Link to the Compiler Explorer: https://godbolt.org/z/a8PTr5sqM The error disappears if I use another definition of max (b > p2 ? b : p2). Reproducer: #include <stdio.h> bool var_0 = (bool)0; unsigned int var_7 = 42; char var_215; const unsigned &a(const unsigned &b, unsigned &p2) { return b < p2 ? p2 : b; } void test() { var_215 = a(var_0, var_7) ^ (var_7 - var_0) ?: 42; } int main() { test(); printf("%d\n", var_215); if (var_215 != 42) __builtin_abort(); } Error: >$ g++ -O1 small.cpp && ./a.out 42 >$ g++ -O2 small.cpp && ./a.out 0 Aborted (core dumped) gcc version 13.0.0 20220819 (81e20a6eb9e6b7eb62a09ac58811387f0343bd14)
Something more reduced: bool var_0 = (bool)0; unsigned int var_7 = 42; char var_215; int main() { unsigned b = var_0; unsigned p2 = var_7; unsigned *tp; if (b < p2) tp = &p2; else tp = &b; unsigned tt = *tp; unsigned t = tt ^ (var_7 - var_0); var_215 = t ? t : 42; if (var_215 != 42) __builtin_abort(); }
Started with r13-438-gcf2141a0c640fc9b.
The master branch has been updated by Andrew Macleod <amacleod@gcc.gnu.org>: https://gcc.gnu.org/g:de6d9e0b3d5c08896cbf047b299fc7f8d1e42be7 commit r13-2147-gde6d9e0b3d5c08896cbf047b299fc7f8d1e42be7 Author: Andrew MacLeod <amacleod@redhat.com> Date: Mon Aug 22 15:40:48 2022 -0400 Return the correct relation With an input condition of op1 > op2, and evaluating the unsigned expression: LHS = op1 - op2 range-ops was returning LHS < op1 , which is incorrect as op2 coould be zero. This patch adjusts it to return LHS <= op1. PR tree-optimization/106687 gcc/ * range-op.cc (operator_minus::lhs_op1_relation): Return VREL_LE for the VREL_GT case as well. gcc/testsuite/ * g++.dg/pr106687.C: New.
fixed.