2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[ConFold]{Constant Folder}
7 check boundaries before folding, e.g. we can fold the Float addition
8 (i1 + i2) only if it results in a valid Float.
11 module PrelRules ( primOpRule, builtinRules ) where
13 #include "HsVersions.h"
16 import Rules ( ProtoCoreRule(..) )
17 import Id ( idUnfolding, mkWildId, isDataConId_maybe )
18 import Literal ( Literal(..), isLitLitLit, mkMachInt, mkMachWord
19 , inIntRange, inWordRange, literalType
20 , word2IntLit, int2WordLit, char2IntLit, int2CharLit
21 , float2IntLit, int2FloatLit, double2IntLit, int2DoubleLit
22 , addr2IntLit, int2AddrLit, float2DoubleLit, double2FloatLit
24 import RdrName ( RdrName )
25 import PrimOp ( PrimOp(..), primOpOcc )
26 import TysWiredIn ( trueDataConId, falseDataConId )
27 import TyCon ( tyConDataConsIfAvailable, isEnumerationTyCon, isNewTyCon )
28 import DataCon ( DataCon, dataConTag, dataConRepArity, dataConTyCon, dataConId, fIRST_TAG )
29 import CoreUnfold ( maybeUnfoldingTemplate )
30 import CoreUtils ( exprIsValue, cheapEqExpr, exprIsConApp_maybe )
31 import Type ( splitTyConApp_maybe )
32 import OccName ( occNameUserString)
33 import PrelNames ( unpackCStringFoldr_RDR )
34 import Unique ( unpackCStringFoldrIdKey, hasKey )
35 import Maybes ( maybeToBool )
36 import Char ( ord, chr )
37 import Bits ( Bits(..) )
38 import PrelAddr ( wordToInt )
39 import Word ( Word64 )
42 #if __GLASGOW_HASKELL__ > 405
43 import PrelAddr ( intToWord )
45 import PrelAddr ( Word(..) )
46 import PrelGHC ( int2Word# )
47 intToWord :: Int -> Word
48 intToWord (I# i#) = W# (int2Word# i#)
55 primOpRule :: PrimOp -> CoreRule
57 = BuiltinRule (primop_rule op)
59 op_name = _PK_ (occNameUserString (primOpOcc op))
60 op_name_case = op_name _APPEND_ SLIT("->case")
62 -- ToDo: something for integer-shift ops?
65 primop_rule SeqOp = seqRule
66 primop_rule TagToEnumOp = tagToEnumRule
67 primop_rule DataToTagOp = dataToTagRule
70 primop_rule IntAddOp = twoLits (intOp2 (+) op_name)
71 primop_rule IntSubOp = twoLits (intOp2 (-) op_name)
72 primop_rule IntMulOp = twoLits (intOp2 (*) op_name)
73 primop_rule IntQuotOp = twoLits (intOp2Z quot op_name)
74 primop_rule IntRemOp = twoLits (intOp2Z rem op_name)
75 primop_rule IntNegOp = oneLit (negOp op_name)
78 primop_rule WordQuotOp = twoLits (wordOp2Z quot op_name)
79 primop_rule WordRemOp = twoLits (wordOp2Z rem op_name)
80 #if __GLASGOW_HASKELL__ >= 407
81 primop_rule AndOp = twoLits (wordBitOp2 (.&.) op_name)
82 primop_rule OrOp = twoLits (wordBitOp2 (.|.) op_name)
83 primop_rule XorOp = twoLits (wordBitOp2 xor op_name)
87 primop_rule Word2IntOp = oneLit (litCoerce word2IntLit op_name)
88 primop_rule Int2WordOp = oneLit (litCoerce int2WordLit op_name)
89 primop_rule OrdOp = oneLit (litCoerce char2IntLit op_name)
90 primop_rule ChrOp = oneLit (litCoerce int2CharLit op_name)
91 primop_rule Float2IntOp = oneLit (litCoerce float2IntLit op_name)
92 primop_rule Int2FloatOp = oneLit (litCoerce int2FloatLit op_name)
