2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
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 #include "HsVersions.h"
13 module ConFold ( completePrim ) where
18 import CoreUnfold ( UnfoldingDetails(..), FormSummary(..) )
20 import Literal ( mkMachInt, mkMachWord, Literal(..) )
21 import MagicUFs ( MagicUnfoldingFun )
22 import PrelInfo ( trueDataCon, falseDataCon )
23 import PrimOp ( PrimOp(..) )
29 completePrim :: SimplEnv
34 In the parallel world, we use _seq_ to control the order in which
35 certain expressions will be evaluated. Operationally, the expression
36 ``_seq_ a b'' evaluates a and then evaluates b. We have an inlining
37 for _seq_ which translates _seq_ to:
39 _seq_ = /\ a b -> \ x::a y::b -> case seq# x of { 0# -> parError#; _ -> y }
41 Now, we know that the seq# primitive will never return 0#, but we
42 don't let the simplifier know that. We also use a special error
43 value, parError#, which is *not* a bottoming Id, so as far as the
44 simplifier is concerned, we have to evaluate seq# a before we know
45 whether or not y will be evaluated.
47 If we didn't have the extra case, then after inlining the compiler might
49 f p q = case seq# p of { _ -> p+q }
51 If it sees that, it can see that f is strict in q, and hence it might
52 evaluate q before p! The "0# ->" case prevents this happening.
53 By having the parError# branch we make sure that anything in the
54 other branch stays there!
56 This is fine, but we'd like to get rid of the extraneous code. Hence,
57 we *do* let the simplifier know that seq# is strict in its argument.
58 As a result, we hope that `a' will be evaluated before seq# is called.
59 At this point, we have a very special and magical simpification which
60 says that ``seq# a'' can be immediately simplified to `1#' if we
61 know that `a' is already evaluated.
63 NB: If we ever do case-floating, we have an extra worry:
66 a' -> let b' = case seq# a of { True -> b; False -> parError# }
72 a' -> let b' = case True of { True -> b; False -> parError# }
86 The second case must never be floated outside of the first!
89 completePrim env SeqOp [TyArg ty, LitArg lit]
90 = returnSmpl (Lit (mkMachInt 1))
92 completePrim env op@SeqOp args@[TyArg ty, VarArg var]
93 = case (lookupUnfolding env var) of
94 NoUnfoldingDetails -> give_up
96 OtherLitForm _ -> hooray
98 OtherConForm _ -> hooray
99 GenForm _ WhnfForm _ _ -> hooray
102 give_up = returnSmpl (Prim op args)
103 hooray = returnSmpl (Lit (mkMachInt 1))
107 completePrim env op args
109 [LitArg (MachChar char_lit)] -> oneCharLit op char_lit
110 [LitArg (MachInt int_lit signed)] -> (if signed then oneIntLit else oneWordLit)
112 [LitArg (MachFloat float_lit)] -> oneFloatLit op float_lit
113 [LitArg (MachDouble double_lit)] -> oneDoubleLit op double_lit
114 [LitArg other_lit] -> oneLit op other_lit
116 [LitArg (MachChar char_lit1),
117 LitArg (MachChar char_lit2)] -> twoCharLits op char_lit1 char_lit2
119 [LitArg (MachInt int_lit1 True), -- both *signed* literals
120 LitArg (MachInt int_lit2 True)] -> twoIntLits op int_lit1 int_lit2
122 [LitArg (MachInt int_lit1 False), -- both *unsigned* literals
123 LitArg (MachInt int_lit2 False)] -> twoWordLits op int_lit1 int_lit2
125 [LitArg (MachInt int_lit1 False), -- unsigned+signed (shift ops)
126 LitArg (MachInt int_lit2 True)] -> oneWordOneIntLit op int_lit1 int_lit2
128 [LitArg (MachFloat float_lit1),
129 LitArg (MachFloat float_lit2)] -> twoFloatLits op float_lit1 float_lit2
131 [LitArg (MachDouble double_lit1),
132 LitArg (MachDouble double_lit2)] -> twoDoubleLits op double_lit1 double_lit2
134 [LitArg lit, VarArg var] -> litVar op lit var
135 [VarArg var, LitArg lit] -> litVar op lit var
139 give_up = returnSmpl (Prim op args)
141 return_char c = returnSmpl (Lit (MachChar c))
142 return_int i = returnSmpl (Lit (mkMachInt i))
143 return_word i = returnSmpl (Lit (mkMachWord i))
144 return_float f = returnSmpl (Lit (MachFloat f))
145 return_double d = returnSmpl (Lit (MachDouble d))
146 return_lit lit = returnSmpl (Lit lit)
148 return_bool True = returnSmpl trueVal
149 return_bool False = returnSmpl falseVal
151 return_prim_case var lit val_if_eq val_if_neq
152 = newId (idType var) `thenSmpl` \ unused_binder ->
156 (PrimAlts [(lit,val_if_eq)]
157 (BindDefault unused_binder val_if_neq))
161 --------- Ints --------------
162 oneIntLit IntNegOp i = return_int (-i)
163 oneIntLit ChrOp i = return_char (chr (fromInteger i))
164 -- SIGH: these two cause trouble in unfoldery
165 -- as we can't distinguish unsigned literals in interfaces (ToDo?)
