[AVR] Fix and clean up the inline assembly tests

There was a bug where we would hit an assertion if 'Q' was used as a
constraint.

I also removed hardcoded register names to prefer regexes so the tests
don't break when the register allocator changes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@289325 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/AVR/AVRISelDAGToDAG.cpp

@@ -205,7 +205,9 @@ bool AVRDAGToDAGISel::SelectInlineAsmMemoryOperand(const SDValue &Op,
                                                    std::vector<SDValue> &OutOps) {
   // Yes hardcoded 'm' symbol. Just because it also has been hardcoded in
   // SelectionDAGISel (callee for this method).
-  assert(ConstraintCode == InlineAsm::Constraint_m && "Unexpected asm memory constraint");
+  assert(ConstraintCode == InlineAsm::Constraint_m ||
+         ConstraintCode == InlineAsm::Constraint_Q &&
+      "Unexpected asm memory constraint");
 
   MachineRegisterInfo &RI = MF->getRegInfo();
   const AVRSubtarget &STI = MF->getSubtarget<AVRSubtarget>();