https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113295
--- Comment #7 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The trunk branch has been updated by Richard Sandiford <rsand...@gcc.gnu.org>: https://gcc.gnu.org/g:8a16e06da97f51574cfad17e2cece2e58571305d commit r14-9155-g8a16e06da97f51574cfad17e2cece2e58571305d Author: Richard Sandiford <richard.sandif...@arm.com> Date: Fri Feb 23 14:12:54 2024 +0000 aarch64: Add missing early-ra bookkeeping [PR113295] 416.gamess showed up two wrong-code bugs in early-ra. This patch fixes the first of them. It was difficult to reduce the source code to something that would meaningfully show the situation, so the testcase uses a direct RTL sequence instead. In the sequence: (a) register <2> is set more than once (b) register <2> is copied to a temporary (<4>) (c) register <2> is the destination of an FCSEL between <4> and another value (<5>) (d) <4> and <2> are equivalent for <4>'s live range (e) <5>'s and <2>'s live ranges do not intersect, and there is a pseudo-copy between <5> and <2> On its own, (d) implies that <4> can be treated as equivalent to <2>. And on its own, (e) implies that <5> can share <2>'s register. But <4>'s and <5>'s live ranges conflict, meaning that they cannot both share the register together. A bit of missing bookkeeping meant that the mechanism for detecting this didn't fire. We therefore ended up with an FCSEL in which both inputs were the same register. gcc/ PR target/113295 * config/aarch64/aarch64-early-ra.cc (early_ra::find_related_start): Account for definitions by shared registers when testing for a single register definition. (early_ra::accumulate_defs): New function. (early_ra::record_copy): If A shares B's register, fold A's definition information into B's. Fold A's use information into B's. gcc/testsuite/ PR target/113295 * gcc.dg/rtl/aarch64/pr113295-1.c: New test.
