[X86] Fix a bug in getMemOpBaseRegImmOfs

Fix a crash in `getMemOpBaseRegImmOfs` that happens if the base of
`MemOp` is a frame index memory operand.  The fix is to have
`getMemOpBaseRegImmOfs` bail out in such cases.  We can possibly be more
clever here, if needed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@259456 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed