https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114277
--- Comment #13 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jeff Law <l...@gcc.gnu.org>: https://gcc.gnu.org/g:2c0a9b7fb7902522fb8484342fcc19fd44df53e6 commit r15-7313-g2c0a9b7fb7902522fb8484342fcc19fd44df53e6 Author: Jeff Law <j...@ventanamicro.com> Date: Fri Jan 31 16:59:35 2025 -0700 [committed][PR tree-optimization/114277] Fix missed optimization for multiplication against boolean value Andrew, Raphael and I have all poked at it in various ways over the last year or so. I think when Raphael and I first looked at it I sent us down a bit of rathole. In particular it's odd that we're using a multiply to implement a select and it seemed like recognizing the idiom and rewriting into a conditional move was the right path. That looked reasonably good for the test, but runs into problems with min/max detection elsewhere. I think that initial investigation somewhat polluted our thinking. The regression can be fixed with a fairly simple match.pd pattern. Essentially we want to handle x * (x || b) -> x x * !(x || b) -> 0 There's simplifications that can be made for "&&" cases, but I haven't seen them in practice. Rather than drop in untested patterns, I'm leaving that as a future todo. My original was two match.pd patterns. Andrew combined them into a single pattern. I've made this conditional on GIMPLE as an earlier version that simplified to a conditional move showed that when applied on GENERIC we could drop an operand with a side effect which is clearly not good. I've bootstrapped and regression tested this on x86. I've also tested on the various embedded targets in my tester. PR tree-optimization/114277 gcc/ * match.pd (a * (a || b) -> a): New pattern. (a * !(a || b) -> 0): Likewise. gcc/testsuite * gcc.target/i386/pr114277.c: New test. * gcc.target/riscv/pr114277.c: Likewise. Co-author: Andrew Pinski <quic_apin...@quicinc.com>
