[Bug bootstrap/53728] New: [4.6 regression] Bootstrap comparison failure (gcc/varasm.o differs) with CFLAGS="-O2 -march=pentium3"

[xarthisius.kk at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53728

             Bug #: 53728
           Summary: [4.6 regression] Bootstrap comparison failure
                    (gcc/varasm.o differs) with CFLAGS="-O2
                    -march=pentium3"
    Classification: Unclassified
           Product: gcc
           Version: 4.6.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: bootstrap
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: xarthisius.kk@gmail.com


Following steps are needed to reproduce:

./configure --host=i686-pc-linux-gnu --build=i686-pc-linux-gnu
--disable-altivec --disable-fixed-point --with-ppl --with-cloog
--disable-ppl-version-check --with-cloog-include=/usr/include/cloog-ppl
--enable-lto --enable-nls --without-included-gettext --with-system-zlib
--enable-obsolete --disable-werror --enable-secureplt --disable-multilib
--enable-libmudflap --disable-libssp --enable-libgomp --enable-checking=release
--disable-libgcj --with-arch=i686 --enable-languages=c,c++ --enable-shared
--enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu
--enable-targets=all
make -j24 'LDFLAGS=-Wl,-O1 -Wl,--as-needed' STAGE1_CFLAGS= 'BOOT_CFLAGS= -O2
-march=pentium3 -pipe' bootstrap-lean

Results in:
...
Comparing stages 2 and 3
warning: gcc/cc1plus-checksum.o differs
warning: gcc/cc1-checksum.o differs
Bootstrap comparison failure!
gcc/varasm.o differs

Regression was introduced with:

Turn on -fomit-frame-pointer by default for 32bit Linux/x86.

2010-08-12  H.J. Lu  <hongjiu.lu@intel.com>

   Uros Bizjak  <ubizjak@gmail.com>

    * config.gcc: Handle --enable-frame-pointer.
    * configure.ac: Add --enable-frame-pointer.
    * configure: Regenerated.
    * config/i386/i386.c (USE_IX86_FRAME_POINTER): Default to 0.
    (override_options): If not configured with --enable-frame-pointer,
    enable -fomit-frame-pointer (but not for TARGET_MACHO or when
    optimizing for size), -fasynchronous-unwind-tables and
    -maccumulate-outgoing-args by default.

http://gcc.gnu.org/viewcvs?view=revision&revision=163196

and seems to be gone with:

http://gcc.gnu.org/viewcvs?view=revision&revision=171649