https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95527
--- Comment #5 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:75f8900159133ce069ef1d2edf3b67c7bc82e305 commit r12-151-g75f8900159133ce069ef1d2edf3b67c7bc82e305 Author: Jakub Jelinek <ja...@redhat.com> Date: Tue Apr 27 14:47:54 2021 +0200 match.pd: Add some __builtin_ctz (x) cmp cst simplifications [PR95527] This patch adds some ctz simplifications (e.g. ctz (x) >= 3 can be done by testing if the low 3 bits are zero, etc.). In addition, I've noticed that in the CLZ case, the #ifdef CLZ_DEFINED_VALUE_AT_ZERO don't really work as intended, they are evaluated during genmatch and the macro is not defined then (but, because of the missing tm.h includes it isn't defined in gimple-match.c or generic-match.c either). And when tm.h is included, defaults.h is included which defines a fallback version of that macro. For GCC 12, I wonder if it wouldn't be better to say in addition to __builtin_c[lt]z* is always UB at zero that it would be undefined for .C[LT]Z ifn too if it has just one operand and use a second operand to be the constant we expect at zero. 2021-04-27 Jakub Jelinek <ja...@redhat.com> PR tree-optimization/95527 * generic-match-head.c: Include tm.h. * gimple-match-head.c: Include tm.h. * match.pd (CLZ == INTEGER_CST): Don't use #ifdef CLZ_DEFINED_VALUE_AT_ZERO, only test CLZ_DEFINED_VALUE_AT_ZERO if clz == CFN_CLZ. Add missing val declaration. (CTZ cmp CST): New simplifications. * gcc.dg/tree-ssa/pr95527-2.c: New test.
