[llvm] [RegAllocFast] Replace UsedInInstr with vector (PR #96323)

[Alexis Engelke via llvm-commits]

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@@ -1382,7 +1389,12 @@ void RegAllocFastImpl::allocateInstruction(MachineInstr &MI) {
   // - The "free def operands" step has to come last instead of first for tied
   //   operands and early-clobbers.
 
-  UsedInInstr.clear();
+  InstrGen += 2;
+  // In the event we ever get more than 2**31 instructions...
+  if (InstrGen == 0) {
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aengelke wrote:

Didn't change assembly, but added it anyway for clarity.

https://github.com/llvm/llvm-project/pull/96323