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From: "skvadrik at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/64541] New: .fre1 pass optimization failure
Date: Thu, 08 Jan 2015 16:06:00 -0000 [thread overview]
Message-ID: <bug-64541-4@http.gcc.gnu.org/bugzilla/> (raw)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64541
Bug ID: 64541
Summary: .fre1 pass optimization failure
Product: gcc
Version: 5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: skvadrik at gmail dot com
Created attachment 34403
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34403&action=edit
1.c 2.c 1.c.028t.esra 2.c.028t.esra 1.c.030t.fre1 2.c.030t.fre1 1.s 2.s
compile_gcc.sh
Files 1.c and 2.c in attach are equivalent from C/C++ standpoint:
$ diff 1.c 2.c
3c3,5
< return *(*q = ++*p);
---
> ++*p;
> *q = *p;
> return **p;
Compiled with gcc-5.0.0, disassembled with objdump (GNU Binutils) 2.24
(see full script compile_gcc.sh in attach).
For 1.c gcc generates better code than for 2.c
(compare 1.s vs 2.s in attach).
I looked at GIMPLE optimization dumps (-fdump-tree-all) and found that
up to *.029t.ealias pass dumps differ insignificantly (attached
*.028t.esra dumps as they are shorter), but .030t.fre1 pass fails to
reduce intermediate variable '_9' in the second case (attached *.030t.fre
dumps).
Looks like a bug in full redundancy elimination.
next reply other threads:[~2015-01-08 16:06 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-08 16:06 skvadrik at gmail dot com [this message]
2015-01-14 11:56 ` [Bug tree-optimization/64541] FRE " skvadrik at gmail dot com
2015-01-14 12:00 ` rguenther at suse dot de
2015-01-14 12:03 ` skvadrik at gmail dot com
2021-12-15 21:43 ` pinskia at gcc dot gnu.org
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