[all-commits] [llvm/llvm-project] 1a114f: RegAlloc: Use new approach to handling failed allo...

[Matt Arsenault via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 1a114fa302b48fc761a58a8d3be5962d92fa581b
      https://github.com/llvm/llvm-project/commit/1a114fa302b48fc761a58a8d3be5962d92fa581b
  Author: Matt Arsenault <Matthew.Arsenault at amd.com>
  Date:   2025-02-26 (Wed, 26 Feb 2025)

  Changed paths:
    M llvm/lib/CodeGen/RegAllocBase.cpp
    M llvm/lib/CodeGen/RegAllocBase.h
    M llvm/lib/CodeGen/RegAllocBasic.cpp
    M llvm/lib/CodeGen/RegAllocGreedy.cpp
    M llvm/lib/CodeGen/VirtRegMap.cpp
    A llvm/test/CodeGen/AMDGPU/agpr-copy-no-free-registers-assertion-after-ra-failure.ll
    R llvm/test/CodeGen/AMDGPU/agpr-copy-no-free-registers-assertion-after-ra-failure.xfail.ll
    M llvm/test/CodeGen/AMDGPU/illegal-eviction-assert.mir
    M llvm/test/CodeGen/AMDGPU/inflated-reg-class-snippet-copy-use-after-free.mir
    M llvm/test/CodeGen/AMDGPU/issue48473.mir
    M llvm/test/CodeGen/AMDGPU/register-killed-error-after-alloc-failure0.mir

  Log Message:
  -----------
  RegAlloc: Use new approach to handling failed allocations (#128469)

This fixes an assert after allocation failure.

Rather than collecting failed virtual registers and hacking
on the uses after the fact, directly hack on the uses and rewrite
the registers to the dummy assignment immediately.

Previously we were bypassing LiveRegMatrix and directly assigning
in the VirtRegMap. This resulted in inconsistencies where illegal
overlapping assignments were missing. Rather than try to hack in
some system to manage these in LiveRegMatrix (i.e. hacking around
cases with invalid iterators), avoid this by directly using the
physreg. This should also allow removal of special casing in
virtregrewriter for failed allocations.



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