166 -- oneIntLit Int2WordOp i = ASSERT( i>=0 ) return_word i
167 -- oneIntLit Int2AddrOp i = ASSERT( i>=0 ) return_lit (MachAddr i)
168 oneIntLit Int2FloatOp i = return_float (fromInteger i)
169 oneIntLit Int2DoubleOp i = return_double (fromInteger i)
170 oneIntLit _ _ = {-trace "oneIntLit: giving up"-} give_up
172 oneWordLit Word2IntOp w = {-lazy:ASSERT( w<= maxInt)-} return_int w
173 -- oneWordLit NotOp w = ??? ToDo: sort-of a pain
174 oneWordLit _ _ = {-trace "oneIntLit: giving up"-} give_up
176 twoIntLits IntAddOp i1 i2 = return_int (i1+i2)
177 twoIntLits IntSubOp i1 i2 = return_int (i1-i2)
178 twoIntLits IntMulOp i1 i2 = return_int (i1*i2)
179 twoIntLits IntQuotOp i1 i2 | i2 /= 0 = return_int (i1 `quot` i2)
180 twoIntLits IntRemOp i1 i2 | i2 /= 0 = return_int (i1 `rem` i2)
181 twoIntLits IntGtOp i1 i2 = return_bool (i1 > i2)
182 twoIntLits IntGeOp i1 i2 = return_bool (i1 >= i2)
183 twoIntLits IntEqOp i1 i2 = return_bool (i1 == i2)
184 twoIntLits IntNeOp i1 i2 = return_bool (i1 /= i2)
185 twoIntLits IntLtOp i1 i2 = return_bool (i1 < i2)
186 twoIntLits IntLeOp i1 i2 = return_bool (i1 <= i2)
187 -- ToDo: something for integer-shift ops?
188 twoIntLits _ _ _ = give_up
190 twoWordLits WordGtOp w1 w2 = return_bool (w1 > w2)
191 twoWordLits WordGeOp w1 w2 = return_bool (w1 >= w2)
192 twoWordLits WordEqOp w1 w2 = return_bool (w1 == w2)
193 twoWordLits WordNeOp w1 w2 = return_bool (w1 /= w2)
194 twoWordLits WordLtOp w1 w2 = return_bool (w1 < w2)
195 twoWordLits WordLeOp w1 w2 = return_bool (w1 <= w2)
196 -- ToDo: something for AndOp, OrOp?
