[llvm] [AMDGPU][Scheduler] Fix usage of `TII.reMaterialize` (NFC) (PR #150259)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-amdgpu

Author: Lucas Ramirez (lucas-rami)

<details>
<summary>Changes</summary>

Any non-zero `SubIdx` passed to the method is composed with the rematerialized instruction's first operand's subregister to determine the new register's subregister. In our case we want the new register to have the same subregister as the old one, so we should pass 0.

---
Full diff: https://github.com/llvm/llvm-project/pull/150259.diff


1 Files Affected:

- (modified) llvm/lib/Target/AMDGPU/GCNSchedStrategy.cpp (+2-6) 


``````````diff
diff --git a/llvm/lib/Target/AMDGPU/GCNSchedStrategy.cpp b/llvm/lib/Target/AMDGPU/GCNSchedStrategy.cpp
index fce8f36d45969..20e489aa39023 100644
--- a/llvm/lib/Target/AMDGPU/GCNSchedStrategy.cpp
+++ b/llvm/lib/Target/AMDGPU/GCNSchedStrategy.cpp
@@ -1910,14 +1910,12 @@ void PreRARematStage::rematerialize() {
   for (auto &[DefMI, Remat] : Rematerializations) {
     MachineBasicBlock::iterator InsertPos(Remat.UseMI);
     Register Reg = DefMI->getOperand(0).getReg();
-    unsigned SubReg = DefMI->getOperand(0).getSubReg();
     unsigned DefRegion = MIRegion.at(DefMI);
 
     // Rematerialize DefMI to its use block.
-    TII->reMaterialize(*InsertPos->getParent(), InsertPos, Reg, SubReg, *DefMI,
+    TII->reMaterialize(*InsertPos->getParent(), InsertPos, Reg, 0, *DefMI,
                        *DAG.TRI);
     Remat.RematMI = &*std::prev(InsertPos);
-    Remat.RematMI->getOperand(0).setSubReg(SubReg);
     DAG.LIS->InsertMachineInstrInMaps(*Remat.RematMI);
 
     // Update region boundaries in regions we sinked from (remove defining MI)
@@ -2063,14 +2061,12 @@ void PreRARematStage::finalizeGCNSchedStage() {
     MachineBasicBlock::iterator InsertPos(DAG.Regions[DefRegion].second);
     MachineBasicBlock *MBB = RegionBB[DefRegion];
     Register Reg = RematMI.getOperand(0).getReg();
-    unsigned SubReg = RematMI.getOperand(0).getSubReg();
 
     // Re-rematerialize MI at the end of its original region. Note that it may
     // not be rematerialized exactly in the same position as originally within
     // the region, but it should not matter much.
-    TII->reMaterialize(*MBB, InsertPos, Reg, SubReg, RematMI, *DAG.TRI);
+    TII->reMaterialize(*MBB, InsertPos, Reg, 0, RematMI, *DAG.TRI);
     MachineInstr *NewMI = &*std::prev(InsertPos);
-    NewMI->getOperand(0).setSubReg(SubReg);
     DAG.LIS->InsertMachineInstrInMaps(*NewMI);
 
     auto UseRegion = MIRegion.find(Remat.UseMI);

``````````

</details>


https://github.com/llvm/llvm-project/pull/150259