[Bug tree-optimization/47708] incorrect code on -O2 without -fno-tree-pre

[pinskia at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47708

--- Comment #1 from pinskia at gmail dot com <pinskia at gmail dot com> 
2011-02-12 06:36:09 UTC ---
You are violating c/c++ aliasing rules. &nbsp;The code is undefined.



Sent from my Palm Pre on AT&amp;T
On Feb 11, 2011 22:27, zephyrtronium at gmail dot com
&lt;gcc-bugzi...@gcc.gnu.org&gt; wrote: 

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47708



           Summary: incorrect code on -O2 without -fno-tree-pre

           Product: gcc

           Version: 4.5.2

            Status: UNCONFIRMED

          Severity: normal

          Priority: P3

         Component: tree-optimization

        AssignedTo: unassig...@gcc.gnu.org

        ReportedBy: zephyrtron...@gmail.com





Created attachment 23310

  --&gt; http://gcc.gnu.org/bugzilla/attachment.cgi?id=23310

minimal case



gcc -v

Using built-in specs.

COLLECT_GCC=gcc

COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc/x86_64-unknown-linux-gnu/4.5.2/lto-wrapper

Target: x86_64-unknown-linux-gnu

Configured with: ../gcc-4.5.2/configure --enable-lto

Thread model: posix

gcc version 4.5.2 (GCC)



Compiling the following minimal case on -O2 or -O3 and running results in

incorrect output; with -O0, -O1, or -Os, it is correct. -O2 -fno-tree-pre

results in correct output, but -O1 -ftree-pre is also correct. GCC 4.4.3

appears to work.