[DAGCombine] Transform (fadd A, (fmul B, -2.0)) -> (fsub A, (fadd B, B)).

Differential Revision: http://reviews.llvm.org/D32596

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@302153 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed