https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105338
Bug ID: 105338 Summary: Regression: jump or cmove generated for pattern (x ? CST : 0) Product: gcc Version: 12.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: rtl-optimization Assignee: unassigned at gcc dot gnu.org Reporter: denis.campredon at gmail dot com Target Milestone: --- int f(int i) { return i ? 5 : 0; } int g(int i) { return i ? -2 : 0; } int h(int b) { return !!b * -2; } int i(int b) { return !!b * 5; } int j(int b) { if (!b) return 0; return -2; } ------------- With -02 gcc 11.2 the five functions above output branchless code like: f(int): neg edi sbb eax, eax and eax, 5 ret g(int): neg edi sbb eax, eax and eax, -2 ret ... -------------- Whereas -02 gcc 12 now outputs a cmov or jump depending of sign of the constant: f(int): mov eax, edi test edi, edi mov edx, 5 cmovne eax, edx ret g(int): mov eax, edi test edi, edi jne .L11 ret .L11: mov eax, -2 ret h(int): mov eax, edi test edi, edi jne .L17 ret .L17: mov eax, -2 ret i(int): mov eax, edi test edi, edi mov edx, 5 cmovne eax, edx ret j(int): mov eax, edi test edi, edi mov edx, -2 cmovne eax, edx ret --------------------------- Alternatively, with the following code int k(int b) { bool b2 = b; return b2 * 5; } ---------------- Both gcc 12 and 11.2 are outputing k(int): xor eax, eax test edi, edi setne al lea eax, [rax+rax*4] ret