CodeGen: BranchFolding: Merge identical blocks, even if they are short.

Merging identical blocks when it doesn't reduce fallthrough. It is common for
the blocks created from critical edge splitting to be identical. We would like
to merge these blocks whenever doing so would not reduce fallthrough.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@299890 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed