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From: "bernhard.kaindl at thalesgroup dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/48181] [4.8/4.9 Regression] wrong code with -O -fgcse --param ira-max-conflict-table-size=0
Date: Wed, 10 Jun 2015 00:49:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=48181

Bernhard Kaindl <bernhard.kaindl at thalesgroup dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |bernhard.kaindl@thalesgroup
                   |                            |.com

--- Comment #11 from Bernhard Kaindl <bernhard.kaindl at thalesgroup dot com> ---
Checked what Steven Bosscher said in comment #5 and what I understood from
Comment 6 that LRA fixed this issue:

> FWIW I can't reproduce the problem with trunk.  I see rcx being saved
> and restored around the calls, e.g.:
> 
>         movq    %rcx, (%rsp)
>         call    bar
>         movq    (%rsp), %rcx
> 
> and likewise around the second memcpy.  Unfortunately (an old) valgrind
> on gcc17 doesn't work with with "valgrind -q ./a.out" as in comment #0.

> http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=192719
> fixed this (so, most likely reproduceable by disabling LRA).

Indeed, gcc-4.8.4 and gcc-4.9.2 save and restore rcx as described,
valgrind-3.10.1 (current release) does not show an error,
and program does not crash at all.

So affected are only gcc-4.5, 4.6 and 4.7,
and only with --param ira-max-conflict-table-size=0 & -fgcse active.