197 twoWordLits _ _ _ = give_up
199 -- ToDo: something for shifts
200 oneWordOneIntLit _ _ _ = give_up
202 --------- Floats --------------
203 oneFloatLit FloatNegOp f = return_float (-f)
204 #if __GLASGOW_HASKELL__ <= 22
205 oneFloatLit FloatExpOp f = return_float (exp f)
206 oneFloatLit FloatLogOp f = return_float (log f)
207 oneFloatLit FloatSqrtOp f = return_float (sqrt f)
208 oneFloatLit FloatSinOp f = return_float (sin f)
209 oneFloatLit FloatCosOp f = return_float (cos f)
210 oneFloatLit FloatTanOp f = return_float (tan f)
211 oneFloatLit FloatAsinOp f = return_float (asin f)
212 oneFloatLit FloatAcosOp f = return_float (acos f)
213 oneFloatLit FloatAtanOp f = return_float (atan f)
214 oneFloatLit FloatSinhOp f = return_float (sinh f)
215 oneFloatLit FloatCoshOp f = return_float (cosh f)
216 oneFloatLit FloatTanhOp f = return_float (tanh f)
218 -- hard to do all that in Rationals ?? (WDP 94/10) ToDo
220 oneFloatLit _ _ = give_up
222 twoFloatLits FloatGtOp f1 f2 = return_bool (f1 > f2)
223 twoFloatLits FloatGeOp f1 f2 = return_bool (f1 >= f2)
224 twoFloatLits FloatEqOp f1 f2 = return_bool (f1 == f2)
225 twoFloatLits FloatNeOp f1 f2 = return_bool (f1 /= f2)
226 twoFloatLits FloatLtOp f1 f2 = return_bool (f1 < f2)
227 twoFloatLits FloatLeOp f1 f2 = return_bool (f1 <= f2)
228 twoFloatLits FloatAddOp f1 f2 = return_float (f1 + f2)
229 twoFloatLits FloatSubOp f1 f2 = return_float (f1 - f2)
230 twoFloatLits FloatMulOp f1 f2 = return_float (f1 * f2)
231 twoFloatLits FloatDivOp f1 f2 | f2 /= 0 = return_float (f1 / f2)
232 twoFloatLits _ _ _ = give_up
234 --------- Doubles --------------
235 oneDoubleLit DoubleNegOp d = return_double (-d)
236 oneDoubleLit _ _ = give_up
238 twoDoubleLits DoubleGtOp d1 d2 = return_bool (d1 > d2)
239 twoDoubleLits DoubleGeOp d1 d2 = return_bool (d1 >= d2)
240 twoDoubleLits DoubleEqOp d1 d2 = return_bool (d1 == d2)
241 twoDoubleLits DoubleNeOp d1 d2 = return_bool (d1 /= d2)
242 twoDoubleLits DoubleLtOp d1 d2 = return_bool (d1 < d2)
243 twoDoubleLits DoubleLeOp d1 d2 = return_bool (d1 <= d2)
244 twoDoubleLits DoubleAddOp d1 d2 = return_double (d1 + d2)
245 twoDoubleLits DoubleSubOp d1 d2 = return_double (d1 - d2)
246 twoDoubleLits DoubleMulOp d1 d2 = return_double (d1 * d2)
247 twoDoubleLits DoubleDivOp d1 d2 | d2 /= 0 = return_double (d1 / d2)
248 twoDoubleLits _ _ _ = give_up
250 --------- Characters --------------
251 oneCharLit OrdOp c = return_int (fromInt (ord c))
252 oneCharLit _ _ = give_up
254 twoCharLits CharGtOp c1 c2 = return_bool (c1 > c2)
255 twoCharLits CharGeOp c1 c2 = return_bool (c1 >= c2)
256 twoCharLits CharEqOp c1 c2 = return_bool (c1 == c2)
257 twoCharLits CharNeOp c1 c2 = return_bool (c1 /= c2)
258 twoCharLits CharLtOp c1 c2 = return_bool (c1 < c2)
259 twoCharLits CharLeOp c1 c2 = return_bool (c1 <= c2)
260 twoCharLits _ _ _ = give_up
262 --------- Miscellaneous --------------
263 oneLit Addr2IntOp (MachAddr i) = return_int i
264 oneLit op lit = give_up
266 --------- Equality and inequality for Int/Char --------------
274 -- This is a Good Thing, because it allows case-of case things
275 -- to happen, and case-default absorption to happen. For
278 -- if (n ==# 3#) || (n ==# 4#) then e1 else e2
284 -- (modulo the usual precautions to avoid duplicating e1)
286 litVar IntEqOp lit var = return_prim_case var lit trueVal falseVal
287 litVar IntNeOp lit var = return_prim_case var lit falseVal trueVal
288 litVar CharEqOp lit var = return_prim_case var lit trueVal falseVal
289 litVar CharNeOp lit var = return_prim_case var lit falseVal trueVal
290 litVar other_op lit var = give_up
293 trueVal = Con trueDataCon []
294 falseVal = Con falseDataCon []