[llvm] [X86][NFC] Reorder the registers to reduce unnecessary iterations (PR #70222)

[Shengchen Kan via llvm-commits]

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@@ -406,11 +406,11 @@ bool LiveVariables::HandlePhysRegKill(Register Reg, MachineInstr *MI) {
   return true;
 }
 
-void LiveVariables::HandleRegMask(const MachineOperand &MO) {
+void LiveVariables::HandleRegMask(const MachineOperand &MO, unsigned NumRegs) {
   // Call HandlePhysRegKill() for all live registers clobbered by Mask.
   // Clobbered registers are always dead, sp there is no need to use
   // HandlePhysRegDef().
-  for (unsigned Reg = 1, NumRegs = TRI->getNumRegs(); Reg != NumRegs; ++Reg) {
+  for (unsigned Reg = 1; Reg != NumRegs; ++Reg) {
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KanRobert wrote:

I see. But currently LiveVariables brings about 0.3% instruction count regression when I introduce new registers in #67702. If the regression is intolerable, then it will block my APX enabling work. I have to resolve it to before the migration is complete.

https://github.com/llvm/llvm-project/pull/70222