[llvm] [AMDGPU] Update live interval in `convertToThreeAddress` (PR #98781)

[via llvm-commits]

https://github.com/paperchalice updated https://github.com/llvm/llvm-project/pull/98781

>From 728aafcd5c4ee599e73a3245c218410cd0049440 Mon Sep 17 00:00:00 2001
From: PaperChalice <liujunchang97 at outlook.com>
Date: Sun, 14 Jul 2024 08:47:03 +0800
Subject: [PATCH] [AMDGPU] Update live interval in `convertToThreeAddress`

---
 llvm/lib/CodeGen/TwoAddressInstructionPass.cpp | 2 +-
 llvm/lib/Target/AMDGPU/SIInstrInfo.cpp         | 7 +++----
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp b/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
index 73385fee019b0..711ef71e975d9 100644
--- a/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
+++ b/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
@@ -713,7 +713,6 @@ bool TwoAddressInstructionPass::isProfitableToConv3Addr(Register RegA,
 bool TwoAddressInstructionPass::convertInstTo3Addr(
     MachineBasicBlock::iterator &mi, MachineBasicBlock::iterator &nmi,
     Register RegA, Register RegB, unsigned &Dist) {
-  MachineInstrSpan MIS(mi, MBB);
   MachineInstr *NewMI = TII->convertToThreeAddress(*mi, LV, LIS);
   if (!NewMI)
     return false;
@@ -736,6 +735,7 @@ bool TwoAddressInstructionPass::convertInstTo3Addr(
                                    std::make_pair(NewInstrNum, NewIdx));
   }
 
+  MachineInstrSpan MIS(mi, MBB);
   MBB->erase(mi); // Nuke the old inst.
 
   for (MachineInstr &MI : MIS)
diff --git a/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp b/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
index cc1b9ac0c9ecd..2d8b79714e074 100644
--- a/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
@@ -3952,12 +3952,11 @@ MachineInstr *SIInstrInfo::convertToThreeAddress(MachineInstr &MI,
       Register DefReg = DefMI->getOperand(0).getReg();
       if (!MRI.hasOneNonDBGUse(DefReg))
         return;
-      // We cannot just remove the DefMI here, calling pass will crash.
-      DefMI->setDesc(get(AMDGPU::IMPLICIT_DEF));
-      for (unsigned I = DefMI->getNumOperands() - 1; I != 0; --I)
-        DefMI->removeOperand(I);
       if (LV)
         LV->getVarInfo(DefReg).AliveBlocks.clear();
+      if (LIS)
+        LIS->removeInterval(DefReg);
+      DefMI->eraseFromParent();
     };
 
     int64_t Imm;