[InstSimplify] add tests for select+fcmp; NFC

These are translated from InstCombine's test file with the same name.
We should move the transform from InstCombine to InstSimplify.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@346168 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed