From patchwork Sun Aug  1 18:44:18 2010
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Subject: [alpha] : Fix PR target/41089, stdarg pass produces wrong code
Date: Sun, 01 Aug 2010 08:44:18 -0000
From: Uros Bizjak <ubizjak@gmail.com>
X-Patchwork-Id: 60488
Message-Id: <AANLkTingvVPJPfnaheLHWgpyGPuGbxGLXERsP+j0zjx5@mail.gmail.com>
To: gcc-patches@gcc.gnu.org
Cc: Richard Henderson <rth@redhat.com>, Richard Guenther <rguenther@suse.de>, 
 Jakub Jelinek <jakub@redhat.com>

Hello!

As discussed in the PR, stdarg pass depends on number of assignments
to ap.__offset location for correct operation. However, recent FRE/DCE
enhancements remove one assignment as a dead code, causing the test
failure:

FAIL: gcc.c-torture/execute/stdarg-1.c execution,  -O3 -fomit-frame-pointer
FAIL: gcc.c-torture/execute/stdarg-1.c execution,  -O3 -g

Attached patch marks __offset as volatile (suggested by Richi in
comment #39), preventing optimizations that could otherwise confuse
stdarg pass.

2010-08-01  Uros Bizjak  <ubizjak@gmail.com>

	PR target/41089
	* config/alpha/alpha.c (alpha_build_builtin_va_list): Mark __offset
	as volatile.

Patch was bootstrapped and regression tested on
alphaev68-pc-linux-gnu, where it fixes the failure.

OK for mainline/4.5?

Uros.


Index: config/alpha/alpha.c
===================================================================
--- config/alpha/alpha.c	(revision 162794)
+++ config/alpha/alpha.c	(working copy)
@@ -5948,6 +5948,7 @@ alpha_build_builtin_va_list (void)
   ofs = build_decl (BUILTINS_LOCATION,
 		    FIELD_DECL, get_identifier ("__offset"),
 		    integer_type_node);
+  TREE_THIS_VOLATILE (ofs) = 1;
   DECL_FIELD_CONTEXT (ofs) = record;
   DECL_CHAIN (ofs) = space;