[all-commits] [llvm/llvm-project] 61a06c: BPF: add a test for selectiondag alias analysis w....

[yonghong-song via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 61a06c071dd16a9725d3b7bfac806520dc1b95aa
      https://github.com/llvm/llvm-project/commit/61a06c071dd16a9725d3b7bfac806520dc1b95aa
  Author: Yonghong Song <yhs at fb.com>
  Date:   2020-12-02 (Wed, 02 Dec 2020)

  Changed paths:
    A llvm/test/CodeGen/BPF/selectiondag-bug.ll

  Log Message:
  -----------
  BPF: add a test for selectiondag alias analysis w.r.t. lifetime

This adds a test for the bug
  https://bugs.llvm.org/show_bug.cgi?id=47591

Previously, selection dag has a bug which may incorrectly
assume no alias when crossing a lifetime boundary and this
may generate incorrect code as demonstrated in the above bug.

It looks the bug is fixed by https://reviews.llvm.org/D91833.
Basically, when comparing two potential memory access dag nodes,
  a store and a lifetime.start,
with the same frame index.
Previously, it may be decided no alias. With the above fix,
these two will be considered aliasing which will prevent
incorrect code scheduling.

Differential Revision: https://reviews.llvm.org/D92451