RegisterCoalescer: Remap subregister lanemasks before exchanging operands

Rematerializing and merging into a bigger register class at the same
time, requires the subregister range lanemasks getting remapped to the
new register class.

This fixes http://llvm.org/PR26805

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@262768 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed