X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2FcoreSyn%2FCoreUtils.lhs;h=05ef9a376d69969ac84e6e554e337f80e6c9852c;hb=356e6869dec4b623a3aba239e72c682667a2b85e;hp=ed8d6f2bed28ea117aa1ff7d01da259bf4835788;hpb=08579b108d0b021e0d3f05d4c5af0259a3907864;p=ghc-hetmet.git diff --git a/compiler/coreSyn/CoreUtils.lhs b/compiler/coreSyn/CoreUtils.lhs index ed8d6f2..05ef9a3 100644 --- a/compiler/coreSyn/CoreUtils.lhs +++ b/compiler/coreSyn/CoreUtils.lhs @@ -36,7 +36,7 @@ module CoreUtils ( hashExpr, -- * Equality - cheapEqExpr, eqExpr, + cheapEqExpr, eqExpr, eqExprX, -- * Manipulating data constructors and types applyTypeToArgs, applyTypeToArg, @@ -469,8 +469,8 @@ dupAppSize = 4 -- Size of application we are prepared to duplicate %* * %************************************************************************ -Note [exprIsCheap] -~~~~~~~~~~~~~~~~~~ +Note [exprIsCheap] See also Note [Interaction of exprIsCheap and lone variables] +~~~~~~~~~~~~~~~~~~ in CoreUnfold.lhs @exprIsCheap@ looks at a Core expression and returns \tr{True} if it is obviously in weak head normal form, or is cheap to get to WHNF. [Note that that's not the same as exprIsDupable; an expression might be @@ -499,6 +499,13 @@ shared. The main examples of things which aren't WHNF but are Notice that a variable is considered 'cheap': we can push it inside a lambda, because sharing will make sure it is only evaluated once. +Note [exprIsCheap and exprIsHNF] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Note that exprIsHNF does not imply exprIsCheap. Eg + let x = fac 20 in Just x +This responds True to exprIsHNF (you can discard a seq), but +False to exprIsCheap. + \begin{code} exprIsCheap :: CoreExpr -> Bool exprIsCheap = exprIsCheap' isCheapApp @@ -524,11 +531,12 @@ exprIsCheap' good_app (Case e _ _ alts) = exprIsCheap' good_app e && -- there is only dictionary selection (no construction) involved exprIsCheap' good_app (Let (NonRec x _) e) - | isUnLiftedType (idType x) = exprIsCheap' good_app e - | otherwise = False + | isUnLiftedType (idType x) = exprIsCheap' good_app e + | otherwise = False -- Strict lets always have cheap right hand sides, -- and do no allocation, so just look at the body -- Non-strict lets do allocation so we don't treat them as cheap + -- See also exprIsCheap' good_app other_expr -- Applications and variables = go other_expr [] @@ -625,11 +633,8 @@ it's applied only to dictionaries. -- Precisely, it returns @True@ iff: -- -- * The expression guarantees to terminate, --- -- * soon, --- -- * without raising an exception, --- -- * without causing a side effect (e.g. writing a mutable variable) -- -- Note that if @exprIsHNF e@, then @exprOkForSpecuation e@. @@ -741,7 +746,7 @@ The inner case is redundant, and should be nuked. %************************************************************************ \begin{code} --- Note [exprIsHNF] +-- Note [exprIsHNF] See also Note [exprIsCheap and exprIsHNF] -- ~~~~~~~~~~~~~~~~ -- | exprIsHNF returns true for expressions that are certainly /already/ -- evaluated to /head/ normal form. This is used to decide whether it's ok @@ -966,36 +971,62 @@ exprIsBig _ = True eqExpr :: InScopeSet -> CoreExpr -> CoreExpr -> Bool -- Compares for equality, modulo alpha eqExpr in_scope e1 e2 - = go (mkRnEnv2 in_scope) e1 e2 + = eqExprX id_unf (mkRnEnv2 in_scope) e1 e2 + where + id_unf _ = noUnfolding -- Don't expand +\end{code} + +\begin{code} +eqExprX :: IdUnfoldingFun -> RnEnv2 -> CoreExpr -> CoreExpr -> Bool +-- ^ Compares expressions for equality, modulo alpha. +-- Does /not/ look through newtypes or predicate types +-- Used in rule matching, and also CSE + +eqExprX id_unfolding_fun env e1 e2 + = go env e1 e2 where - go _ (Lit lit1) (Lit lit2) = lit1 == lit2 - go env (Type t1) (Type t2) = coreEqType2 env t1 t2 - go env (Var v1) (Var v2) = rnOccL env v1 == rnOccR env v2 - go env (Cast e1 t1) (Cast e2 t2) = go env e1 e2 && coreEqCoercion2 env t1 t2 - go env (App f1 a1) (App f2 a2) = go env f1 f2 && go env a1 a2 + go env (Var v1) (Var v2) + | rnOccL env v1 == rnOccR env v2 + = True + + -- The next two rules expand non-local variables + -- C.f. Note [Expanding variables] in Rules.lhs + -- and Note [Do not expand locally-bound variables] in Rules.lhs + go env (Var v1) e2 + | not (locallyBoundL env v1) + , Just e1' <- expandUnfolding_maybe (id_unfolding_fun (lookupRnInScope env v1)) + = go (nukeRnEnvL env) e1' e2 + + go env e1 (Var v2) + | not (locallyBoundR env v2) + , Just e2' <- expandUnfolding_maybe (id_unfolding_fun (lookupRnInScope env v2)) + = go (nukeRnEnvR env) e1 e2' + + go _ (Lit lit1) (Lit lit2) = lit1 == lit2 + go env (Type t1) (Type t2) = tcEqTypeX env t1 t2 + go env (Cast e1 co1) (Cast e2 co2) = tcEqTypeX env co1 co2 && go env e1 e2 + go env (App f1 a1) (App f2 a2) = go env f1 f2 && go env a1 a2 + go env (Note n1 e1) (Note n2 e2) = go_note n1 n2 && go env e1 e2 go env (Lam b1 e1) (Lam b2 e2) - = coreEqType2 env (varType b1) (varType b2) -- Will return False for Id/TyVar combination + = tcEqTypeX env (varType b1) (varType b2) -- False for Id/TyVar combination && go (rnBndr2 env b1 b2) e1 e2 + go env (Let (NonRec v1 r1) e1) (Let (NonRec v2 r2) e2) + = go env r1 r2 -- No need to check binder types, since RHSs match + && go (rnBndr2 env v1 v2) e1 e2 + + go env (Let (Rec ps1) e1) (Let (Rec ps2) e2) + = all2 (go env') rs1 rs2 && go env' e1 e2 + where + (bs1,rs1) = unzip ps1 + (bs2,rs2) = unzip ps2 + env' = rnBndrs2 env bs1 bs2 + go env (Case e1 b1 _ a1) (Case e2 b2 _ a2) = go env e1 e2 - && coreEqType2 env (idType b1) (idType b2) + && tcEqTypeX env (idType b1) (idType b2) && all2 (go_alt (rnBndr2 env b1 b2)) a1 a2 - - go env (Let (NonRec b1 r1) e1) (Let (NonRec b2 r2) e2) - = go env r1 r2 -- No need to check binder types, since RHSs match - && go (rnBndr2 env b1 b2) e1 e2 - - go env (Let (Rec p1) e1) (Let (Rec p2) e2) - | equalLength p1 p2 - = all2 (go env') rs1 rs2 && go env' e1 e2 - where - (bs1,rs1) = unzip p1 - (bs2,rs2) = unzip p2 - env' = rnBndrs2 env bs1 bs2 - - go env (Note n1 e1) (Note n2 e2) = go_note n1 n2 && go env e1 e2 go _ _ _ = False @@ -1004,11 +1035,19 @@ eqExpr in_scope e1 e2 = c1 == c2 && go (rnBndrs2 env bs1 bs2) e1 e2 ----------- - go_note (SCC cc1) (SCC cc2) = cc1==cc2 - go_note (CoreNote s1) (CoreNote s2) = s1==s2 - go_note _ _ = False + go_note (SCC cc1) (SCC cc2) = cc1 == cc2 + go_note (CoreNote s1) (CoreNote s2) = s1 == s2 + go_note _ _ = False \end{code} - + +Auxiliary functions + +\begin{code} +locallyBoundL, locallyBoundR :: RnEnv2 -> Var -> Bool +locallyBoundL rn_env v = inRnEnvL rn_env v +locallyBoundR rn_env v = inRnEnvR rn_env v +\end{code} + %************************************************************************ %* *