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Re: [patch] Perform anonymous constant propagation during inlining
- From: Eric Botcazou <ebotcazou at adacore dot com>
- To: Richard Biener <richard dot guenther at gmail dot com>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Fri, 01 May 2015 20:09:50 +0200
- Subject: Re: [patch] Perform anonymous constant propagation during inlining
- Authentication-results: sourceware.org; auth=none
- References: <6476732 dot lMFodJZTVz at polaris> <0ADD2F35-3576-4FDE-8473-17ADED030B92 at gmail dot com> <3882455 dot jixBbSixVe at polaris>
> OK, how aggressive then? We could as well do the substitution for all
> copies:
>
> /* For EXPAND_INITIALIZER try harder to get something simpler.
> Otherwise, substitute copies on the RHS, this can propagate
> constants at -O0 and thus simplify arithmetic operations. */
> if (g == NULL
> && !SSA_NAME_IS_DEFAULT_DEF (exp)
> && (optimize || DECL_IGNORED_P (SSA_NAME_VAR (exp)))
> && (modifier == EXPAND_INITIALIZER
>
> || (modifier != EXPAND_WRITE
>
> && gimple_assign_copy_p (SSA_NAME_DEF_STMT (exp))))
> && stmt_is_replaceable_p (SSA_NAME_DEF_STMT (exp)))
> g = SSA_NAME_DEF_STMT (exp);
This doesn't work (this generates wrong code because this creates overlapping
live ranges for SSA_NAMEs with the same base variable). Here's the latest
working version, all the predicates and accessors used are inlined.
Tested on x86_64-suse-linux, OK for the mainline?
2015-05-01 Eric Botcazou <ebotcazou@adacore.com>
* expr.c (expand_expr_real_1) <SSA_NAME>: Try to substitute constants
on the RHS of expressions.
* gimple-expr.h (is_gimple_constant): Reorder.
--
Eric Botcazou
Index: expr.c
===================================================================
--- expr.c (revision 222673)
+++ expr.c (working copy)
@@ -9511,11 +9511,17 @@ expand_expr_real_1 (tree exp, rtx target
}
g = get_gimple_for_ssa_name (exp);
- /* For EXPAND_INITIALIZER try harder to get something simpler. */
+ /* For EXPAND_INITIALIZER try harder to get something simpler.
+ Otherwise, substitute constants on the RHS, this can make
+ it possible to simplify arithmetic operations at -O0. */
if (g == NULL
- && modifier == EXPAND_INITIALIZER
&& !SSA_NAME_IS_DEFAULT_DEF (exp)
&& (optimize || DECL_IGNORED_P (SSA_NAME_VAR (exp)))
+ && (modifier == EXPAND_INITIALIZER
+ || (modifier != EXPAND_WRITE
+ && gimple_assign_single_p (SSA_NAME_DEF_STMT (exp))
+ && is_gimple_constant
+ (gimple_assign_rhs1 (SSA_NAME_DEF_STMT (exp)))))
&& stmt_is_replaceable_p (SSA_NAME_DEF_STMT (exp)))
g = SSA_NAME_DEF_STMT (exp);
if (g)
Index: gimple-expr.h
===================================================================
--- gimple-expr.h (revision 222673)
+++ gimple-expr.h (working copy)
@@ -136,9 +136,9 @@ is_gimple_constant (const_tree t)
case INTEGER_CST:
case REAL_CST:
case FIXED_CST:
- case STRING_CST:
case COMPLEX_CST:
case VECTOR_CST:
+ case STRING_CST:
return true;
default: