[llvm] [clang] Add SME2 builtins for zero { zt0 } (PR #72274)

[Sander de Smalen via cfe-commits]

================
@@ -2746,19 +2746,25 @@ AArch64TargetLowering::EmitFill(MachineInstr &MI, MachineBasicBlock *BB) const {
   return BB;
 }
 
-MachineBasicBlock *AArch64TargetLowering::EmitZTSpillFill(MachineInstr &MI,
-                                                          MachineBasicBlock *BB,
-                                                          bool IsSpill) const {
+MachineBasicBlock *AArch64TargetLowering::EmitZTInstr(MachineInstr &MI,
+                                                      MachineBasicBlock *BB,
+                                                      unsigned Opcode,
+                                                      bool IsZTDest) const {
   const TargetInstrInfo *TII = Subtarget->getInstrInfo();
   MachineInstrBuilder MIB;
-  if (IsSpill) {
-    MIB = BuildMI(*BB, MI, MI.getDebugLoc(), TII->get(AArch64::STR_TX));
-    MIB.addReg(MI.getOperand(0).getReg());
-  } else
-    MIB = BuildMI(*BB, MI, MI.getDebugLoc(), TII->get(AArch64::LDR_TX),
+
+  if (IsZTDest)
+    MIB = BuildMI(*BB, MI, MI.getDebugLoc(), TII->get(Opcode),
                   MI.getOperand(0).getReg());
-  MIB.add(MI.getOperand(1)); // Base
-  MI.eraseFromParent();      // The pseudo is gone now.
+  else {
+    MIB = BuildMI(*BB, MI, MI.getDebugLoc(), TII->get(Opcode));
+    MIB.addReg(MI.getOperand(0).getReg());
+  }
+
+  for (unsigned I = 1; I < MI.getNumOperands(); ++I)
+    MIB.add(MI.getOperand(I));
----------------
sdesmalen-arm wrote:

Can we write this as:
```
 MIB = BuildMI(*BB, MI, MI.getDebugLoc(), TII->getOpcode())
           .addReg(MI.getOperand(0).getReg(), IsZTDest ? RegState::Define : 0);
 for (unsigned I = 1; I < MI.getNumOperands(); ++I)
     MIB.add(MI.getOperand(I));
```

https://github.com/llvm/llvm-project/pull/72274