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, literalType
19 , word2IntLit, int2WordLit, char2IntLit, int2CharLit
20 , float2IntLit, int2FloatLit, double2IntLit, int2DoubleLit
21 , addr2IntLit, int2AddrLit, float2DoubleLit, double2FloatLit
23 import RdrName ( RdrName )
24 import PrimOp ( PrimOp(..), primOpOcc )
25 import TysWiredIn ( trueDataConId, falseDataConId )
26 import TyCon ( tyConDataConsIfAvailable, isEnumerationTyCon, isNewTyCon )
27 import DataCon ( DataCon, dataConTag, dataConRepArity, dataConTyCon, dataConId, fIRST_TAG )
28 import CoreUnfold ( maybeUnfoldingTemplate )
29 import CoreUtils ( exprIsValue, cheapEqExpr, exprIsConApp_maybe )
30 import Type ( splitTyConApp_maybe )
31 import OccName ( occNameUserString)
32 import PrelNames ( unpackCStringFoldr_RDR )
33 import Unique ( unpackCStringFoldrIdKey, hasKey )
34 import Maybes ( maybeToBool )
35 import Char ( ord, chr )
36 import Bits ( Bits(..) )
37 import PrelAddr ( wordToInt )
38 import Word ( Word64 )
41 #if __GLASGOW_HASKELL__ > 405
42 import PrelAddr ( intToWord )
44 import PrelAddr ( Word(..) )
45 import PrelGHC ( int2Word# )
46 intToWord :: Int -> Word
47 intToWord (I# i#) = W# (int2Word# i#)
54 primOpRule :: PrimOp -> CoreRule
56 = BuiltinRule (primop_rule op)
58 op_name = _PK_ (occNameUserString (primOpOcc op))
59 op_name_case = op_name _APPEND_ SLIT("->case")
61 -- ToDo: something for integer-shift ops?
64 primop_rule SeqOp = seqRule
65 primop_rule TagToEnumOp = tagToEnumRule
66 primop_rule DataToTagOp = dataToTagRule
69 primop_rule IntAddOp = twoLits (intOp2 (+) op_name)
70 primop_rule IntSubOp = twoLits (intOp2 (-) op_name)
71 primop_rule IntMulOp = twoLits (intOp2 (*) op_name)
72 primop_rule IntQuotOp = twoLits (intOp2Z quot op_name)
73 primop_rule IntRemOp = twoLits (intOp2Z rem op_name)
74 primop_rule IntNegOp = oneLit (negOp op_name)
77 primop_rule WordQuotOp = twoLits (wordOp2Z quot op_name)
78 primop_rule WordRemOp = twoLits (wordOp2Z rem op_name)
79 #if __GLASGOW_HASKELL__ >= 407
80 primop_rule AndOp = twoLits (wordBitOp2 (.&.) op_name)
81 primop_rule OrOp = twoLits (wordBitOp2 (.|.) op_name)
82 primop_rule XorOp = twoLits (wordBitOp2 xor op_name)
86 primop_rule Word2IntOp = oneLit (litCoerce word2IntLit op_name)
87 primop_rule Int2WordOp = oneLit (litCoerce int2WordLit op_name)
88 primop_rule OrdOp = oneLit (litCoerce char2IntLit op_name)
89 primop_rule ChrOp = oneLit (litCoerce int2CharLit op_name)
90 primop_rule Float2IntOp = oneLit (litCoerce float2IntLit op_name)
91 primop_rule Int2FloatOp = oneLit (litCoerce int2FloatLit op_name)
92 primop_rule Double2IntOp = oneLit (litCoerce double2IntLit op_name)
93 primop_rule Int2DoubleOp = oneLit (litCoerce int2DoubleLit op_name)
94 primop_rule Addr2IntOp = oneLit (litCoerce addr2IntLit op_name)
95 primop_rule Int2AddrOp = oneLit (litCoerce int2AddrLit op_name)
96 -- SUP: Not sure what the standard says about precision in the following 2 cases
97 primop_rule Float2DoubleOp = oneLit (litCoerce float2DoubleLit op_name)
98 primop_rule Double2FloatOp = oneLit (litCoerce double2FloatLit op_name)
101 primop_rule FloatAddOp = twoLits (floatOp2 (+) op_name)
102 primop_rule FloatSubOp = twoLits (floatOp2 (-) op_name)
103 primop_rule FloatMulOp = twoLits (floatOp2 (*) op_name)
104 primop_rule FloatDivOp = twoLits (floatOp2Z (/) op_name)
105 primop_rule FloatNegOp = oneLit (negOp op_name)
108 primop_rule DoubleAddOp = twoLits (doubleOp2 (+) op_name)
109 primop_rule DoubleSubOp = twoLits (doubleOp2 (-) op_name)
110 primop_rule DoubleMulOp = twoLits (doubleOp2 (*) op_name)
111 primop_rule DoubleDivOp = twoLits (doubleOp2Z (/) op_name)
112 primop_rule DoubleNegOp = oneLit (negOp op_name)
114 -- Relational operators
115 primop_rule IntEqOp = relop (==) `or_rule` litEq True op_name_case
