[NewGVN] Introduce a definesNoMemory() helper and use it.

This is nice as is, but it will be used in my next patch to
fix a bug. Suggested by Daniel Berlin.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@302714 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed