https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114969
Bug ID: 114969 Summary: [11/12/13/14/15 Regression] Missed optimization: (bool)((std::max((unsigned long long) 0, (unsigned long long) var_0)) | ( var_0 ? 1 : 0)) => (bool) var_0 Product: gcc Version: 15.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: 652023330028 at smail dot nju.edu.cn Target Milestone: --- Hello, we noticed that the code below can be optimized as stated in the title ((bool)((std::max((unsigned long long) 0, (unsigned long long) var_0)) | ( var_0 ? 1 : 0)) => (bool) var_0), but gcc -O3 seems to have missed it. This is a regression from GCC-4.8.1. https://godbolt.org/z/zo86Gz74r #include <algorithm> bool result; void func(unsigned long long var_0) { result = (std::max((unsigned long long) 0, (unsigned long long) var_0)) | ( var_0 ? 1 : 0); } GCC -O3: <bb 2> [local count: 1073741824]: # DEBUG BEGIN_STMT _7 = var_0_5(D) != 0; _8 = (long long unsigned int) _7; _1 = var_0_5(D) | _8; _2 = _1 != 0; result = _2; return; func(unsigned long long): xor eax, eax test rdi, rdi setne al or rax, rdi setne BYTE PTR result[rip] ret Expected code (GCC-4.7.4): <bb 2>: # DEBUG __a => &D.9143 # DEBUG __b => &D.9144 D.9181_24 = var_0_2(D) != 0; result = D.9181_24; return; func(unsigned long long): test rdi, rdi setne BYTE PTR result[rip] ret Thank you very much for your time and effort! We look forward to hearing from you.