https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82574
Bug ID: 82574 Summary: wrong code at -O3 on x86_64-linux-gnu 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 Target Milestone: --- This seems to be a recent regression. $ gcctk -v Using built-in specs. COLLECT_GCC=gcctk COLLECT_LTO_WRAPPER=/home/su/software/tmp/gcc/gcc-trunk/libexec/gcc/x86_64-pc-linux-gnu/8.0.0/lto-wrapper Target: x86_64-pc-linux-gnu Configured with: ../gcc-source-trunk/configure --enable-languages=c,c++,lto --prefix=/home/su/software/tmp/gcc/gcc-trunk --disable-bootstrap Thread model: posix gcc version 8.0.0 20171016 (experimental) [trunk revision 253793] (GCC) $ $ gcctk -O2 small.c; ./a.out; echo $? 0 $ gcc-7.2.0 -O3 small.c; ./a.out; echo $? 0 $ $ gcctk -O3 small.c; ./a.out; echo $? 1 $ ------------------------------- char a, b, c, d[2][3]; int main () { for (; a < 2; a++) for (b = 0; b < 3; b++) if (c) d[a][b] = 1; return d[0][0]; }