hashExpr,
-- * Equality
- cheapEqExpr, eqExpr,
+ cheapEqExpr, eqExpr, eqExprX,
-- * Manipulating data constructors and types
applyTypeToArgs, applyTypeToArg,
%* *
%************************************************************************
-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
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
-- 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 []
-- 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@.
%************************************************************************
\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
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
= 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}
+
%************************************************************************
%* *
projects / ghc-hetmet.git / blobdiff