https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116999
--- Comment #2 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The trunk branch has been updated by Richard Sandiford <rsand...@gcc.gnu.org>: https://gcc.gnu.org/g:50e7c51b0a0e9dc1d93f829016ae743b4f2e5070 commit r15-4316-g50e7c51b0a0e9dc1d93f829016ae743b4f2e5070 Author: Richard Sandiford <richard.sandif...@arm.com> Date: Mon Oct 14 09:52:44 2024 +0100 aarch64: Fix folding of degenerate svwhilele case [PR117045] The svwhilele folder mishandled the degenerate case in which the second argument is the maximum integer. In that case, the result is all-true regardless of the first parameter: If the second scalar operand is equal to the maximum signed integer value then a condition which includes an equality test can never fail and the result will be an all-true predicate. This is because the conceptual "increment the first operand by 1 after each element" is done modulo the range of the operand. The GCC code was instead treating it as infinite precision. whilele_5.c even had a test for the incorrect behaviour. The easiest fix seemed to be to handle that case specially before doing constant folding. This also copes with variable first operands. gcc/ PR target/116999 PR target/117045 * config/aarch64/aarch64-sve-builtins-base.cc (svwhilelx_impl::fold): Check for WHILELTs of the minimum value and WHILELEs of the maximum value. Fold them to all-false and all-true respectively. gcc/testsuite/ PR target/116999 PR target/117045 * gcc.target/aarch64/sve/acle/general/whilele_5.c: Fix bogus expected result. * gcc.target/aarch64/sve/acle/general/whilele_11.c: New test. * gcc.target/aarch64/sve/acle/general/whilele_12.c: Likewise.
