https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118206
--- Comment #16 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:c96a6c2c264776d8138c6b303d005e74f047cfa0 commit r15-6773-gc96a6c2c264776d8138c6b303d005e74f047cfa0 Author: Alexandre Oliva <ol...@adacore.com> Date: Fri Jan 10 09:32:33 2025 -0300 [ifcombine] adjust for narrowing converts before shifts [PR118206] A narrowing conversion and a shift both drop bits from the loaded value, but we need to take into account which one comes first to get the right number of bits and mask. Fold when applying masks to parts, comparing the parts, and combining the results, in the odd chance either mask happens to be zero. for gcc/ChangeLog PR tree-optimization/118206 * gimple-fold.cc (decode_field_reference): Account for upper bits dropped by narrowing conversions whether before or after a right shift. (fold_truth_andor_for_ifcombine): Fold masks, compares, and combined results. for gcc/testsuite/ChangeLog PR tree-optimization/118206 * gcc.dg/field-merge-18.c: New.