93 primop_rule Double2IntOp = oneLit (litCoerce double2IntLit op_name)
94 primop_rule Int2DoubleOp = oneLit (litCoerce int2DoubleLit op_name)
95 primop_rule Addr2IntOp = oneLit (litCoerce addr2IntLit op_name)
96 primop_rule Int2AddrOp = oneLit (litCoerce int2AddrLit op_name)
97 -- SUP: Not sure what the standard says about precision in the following 2 cases
98 primop_rule Float2DoubleOp = oneLit (litCoerce float2DoubleLit op_name)
99 primop_rule Double2FloatOp = oneLit (litCoerce double2FloatLit op_name)
102 primop_rule FloatAddOp = twoLits (floatOp2 (+) op_name)
103 primop_rule FloatSubOp = twoLits (floatOp2 (-) op_name)
104 primop_rule FloatMulOp = twoLits (floatOp2 (*) op_name)
105 primop_rule FloatDivOp = twoLits (floatOp2Z (/) op_name)
106 primop_rule FloatNegOp = oneLit (negOp op_name)
109 primop_rule DoubleAddOp = twoLits (doubleOp2 (+) op_name)
110 primop_rule DoubleSubOp = twoLits (doubleOp2 (-) op_name)
111 primop_rule DoubleMulOp = twoLits (doubleOp2 (*) op_name)
112 primop_rule DoubleDivOp = twoLits (doubleOp2Z (/) op_name)
113 primop_rule DoubleNegOp = oneLit (negOp op_name)
115 -- Relational operators
116 primop_rule IntEqOp = relop (==) `or_rule` litEq True op_name_case
117 primop_rule IntNeOp = relop (/=) `or_rule` litEq False op_name_case
118 primop_rule CharEqOp = relop (==) `or_rule` litEq True op_name_case
119 primop_rule CharNeOp = relop (/=) `or_rule` litEq False op_name_case
121 primop_rule IntGtOp = relop (>)
122 primop_rule IntGeOp = relop (>=)
123 primop_rule IntLeOp = relop (<=)
124 primop_rule IntLtOp = relop (<)
126 primop_rule CharGtOp = relop (>)
127 primop_rule CharGeOp = relop (>=)
128 primop_rule CharLeOp = relop (<=)
129 primop_rule CharLtOp = relop (<)
131 primop_rule FloatGtOp = relop (>)
132 primop_rule FloatGeOp = relop (>=)
133 primop_rule FloatLeOp = relop (<=)
134 primop_rule FloatLtOp = relop (<)
135 primop_rule FloatEqOp = relop (==)
136 primop_rule FloatNeOp = relop (/=)
138 primop_rule DoubleGtOp = relop (>)
139 primop_rule DoubleGeOp = relop (>=)
140 primop_rule DoubleLeOp = relop (<=)
141 primop_rule DoubleLtOp = relop (<)
142 primop_rule DoubleEqOp = relop (==)
143 primop_rule DoubleNeOp = relop (/=)
145 primop_rule WordGtOp = relop (>)
146 primop_rule WordGeOp = relop (>=)
147 primop_rule WordLeOp = relop (<=)
148 primop_rule WordLtOp = relop (<)
149 primop_rule WordEqOp = relop (==)
150 primop_rule WordNeOp = relop (/=)
152 primop_rule other = \args -> Nothing
155 relop cmp = twoLits (cmpOp (\ord -> ord `cmp` EQ) op_name)
156 -- Cunning. cmpOp compares the values to give an Ordering.
157 -- It applies its argument to that ordering value to turn
158 -- the ordering into a boolean value. (`cmp` EQ) is just the job.
161 %************************************************************************
163 \subsection{Doing the business}
165 %************************************************************************
169 In all these operations we might find a LitLit as an operand; that's
170 why we have the catch-all Nothing case.
