[all-commits] [llvm/llvm-project] 738053: [RegisterCoalescer] Pass Undefs to extendToIndices()

[Ruiling, Song via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 73805329baa0f5c463b70d16f18555365d3a020e
      https://github.com/llvm/llvm-project/commit/73805329baa0f5c463b70d16f18555365d3a020e
  Author: Ruiling Song <ruiling.song at amd.com>
  Date:   2020-09-29 (Tue, 29 Sep 2020)

  Changed paths:
    M llvm/lib/CodeGen/RegisterCoalescer.cpp
    A llvm/test/CodeGen/AMDGPU/coalescer-removepartial-extend-undef-subrange.mir

  Log Message:
  -----------
  [RegisterCoalescer] Pass Undefs to extendToIndices()

When extending the subranges, the reaching-def may be an undefs. When
extending such kind of subrange, it will try to search for the reaching
def first. If the reaching def is an undef and we did not provide 'Undefs',
The findReachingDefs() will fail with message:
"Use of $noreg does not have a corresponding definition on every path:
 LLVM ERROR: Use not jointly dominated by defs."
So we computeSubRangeUndefs() and pass the result to extendToIndices().

Reviewed By: arsenm

Differential Revision: https://reviews.llvm.org/D87744