[all-commits] [llvm/llvm-project] 9969c3: [DSE, MemorySSA] Handle atomic stores explicitly in...

[Florian Hahn via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 9969c317ff0877ed6155043422c70e1d4c028a35
      https://github.com/llvm/llvm-project/commit/9969c317ff0877ed6155043422c70e1d4c028a35
  Author: Florian Hahn <flo at fhahn.com>
  Date:   2020-09-09 (Wed, 09 Sep 2020)

  Changed paths:
    M llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
    M llvm/test/Transforms/DeadStoreElimination/MSSA/atomic-todo.ll
    M llvm/test/Transforms/DeadStoreElimination/MSSA/atomic.ll

  Log Message:
  -----------
  [DSE,MemorySSA] Handle atomic stores explicitly in isReadClobber.

Atomic stores are modeled as MemoryDef to model the fact that they may
not be reordered, depending on the ordering constraints.

Atomic stores that are monotonic or weaker do not limit re-ordering, so
we do not have to treat them as potential read clobbers.

Note that llvm/test/Transforms/DeadStoreElimination/MSSA/atomic.ll
already contains a set of negative test cases.

Reviewed By: asbirlea

Differential Revision: https://reviews.llvm.org/D87386