173 --------------------------
174 litCoerce :: (Literal -> Literal) -> RuleName -> Literal -> Maybe (RuleName, CoreExpr)
175 litCoerce fn name lit | isLitLitLit lit = Nothing
176 | otherwise = Just (name, Lit (fn lit))
178 --------------------------
179 cmpOp :: (Ordering -> Bool) -> FAST_STRING -> Literal -> Literal -> Maybe (RuleName, CoreExpr)
183 done res | cmp res = Just (name, trueVal)
184 | otherwise = Just (name, falseVal)
186 -- These compares are at different types
187 go (MachChar i1) (MachChar i2) = done (i1 `compare` i2)
188 go (MachInt i1) (MachInt i2) = done (i1 `compare` i2)
189 go (MachInt64 i1) (MachInt64 i2) = done (i1 `compare` i2)
190 go (MachWord i1) (MachWord i2) = done (i1 `compare` i2)
191 go (MachWord64 i1) (MachWord64 i2) = done (i1 `compare` i2)
192 go (MachFloat i1) (MachFloat i2) = done (i1 `compare` i2)
193 go (MachDouble i1) (MachDouble i2) = done (i1 `compare` i2)
196 --------------------------
198 negOp name (MachFloat f) = Just (name, mkFloatVal (-f))
199 negOp name (MachDouble d) = Just (name, mkDoubleVal (-d))
200 negOp name l@(MachInt i) = intResult name (ppr l) (-i)
201 negOp name l = Nothing
203 --------------------------
204 intOp2 op name l1@(MachInt i1) l2@(MachInt i2)
205 = intResult name (ppr l1 <+> ppr l2) (i1 `op` i2)
206 intOp2 op name l1 l2 = Nothing -- Could find LitLit
208 intOp2Z op name (MachInt i1) (MachInt i2)
209 | i2 /= 0 = Just (name, mkIntVal (i1 `op` i2))
210 intOp2Z op name l1 l2 = Nothing -- LitLit or zero dividend
212 --------------------------
213 -- Integer is not an instance of Bits, so we operate on Word64
214 wordBitOp2 op name l1@(MachWord w1) l2@(MachWord w2)
215 = wordResult name (ppr l1 <+> ppr l2)
216 ((fromIntegral::Word64->Integer) (fromIntegral w1 `op` fromIntegral w2))
217 wordBitOp2 op name l1 l2 = Nothing -- Could find LitLit
219 wordOp2Z op name (MachWord w1) (MachWord w2)
220 | w2 /= 0 = Just (name, mkWordVal (w1 `op` w2))
221 wordOp2Z op name l1 l2 = Nothing -- LitLit or zero dividend
223 --------------------------
224 floatOp2 op name (MachFloat f1) (MachFloat f2)
225 = Just (name, mkFloatVal (f1 `op` f2))
226 floatOp2 op name l1 l2 = Nothing
228 floatOp2Z op name (MachFloat f1) (MachFloat f2)
229 | f1 /= 0 = Just (name, mkFloatVal (f1 `op` f2))
230 floatOp2Z op name l1 l2 = Nothing
232 --------------------------
233 doubleOp2 op name (MachDouble f1) (MachDouble f2)
234 = Just (name, mkDoubleVal (f1 `op` f2))
235 doubleOp2 op name l1 l2 = Nothing
237 doubleOp2Z op name (MachDouble f1) (MachDouble f2)
238 | f1 /= 0 = Just (name, mkDoubleVal (f1 `op` f2))
239 doubleOp2Z op name l1 l2 = Nothing
242 --------------------------
250 -- This is a Good Thing, because it allows case-of case things
251 -- to happen, and case-default absorption to happen. For
254 -- if (n ==# 3#) || (n ==# 4#) then e1 else e2
260 -- (modulo the usual precautions to avoid duplicating e1)
262 litEq :: Bool -- True <=> equality, False <=> inequality
265 litEq is_eq name [Lit lit, expr] = do_lit_eq is_eq name lit expr
266 litEq is_eq name [expr, Lit lit] = do_lit_eq is_eq name lit expr
267 litEq is_eq name other = Nothing
269 do_lit_eq is_eq name lit expr
270 = Just (name, Case expr (mkWildId (literalType lit))
271 [(LitAlt lit, [], val_if_eq),
272 (DEFAULT, [], val_if_neq)])
274 val_if_eq | is_eq = trueVal
275 | otherwise = falseVal
276 val_if_neq | is_eq = falseVal
277 | otherwise = trueVal
279 -- TODO: Merge intResult/wordResult
280 intResult name pp_args result
281 | not (inIntRange result)
282 -- Better tell the user that we've overflowed...
283 -- ..not that it stops us from actually folding!
285 = pprTrace "Warning:" (text "Integer overflow in:" <+> ppr name <+> pp_args)
286 Just (name, mkIntVal (squashInt result))
289 = Just (name, mkIntVal result)
291 wordResult name pp_args result
292 | not (inWordRange result)
293 -- Better tell the user that we've overflowed...
294 -- ..not that it stops us from actually folding!
