https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97979
--- Comment #4 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:39f5e9aded23e8b7e0e7080fc6020478b9c5b7b5 commit r11-5433-g39f5e9aded23e8b7e0e7080fc6020478b9c5b7b5 Author: Jakub Jelinek <ja...@redhat.com> Date: Thu Nov 26 10:50:23 2020 +0100 match.pd: Avoid ICE with shifts [PR97979] My recent wide_int_binop changes caused ICE on this testcase. The problem is that for shift where amount has MSB set now fails to optimize into a constant (IMHO we should treat out of bounds shifts the same later), but there is a precedent for that already - e.g. division by zero fails to optimize into a constant too. I think it is better if path isolation checks for these UBs and does something the user chooses (__builtin_trap vs. __builtin_unreachable, and either a deferred warning about the UB or nothing). This patch just doesn't optimize if int_const_binop failed. 2020-11-26 Jakub Jelinek <ja...@redhat.com> PR tree-optimization/97979 * match.pd ((X {&,^,|} C2) << C1 into (X << C1) {&,^,|} (C2 << C1)): Only optimize if int_const_binop returned non-NULL. * gcc.dg/pr97979.c: New test. * gcc.c-torture/compile/pr97979.c: New test.
