https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107293
Bug ID: 107293 Summary: Wrong code at -Os on x86_64-linux-gnu Product: gcc Version: 13.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: shaohua.li at inf dot ethz.ch Target Milestone: --- % gcc-tk -v Using built-in specs. COLLECT_GCC=gcc-tk COLLECT_LTO_WRAPPER=/zdata/shaoli/compilers/ccbuilder-compilers/gcc-acdb24166d13d87c374e578d2ad5d58249171930/libexec/gcc/x86_64-pc-linux-gnu/13.0.0/lto-wrapper Target: x86_64-pc-linux-gnu Configured with: ../configure --disable-multilib --disable-bootstrap --enable-languages=c,c++ --prefix=/zdata/shaoli/compilers/ccbuilder-compilers/gcc-acdb24166d13d87c374e578d2ad5d58249171930 Thread model: posix Supported LTO compression algorithms: zlib gcc version 13.0.0 20221017 (experimental) (GCC) % % gcc-tk -w -O0 a.c && ./a.out 1 % gcc-tk -w -Os a.c && ./a.out 0 % cat a.c short a; int b[1]; int c(int p) { return (p < 0) ? 0 : 10 + ((p / 100 - 16) / 4); } void f(int n) { while (1) { int m = n; while ((m ) ) m /= 2; break; } } void g() { int h = a = 0; for (; h + a <= 0; a++) { if (b[c(a - 6)]) break; f(a); } } int main() { g(); __builtin_printf("%d\n", a); } % Compiler explorer: https://godbolt.org/z/e7sssT7cq