Fix assertions in updateRegMaskSlots().

The RegMaskSlots contains 'r' slots while NewIdx and OldIdx are 'B'
slots. This broke the checks in the assertions.

This fixes PR14302.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167625 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed