https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118184
--- Comment #10 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:2b687ad95de61091105d040d6bc06cb3d44ac3d1 commit r15-6503-g2b687ad95de61091105d040d6bc06cb3d44ac3d1 Author: Richard Sandiford <richard.sandif...@arm.com> Date: Thu Jan 2 11:34:52 2025 +0000 aarch64: Detect word-level modification in early-ra [PR118184] REGMODE_NATURAL_SIZE is set to 64 bits for everything except VLA SVE modes. This means that it's possible to modify (say) the highpart of a TI pseudo or a V2DI pseudo independently of the lowpart. Modifying such highparts requires a reload if the highpart ends up in the upper 64 bits of an FPR, since RTL semantics do not allow the highpart of a single hard register to be modified independently of the lowpart. early-ra missed a check for this case, which meant that it effectively treated an assignment to (subreg:DI (reg:TI R) 0) as an assignment to the whole of R. gcc/ PR target/118184 * config/aarch64/aarch64-early-ra.cc (allocno_assignment_is_rmw): New function. (early_ra::record_insn_defs): Mark the live range information as untrustworthy if an assignment would change part of an allocno but preserve the rest. gcc/testsuite/ * gcc.dg/torture/pr118184.c: New test.