116 primop_rule IntNeOp = relop (/=) `or_rule` litEq False op_name_case
117 primop_rule CharEqOp = relop (==) `or_rule` litEq True op_name_case
118 primop_rule CharNeOp = relop (/=) `or_rule` litEq False op_name_case
120 primop_rule IntGtOp = relop (>)
121 primop_rule IntGeOp = relop (>=)
122 primop_rule IntLeOp = relop (<=)
123 primop_rule IntLtOp = relop (<)
125 primop_rule CharGtOp = relop (>)
126 primop_rule CharGeOp = relop (>=)
127 primop_rule CharLeOp = relop (<=)
128 primop_rule CharLtOp = relop (<)
130 primop_rule FloatGtOp = relop (>)
131 primop_rule FloatGeOp = relop (>=)
132 primop_rule FloatLeOp = relop (<=)
133 primop_rule FloatLtOp = relop (<)
134 primop_rule FloatEqOp = relop (==)
135 primop_rule FloatNeOp = relop (/=)
137 primop_rule DoubleGtOp = relop (>)
138 primop_rule DoubleGeOp = relop (>=)
139 primop_rule DoubleLeOp = relop (<=)
140 primop_rule DoubleLtOp = relop (<)
141 primop_rule DoubleEqOp = relop (==)
142 primop_rule DoubleNeOp = relop (/=)
144 primop_rule WordGtOp = relop (>)
145 primop_rule WordGeOp = relop (>=)
146 primop_rule WordLeOp = relop (<=)
147 primop_rule WordLtOp = relop (<)
148 primop_rule WordEqOp = relop (==)
149 primop_rule WordNeOp = relop (/=)
151 primop_rule other = \args -> Nothing
154 relop cmp = twoLits (cmpOp (\ord -> ord `cmp` EQ) op_name)
155 -- Cunning. cmpOp compares the values to give an Ordering.
156 -- It applies its argument to that ordering value to turn
157 -- the ordering into a boolean value. (`cmp` EQ) is just the job.
160 %************************************************************************
162 \subsection{Doing the business}
164 %************************************************************************
168 In all these operations we might find a LitLit as an operand; that's
169 why we have the catch-all Nothing case.
172 --------------------------
173 litCoerce :: (Literal -> Literal) -> RuleName -> Literal -> Maybe (RuleName, CoreExpr)
174 litCoerce fn name lit | isLitLitLit lit = Nothing
175 | otherwise = Just (name, Lit (fn lit))
177 --------------------------
178 cmpOp :: (Ordering -> Bool) -> FAST_STRING -> Literal -> Literal -> Maybe (RuleName, CoreExpr)
182 done res | cmp res = Just (name, trueVal)
183 | otherwise = Just (name, falseVal)
185 -- These compares are at different types
186 go (MachChar i1) (MachChar i2) = done (i1 `compare` i2)
187 go (MachInt i1) (MachInt i2) = done (i1 `compare` i2)
188 go (MachInt64 i1) (MachInt64 i2) = done (i1 `compare` i2)
189 go (MachWord i1) (MachWord i2) = done (i1 `compare` i2)
190 go (MachWord64 i1) (MachWord64 i2) = done (i1 `compare` i2)
191 go (MachFloat i1) (MachFloat i2) = done (i1 `compare` i2)
192 go (MachDouble i1) (MachDouble i2) = done (i1 `compare` i2)
195 --------------------------
197 negOp name (MachFloat f) = Just (name, mkFloatVal (-f))
198 negOp name (MachDouble d) = Just (name, mkDoubleVal (-d))
199 negOp name l@(MachInt i) = intResult name (-i)
200 negOp name l = Nothing
202 --------------------------
203 intOp2 op name l1@(MachInt i1) l2@(MachInt i2)
204 = intResult name (i1 `op` i2)
205 intOp2 op name l1 l2 = Nothing -- Could find LitLit
207 intOp2Z op name (MachInt i1) (MachInt i2)
208 | i2 /= 0 = Just (name, mkIntVal (i1 `op` i2))
209 intOp2Z op name l1 l2 = Nothing -- LitLit or zero dividend
211 --------------------------
212 -- Integer is not an instance of Bits, so we operate on Word64
213 wordBitOp2 op name l1@(MachWord w1) l2@(MachWord w2)
214 = Just (name, mkWordVal ((fromIntegral::Word64->Integer) (fromIntegral w1 `op` fromIntegral w2)))
215 wordBitOp2 op name l1 l2 = Nothing -- Could find LitLit
217 wordOp2Z op name (MachWord w1) (MachWord w2)
218 | w2 /= 0 = Just (name, mkWordVal (w1 `op` w2))
219 wordOp2Z op name l1 l2 = Nothing -- LitLit or zero dividend
221 --------------------------
222 floatOp2 op name (MachFloat f1) (MachFloat f2)
223 = Just (name, mkFloatVal (f1 `op` f2))
224 floatOp2 op name l1 l2 = Nothing
226 floatOp2Z op name (MachFloat f1) (MachFloat f2)
227 | f2 /= 0 = Just (name, mkFloatVal (f1 `op` f2))
228 floatOp2Z op name l1 l2 = Nothing
230 --------------------------
231 doubleOp2 op name (MachDouble f1) (MachDouble f2)
232 = Just (name, mkDoubleVal (f1 `op` f2))
233 doubleOp2 op name l1 l2 = Nothing
235 doubleOp2Z op name (MachDouble f1) (MachDouble f2)
236 | f2 /= 0 = Just (name, mkDoubleVal (f1 `op` f2))
237 doubleOp2Z op name l1 l2 = Nothing
240 --------------------------
248 -- This is a Good Thing, because it allows case-of case things
249 -- to happen, and case-default absorption to happen. For
252 -- if (n ==# 3#) || (n ==# 4#) then e1 else e2
258 -- (modulo the usual precautions to avoid duplicating e1)
260 litEq :: Bool -- True <=> equality, False <=> inequality
263 litEq is_eq name [Lit lit, expr] = do_lit_eq is_eq name lit expr
264 litEq is_eq name [expr, Lit lit] = do_lit_eq is_eq name lit expr
265 litEq is_eq name other = Nothing
267 do_lit_eq is_eq name lit expr
268 = Just (name, Case expr (mkWildId (literalType lit))
269 [(LitAlt lit, [], val_if_eq),
270 (DEFAULT, [], val_if_neq)])
272 val_if_eq | is_eq = trueVal
273 | otherwise = falseVal
274 val_if_neq | is_eq = falseVal
275 | otherwise = trueVal
277 -- Note that we *don't* warn the user about overflow. It's not done at
278 -- runtime either, and compilation of completely harmless things like
279 -- ((124076834 :: Word32) + (2147483647 :: Word32))
280 -- would yield a warning. Instead we simply squash the value into the
281 -- Int range, but not in a way suitable for cross-compiling... :-(
282 intResult :: RuleName -> Integer -> Maybe (RuleName, CoreExpr)
283 intResult name result
284 = Just (name, mkIntVal (toInteger ((fromInteger result)::Int)))
288 %************************************************************************
290 \subsection{Vaguely generic functions
292 %************************************************************************
295 type RuleFun = [CoreExpr] -> Maybe (RuleName, CoreExpr)
297 or_rule :: RuleFun -> RuleFun -> RuleFun
298 or_rule r1 r2 args = case r1 args of
299 Just stuff -> Just stuff
302 twoLits :: (Literal -> Literal -> Maybe (RuleName, CoreExpr)) -> RuleFun
303 twoLits rule [Lit l1, Lit l2] = rule l1 l2
304 twoLits rule other = Nothing
306 oneLit :: (Literal -> Maybe (RuleName, CoreExpr)) -> RuleFun
307 oneLit rule [Lit l1] = rule l1
308 oneLit rule other = Nothing
311 trueVal = Var trueDataConId
312 falseVal = Var falseDataConId
313 mkIntVal i = Lit (mkMachInt i)
314 mkWordVal w = Lit (mkMachWord w)
315 mkCharVal c = Lit (MachChar c)
316 mkFloatVal f = Lit (MachFloat f)
317 mkDoubleVal d = Lit (MachDouble d)
321 %************************************************************************
323 \subsection{Special rules for seq, tagToEnum, dataToTag}
325 %************************************************************************
327 In the parallel world, we use _seq_ to control the order in which
328 certain expressions will be evaluated. Operationally, the expression
329 ``_seq_ a b'' evaluates a and then evaluates b. We have an inlining
330 for _seq_ which translates _seq_ to:
332 _seq_ = /\ a b -> \ x::a y::b -> case seq# x of { 0# -> parError#; _ -> y }
334 Now, we know that the seq# primitive will never return 0#, but we
335 don't let the simplifier know that. We also use a special error
336 value, parError#, which is *not* a bottoming Id, so as far as the
337 simplifier is concerned, we have to evaluate seq# a before we know
338 whether or not y will be evaluated.
