https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85529
Bug ID: 85529 Summary: wrong code at -O2 and -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: --- It appears 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/9.0.0/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 9.0.0 20180426 (experimental) [trunk revision 259666] (GCC) $ $ gcctk -Os small.c; ./a.out 1 $ gcc-7.3.0 -O2 small.c; ./a.out 1 $ $ gcctk -O2 small.c $ ./a.out 0 $ -------------------------------------- int printf (const char *, ...); struct S { int a; }; int b, c = 1, d, e, f; static int g; volatile struct S s; char h (char i, int j) { return i < 0 ? i : i << j; } int main () { char k = -83; if (!d) goto L; k = e || f; L: for (; b < 1; b++) s.a != (k < h (k, 2) && (c = k = g)); printf ("%d\n", c); return 0; }