https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102207
--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:8a4602c2e0f81895415ba7ee23bf81dc795d1103 commit r12-3365-g8a4602c2e0f81895415ba7ee23bf81dc795d1103 Author: Jakub Jelinek <ja...@redhat.com> Date: Mon Sep 6 10:08:16 2021 +0200 match.pd: Fix up __builtin_*_overflow arg demotion [PR102207] My earlier patch to demote arguments of __builtin_*_overflow unfortunately caused a wrong-code regression. The builtins operate on infinite precision arguments, outer_prec > inner_prec signed -> signed, unsigned -> unsigned promotions there are just repeating the sign or 0s and can be demoted, similarly unsigned -> signed which also is repeating 0s, but as the testcase shows, signed -> unsigned promotions need to be preserved (unless we'd know the inner arguments can't be negative), because for negative numbers such promotion sets the outer_prec -> inner_prec bits to 1 bit the bits above that to 0 in the infinite precision. So, the following patch avoids the demotions for the signed -> unsigned promotions. 2021-09-06 Jakub Jelinek <ja...@redhat.com> PR tree-optimization/102207 * match.pd: Don't demote operands of IFN_{ADD,SUB,MUL}_OVERFLOW if they were promoted from signed to wider unsigned type. * gcc.dg/pr102207.c: New test.
