https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118572
--- Comment #10 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Alexandre Oliva <aol...@gcc.gnu.org>: https://gcc.gnu.org/g:91fa9c15cc4fb9947e7e2f7990f7d5a58845d5cf commit r15-7173-g91fa9c15cc4fb9947e7e2f7990f7d5a58845d5cf Author: Alexandre Oliva <ol...@adacore.com> Date: Thu Jan 23 23:23:16 2025 -0300 [ifcombine] check for more zero-extension cases [PR118572] When comparing a signed narrow variable with a wider constant that has the bit corresponding to the variable's sign bit set, we would check that the constant is a sign-extension from that sign bit, and conclude that the compare fails if it isn't. When the signed variable is masked without getting the [lr]l_signbit variable set, or when the sign bit itself is masked out, we know the sign-extension bits from the extended variable are going to be zero, so the constant will only compare equal if it is a zero- rather than sign-extension from the narrow variable's precision, therefore, check that it satisfies this property, and yield a false compare result otherwise. for gcc/ChangeLog PR tree-optimization/118572 * gimple-fold.cc (fold_truth_andor_for_ifcombine): Compare as unsigned the variables whose extension bits are masked out. for gcc/testsuite/ChangeLog PR tree-optimization/118572 * gcc.dg/field-merge-24.c: New.
