AArch64: avoid assertion on illegal types in performFDivCombine.

In the code to detect fixed-point conversions and make use of AArch64's special
instructions, we weren't prepared for weird types. The fptosi direction got
fixed recently, but not the similar sitofp code.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279852 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed