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From: "su at cs dot ucdavis.edu" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug lto/61969] New: wrong code by LTO on x86_64-linux-gnu (affecting trunk, 4.9.x, and 4.8.x)
Date: Wed, 30 Jul 2014 20:46:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61969

            Bug ID: 61969
           Summary: wrong code by LTO on x86_64-linux-gnu (affecting
                    trunk, 4.9.x, and 4.8.x)
           Product: gcc
           Version: 4.10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: lto
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu

Created attachment 33217
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33217&action=edit
test files and compilation script

The current gcc trunk (as well as gcc 4.8.x and 4.9.x) miscompiles the attached
code when using LTO on x86_64-linux-gnu in 64-bit mode (but not in 32-bit
mode). 

This is a regression from 4.7.x.

Sorry that the test case is still pretty complex. It seems very difficult to be
reduced further --- any small changes to the code seem to hide the bug.

$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-unknown-linux-gnu/4.10.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-trunk/configure --prefix=/usr/local/gcc-trunk
--enable-languages=c,c++ --disable-werror --enable-multilib
Thread model: posix
gcc version 4.10.0 20140730 (experimental) [trunk revision 213231] (GCC) 
$ 
$ compile.sh 
Usage: ./compile.sh <cc> <mode> <lto: 1 | 0>
$ compile.sh gcc-trunk 64 0; t
-25246
$ compile.sh gcc-trunk 64 1; t
-25246
$ compile.sh gcc-trunk 32 0; t
-25246
$ compile.sh gcc-trunk 32 1; t
0 
$ compile.sh gcc-4.9 32 1; t
0
$ compile.sh gcc-4.8 32 1; t
2052
$ compile.sh gcc-4.7 32 1; t
-25246
$