOpts ( opt_SimplExcessPrecision )
56 primOpRules :: PrimOp -> [CoreRule]
57 primOpRules op = primop_rule op
59 op_name = _PK_ (occNameUserString (primOpOcc op))
60 op_name_case = op_name _APPEND_ SLIT("->case")
63 one_rule rule_fn = [BuiltinRule op_name rule_fn]
65 -- ToDo: something for integer-shift ops?
68 primop_rule SeqOp = one_rule seqRule
69 primop_rule TagToEnumOp = one_rule tagToEnumRule
70 primop_rule DataToTagOp = one_rule dataToTagRule
73 primop_rule IntAddOp = one_rule (twoLits (intOp2 (+)))
74 primop_rule IntSubOp = one_rule (twoLits (intOp2 (-)))
75 primop_rule IntMulOp = one_rule (twoLits (intOp2 (*)))
76 primop_rule IntQuotOp = one_rule (twoLits (intOp2Z quot))
77 primop_rule IntRemOp = one_rule (twoLits (intOp2Z rem))
78 primop_rule IntNegOp = one_rule (oneLit negOp)
81 #if __GLASGOW_HASKELL__ >= 500
82 primop_rule WordAddOp = one_rule (twoLits (wordOp2 (+)))
83 primop_rule WordSubOp = one_rule (twoLits (wordOp2 (-)))
84 primop_rule WordMulOp = one_rule (twoLits (wordOp2 (*)))
86 primop_rule WordQuotOp = one_rule (twoLits (wordOp2Z quot))
87 primop_rule WordRemOp = one_rule (twoLits (wordOp2Z rem))
88 #if __GLASGOW_HASKELL__ >= 407
89 primop_rule AndOp = one_rule (twoLits (wordBitOp2 (.&.)))
90 primop_rule OrOp = one_rule (twoLits (wordBitOp2 (.|.)))
91 primop_rule XorOp = one_rule (twoLits (wordBitOp2 xor))
95 primop_rule Word2IntOp = one_rule (oneLit (litCoerce word2IntLit))
96 primop_rule Int2WordOp = one_rule (oneLit (litCoerce int2WordLit))
97 primop_rule Narrow8IntOp = one_rule (oneLit (litCoerce narrow8IntLit))
98 primop_rule Narrow16IntOp = one_rule (oneLit (litCoerce narrow16IntLit))
99 primop_rule Narrow32IntOp = one_rule (oneLit (litCoerce narrow32IntLit))
100 primop_rule Narrow8WordOp = one_rule (oneLit (litCoerce narrow8WordLit))
101 primop_rule Narrow16WordOp = one_rule (oneLit (litCoerce narrow16WordLit))
102 primop_rule Narrow32WordOp = one_rule (oneLit (litCoerce narrow32WordLit))
103 primop_rule OrdOp = one_rule (oneLit (litCoerce char2IntLit))
104 primop_rule ChrOp = one_rule (oneLit (litCoerce int2CharLit))
105 primop_rule Float2IntOp = one_rule (oneLit (litCoerce float2IntLit))
106 primop_rule Int2FloatOp = one_rule (oneLit (litCoerce int2FloatLit))
107 primop_rule Double2IntOp = one_rule (oneLit (litCoerce double2IntLit))
108 primop_rule Int2DoubleOp = one_rule (oneLit (litCoerce int2DoubleLit))
109 -- SUP: Not sure what the standard says about precision in the following 2 cases
110 primop_rule Float2DoubleOp = one_rule (oneLit (litCoerce float2DoubleLit))
111 primop_rule Double2FloatOp = one_rule (oneLit (litCoerce double2FloatLit))
114 primop_rule FloatAddOp = one_rule (twoLits (floatOp2 (+)))
115 primop_rule FloatSubOp = one_rule (twoLits (floatOp2 (-)))
116 primop_rule FloatMulOp = one_rule (twoLits (floatOp2 (*)))
117 primop_rule FloatDivOp = one_rule (twoLits (floatOp2Z (/)))
118 primop_rule FloatNegOp = one_rule (oneLit negOp)
121 primop_rule DoubleAddOp = one_rule (twoLits (doubleOp2 (+)))
122 primop_rule DoubleSubOp = one_rule (twoLits (doubleOp2 (-)))
123 primop_rule DoubleMulOp = one_rule (twoLits (doubleOp2 (*)))
124 primop_rule DoubleDivOp = one_rule (twoLits (doubleOp2Z (/)))
125 primop_rule DoubleNegOp = one_rule (oneLit negOp)
127 -- Relational operators
128 primop_rule IntEqOp = [BuiltinRule op_name (relop (==)), BuiltinRule op_name_case (litEq True)]
129 primop_rule IntNeOp = [BuiltinRule op_name (relop (/=)), BuiltinRule op_name_case (litEq False)]
130 primop_rule CharEqOp = [BuiltinRule op_name (relop (==)), BuiltinRule op_name_case (litEq True)]
131 primop_rule CharNeOp = [BuiltinRule op_name (relop (/=)), BuiltinRule op_name_case (litEq False)]
133 primop_rule IntGtOp = one_rule (relop (>))
134 primop_rule IntGeOp = one_rule (relop (>=))
135 primop_rule IntLeOp = one_rule (relop (<=))
136 primop_rule IntLtOp = one_rule (relop (<))
138 primop_rule CharGtOp = one_rule (relop (>))
139 primop_rule CharGeOp = one_rule (relop (>=))
140 primop_rule CharLeOp = one_rule (relop (<=))
141 primop_rule CharLtOp = one_rule (relop (<))
143 primop_rule FloatGtOp = one_rule (relop (>))
144 primop_rule FloatGeOp = one_rule (relop (>=))
145 primop_rule FloatLeOp = one_rule (relop (<=))
146 primop_rule FloatLtOp = one_rule (relop (<))
147 primop_rule FloatEqOp = one_rule (relop (==))
148 primop_rule FloatNeOp = one_rule (relop (/=))
150 primop_rule DoubleGtOp = one_rule (relop (>))
151 primop_rule DoubleGeOp = one_rule (relop (>=))
152 primop_rule DoubleLeOp = one_rule (relop (<=))
153 primop_rule DoubleLtOp = one_rule (relop (<))
154 primop_rule DoubleEqOp = one_rule (relop (==))
155 primop_rule DoubleNeOp = one_rule (relop (/=))
157 primop_rule WordGtOp = one_rule (relop (>))
158 primop_rule WordGeOp = one_rule (relop (>=))
159 primop_rule WordLeOp = one_rule (relop (<=))
160 primop_rule WordLtOp = one_rule (relop (<))
161 primop_rule WordEqOp = one_rule (relop (==))
162 primop_rule WordNeOp = one_rule (relop (/=))
164 primop_rule other = []
167 relop cmp = twoLits (cmpOp (\ord -> ord `cmp` EQ))
168 -- Cunning. cmpOp compares the values to give an Ordering.
169 -- It applies its argument to that ordering value to turn
170 -- the ordering into a boolean value. (`cmp` EQ) is just the job.
173 %************************************************************************
175 \subsection{Doing the business}
177 %************************************************************************
181 In all these operations we might find a LitLit as an operand; that's
182 why we have the catch-all Nothing case.
185 --------------------------
186 litCoerce :: (Literal -> Literal) -> Literal -> Maybe CoreExpr
187 litCoerce fn lit | isLitLitLit lit = Nothing
188 | otherwise = 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 f) = Just (mkFloatVal (-f))
211 negOp (MachDouble d) = Just (mkDoubleVal (-d))
212 negOp (MachInt i) = intResult (-i)
215 --------------------------
216 intOp2 op (MachInt i1) (MachInt i2) = intResult (i1 `op` i2)
217 intOp2 op l1 l2 = Nothing -- Could find LitLit
219 intOp2Z op (MachInt i1) (MachInt i2)
220 | i2 /= 0 = Just (mkIntVal (i1 `op` i2))
221 intOp2Z op l1 l2 = Nothing -- LitLit or zero dividend
223 --------------------------
224 #if __GLASGOW_HASKELL__ >= 500
225 wordOp2 op (MachWord w1) (MachWord w2)
226 = wordResult (w1 `op` w2)
227 wordOp2 op l1 l2 = Nothing -- Could find LitLit
230 wordOp2Z op (MachWord w1) (MachWord w2)
231 | w2 /= 0 = Just (mkWordVal (w1 `op` w2))
232 wordOp2Z op l1 l2 = Nothing -- LitLit or zero dividend
234 #if __GLASGOW_HASKELL__ >= 500
235 wordBitOp2 op l1@(MachWord w1) l2@(MachWord w2)
236 = Just (mkWordVal (w1 `op` w2))
238 -- Integer is not an instance of Bits, so we operate on Word64
239 wordBitOp2 op l1@(MachWord w1) l2@(MachWord w2)
240 = Just (mkWordVal ((fromIntegral::Word64->Integer) (fromIntegral w1 `op` fromIntegral w2)))
242 wordBitOp2 op l1 l2 = Nothing -- Could find LitLit
244 --------------------------
245 floatOp2 op (MachFloat f1) (MachFloat f2)
246 = Just (mkFloatVal (f1 `op` f2))
247 floatOp2 op l1 l2 = Nothing
249 floatOp2Z op (MachFloat f1) (MachFloat f2)
250 | f2 /= 0 = Just (mkFloatVal (f1 `op` f2))
251 floatOp2Z op l1 l2 = Nothing
253 --------------------------
254 doubleOp2 op (MachDouble f1) (MachDouble f2)
255 = Just (mkDoubleVal (f1 `op` f2))
256 doubleOp2 op l1 l2 = Nothing
258 doubleOp2Z op (MachDouble f1) (MachDouble f2)
259 | f2 /= 0 = Just (mkDoubleVal (f1 `op` f2))
260 doubleOp2Z op l1 l2 = Nothing
263 --------------------------
271 -- This is a Good Thing, because it allows case-of case things
272 -- to happen, and case-default absorption to happen. For
275 -- if (n ==# 3#) || (n ==# 4#) then e1 else e2
281 -- (modulo the usual precautions to avoid duplicating e1)
283 litEq :: Bool -- True <=> equality, False <=> inequality
285 litEq is_eq [Lit lit, expr] = do_lit_eq is_eq lit expr
286 litEq is_eq [expr, Lit lit] = do_lit_eq is_eq lit expr
287 litEq is_eq other = Nothing
289 do_lit_eq is_eq lit expr
290 = Just (Case expr (mkWildId (literalType lit))
291 [(DEFAULT, [], val_if_neq),
292 (LitAlt lit, [], val_if_eq)])
294 val_if_eq | is_eq = trueVal
295 | otherwise = falseVal
296 val_if_neq | is_eq = falseVal
297 | otherwise = trueVal
299 -- Note that we *don't* warn the user about overflow. It's not done at
300 -- runtime either, and compilation of completely harmless things like
301 -- ((124076834 :: Word32) + (2147483647 :: Word32))
302 -- would yield a warning. Instead we simply squash the value into the
303 -- Int range, but not in a way suitable for cross-compiling... :-(
304 intResult :: Integer -> Maybe CoreExpr
306 = Just (mkIntVal (toInteger (fromInteger result :: Int)))
308 #if __GLASGOW_HASKELL__ >= 500
309 wordResult :: Integer -> Maybe CoreExpr
311 = Just (mkWordVal (toInteger (fromInteger result :: Word)))
316 %************************************************************************
318 \subsection{Vaguely generic functions
320 %************************************************************************
323 type RuleFun = [CoreExpr] -> Maybe CoreExpr
325 twoLits :: (Literal -> Literal -> Maybe CoreExpr) -> RuleFun
326 twoLits rule [Lit l1, Lit l2] = rule (convFloating l1) (convFloating l2)
327 twoLits rule _ = Nothing
329 oneLit :: (Literal -> Maybe CoreExpr) -> RuleFun
330 oneLit rule [Lit l1] = rule (convFloating l1)
331 oneLit rule _ = Nothing
333 -- When excess precision is not requested, cut down the precision of the
334 -- Rational value to that of Float/Double. We confuse host architecture
335 -- and target architecture here, but it's convenient (and wrong :-).
336 convFloating :: Literal -> Literal
337 convFloating (MachFloat f) | not opt_SimplExcessPrecision =
338 MachFloat (toRational ((fromRational f) :: Float ))
339 convFloating (MachDouble d) | not opt_SimplExcessPrecision =
340 MachDouble (toRational ((fromRational d) :: Double))
344 trueVal = Var trueDataConId
345 falseVal = Var falseDataConId
346 mkIntVal i = Lit (mkMachInt i)
347 mkWordVal w = Lit (mkMachWord w)
348 mkFloatVal f = Lit (convFloating (MachFloat f))
349 mkDoubleVal d = Lit (convFloating (MachDouble d))
353 %************************************************************************
355 \subsection{Special rules for seq, tagToEnum, dataToTag}
357 %************************************************************************
359 In the parallel world, we use _seq_ to control the order in which
360 certain expressions will be evaluated. Operationally, the expression
361 ``_seq_ a b'' evaluates a and then evaluates b. We have an inlining
362 for _seq_ which translates _seq_ to:
364 _seq_ = /\ a b -> \ x::a y::b -> case seq# x of { 0# -> parError#; _ -> y }
366 Now, we know that the seq# primitive will never return 0#, but we
367 don't let the simplifier know that. We also use a special error
368 value, parError#, which is *not* a bottoming Id, so as far as the
369 simplifier is concerned, we have to evaluate seq# a before we know
370 whether or not y will be evaluated.
372 If we didn't have the extra case, then after inlining the compiler might
374 f p q = case seq# p of { _ -> p+q }
376 If it sees that, it can see that f is strict in q, and hence it might
377 evaluate q before p! The "0# ->" case prevents this happening.
378 By having the parError# branch we make sure that anything in the
379 other branch stays there!
381 This is fine, but we'd like to get rid of the extraneous code. Hence,
382 we *do* let the simplifier know that seq# is strict in its argument.
383 As a result, we hope that `a' will be evaluated before seq# is called.
384 At this point, we have a very special and magical simpification which
385 says that ``seq# a'' can be immediately simplified to `1#' if we
386 know that `a' is already evaluated.
388 NB: If we ever do case-floating, we have an extra worry:
391 a' -> let b' = case seq# a of { True -> b; False -> parError# }
397 a' -> let b' = case True of { True -> b; False -> parError# }
411 The second case must never be floated outside of the first!
414 seqRule [Type ty, arg] | exprIsValue arg = Just (mkIntVal 1)
415 seqRule other = Nothing
420 tagToEnumRule [Type ty, Lit (MachInt i)]
421 = ASSERT( isEnumerationTyCon tycon )
422 case filter correct_tag (tyConDataCons_maybe tycon `orElse` []) of
425 [] -> Nothing -- Abstract type
426 (dc:rest) -> ASSERT( null rest )
427 Just (Var (dataConId dc))
429 correct_tag dc = (dataConTag dc - fIRST_TAG) == tag
431 tycon = tyConAppTyCon ty
433 tagToEnumRule other = Nothing
436 For dataToTag#, we can reduce if either
438 (a) the argument is a constructor
439 (b) the argument is a variable whose unfolding is a known constructor
442 dataToTagRule [_, val_arg]
443 = case exprIsConApp_maybe val_arg of
444 Just (dc,_) -> ASSERT( not (isNewTyCon (dataConTyCon dc)) )
445 Just (mkIntVal (toInteger (dataConTag dc - fIRST_TAG)))
449 dataToTagRule other = Nothing
452 %************************************************************************
454 \subsection{Built in rules}
456 %************************************************************************
459 builtinRules :: [(Name, CoreRule)]
460 -- Rules for non-primops that can't be expressed using a RULE pragma
462 = [ (unpackCStringFoldrName, BuiltinRule SLIT("AppendLitString") match_append_lit),
463 (eqStringName, BuiltinRule SLIT("EqString") match_eq_string)
468 -- unpackFoldrCString# "foo" c (unpackFoldrCString# "baz" c n) = unpackFoldrCString# "foobaz" c n
470 match_append_lit [Type ty1,
473 Var unpk `App` Type ty2
474 `App` Lit (MachStr s2)
478 | unpk `hasKey` unpackCStringFoldrIdKey &&
480 = ASSERT( ty1 `eqType` ty2 )
481 Just (Var unpk `App` Type ty1
482 `App` Lit (MachStr (s1 _APPEND_ s2))
486 match_append_lit other = Nothing
489 -- eqString (unpackCString# (Lit s1)) (unpackCString# (Lit s2) = s1==s2
491 match_eq_string [Var unpk1 `App` Lit (MachStr s1),
492 Var unpk2 `App` Lit (MachStr s2)]
493 | unpk1 `hasKey` unpackCStringIdKey,
494 unpk2 `hasKey` unpackCStringIdKey
495 = Just (if s1 == s2 then trueVal else falseVal)
497 match_eq_string other = Nothing