[llvm] [RISCV] Rematerialize load (PR #73924)

[Craig Topper via llvm-commits]

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@@ -1567,6 +1573,37 @@ bool RISCVInstrInfo::isAsCheapAsAMove(const MachineInstr &MI) const {
   return MI.isAsCheapAsAMove();
 }
 
+bool RISCVInstrInfo::isReallyTriviallyReMaterializable(
+    const MachineInstr &MI) const {
+
+  if (TargetInstrInfo::isReallyTriviallyReMaterializable(MI))
+    return true;
+
+  if (MI.mayLoad() && AggressiveLoadRemat) {
+    const MachineFunction &MF = *MI.getMF();
+    const MachineRegisterInfo &MRI = MF.getRegInfo();
+
+    const MachineOperand &Dest = MI.getOperand(0);
+    if (!MRI.hasOneUse(Dest.getReg()))
+      return false;
+
+    MachineInstr *UseMI = &*MRI.use_instr_begin(Dest.getReg());
+    MachineBasicBlock::const_iterator DefItr(MI);
+    MachineBasicBlock::const_iterator UseItr(UseMI);
+    const MachineBasicBlock *MBB = nullptr;
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topperc wrote:

Why is this initialized to nullptr instead of MI.getParent()?

https://github.com/llvm/llvm-project/pull/73924