296 = pprTrace "Warning:" (text "Word overflow in:" <+> ppr name <+> pp_args)
297 Just (name, mkWordVal (squashInt result))
300 = Just (name, mkWordVal result)
302 squashInt :: Integer -> Integer -- Squash into Int range
303 squashInt i = toInteger ((fromInteger i)::Int)
307 %************************************************************************
309 \subsection{Vaguely generic functions
311 %************************************************************************
314 type RuleFun = [CoreExpr] -> Maybe (RuleName, CoreExpr)
316 or_rule :: RuleFun -> RuleFun -> RuleFun
317 or_rule r1 r2 args = case r1 args of
318 Just stuff -> Just stuff
321 twoLits :: (Literal -> Literal -> Maybe (RuleName, CoreExpr)) -> RuleFun
322 twoLits rule [Lit l1, Lit l2] = rule l1 l2
323 twoLits rule other = Nothing
325 oneLit :: (Literal -> Maybe (RuleName, CoreExpr)) -> RuleFun
326 oneLit rule [Lit l1] = rule l1
327 oneLit rule other = Nothing
330 trueVal = Var trueDataConId
331 falseVal = Var falseDataConId
332 mkIntVal i = Lit (mkMachInt i)
333 mkWordVal w = Lit (mkMachWord w)
334 mkCharVal c = Lit (MachChar c)
335 mkFloatVal f = Lit (MachFloat f)
336 mkDoubleVal d = Lit (MachDouble d)
340 %************************************************************************
342 \subsection{Special rules for seq, tagToEnum, dataToTag}
344 %************************************************************************
346 In the parallel world, we use _seq_ to control the order in which
347 certain expressions will be evaluated. Operationally, the expression
348 ``_seq_ a b'' evaluates a and then evaluates b. We have an inlining
349 for _seq_ which translates _seq_ to:
351 _seq_ = /\ a b -> \ x::a y::b -> case seq# x of { 0# -> parError#; _ -> y }
353 Now, we know that the seq# primitive will never return 0#, but we
354 don't let the simplifier know that. We also use a special error
355 value, parError#, which is *not* a bottoming Id, so as far as the
356 simplifier is concerned, we have to evaluate seq# a before we know
357 whether or not y will be evaluated.
359 If we didn't have the extra case, then after inlining the compiler might
361 f p q = case seq# p of { _ -> p+q }
363 If it sees that, it can see that f is strict in q, and hence it might
364 evaluate q before p! The "0# ->" case prevents this happening.
365 By having the parError# branch we make sure that anything in the
366 other branch stays there!
368 This is fine, but we'd like to get rid of the extraneous code. Hence,
369 we *do* let the simplifier know that seq# is strict in its argument.
370 As a result, we hope that `a' will be evaluated before seq# is called.
371 At this point, we have a very special and magical simpification which
372 says that ``seq# a'' can be immediately simplified to `1#' if we
373 know that `a' is already evaluated.
375 NB: If we ever do case-floating, we have an extra worry:
378 a' -> let b' = case seq# a of { True -> b; False -> parError# }
384 a' -> let b' = case True of { True -> b; False -> parError# }
398 The second case must never be floated outside of the first!
401 seqRule [Type ty, arg] | exprIsValue arg = Just (SLIT("Seq"), mkIntVal 1)
402 seqRule other = Nothing
407 tagToEnumRule [Type ty, Lit (MachInt i)]
408 = ASSERT( isEnumerationTyCon tycon )
409 case filter correct_tag (tyConDataConsIfAvailable tycon) of
412 [] -> Nothing -- Abstract type
413 (dc:rest) -> ASSERT( null rest )
414 Just (SLIT("TagToEnum"), Var (dataConId dc))
416 correct_tag dc = (dataConTag dc - fIRST_TAG) == tag
418 (Just (tycon,_)) = splitTyConApp_maybe ty
420 tagToEnumRule other = Nothing
423 For dataToTag#, we can reduce if either
425 (a) the argument is a constructor
426 (b) the argument is a variable whose unfolding is a known constructor
429 dataToTagRule [_, val_arg]
430 = case exprIsConApp_maybe val_arg of
431 Just (dc,_) -> ASSERT( not (isNewTyCon (dataConTyCon dc)) )
432 Just (SLIT("DataToTag"),
433 mkIntVal (toInteger (dataConTag dc - fIRST_TAG)))
437 dataToTagRule other = Nothing
440 %************************************************************************
442 \subsection{Built in rules}
444 %************************************************************************
447 builtinRules :: [(RdrName, CoreRule)]
448 -- Rules for non-primops that can't be expressed using a RULE pragma
450 = [ (unpackCStringFoldr_RDR, BuiltinRule match_append_lit_str)
454 -- unpackFoldrCString# "foo" c (unpackFoldrCString# "baz" c n) = unpackFoldrCString# "foobaz" c n
456 match_append_lit_str [Type ty1,
459 Var unpk `App` Type ty2
460 `App` Lit (MachStr s2)
464 | unpk `hasKey` unpackCStringFoldrIdKey &&
466 = ASSERT( ty1 == ty2 )
467 Just (SLIT("AppendLitString"),
468 Var unpk `App` Type ty1
469 `App` Lit (MachStr (s1 _APPEND_ s2))
473 match_append_lit_str other = Nothing