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 PrimOp ( PrimOp(..), primOpOcc )
25 import TysWiredIn ( trueDataConId, falseDataConId )
26 import TyCon ( tyConDataCons, 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 ThinAir ( unpackCStringFoldrId )
33 import Maybes ( maybeToBool )
34 import Char ( ord, chr )
35 import Bits ( Bits(..) )
36 import PrelAddr ( wordToInt )
37 import Word ( Word64 )
40 #if __GLASGOW_HASKELL__ > 404
41 import PrelAddr ( intToWord )
43 import PrelAddr ( Word(..) )
44 import PrelGHC ( int2Word# )
45 intToWord :: Int -> Word
46 intToWord (I# i#) = W# (int2Word# i#)
53 primOpRule :: PrimOp -> CoreRule
55 = BuiltinRule (primop_rule op)
57 op_name = _PK_ (occNameUserString (primOpOcc op))
58 op_name_case = op_name _APPEND_ SLIT("case")
60 -- ToDo: something for integer-shift ops?
63 primop_rule SeqOp = seqRule
64 primop_rule TagToEnumOp = tagToEnumRule
65 primop_rule DataToTagOp = dataToTagRule
68 primop_rule IntAddOp = twoLits (intOp2 (+) op_name)
69 primop_rule IntSubOp = twoLits (intOp2 (-) op_name)
70 primop_rule IntMulOp = twoLits (intOp2 (*) op_name)
71 primop_rule IntQuotOp = twoLits (intOp2Z quot op_name)
72 primop_rule IntRemOp = twoLits (intOp2Z rem op_name)
73 primop_rule IntNegOp = oneLit (negOp op_name)
76 primop_rule WordQuotOp = twoLits (wordOp2Z quot op_name)
77 primop_rule WordRemOp = twoLits (wordOp2Z rem op_name)
78 #if __GLASGOW_HASKELL__ >= 407
79 primop_rule AndOp = twoLits (wordBitOp2 (.&.) op_name)
80 primop_rule OrOp = twoLits (wordBitOp2 (.|.) op_name)
81 primop_rule XorOp = twoLits (wordBitOp2 xor op_name)
85 primop_rule Word2IntOp = oneLit (litCoerce word2IntLit op_name)
86 primop_rule Int2WordOp = oneLit (litCoerce int2WordLit op_name)
87 primop_rule OrdOp = oneLit (litCoerce char2IntLit op_name)
88 primop_rule ChrOp = oneLit (litCoerce int2CharLit op_name)
89 primop_rule Float2IntOp = oneLit (litCoerce float2IntLit op_name)
90 primop_rule Int2FloatOp = oneLit (litCoerce int2FloatLit op_name)
91 primop_rule Double2IntOp = oneLit (litCoerce double2IntLit op_name)
92 primop_rule Int2DoubleOp = oneLit (litCoerce int2DoubleLit op_name)
93 primop_rule Addr2IntOp = oneLit (litCoerce addr2IntLit op_name)
94 primop_rule Int2AddrOp = oneLit (litCoerce int2AddrLit op_name)
95 -- SUP: Not sure what the standard says about precision in the following 2 cases
96 primop_rule Float2DoubleOp = oneLit (litCoerce float2DoubleLit op_name)
97 primop_rule Double2FloatOp = oneLit (litCoerce double2FloatLit op_name)
100 primop_rule FloatAddOp = twoLits (floatOp2 (+) op_name)
101 primop_rule FloatSubOp = twoLits (floatOp2 (-) op_name)
102 primop_rule FloatMulOp = twoLits (floatOp2 (*) op_name)
103 primop_rule FloatDivOp = twoLits (floatOp2Z (/) op_name)
104 primop_rule FloatNegOp = oneLit (negOp op_name)
107 primop_rule DoubleAddOp = twoLits (doubleOp2 (+) op_name)
108 primop_rule DoubleSubOp = twoLits (doubleOp2 (-) op_name)
109 primop_rule DoubleMulOp = twoLits (doubleOp2 (*) op_name)
110 primop_rule DoubleDivOp = twoLits (doubleOp2Z (/) op_name)
111 primop_rule DoubleNegOp = oneLit (negOp op_name)
113 -- Relational operators
114 primop_rule IntEqOp = relop (==) `or_rule` litEq True op_name_case
115 primop_rule IntNeOp = relop (/=) `or_rule` litEq False op_name_case
116 primop_rule CharEqOp = relop (==) `or_rule` litEq True op_name_case
117 primop_rule CharNeOp = relop (/=) `or_rule` litEq False op_name_case
119 primop_rule IntGtOp = relop (>)
120 primop_rule IntGeOp = relop (>=)
121 primop_rule IntLeOp = relop (<=)
122 primop_rule IntLtOp = relop (<)
124 primop_rule CharGtOp = relop (>)
125 primop_rule CharGeOp = relop (>=)
126 primop_rule CharLeOp = relop (<=)
127 primop_rule CharLtOp = relop (<)
129 primop_rule FloatGtOp = relop (>)
130 primop_rule FloatGeOp = relop (>=)
131 primop_rule FloatLeOp = relop (<=)
132 primop_rule FloatLtOp = relop (<)
133 primop_rule FloatEqOp = relop (==)
134 primop_rule FloatNeOp = relop (/=)
136 primop_rule DoubleGtOp = relop (>)
137 primop_rule DoubleGeOp = relop (>=)
138 primop_rule DoubleLeOp = relop (<=)
139 primop_rule DoubleLtOp = relop (<)
140 primop_rule DoubleEqOp = relop (==)
141 primop_rule DoubleNeOp = relop (/=)
143 primop_rule WordGtOp = relop (>)
144 primop_rule WordGeOp = relop (>=)
145 primop_rule WordLeOp = relop (<=)
146 primop_rule WordLtOp = relop (<)
147 primop_rule WordEqOp = relop (==)
148 primop_rule WordNeOp = relop (/=)
150 primop_rule other = \args -> Nothing
153 relop cmp = twoLits (cmpOp (\ord -> ord `cmp` EQ) op_name)
154 -- Cunning. cmpOp compares the values to give an Ordering.
