https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110598
Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Last reconfirmed| |2023-07-08 Status|UNCONFIRMED |NEW Target Milestone|--- |14.0 Keywords| |wrong-code Summary|[14 Regression] wrong code |[14 Regression] wrong code |on llvm-14.0.6 |on llvm-14.0.6 due to | |memcmp being miscompiled Ever confirmed|0 |1 Component|c++ |target --- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Confirmed looks like a target issue dealing with memcmp. Take: ``` // $ cat bug.cpp #include <iterator> typedef unsigned long long u64; const unsigned MAX_SUBTARGET_WORDS = 4; [[gnu::noipa]] int notequal(const void *a, const void *b) { return __builtin_memcmp(a,b,MAX_SUBTARGET_WORDS*sizeof(u64)) != 0; } struct FeatureBitset { u64 Bits[MAX_SUBTARGET_WORDS] = {0, 0, 0, 0}; constexpr FeatureBitset() = default; constexpr FeatureBitset(std::initializer_list<unsigned> Init) { for (auto I : Init) { Bits[I] = 1; } } constexpr FeatureBitset operator&(const FeatureBitset &RHS) const { FeatureBitset Result = *this; for (unsigned I = 0, E = MAX_SUBTARGET_WORDS; I != E; ++I) { Result.Bits[I] &= RHS.Bits[I]; } return Result; } bool operator!=(const FeatureBitset &RHS) const { return notequal(Bits, RHS.Bits); } }; static constexpr const FeatureBitset TargetFeatures = { 0, 0, 0, 0, }; __attribute__((noipa)) bool is_eq_buggy (const FeatureBitset & lf, const FeatureBitset & rf) { if ((lf & TargetFeatures) != (rf & TargetFeatures)) return false; return true; } __attribute__((noipa)) void bug(void) { FeatureBitset lf, rf; lf.Bits[0] = rf.Bits[0] = 1; lf.Bits[1] = rf.Bits[1] = 1; lf.Bits[2] = rf.Bits[2] = 1; lf.Bits[3] = rf.Bits[3] = 1; bool r = is_eq_buggy (lf, rf); if (!r) __builtin_trap(); } __attribute__((noipa)) int main(void) { bug(); } ``` The above is not miscompiled but once the gnu::noipa on the notequal is removed, it is.