https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78856
Bug ID: 78856 Summary: wrong code at -O3 on x86_64-linux-gnu (in both 32-bit and 64-bit modes) 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: --- It affects 6.x and later, and is a regression from 5.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/7.0.0/lto-wrapper Target: x86_64-pc-linux-gnu Configured with: ../gcc-source-trunk/configure --enable-languages=c,c++,lto --prefix=/usr/local/gcc-trunk --disable-bootstrap Thread model: posix gcc version 7.0.0 20161218 (experimental) [trunk revision 243783] (GCC) $ $ gcc-trunk -O2 small.c; ./a.out $ gcc-5.4 -O3 small.c; ./a.out $ $ gcc-trunk -O3 small.c $ timeout -s 9 5 ./a.out Killed $ -------------------------------------------- int a, b, c, d, e, f[3]; int main() { while (d) while (1) ; int g = 0, h, i = 0; for (; g < 21; g += 9) { int j = 1; for (h = 0; h < 3; h++) f[h] = 1; for (; j < 10; j++) { d = i && (b ? 0 : c); i = 1; if (g) a = e; } } return 0; }