https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105197
--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Tamar Christina <tnfch...@gcc.gnu.org>: https://gcc.gnu.org/g:78c718490bc2843d4dadcef8a0ae14aed1d15a32 commit r12-8080-g78c718490bc2843d4dadcef8a0ae14aed1d15a32 Author: Tamar Christina <tamar.christ...@arm.com> Date: Mon Apr 11 15:09:05 2022 +0100 middle-end: Prevent the use of the cond inversion detection code when both conditions are external. [PR105197] Previously ifcvt used to enforce that a mask A and the inverse of said mask be represented as ~A. So for the masks _25 = _6 != 0; _44 = _4 != 0; ifcvt would produce for an operation requiring the inverse of said mask _26 = ~_25; _43 = ~_44; but now that VN is applied to the entire function body we get a simplification on the mask and produce: _26 = _6 == 0; _43 = _4 == 0; This in itself is not a problem semantically speaking (though it does create more masks that need to be tracked) but when vectorizing the masked conditional we would still detect _26 and _43 to be inverses of _25 and _44 and mark them as requiring their operands be swapped. When vectorizing we swap the operands but don't find the BIT_NOT_EXPR to remove and so we leave the condition as is which produces invalid code: ------>vectorizing statement: _ifc__41 = _43 ? 0 : _ifc__40; created new init_stmt: vect_cst__136 = { 0, ... } add new stmt: _137 = mask__43.26_135 & loop_mask_111 note: add new stmt: vect__ifc__41.27_138 = VEC_COND_EXPR <_137, vect__ifc__40.25_133, vect_cst__136>; This fixes disabling the inversion detection code when the loop isn't masked since both conditional would be external. We'd then not use the new cond_code and would incorrectly still swap the operands. The resulting code is also better than GCC-11 with most operations now predicated on the loop mask rather than a ptrue. gcc/ChangeLog: PR target/105197 * tree-vect-stmts.cc (vectorizable_condition): Prevent cond swap when not masked. gcc/testsuite/ChangeLog: PR target/105197 * gcc.target/aarch64/sve/pr105197-1.c: New test. * gcc.target/aarch64/sve/pr105197-2.c: New test.
