https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68185
Bug ID: 68185 Summary: wrong code at -O3 on x86_64-linux-gnu (in 64-bit mode) Product: gcc Version: 6.0 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: --- The current gcc trunk miscompiles the following code on x86_64-linux-gnu at -O3 in the 64-bit mode (but not in the 32-bit mode). This is a regression from 5.2.x. $ gcc-trunk -v Using built-in specs. COLLECT_GCC=gcc-trunk COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-pc-linux-gnu/6.0.0/lto-wrapper Target: x86_64-pc-linux-gnu Configured with: ../gcc-trunk/configure --prefix=/usr/local/gcc-trunk --enable-languages=c,c++ --disable-werror --enable-multilib Thread model: posix gcc version 6.0.0 20151101 (experimental) [trunk revision 229639] (GCC) $ $ gcc-trunk -m64 -O2 small.c; ./a.out $ gcc-trunk -m32 -O3 small.c; ./a.out $ gcc-5.2 -m64 -O3 small.c; ./a.out $ $ gcc-trunk -m64 -O3 small.c $ ./a.out Aborted (core dumped) $ --------------------------------------- int a, b, d = 1, e, f, o, u, w = 1, z; short c, q, t; int main () { char g; for (; d; d--) { while (o) for (; e;) { c = b; int h = o = z; for (; u;) for (; a;) ; } if (t < 1) g = w; f = g; g && (q = 1); } if (q != 1) __builtin_abort (); return 0; }