[llvm] [NFC] Use references to avoid copying (PR #99863)

[Haohai Wen via llvm-commits]

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@@ -584,7 +584,7 @@ void RegAllocFastImpl::spill(MachineBasicBlock::iterator Before,
       SpilledOperandsMap;
   for (MachineOperand *MO : LRIDbgOperands)
     SpilledOperandsMap[MO->getParent()].push_back(MO);
-  for (auto MISpilledOperands : SpilledOperandsMap) {
+  for (auto &MISpilledOperands : SpilledOperandsMap) {
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HaohaiWen wrote:

Why not add const here.

https://github.com/llvm/llvm-project/pull/99863