[llvm] [RISCV] Add XSfmm pseudo instruction and vset* insertion support (PR #143068)

[Brandon Wu via llvm-commits]

================
@@ -1784,6 +1899,83 @@ void RISCVInsertVSETVLI::insertReadVL(MachineBasicBlock &MBB) {
   }
 }
 
+static void shrinkIntervalAndRemoveDeadMI(MachineOperand &MO,
+                                          LiveIntervals *LIS,
+                                          const TargetInstrInfo *TII) {
+  Register Reg = MO.getReg();
+  MO.setReg(RISCV::NoRegister);
+  MO.setIsKill(false);
+
+  if (!LIS)
+    return;
+
+  LiveInterval &LI = LIS->getInterval(Reg);
+
+  // Erase the AVL operand from the instruction.
+  SmallVector<MachineInstr *> DeadMIs;
+  LIS->shrinkToUses(&LI, &DeadMIs);
+  // TODO: Enable this once needVSETVLIPHI is supported.
+  // SmallVector<LiveInterval *> SplitLIs;
+  // LIS->splitSeparateComponents(LI, SplitLIs);
+
+  for (MachineInstr *DeadMI : DeadMIs) {
+    if (!TII->isAddImmediate(*DeadMI, Reg))
+      continue;
+    LIS->RemoveMachineInstrFromMaps(*DeadMI);
+    DeadMI->eraseFromParent();
----------------
4vtomat wrote:

I think DeadMI doesn't include MI right? like https://github.com/llvm/llvm-project/blob/main/llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp#L1472

https://github.com/llvm/llvm-project/pull/143068