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.
15 module PrelRules ( primOpRule, builtinRules ) where
17 #include "HsVersions.h"
20 import Id ( mkWildId )
21 import Literal ( Literal(..), isLitLitLit, mkMachInt, mkMachWord
23 , word2IntLit, int2WordLit, char2IntLit, int2CharLit
24 , float2IntLit, int2FloatLit, double2IntLit, int2DoubleLit
25 , addr2IntLit, int2AddrLit, float2DoubleLit, double2FloatLit
27 import PrimOp ( PrimOp(..), primOpOcc )
28 import TysWiredIn ( trueDataConId, falseDataConId )
29 import TyCon ( tyConDataConsIfAvailable, isEnumerationTyCon, isNewTyCon )
30 import DataCon ( dataConTag, dataConTyCon, dataConId, fIRST_TAG )
31 import CoreUtils ( exprIsValue, cheapEqExpr, exprIsConApp_maybe )
32 import Type ( tyConAppTyCon )
33 import OccName ( occNameUserString)
34 import PrelNames ( unpackCStringFoldrName, unpackCStringFoldrIdKey, hasKey )
36 import Bits ( Bits(..) )
37 #if __GLASGOW_HASKELL__ >= 500
40 import Word ( Word64 )
43 import CmdLineOpts ( opt_SimplExcessPrecision )
48 primOpRule :: PrimOp -> CoreRule
50 = BuiltinRule (primop_rule op)
52 op_name = _PK_ (occNameUserString (primOpOcc op))
53 op_name_case = op_name _APPEND_ SLIT("->case")
55 -- ToDo: something for integer-shift ops?
58 primop_rule SeqOp = seqRule
59 primop_rule TagToEnumOp = tagToEnumRule
60 primop_rule DataToTagOp = dataToTagRule
63 primop_rule IntAddOp = twoLits (intOp2 (+) op_name)
64 primop_rule IntSubOp = twoLits (intOp2 (-) op_name)
65 primop_rule IntMulOp = twoLits (intOp2 (*) op_name)
66 primop_rule IntQuotOp = twoLits (intOp2Z quot op_name)
67 primop_rule IntRemOp = twoLits (intOp2Z rem op_name)
68 primop_rule IntNegOp = oneLit (negOp op_name)
71 #if __GLASGOW_HASKELL__ >= 500
72 primop_rule WordAddOp = twoLits (wordOp2 (+) op_name)
73 primop_rule WordSubOp = twoLits (wordOp2 (-) op_name)
74 primop_rule WordMulOp = twoLits (wordOp2 (*) 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 (MachInt i) = intResult name (-i)
199 negOp name l = Nothing
201 --------------------------
202 intOp2 op name (MachInt i1) (MachInt i2)
203 = intResult name (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 #if __GLASGOW_HASKELL__ >= 500
212 wordOp2 op name (MachWord w1) (MachWord w2)
213 = wordResult name (w1 `op` w2)
214 wordOp2 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 #if __GLASGOW_HASKELL__ >= 500
222 wordBitOp2 op name l1@(MachWord w1) l2@(MachWord w2)
223 = Just (name, mkWordVal (w1 `op` w2))
225 -- Integer is not an instance of Bits, so we operate on Word64
226 wordBitOp2 op name l1@(MachWord w1) l2@(MachWord w2)
227 = Just (name, mkWordVal ((fromIntegral::Word64->Integer) (fromIntegral w1 `op` fromIntegral w2)))
229 wordBitOp2 op name l1 l2 = Nothing -- Could find LitLit
231 --------------------------
232 floatOp2 op name (MachFloat f1) (MachFloat f2)
233 = Just (name, mkFloatVal (f1 `op` f2))
234 floatOp2 op name l1 l2 = Nothing
236 floatOp2Z op name (MachFloat f1) (MachFloat f2)
237 | f2 /= 0 = Just (name, mkFloatVal (f1 `op` f2))
238 floatOp2Z op name l1 l2 = Nothing
240 --------------------------
241 doubleOp2 op name (MachDouble f1) (MachDouble f2)
242 = Just (name, mkDoubleVal (f1 `op` f2))
243 doubleOp2 op name l1 l2 = Nothing
245 doubleOp2Z op name (MachDouble f1) (MachDouble f2)
246 | f2 /= 0 = Just (name, mkDoubleVal (f1 `op` f2))
247 doubleOp2Z op name l1 l2 = Nothing
250 --------------------------
258 -- This is a Good Thing, because it allows case-of case things
259 -- to happen, and case-default absorption to happen. For
262 -- if (n ==# 3#) || (n ==# 4#) then e1 else e2
268 -- (modulo the usual precautions to avoid duplicating e1)
270 litEq :: Bool -- True <=> equality, False <=> inequality
273 litEq is_eq name [Lit lit, expr] = do_lit_eq is_eq name lit expr
274 litEq is_eq name [expr, Lit lit] = do_lit_eq is_eq name lit expr
275 litEq is_eq name other = Nothing
277 do_lit_eq is_eq name lit expr
278 = Just (name, Case expr (mkWildId (literalType lit))
279 [(LitAlt lit, [], val_if_eq),
280 (DEFAULT, [], val_if_neq)])
282 val_if_eq | is_eq = trueVal
283 | otherwise = falseVal
284 val_if_neq | is_eq = falseVal
285 | otherwise = trueVal
287 -- Note that we *don't* warn the user about overflow. It's not done at
288 -- runtime either, and compilation of completely harmless things like
289 -- ((124076834 :: Word32) + (2147483647 :: Word32))
290 -- would yield a warning. Instead we simply squash the value into the
291 -- Int range, but not in a way suitable for cross-compiling... :-(
292 intResult :: RuleName -> Integer -> Maybe (RuleName, CoreExpr)
293 intResult name result
294 = Just (name, mkIntVal (toInteger (fromInteger result :: Int)))
296 #if __GLASGOW_HASKELL__ >= 500
297 wordResult :: RuleName -> Integer -> Maybe (RuleName, CoreExpr)
298 wordResult name result
299 = Just (name, mkWordVal (toInteger (fromInteger result :: Word)))
304 %************************************************************************
306 \subsection{Vaguely generic functions
308 %************************************************************************
311 type RuleFun = [CoreExpr] -> Maybe (RuleName, CoreExpr)
313 or_rule :: RuleFun -> RuleFun -> RuleFun
314 or_rule r1 r2 args = maybe (r2 args) Just (r1 args) -- i.e.: r1 args `mplus` r2 args
316 twoLits :: (Literal -> Literal -> Maybe (RuleName, CoreExpr)) -> RuleFun
317 twoLits rule [Lit l1, Lit l2] = rule (convFloating l1) (convFloating l2)
318 twoLits rule other = Nothing
320 oneLit :: (Literal -> Maybe (RuleName, CoreExpr)) -> RuleFun
321 oneLit rule [Lit l1] = rule (convFloating l1)
322 oneLit rule other = Nothing
324 -- When excess precision is not requested, cut down the precision of the
325 -- Rational value to that of Float/Double. We confuse host architecture
326 -- and target architecture here, but it's convenient (and wrong :-).
327 convFloating :: Literal -> Literal
328 convFloating (MachFloat f) | not opt_SimplExcessPrecision =
329 MachFloat (toRational ((fromRational f) :: Float ))
330 convFloating (MachDouble d) | not opt_SimplExcessPrecision =
331 MachDouble (toRational ((fromRational d) :: Double))
335 trueVal = Var trueDataConId
336 falseVal = Var falseDataConId
337 mkIntVal i = Lit (mkMachInt i)
338 mkWordVal w = Lit (mkMachWord w)
339 mkFloatVal f = Lit (convFloating (MachFloat f))
340 mkDoubleVal d = Lit (convFloating (MachDouble d))
344 %************************************************************************
346 \subsection{Special rules for seq, tagToEnum, dataToTag}
348 %************************************************************************
350 In the parallel world, we use _seq_ to control the order in which
351 certain expressions will be evaluated. Operationally, the expression
352 ``_seq_ a b'' evaluates a and then evaluates b. We have an inlining
353 for _seq_ which translates _seq_ to:
355 _seq_ = /\ a b -> \ x::a y::b -> case seq# x of { 0# -> parError#; _ -> y }
357 Now, we know that the seq# primitive will never return 0#, but we
358 don't let the simplifier know that. We also use a special error
359 value, parError#, which is *not* a bottoming Id, so as far as the
360 simplifier is concerned, we have to evaluate seq# a before we know
361 whether or not y will be evaluated.
363 If we didn't have the extra case, then after inlining the compiler might
365 f p q = case seq# p of { _ -> p+q }
367 If it sees that, it can see that f is strict in q, and hence it might
368 evaluate q before p! The "0# ->" case prevents this happening.
369 By having the parError# branch we make sure that anything in the
370 other branch stays there!
372 This is fine, but we'd like to get rid of the extraneous code. Hence,
373 we *do* let the simplifier know that seq# is strict in its argument.
374 As a result, we hope that `a' will be evaluated before seq# is called.
375 At this point, we have a very special and magical simpification which
376 says that ``seq# a'' can be immediately simplified to `1#' if we
377 know that `a' is already evaluated.
379 NB: If we ever do case-floating, we have an extra worry:
382 a' -> let b' = case seq# a of { True -> b; False -> parError# }
388 a' -> let b' = case True of { True -> b; False -> parError# }
402 The second case must never be floated outside of the first!
405 seqRule [Type ty, arg] | exprIsValue arg = Just (SLIT("Seq"), mkIntVal 1)
406 seqRule other = Nothing
411 tagToEnumRule [Type ty, Lit (MachInt i)]
412 = ASSERT( isEnumerationTyCon tycon )
413 case filter correct_tag (tyConDataConsIfAvailable tycon) of
416 [] -> Nothing -- Abstract type
417 (dc:rest) -> ASSERT( null rest )
418 Just (SLIT("TagToEnum"), Var (dataConId dc))
420 correct_tag dc = (dataConTag dc - fIRST_TAG) == tag
422 tycon = tyConAppTyCon ty
424 tagToEnumRule other = Nothing
427 For dataToTag#, we can reduce if either
429 (a) the argument is a constructor
430 (b) the argument is a variable whose unfolding is a known constructor
433 dataToTagRule [_, val_arg]
434 = case exprIsConApp_maybe val_arg of
435 Just (dc,_) -> ASSERT( not (isNewTyCon (dataConTyCon dc)) )
436 Just (SLIT("DataToTag"),
437 mkIntVal (toInteger (dataConTag dc - fIRST_TAG)))
441 dataToTagRule other = Nothing
444 %************************************************************************
446 \subsection{Built in rules}
448 %************************************************************************
451 builtinRules :: [(Name, CoreRule)]
452 -- Rules for non-primops that can't be expressed using a RULE pragma
454 = [ (unpackCStringFoldrName, BuiltinRule match_append_lit_str)
459 -- unpackFoldrCString# "foo" c (unpackFoldrCString# "baz" c n) = unpackFoldrCString# "foobaz" c n
461 match_append_lit_str [Type ty1,
464 Var unpk `App` Type ty2
465 `App` Lit (MachStr s2)
469 | unpk `hasKey` unpackCStringFoldrIdKey &&
471 = ASSERT( ty1 == ty2 )
472 Just (SLIT("AppendLitString"),
473 Var unpk `App` Type ty1
474 `App` Lit (MachStr (s1 _APPEND_ s2))
478 match_append_lit_str other = Nothing