[RegAllocFast] Handle new debug values for spills

These new debug values get inserted after the place where the spill
happens, which means they won't be reached by the reverse traversal of
basic block instructions. This would crash or fail assertions if they
contained any virtual registers to be replaced. We can manually handle
the new debug values right away to resolve this.

Fixes llvm/llvm-project#59172

Reviewed By: StephenTozer

Differential Revision: https://reviews.llvm.org/D139590

llvm/lib/CodeGen/RegAllocFast.cpp

@@ -451,6 +451,9 @@ void RegAllocFast::spill(MachineBasicBlock::iterator Before, Register VirtReg,
     SpilledOperandsMap[MO->getParent()].push_back(MO);
   for (auto MISpilledOperands : SpilledOperandsMap) {
     MachineInstr &DBG = *MISpilledOperands.first;
+    // We don't have enough support for tracking operands of DBG_VALUE_LISTs.
+    if (DBG.isDebugValueList())
+      continue;
     MachineInstr *NewDV = buildDbgValueForSpill(
         *MBB, Before, *MISpilledOperands.first, FI, MISpilledOperands.second);
     assert(NewDV->getParent() == MBB && "dangling parent pointer");