http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58277
Bug ID: 58277 Summary: wrong code at -O3 (affecting 4.7, 4.8, and trunk) Product: gcc Version: unknown Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: su at cs dot ucdavis.edu The current gcc trunk (as well as gcc 4.7 and 4.8) produces wrong code for the attached testcase on x86_64-linux when compiled at -O3 in 32-bit mode. It is a regression from 4.6.x. This one has been quite nasty to reduce; the attached testcase is the simplest I was able to get. I believe it doesn't have any undefined behavior. $ 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/4.9.0/lto-wrapper Target: x86_64-unknown-linux-gnu Configured with: ../gcc-trunk/configure --enable-languages=c,c++,objc,obj-c++,fortran,lto --with-gmp=/usr/local/gcc-trunk --with-mpfr=/usr/local/gcc-trunk --with-mpc=/usr/local/gcc-trunk --with-cloog=/usr/local/gcc-trunk --prefix=/usr/local/gcc-trunk Thread model: posix gcc version 4.9.0 20130829 (experimental) [trunk revision 202067] (GCC) $ gcc-trunk -m32 -O2 small.c $ a.out 0 $ gcc-4.6 -m32 -O3 small.c $ a.out 0 $ gcc-trunk -m32 -O3 small.c $ a.out 0 Aborted (core dumped) $ gcc-4.7 -m32 -O3 small.c $ a.out 0 Aborted (core dumped) $ gcc-4.8 -m32 -O3 small.c $ a.out 0 Aborted (core dumped) $