[InstCombine] move/add tests for fmul reassociation; NFC

This transform may be out-of-scope for instcombine, 
but this is only documenting the current behavior.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@326442 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed