https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95527
Bug ID: 95527 Summary: Failure to optimize __builtin_ffs == 0 Product: gcc Version: 11.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: gabravier at gmail dot com Target Milestone: --- bool f(int x) { return __builtin_ffs(x) == 0; } This can be optimized to `x == 0`. This transformation is done by LLVM, but not by GCC.