https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115877
--- Comment #9 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:91e468b72dafc9dcd5dcf7915f1d0ef172264d53 commit r15-2185-g91e468b72dafc9dcd5dcf7915f1d0ef172264d53 Author: Jeff Law <j...@ventanamicro.com> Date: Sun Jul 21 07:36:37 2024 -0600 [PR rtl-optimization/115877] Fix livein computation for ext-dce So I'm not yet sure how I'm going to break everything down, but this is easy enough to break out as 1/N of ext-dce fixes/improvements. When handling uses in an insn, we first determine what bits are set in the destination which is represented in DST_MASK. Then we use that to refine what bits are live in the source operands. In the source operand handling section we *modify* DST_MASK if the source operand is a SUBREG (ugh!). So if the first operand is a SUBREG, then we can incorrectly compute which bit groups are live in the second operand, especially if it is a SUBREG as well. This was seen when testing a larger set of patches on the rl78 port (builtin-arith-overflow-p-7 & pr71631 execution failures), so no new test for this bugfix. Run through my tester (in conjunction with other ext-dce changes) on the various cross targets. Run individually through a bootstrap and regression test cycle on x86_64 as well. Pushing to the trunk. PR rtl-optimization/115877 gcc/ * ext-dce.cc (ext_dce_process_uses): Restore the value of DST_MASK for reach operand.
