[LoopUnrollAnalyzer] Take into account cost of instructions controlling branches, along with their operands.

Previously, we didn't add their and their operands cost, which could've
resulted in unrolling loops for no actual benefit.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@269985 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed