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 Id ( mkWildId )
17 import Literal ( Literal(..), isLitLitLit, mkMachInt, mkMachWord
18 , inIntRange, inWordRange, 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 ( dataConTag, dataConTyCon, dataConId, fIRST_TAG )
28 import CoreUtils ( exprIsValue, cheapEqExpr, exprIsConApp_maybe )
29 import Type ( splitTyConApp_maybe )
30 import OccName ( occNameUserString)
31 import PrelNames ( unpackCStringFoldr_RDR )
32 import Unique ( unpackCStringFoldrIdKey, hasKey )
33 import Bits ( Bits(..) )
34 import Word ( Word64 )
40 primOpRule :: PrimOp -> CoreRule
42 = BuiltinRule (primop_rule op)
44 op_name = _PK_ (occNameUserString (primOpOcc op))
45 op_name_case = op_name _APPEND_ SLIT("->case")
47 -- ToDo: something for integer-shift ops?
50 primop_rule SeqOp = seqRule
51 primop_rule TagToEnumOp = tagToEnumRule
52 primop_rule DataToTagOp = dataToTagRule
55 primop_rule IntAddOp = twoLits (intOp2 (+) op_name)
56 primop_rule IntSubOp = twoLits (intOp2 (-) op_name)
57 primop_rule IntMulOp = twoLits (intOp2 (*) op_name)
58 primop_rule IntQuotOp = twoLits (intOp2Z quot op_name)
59 primop_rule IntRemOp = twoLits (intOp2Z rem op_name)
60 primop_rule IntNegOp = oneLit (negOp op_name)
63 primop_rule WordQuotOp = twoLits (wordOp2Z quot op_name)
64 primop_rule WordRemOp = twoLits (wordOp2Z rem op_name)
65 #if __GLASGOW_HASKELL__ >= 407
66 primop_rule AndOp = twoLits (wordBitOp2 (.&.) op_name)
67 primop_rule OrOp = twoLits (wordBitOp2 (.|.) op_name)
68 primop_rule XorOp = twoLits (wordBitOp2 xor op_name)
72 primop_rule Word2IntOp = oneLit (litCoerce word2IntLit op_name)
73 primop_rule Int2WordOp = oneLit (litCoerce int2WordLit op_name)
74 primop_rule OrdOp = oneLit (litCoerce char2IntLit op_name)
75 primop_rule ChrOp = oneLit (litCoerce int2CharLit op_name)
76 primop_rule Float2IntOp = oneLit (litCoerce float2IntLit op_name)
77 primop_rule Int2FloatOp = oneLit (litCoerce int2FloatLit op_name)
78 primop_rule Double2IntOp = oneLit (litCoerce double2IntLit op_name)
79 primop_rule Int2DoubleOp = oneLit (litCoerce int2DoubleLit op_name)
80 primop_rule Addr2IntOp = oneLit (litCoerce addr2IntLit op_name)
81 primop_rule Int2AddrOp = oneLit (litCoerce int2AddrLit op_name)
82 -- SUP: Not sure what the standard says about precision in the following 2 cases
83 primop_rule Float2DoubleOp = oneLit (litCoerce float2DoubleLit op_name)
84 primop_rule Double2FloatOp = oneLit (litCoerce double2FloatLit op_name)
87 primop_rule FloatAddOp = twoLits (floatOp2 (+) op_name)
88 primop_rule FloatSubOp = twoLits (floatOp2 (-) op_name)
89 primop_rule FloatMulOp = twoLits (floatOp2 (*) op_name)
90 primop_rule FloatDivOp = twoLits (floatOp2Z (/) op_name)
91 primop_rule FloatNegOp = oneLit (negOp op_name)
94 primop_rule DoubleAddOp = twoLits (doubleOp2 (+) op_name)
95 primop_rule DoubleSubOp = twoLits (doubleOp2 (-) op_name)
96 primop_rule DoubleMulOp = twoLits (doubleOp2 (*) op_name)
97 primop_rule DoubleDivOp = twoLits (doubleOp2Z (/) op_name)
98 primop_rule DoubleNegOp = oneLit (negOp op_name)
100 -- Relational operators
101 primop_rule IntEqOp = relop (==) `or_rule` litEq True op_name_case
102 primop_rule IntNeOp = relop (/=) `or_rule` litEq False op_name_case
103 primop_rule CharEqOp = relop (==) `or_rule` litEq True op_name_case
104 primop_rule CharNeOp = relop (/=) `or_rule` litEq False op_name_case
106 primop_rule IntGtOp = relop (>)
107 primop_rule IntGeOp = relop (>=)
108 primop_rule IntLeOp = relop (<=)
109 primop_rule IntLtOp = relop (<)
111 primop_rule CharGtOp = relop (>)
112 primop_rule CharGeOp = relop (>=)
113 primop_rule CharLeOp = relop (<=)
114 primop_rule CharLtOp = relop (<)
116 primop_rule FloatGtOp = relop (>)
117 primop_rule FloatGeOp = relop (>=)
118 primop_rule FloatLeOp = relop (<=)
119 primop_rule FloatLtOp = relop (<)
120 primop_rule FloatEqOp = relop (==)
121 primop_rule FloatNeOp = relop (/=)
123 primop_rule DoubleGtOp = relop (>)
124 primop_rule DoubleGeOp = relop (>=)
125 primop_rule DoubleLeOp = relop (<=)
126 primop_rule DoubleLtOp = relop (<)
127 primop_rule DoubleEqOp = relop (==)
128 primop_rule DoubleNeOp = relop (/=)
130 primop_rule WordGtOp = relop (>)
131 primop_rule WordGeOp = relop (>=)
132 primop_rule WordLeOp = relop (<=)
133 primop_rule WordLtOp = relop (<)
134 primop_rule WordEqOp = relop (==)
135 primop_rule WordNeOp = relop (/=)
137 primop_rule other = \args -> Nothing
140 relop cmp = twoLits (cmpOp (\ord -> ord `cmp` EQ) op_name)
141 -- Cunning. cmpOp compares the values to give an Ordering.
142 -- It applies its argument to that ordering value to turn
143 -- the ordering into a boolean value. (`cmp` EQ) is just the job.
146 %************************************************************************
148 \subsection{Doing the business}
150 %************************************************************************
154 In all these operations we might find a LitLit as an operand; that's
155 why we have the catch-all Nothing case.
158 --------------------------
159 litCoerce :: (Literal -> Literal) -> RuleName -> Literal -> Maybe (RuleName, CoreExpr)
160 litCoerce fn name lit | isLitLitLit lit = Nothing
161 | otherwise = Just (name, Lit (fn lit))
163 --------------------------
164 cmpOp :: (Ordering -> Bool) -> FAST_STRING -> Literal -> Literal -> Maybe (RuleName, CoreExpr)
168 done res | cmp res = Just (name, trueVal)
169 | otherwise = Just (name, falseVal)
171 -- These compares are at different types
172 go (MachChar i1) (MachChar i2) = done (i1 `compare` i2)
173 go (MachInt i1) (MachInt i2) = done (i1 `compare` i2)
174 go (MachInt64 i1) (MachInt64 i2) = done (i1 `compare` i2)
175 go (MachWord i1) (MachWord i2) = done (i1 `compare` i2)
176 go (MachWord64 i1) (MachWord64 i2) = done (i1 `compare` i2)
177 go (MachFloat i1) (MachFloat i2) = done (i1 `compare` i2)
178 go (MachDouble i1) (MachDouble i2) = done (i1 `compare` i2)
181 --------------------------
183 negOp name (MachFloat f) = Just (name, mkFloatVal (-f))
184 negOp name (MachDouble d) = Just (name, mkDoubleVal (-d))
185 negOp name l@(MachInt i) = intResult name (-i)
186 negOp name l = Nothing
188 --------------------------
189 intOp2 op name l1@(MachInt i1) l2@(MachInt i2)
190 = intResult name (i1 `op` i2)
191 intOp2 op name l1 l2 = Nothing -- Could find LitLit
193 intOp2Z op name (MachInt i1) (MachInt i2)
194 | i2 /= 0 = Just (name, mkIntVal (i1 `op` i2))
195 intOp2Z op name l1 l2 = Nothing -- LitLit or zero dividend
197 --------------------------
198 -- Integer is not an instance of Bits, so we operate on Word64
199 wordBitOp2 op name l1@(MachWord w1) l2@(MachWord w2)
200 = Just (name, mkWordVal ((fromIntegral::Word64->Integer) (fromIntegral w1 `op` fromIntegral w2)))
201 wordBitOp2 op name l1 l2 = Nothing -- Could find LitLit
203 wordOp2Z op name (MachWord w1) (MachWord w2)
204 | w2 /= 0 = Just (name, mkWordVal (w1 `op` w2))
205 wordOp2Z op name l1 l2 = Nothing -- LitLit or zero dividend
207 --------------------------
208 floatOp2 op name (MachFloat f1) (MachFloat f2)
209 = Just (name, mkFloatVal (f1 `op` f2))
210 floatOp2 op name l1 l2 = Nothing
212 floatOp2Z op name (MachFloat f1) (MachFloat f2)
213 | f2 /= 0 = Just (name, mkFloatVal (f1 `op` f2))
214 floatOp2Z op name l1 l2 = Nothing
216 --------------------------
217 doubleOp2 op name (MachDouble f1) (MachDouble f2)
218 = Just (name, mkDoubleVal (f1 `op` f2))
219 doubleOp2 op name l1 l2 = Nothing
221 doubleOp2Z op name (MachDouble f1) (MachDouble f2)
222 | f2 /= 0 = Just (name, mkDoubleVal (f1 `op` f2))
223 doubleOp2Z op name l1 l2 = Nothing
226 --------------------------
234 -- This is a Good Thing, because it allows case-of case things
235 -- to happen, and case-default absorption to happen. For
238 -- if (n ==# 3#) || (n ==# 4#) then e1 else e2
244 -- (modulo the usual precautions to avoid duplicating e1)
246 litEq :: Bool -- True <=> equality, False <=> inequality
249 litEq is_eq name [Lit lit, expr] = do_lit_eq is_eq name lit expr
250 litEq is_eq name [expr, Lit lit] = do_lit_eq is_eq name lit expr
251 litEq is_eq name other = Nothing
253 do_lit_eq is_eq name lit expr
254 = Just (name, Case expr (mkWildId (literalType lit))
255 [(LitAlt lit, [], val_if_eq),
256 (DEFAULT, [], val_if_neq)])
258 val_if_eq | is_eq = trueVal
259 | otherwise = falseVal
260 val_if_neq | is_eq = falseVal
261 | otherwise = trueVal
263 -- Note that we *don't* warn the user about overflow. It's not done at
264 -- runtime either, and compilation of completely harmless things like
265 -- ((124076834 :: Word32) + (2147483647 :: Word32))
266 -- would yield a warning. Instead we simply squash the value into the
267 -- Int range, but not in a way suitable for cross-compiling... :-(
268 intResult :: RuleName -> Integer -> Maybe (RuleName, CoreExpr)
269 intResult name result
270 = Just (name, mkIntVal (toInteger ((fromInteger result)::Int)))
274 %************************************************************************
276 \subsection{Vaguely generic functions
278 %************************************************************************
281 type RuleFun = [CoreExpr] -> Maybe (RuleName, CoreExpr)
283 or_rule :: RuleFun -> RuleFun -> RuleFun
284 or_rule r1 r2 args = case r1 args of
285 Just stuff -> Just stuff
288 twoLits :: (Literal -> Literal -> Maybe (RuleName, CoreExpr)) -> RuleFun
289 twoLits rule [Lit l1, Lit l2] = rule l1 l2
290 twoLits rule other = Nothing
292 oneLit :: (Literal -> Maybe (RuleName, CoreExpr)) -> RuleFun
293 oneLit rule [Lit l1] = rule l1
294 oneLit rule other = Nothing
297 trueVal = Var trueDataConId
298 falseVal = Var falseDataConId
299 mkIntVal i = Lit (mkMachInt i)
300 mkWordVal w = Lit (mkMachWord w)
301 mkCharVal c = Lit (MachChar c)
302 mkFloatVal f = Lit (MachFloat f)
303 mkDoubleVal d = Lit (MachDouble d)
307 %************************************************************************
309 \subsection{Special rules for seq, tagToEnum, dataToTag}
311 %************************************************************************
313 In the parallel world, we use _seq_ to control the order in which
314 certain expressions will be evaluated. Operationally, the expression
315 ``_seq_ a b'' evaluates a and then evaluates b. We have an inlining
316 for _seq_ which translates _seq_ to:
318 _seq_ = /\ a b -> \ x::a y::b -> case seq# x of { 0# -> parError#; _ -> y }
320 Now, we know that the seq# primitive will never return 0#, but we
321 don't let the simplifier know that. We also use a special error
322 value, parError#, which is *not* a bottoming Id, so as far as the
323 simplifier is concerned, we have to evaluate seq# a before we know
324 whether or not y will be evaluated.
326 If we didn't have the extra case, then after inlining the compiler might
328 f p q = case seq# p of { _ -> p+q }
330 If it sees that, it can see that f is strict in q, and hence it might
331 evaluate q before p! The "0# ->" case prevents this happening.
332 By having the parError# branch we make sure that anything in the
333 other branch stays there!
335 This is fine, but we'd like to get rid of the extraneous code. Hence,
336 we *do* let the simplifier know that seq# is strict in its argument.
337 As a result, we hope that `a' will be evaluated before seq# is called.
338 At this point, we have a very special and magical simpification which
339 says that ``seq# a'' can be immediately simplified to `1#' if we
340 know that `a' is already evaluated.
342 NB: If we ever do case-floating, we have an extra worry:
345 a' -> let b' = case seq# a of { True -> b; False -> parError# }
351 a' -> let b' = case True of { True -> b; False -> parError# }
365 The second case must never be floated outside of the first!
368 seqRule [Type ty, arg] | exprIsValue arg = Just (SLIT("Seq"), mkIntVal 1)
369 seqRule other = Nothing
374 tagToEnumRule [Type ty, Lit (MachInt i)]
375 = ASSERT( isEnumerationTyCon tycon )
376 case filter correct_tag (tyConDataConsIfAvailable tycon) of
379 [] -> Nothing -- Abstract type
380 (dc:rest) -> ASSERT( null rest )
381 Just (SLIT("TagToEnum"), Var (dataConId dc))
383 correct_tag dc = (dataConTag dc - fIRST_TAG) == tag
385 (Just (tycon,_)) = splitTyConApp_maybe ty
387 tagToEnumRule other = Nothing
390 For dataToTag#, we can reduce if either
392 (a) the argument is a constructor
393 (b) the argument is a variable whose unfolding is a known constructor
396 dataToTagRule [_, val_arg]
397 = case exprIsConApp_maybe val_arg of
398 Just (dc,_) -> ASSERT( not (isNewTyCon (dataConTyCon dc)) )
399 Just (SLIT("DataToTag"),
400 mkIntVal (toInteger (dataConTag dc - fIRST_TAG)))
404 dataToTagRule other = Nothing
407 %************************************************************************
409 \subsection{Built in rules}
411 %************************************************************************
414 builtinRules :: [(RdrName, CoreRule)]
415 -- Rules for non-primops that can't be expressed using a RULE pragma
417 = [ (unpackCStringFoldr_RDR, BuiltinRule match_append_lit_str)
421 -- unpackFoldrCString# "foo" c (unpackFoldrCString# "baz" c n) = unpackFoldrCString# "foobaz" c n
423 match_append_lit_str [Type ty1,
426 Var unpk `App` Type ty2
427 `App` Lit (MachStr s2)
431 | unpk `hasKey` unpackCStringFoldrIdKey &&
433 = ASSERT( ty1 == ty2 )
434 Just (SLIT("AppendLitString"),
435 Var unpk `App` Type ty1
436 `App` Lit (MachStr (s1 _APPEND_ s2))
440 match_append_lit_str other = Nothing