Revert "[CodeGen] Don't include aliases in RegisterClassInfo::IgnoreCSRForAllocOrder (#80015)"

This reverts commit f852503.

It was supposed to speed things up but llvm-compile-time-tracker.com
showed a slight slow down.

Author: jayfoad

llvm/lib/CodeGen/RegisterClassInfo.cpp

@@ -93,9 +93,11 @@ void RegisterClassInfo::runOnMachineFunction(const MachineFunction &mf) {
   // Even if CSR list is same, we could have had a different allocation order
   // if ignoreCSRForAllocationOrder is evaluated differently.
   BitVector CSRHintsForAllocOrder(TRI->getNumRegs());
-  for (MCPhysReg I = 1, E = TRI->getNumRegs(); I != E; ++I)
-    CSRHintsForAllocOrder[I] = STI.ignoreCSRForAllocationOrder(mf, I);
-  if (IgnoreCSRForAllocOrder != CSRHintsForAllocOrder) {
+  for (const MCPhysReg *I = CSR; *I; ++I)
+    for (MCRegAliasIterator AI(*I, TRI, true); AI.isValid(); ++AI)
+      CSRHintsForAllocOrder[*AI] = STI.ignoreCSRForAllocationOrder(mf, *AI);
+  if (IgnoreCSRForAllocOrder.size() != CSRHintsForAllocOrder.size() ||
+      IgnoreCSRForAllocOrder != CSRHintsForAllocOrder) {
     Update = true;
     IgnoreCSRForAllocOrder = CSRHintsForAllocOrder;
   }