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

[Valery Pykhtin via llvm-commits]

================
@@ -414,6 +508,64 @@ 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());
+  RegOpers.adjustLaneLiveness(LIS, *MRI, SlotIdx);
+  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;
+
+    // There may be parts of the register that were dead before the
+    // instruction, but became live afterwards. Similarly, some parts
+    // may have been killed in this instruction.
+    CurPressure.inc(Reg, LiveAfter, LiveAfter & LiveBefore, *MRI);
+    CurPressure.inc(Reg, LiveAfter, ~LiveAfter & LiveBefore, *MRI);
+    MaxPressure = max(MaxPressure, CurPressure);
+  }
+  // Generate liveness for uses.
+  for (const RegisterMaskPair &P : RegOpers.Uses) {
+    Register Reg = P.RegUnit;
+    if (!Reg.isVirtual())
+      continue;
+    // If this register was also in a def operand, we've handled it
+    // with defs.
+    if (getRegLanes(RegOpers.Defs, Reg).any())
+      continue;
+    LaneBitmask LiveAfter = LiveRegs[Reg];
+    SlotIndex CurrIdx =
+        LastTrackedMI ? LIS.getInstructionIndex(*LastTrackedMI).getRegSlot()
+                      : LIS.getMBBEndIdx(MI->getParent());
+    ;
+    LaneBitmask LastUseMask = findUseBetween(Reg, P.LaneMask, SlotIdx, CurrIdx,
+                                             *MRI, TRI, &LIS, true);
+    LastUseMask &= ~LiveAfter;
+    LaneBitmask LiveBefore = (LiveAfter | LastUseMask);
+    CurPressure.inc(Reg, LiveAfter, LiveBefore, *MRI);
+  }
+  MaxPressure = max(MaxPressure, CurPressure);
+}
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vpykhtin wrote:

Overall algorithm is really cumbersome. Why do you need findUseBetween? 

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