MemoryDependenceAnalysis: Don't miscompile atomics
r216771 introduced a change to MemoryDependenceAnalysis that allowed it
to reason about acquire/release operations. However, this change does
not ensure that the acquire/release operations pair. Unfortunately,
this leads to miscompiles as we won't see an acquire load as properly
memory effecting. This largely reverts r216771.
This fixes PR22708.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232889 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed