[llvm] AMDGPU: Update live intervals in convertToThreeAddress (PR #104610)

[Carl Ritson via llvm-commits]

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@@ -3934,18 +3934,38 @@ MachineInstr *SIInstrInfo::convertToThreeAddress(MachineInstr &MI,
       (ST.getConstantBusLimit(Opc) > 1 || !Src0->isReg() ||
        !RI.isSGPRReg(MBB.getParent()->getRegInfo(), Src0->getReg()))) {
     MachineInstr *DefMI;
-    const auto killDef = [&]() -> void {
-      const MachineRegisterInfo &MRI = MBB.getParent()->getRegInfo();
+    const auto killDef = [&](SlotIndex OldUseIdx) -> void {
+      MachineRegisterInfo &MRI = MBB.getParent()->getRegInfo();
       // The only user is the instruction which will be killed.
       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 (MRI.hasOneNonDBGUse(DefReg)) {
+        // We cannot just remove the DefMI here, calling pass will crash.
+        DefMI->setDesc(get(AMDGPU::IMPLICIT_DEF));
+        DefMI->getOperand(0).setIsDead(true);
+        for (unsigned I = DefMI->getNumOperands() - 1; I != 0; --I)
+          DefMI->removeOperand(I);
+        if (LV)
+          LV->getVarInfo(DefReg).AliveBlocks.clear();
+      }
+
+      if (LIS) {
+        LiveInterval &DefLI = LIS->getInterval(DefReg);
+
+        // We cannot delete the original instruction here, so hack out the use
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perlfu wrote:

Can you add a test that demonstrates this?

https://github.com/llvm/llvm-project/pull/104610