This commit contains a refactoring that merges AVRRelaxMemOperations
into AVRExpandPseudoInsts, so that we have a single place in code that
expands the STDWPtrQRr opcode.
Seizing the day, I've also fixed a couple of potential bugs with our
previous implementation (e.g. when the destination register was killed,
the previous implementation would try to .addDef() that killed
register, crashing LLVM in the process - that's fixed now, as proved by
the test).
Reviewed By: benshi001
Differential Revision: https://reviews.llvm.org/D122533
d16a631c12