[all-commits] [llvm/llvm-project] 0d1864: [AMDGPU] Recompute liveness in SIOptimizeExecMaski...

[Pierre van Houtryve via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 0d1864a754919deae84605aae2b5db8722ae69d4
      https://github.com/llvm/llvm-project/commit/0d1864a754919deae84605aae2b5db8722ae69d4
  Author: pvanhout <pierre.vanhoutryve at amd.com>
  Date:   2023-05-09 (Tue, 09 May 2023)

  Changed paths:
    M llvm/lib/Target/AMDGPU/SIOptimizeExecMaskingPreRA.cpp
    A llvm/test/CodeGen/AMDGPU/optimize-exec-mask-pre-ra-non-empty-but-used-interval.mir

  Log Message:
  -----------
  [AMDGPU] Recompute liveness in SIOptimizeExecMaskingPreRA

Instead of ad-hoc updating liveness, recompute it completely for the affected register.

This does not affect any existing test and fixes an edge case that
caused a "Non-empty but used interval" error in the register allocator
due to how the pass updated liveranges. It created a "isolated" live-through
segment.

Overall this change just seems to be a net positive with no side effect observed. There may be a compile time impact but it's expected to be minimal.

Fixes SWDEV-388279

Reviewed By: critson

Differential Revision: https://reviews.llvm.org/D150105