https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104639
--- Comment #14 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:a42aa68bf1ad745a6b36ab9beed1fc2e77ac3f88 commit r12-8078-ga42aa68bf1ad745a6b36ab9beed1fc2e77ac3f88 Author: Jakub Jelinek <ja...@redhat.com> Date: Mon Apr 11 10:44:28 2022 +0200 phiopt: Optimize (x != cst1 ? x : cst2) != cst3 [PR104639] Here is an attempt to resolve a P1 regression, where due to threading changes we no longer optimize bool foo(int i) { while (i == 4) i += 2; return i; } to just return i != 0; by enhancing the phiopt value_replacement optimization. Normally it will optimize x != cst1 ? x : cst1 to x. Here we extend it to also optimize x != cst1 ? x : cst2 to x if it (phi result) has a single immediate use which is a comparison with some INTEGER_CST cst3 and we can prove that we don't care whether x is cst1 or cst2 because both compare the same against cst3. 2022-04-11 Jakub Jelinek <ja...@redhat.com> PR tree-optimization/104639 * tree-ssa-phiopt.cc: Include tree-ssa-propagate.h. (value_replacement): Optimize (x != cst1 ? x : cst2) != cst3 into x != cst3. * gcc.dg/tree-ssa/pr104639-1.c: New test. * gcc.dg/tree-ssa/pr104639-2.c: New test.