340 If we didn't have the extra case, then after inlining the compiler might
342 f p q = case seq# p of { _ -> p+q }
344 If it sees that, it can see that f is strict in q, and hence it might
345 evaluate q before p! The "0# ->" case prevents this happening.
346 By having the parError# branch we make sure that anything in the
347 other branch stays there!
349 This is fine, but we'd like to get rid of the extraneous code. Hence,
350 we *do* let the simplifier know that seq# is strict in its argument.
351 As a result, we hope that `a' will be evaluated before seq# is called.
352 At this point, we have a very special and magical simpification which
353 says that ``seq# a'' can be immediately simplified to `1#' if we
354 know that `a' is already evaluated.
356 NB: If we ever do case-floating, we have an extra worry:
359 a' -> let b' = case seq# a of { True -> b; False -> parError# }
365 a' -> let b' = case True of { True -> b; False -> parError# }
379 The second case must never be floated outside of the first!
382 seqRule [Type ty, arg] | exprIsValue arg = Just (SLIT("Seq"), mkIntVal 1)
383 seqRule other = Nothing
388 tagToEnumRule [Type ty, Lit (MachInt i)]
389 = ASSERT( isEnumerationTyCon tycon )
390 case filter correct_tag (tyConDataConsIfAvailable tycon) of
393 [] -> Nothing -- Abstract type
394 (dc:rest) -> ASSERT( null rest )
395 Just (SLIT("TagToEnum"), Var (dataConId dc))
397 correct_tag dc = (dataConTag dc - fIRST_TAG) == tag
399 (Just (tycon,_)) = splitTyConApp_maybe ty
401 tagToEnumRule other = Nothing
404 For dataToTag#, we can reduce if either
406 (a) the argument is a constructor
407 (b) the argument is a variable whose unfolding is a known constructor
410 dataToTagRule [_, val_arg]
411 = case exprIsConApp_maybe val_arg of
412 Just (dc,_) -> ASSERT( not (isNewTyCon (dataConTyCon dc)) )
413 Just (SLIT("DataToTag"),
414 mkIntVal (toInteger (dataConTag dc - fIRST_TAG)))
418 dataToTagRule other = Nothing
421 %************************************************************************
423 \subsection{Built in rules}
425 %************************************************************************
428 builtinRules :: [(RdrName, CoreRule)]
429 -- Rules for non-primops that can't be expressed using a RULE pragma
431 = [ (unpackCStringFoldr_RDR, BuiltinRule match_append_lit_str)
435 -- unpackFoldrCString# "foo" c (unpackFoldrCString# "baz" c n) = unpackFoldrCString# "foobaz" c n
437 match_append_lit_str [Type ty1,
440 Var unpk `App` Type ty2
441 `App` Lit (MachStr s2)
445 | unpk `hasKey` unpackCStringFoldrIdKey &&
447 = ASSERT( ty1 == ty2 )
448 Just (SLIT("AppendLitString"),
449 Var unpk `App` Type ty1
450 `App` Lit (MachStr (s1 _APPEND_ s2))
454 match_append_lit_str other = Nothing