[all-commits] [llvm/llvm-project] 1f5e9a: [MCP] Do not try forward non-existent sub-register...

[Sergei Barannikov via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 1f5e9a3502119f93cfc3a7cf67f43300f759997e
      https://github.com/llvm/llvm-project/commit/1f5e9a3502119f93cfc3a7cf67f43300f759997e
  Author: Sergei Barannikov <barannikov88 at gmail.com>
  Date:   2023-03-30 (Thu, 30 Mar 2023)

  Changed paths:
    M llvm/lib/CodeGen/MachineCopyPropagation.cpp
    A llvm/test/CodeGen/ARM/pr60908.mir

  Log Message:
  -----------
  [MCP] Do not try forward non-existent sub-register of a copy

In this example:
```
$d14 = COPY killed $d18
$s0 = MI $s28
```

$s28 is a sub-register of $d14. However, $d18 does not have
sub-registers and thus cannot be forwarded. Previously, this resulted
in $noreg being substituted in place of the use of $s28, which later
led to an assertion failure.

Fixes https://github.com/llvm/llvm-project/issues/60908, a regression
that was introduced in D141747.

Reviewed By: arsenm

Differential Revision: https://reviews.llvm.org/D146930