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

[Lucas Ramirez via llvm-commits]

https://github.com/lucas-rami created https://github.com/llvm/llvm-project/pull/150259

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.

>From 3341e007619788fdd4cfdebd1a39bae7c954a574 Mon Sep 17 00:00:00 2001
From: Lucas Ramirez <lucas.rami at proton.me>
Date: Wed, 23 Jul 2025 16:42:41 +0000
Subject: [PATCH] Fix usage of rematerialize API

---
 llvm/lib/Target/AMDGPU/GCNSchedStrategy.cpp | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

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);