Handle regmasks in findRegisterDefOperandIdx().

Only accept register masks when looking for an 'overlapping' def. When
Overlap is not set, the function searches for a proper definition of
Reg.

This means MI->modifiesRegister() considers register masks, but
MI->definesRegister() doesn't.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@150529 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed