[llvm] [AMDGPU] Optionally Use GCNRPTrackers during scheduling (PR #93090)

[Matt Arsenault via llvm-commits]

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@@ -414,6 +534,49 @@ void GCNUpwardRPTracker::recede(const MachineInstr &MI) {
   assert(CurPressure == getRegPressure(*MRI, LiveRegs));
 }
 
+void GCNUpwardRPTracker::bumpUpwardPressure(const MachineInstr *MI,
+                                            const SIRegisterInfo *TRI) {
+  assert(!MI->isDebugOrPseudoInstr() && "Expect a nondebug instruction.");
+
+  SlotIndex SlotIdx = LIS.getInstructionIndex(*MI).getRegSlot();
+
+  // Account for register pressure similar to RegPressureTracker::recede().
+  RegisterOperands RegOpers;
+
+  RegOpers.collect(*MI, *TRI, *MRI, true, /*IgnoreDead=*/true);
+  assert(RegOpers.DeadDefs.empty());
+  adjustDefLaneLiveness(RegOpers.Defs, SlotIdx, LIS, *MRI);
+  RegOpers.detectDeadDefs(*MI, LIS);
+
+  // Boost max pressure for all dead defs together.
+  // Since CurrSetPressure and MaxSetPressure
+  bumpDeadDefs(RegOpers.DeadDefs);
+
+  // Kill liveness at live defs.
+  for (const RegisterMaskPair &P : RegOpers.Defs) {
+    Register Reg = P.RegUnit;
+    if (!Reg.isVirtual())
+      continue;
+    LaneBitmask LiveAfter = LiveRegs[Reg];
+    LaneBitmask UseLanes = getRegLanes(RegOpers.Uses, Reg);
+    LaneBitmask DefLanes = P.LaneMask;
+    LaneBitmask LiveBefore = (LiveAfter & ~DefLanes) | UseLanes;
+
+    CurPressure.inc(Reg, LiveAfter, LiveAfter & LiveBefore, *MRI);
+    MaxPressure = max(MaxPressure, CurPressure);
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arsenm wrote:

Unlike the generic version, there's no decrease in pressure for the defs? 

https://github.com/llvm/llvm-project/pull/93090