https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97503
--- Comment #3 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:5244b4af5e47bc98a2a9cf36f048981583a1b163 commit r11-4183-g5244b4af5e47bc98a2a9cf36f048981583a1b163 Author: Jakub Jelinek <ja...@redhat.com> Date: Wed Oct 21 10:51:33 2020 +0200 phiopt: Optimize x ? __builtin_clz (x) : 32 in GIMPLE [PR97503] While we have at the RTL level noce_try_ifelse_collapse combined with simplify_cond_clz_ctz, that optimization doesn't always trigger because e.g. on powerpc there is an define_insn to compare a reg against zero and copy that register to another one and so we end up with a different pseudo in the simplify_cond_clz_ctz test and punt. For targets that define C?Z_DEFINED_VALUE_AT_ZERO to 2 for certain modes, we can optimize it already in phiopt though, just need to ensure that we transform the __builtin_c?z* calls into .C?Z ifns because my recent VRP changes codified that the builtin calls are always undefined at zero, while ifns honor C?Z_DEFINED_VALUE_AT_ZERO equal to 2. And, in phiopt we already have popcount handling that does pretty much the same thing, except for always using a zero value rather than the one set by C?Z_DEFINED_VALUE_AT_ZERO. So, this patch extends that function to handle not just popcount, but also clz and ctz. 2020-10-21 Jakub Jelinek <ja...@redhat.com> PR tree-optimization/97503 * tree-ssa-phiopt.c: Include internal-fn.h. (cond_removal_in_popcount_pattern): Rename to ... (cond_removal_in_popcount_clz_ctz_pattern): ... this. Handle not just popcount, but also clz and ctz if it has C?Z_DEFINED_VALUE_AT_ZERO 2. * gcc.dg/tree-ssa/pr97503.c: New test.
