[Bug tree-optimization/59951] [4.9 Regression] bootstrap comparison failure with -O3 for a week

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59951

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
           Keywords|                            |wrong-code
   Last reconfirmed|                            |2014-01-29
          Component|bootstrap                   |tree-optimization
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org
     Ever confirmed|0                           |1
            Summary|bootstrap comparison        |[4.9 Regression] bootstrap
                   |failure with -O3 for a week |comparison failure with -O3
                   |                            |for a week
   Target Milestone|---                         |4.9.0

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
I can reproduce it with

> CFLAGS="-O3" CXXFLAGS="-O3" /space/rguenther/src/svn/trunk/configure --enable-languages=c,c++ --enable-checking=release --disable-werror
> make -j6 CFLAGS="-O3" CXXFLAGS="-O3" BOOT_CFLAGS="-O3"
...
Comparing stages 2 and 3
warning: gcc/cc1plus-checksum.o differs
warning: gcc/cc1-checksum.o differs
Bootstrap comparison failure!
gcc/bitmap.o differs
gcc/emit-rtl.o differs
libiberty/pic/md5.o differs
libiberty/md5.o differs
make[2]: *** [compare] Error 1

on current trunk (r207234).  Note that only setting BOOT_CFLAGS isn't enough
to trigger it.  I will investigate tomorrow (let's hope adding -g and
--without-build-config --disable-multilib will still reproduce it).