155 -- It applies its argument to that ordering value to turn
156 -- the ordering into a boolean value. (`cmp` EQ) is just the job.
159 %************************************************************************
161 \subsection{Doing the business}
163 %************************************************************************
167 In all these operations we might find a LitLit as an operand; that's
168 why we have the catch-all Nothing case.
171 --------------------------
172 litCoerce :: (Literal -> Literal) -> RuleName -> Literal -> Maybe (RuleName, CoreExpr)
173 litCoerce fn name lit | isLitLitLit lit = Nothing
174 | otherwise = Just (name, Lit (fn lit))
176 --------------------------
177 cmpOp :: (Ordering -> Bool) -> FAST_STRING -> Literal -> Literal -> Maybe (RuleName, CoreExpr)
181 done res | cmp res = Just (name, trueVal)
182 | otherwise = Just (name, falseVal)
184 -- These compares are at different types
185 go (MachChar i1) (MachChar i2) = done (i1 `compare` i2)
186 go (MachInt i1) (MachInt i2) = done (i1 `compare` i2)
187 go (MachInt64 i1) (MachInt64 i2) = done (i1 `compare` i2)
188 go (MachWord i1) (MachWord i2) = done (i1 `compare` i2)
189 go (MachWord64 i1) (MachWord64 i2) = done (i1 `compare` i2)
190 go (MachFloat i1) (MachFloat i2) = done (i1 `compare` i2)
191 go (MachDouble i1) (MachDouble i2) = done (i1 `compare` i2)
194 --------------------------
196 negOp name (MachFloat f) = Just (name, mkFloatVal (-f))
197 negOp name (MachDouble d) = Just (name, mkDoubleVal (-d))
198 negOp name l@(MachInt i) = intResult name (ppr l) (-i)
199 negOp name l = Nothing
201 --------------------------
202 intOp2 op name l1@(MachInt i1) l2@(MachInt i2)
203 = intResult name (ppr l1 <+> ppr l2) (i1 `op` i2)
204 intOp2 op name l1 l2 = Nothing -- Could find LitLit
206 intOp2Z op name (MachInt i1) (MachInt i2)
207 | i2 /= 0 = Just (name, mkIntVal (i1 `op` i2))
208 intOp2Z op name l1 l2 = Nothing -- LitLit or zero dividend
210 --------------------------
211 -- Integer is not an instance of Bits, so we operate on Word64
212 wordBitOp2 op name l1@(MachWord w1) l2@(MachWord w2)
213 = wordResult name (ppr l1 <+> ppr l2)
214 ((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 | f1 /= 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 | f1 /= 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 -- TODO: Merge intResult/wordResult
278 intResult name pp_args result
279 | not (inIntRange result)
280 -- Better tell the user that we've overflowed...
281 -- ..not that it stops us from actually folding!
283 = pprTrace "Warning:" (text "Integer overflow in:" <+> ppr name <+> pp_args)
284 Just (name, mkIntVal (squashInt result))
287 = Just (name, mkIntVal result)
289 wordResult name pp_args result
290 | not (inWordRange result)
291 -- Better tell the user that we've overflowed...
292 -- ..not that it stops us from actually folding!
294 = pprTrace "Warning:" (text "Word overflow in:" <+> ppr name <+> pp_args)
295 Just (name, mkWordVal (squashInt result))
298 = Just (name, mkWordVal result)
300 squashInt :: Integer -> Integer -- Squash into Int range
301 squashInt i = toInteger ((fromInteger i)::Int)
305 %************************************************************************
307 \subsection{Vaguely generic functions
309 %************************************************************************
312 type RuleFun = [CoreExpr] -> Maybe (RuleName, CoreExpr)
314 or_rule :: RuleFun -> RuleFun -> RuleFun
315 or_rule r1 r2 args = case r1 args of
316 Just stuff -> Just stuff
319 twoLits :: (Literal -> Literal -> Maybe (RuleName, CoreExpr)) -> RuleFun
320 twoLits rule [Lit l1, Lit l2] = rule l1 l2
321 twoLits rule other = Nothing
323 oneLit :: (Literal -> Maybe (RuleName, CoreExpr)) -> RuleFun
324 oneLit rule [Lit l1] = rule l1
325 oneLit rule other = Nothing
328 trueVal = Var trueDataConId
329 falseVal = Var falseDataConId
330 mkIntVal i = Lit (mkMachInt i)
331 mkWordVal w = Lit (mkMachWord w)
332 mkCharVal c = Lit (MachChar c)
333 mkFloatVal f = Lit (MachFloat f)
334 mkDoubleVal d = Lit (MachDouble d)
338 %************************************************************************
340 \subsection{Special rules for seq, tagToEnum, dataToTag}
342 %************************************************************************
344 In the parallel world, we use _seq_ to control the order in which
345 certain expressions will be evaluated. Operationally, the expression
346 ``_seq_ a b'' evaluates a and then evaluates b. We have an inlining
347 for _seq_ which translates _seq_ to:
349 _seq_ = /\ a b -> \ x::a y::b -> case seq# x of { 0# -> parError#; _ -> y }
351 Now, we know that the seq# primitive will never return 0#, but we
352 don't let the simplifier know that. We also use a special error
353 value, parError#, which is *not* a bottoming Id, so as far as the
354 simplifier is concerned, we have to evaluate seq# a before we know
355 whether or not y will be evaluated.
357 If we didn't have the extra case, then after inlining the compiler might
359 f p q = case seq# p of { _ -> p+q }
361 If it sees that, it can see that f is strict in q, and hence it might
362 evaluate q before p! The "0# ->" case prevents this happening.
363 By having the parError# branch we make sure that anything in the
364 other branch stays there!
366 This is fine, but we'd like to get rid of the extraneous code. Hence,
367 we *do* let the simplifier know that seq# is strict in its argument.
368 As a result, we hope that `a' will be evaluated before seq# is called.
369 At this point, we have a very special and magical simpification which
370 says that ``seq# a'' can be immediately simplified to `1#' if we
371 know that `a' is already evaluated.
373 NB: If we ever do case-floating, we have an extra worry:
376 a' -> let b' = case seq# a of { True -> b; False -> parError# }
382 a' -> let b' = case True of { True -> b; False -> parError# }
396 The second case must never be floated outside of the first!
399 seqRule [Type ty, arg] | exprIsValue arg = Just (SLIT("Seq"), mkIntVal 1)
400 seqRule other = Nothing
405 tagToEnumRule [Type ty, Lit (MachInt i)]
406 = ASSERT( isEnumerationTyCon tycon )
407 Just (SLIT("TagToEnum"), Var (dataConId dc))
410 constrs = tyConDataCons tycon
411 (dc:_) = [ dc | dc <- constrs, tag == dataConTag dc - fIRST_TAG ]
412 (Just (tycon,_)) = splitTyConApp_maybe ty
414 tagToEnumRule other = Nothing
417 For dataToTag#, we can reduce if either
419 (a) the argument is a constructor
420 (b) the argument is a variable whose unfolding is a known constructor
423 dataToTagRule [_, val_arg]
424 = case exprIsConApp_maybe val_arg of
425 Just (dc,_) -> ASSERT( not (isNewTyCon (dataConTyCon dc)) )
426 Just (SLIT("DataToTag"),
427 mkIntVal (toInteger (dataConTag dc - fIRST_TAG)))
431 dataToTagRule other = Nothing
434 %************************************************************************
436 \subsection{Built in rules}
438 %************************************************************************
441 builtinRules :: [ProtoCoreRule]
442 -- Rules for non-primops that can't be expressed using a RULE pragma
444 = [ ProtoCoreRule False unpackCStringFoldrId
445 (BuiltinRule match_append_lit_str)
449 -- unpack "foo" c (unpack "baz" c n) = unpack "foobaz" c n
451 match_append_lit_str [Type ty1,
454 Var unpk `App` Type ty2
455 `App` Lit (MachStr s2)
459 | unpk == unpackCStringFoldrId &&
461 = ASSERT( ty1 == ty2 )
462 Just (SLIT("AppendLitString"),
463 Var unpk `App` Type ty1
464 `App` Lit (MachStr (s1 _APPEND_ s2))
468 match_append_lit_str other = Nothing