https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94026
--- Comment #12 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Roger Sayle <sa...@gcc.gnu.org>: https://gcc.gnu.org/g:f3f73e86ec8613f176db3e52bbfbfbb9636cb714 commit r13-1281-gf3f73e86ec8613f176db3e52bbfbfbb9636cb714 Author: Roger Sayle <ro...@nextmovesoftware.com> Date: Mon Jun 27 07:44:49 2022 +0100 [PATCH] PR tree-optimization/94026: Simplify (X>>8)&6 != 0 as X&1536 != 0. This patch implements the missed optimization described in PR 94026, where a the shift can be eliminated from the sequence of a shift, followed by a bit-wise AND followed by an equality/inequality test. Specifically, ((X << C1) & C2) cmp C3 into (X & (C2 >> C1)) cmp (C3 >> C1) and likewise ((X >> C1) & C2) cmp C3 into (X & (C2 << C1)) cmp (C3 << C1) where cmp is == or !=, and C1, C2 and C3 are integer constants. The example in the subject line is taken from the hot function self_atari from the Go program Leela (in SPEC CPU 2017). 2022-06-27 Roger Sayle <ro...@nextmovesoftware.com> gcc/ChangeLog PR tree-optimization/94026 * match.pd (((X << C1) & C2) eq/ne C3): New simplification. (((X >> C1) & C2) eq/ne C3): Likewise. gcc/testsuite/ChangeLog PR tree-optimization/94026 * gcc.dg/pr94026.c: New test case.
