[llvm] [AMDGPU] Added hot-block-rematerialize pass (PR #136631)

[Matt Arsenault via llvm-commits]

================
@@ -0,0 +1,657 @@
+//===------- AMDGPUMIRUtils.cpp - Helpers for MIR passes ------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+/// \file
+/// \brief Helper functions for MIR passes.
+//
+//===----------------------------------------------------------------------===//
+
+#include "AMDGPUMIRUtils.h"
+#include "SIInstrInfo.h"
+#include "SIRegisterInfo.h"
+
+#include "llvm/CodeGen/LiveInterval.h"
+#include "llvm/CodeGen/MachineLoopInfo.h"
+#include "llvm/CodeGen/MachinePostDominators.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+
+#define DEBUG_TYPE "xb-mir-util"
+using namespace llvm;
+
+namespace llvm {
+bool getNonDebugMBBEnd(MachineBasicBlock::reverse_iterator &BBEnd,
+                       MachineBasicBlock &MBB) {
+  // R.End doesn't point to the boundary instruction.
+  // Skip Debug instr.
+  while (BBEnd != MBB.rend() && BBEnd->isDebugInstr())
+    BBEnd++;
+  return BBEnd != MBB.rend();
+}
+} // namespace llvm
+
+namespace {
+bool isLocalSegment(const LiveRange::Segment *Seg, SlotIndexes *Indexes,
+                    SmallDenseSet<MachineBasicBlock *, 2> &TouchedMBBSet) {
+  MachineInstr *StartMI = Indexes->getInstructionFromIndex(Seg->start);
+  MachineInstr *EndMI = Indexes->getInstructionFromIndex(Seg->end);
+  // Treat non inst as not local.
+  if (!StartMI || !EndMI)
+    return false;
+  // is local when parent MBB the same.
+  bool IsSameMBB = StartMI->getParent() == EndMI->getParent();
+  if (!IsSameMBB)
+    return false;
+  // Collect touched MBB.
+  MachineBasicBlock *MBB = StartMI->getParent();
+  TouchedMBBSet.insert(MBB);
+  return true;
+}
+
+bool isLocalLiveRange(const LiveRange *Range, SlotIndexes *Indexes,
+                      SmallDenseSet<MachineBasicBlock *, 2> &TouchedMBBSet) {
+  for (const LiveRange::Segment &Seg : Range->segments) {
+    if (!isLocalSegment(&Seg, Indexes, TouchedMBBSet))
+      return false;
+  }
+  return true;
+}
+
+bool isLocalSegment(const LiveRange::Segment *Seg, SlotIndexes *Indexes) {
+  MachineInstr *StartMI = Indexes->getInstructionFromIndex(Seg->start);
+  MachineInstr *EndMI = Indexes->getInstructionFromIndex(Seg->end);
+  // Treat non inst as not local.
+  if (!StartMI || !EndMI)
+    return false;
+  // is local when parent MBB the same.
+  return StartMI->getParent() == EndMI->getParent();
+}
+
+bool isLocalLiveRange(const LiveRange *Range, SlotIndexes *Indexes) {
+  for (const LiveRange::Segment &Seg : Range->segments) {
+    if (!isLocalSegment(&Seg, Indexes))
+      return false;
+  }
+  return true;
+}
+
+// LoopInfo contains a mapping from basic block to the innermost loop. Find
+// the outermost loop in the loop nest that contains BB.
+const MachineLoop *getOutermostLoop(const MachineLoopInfo *LI,
+                                    const MachineBasicBlock *BB) {
+  const MachineLoop *L = LI->getLoopFor(BB);
+  if (L) {
+    while (const MachineLoop *Parent = L->getParentLoop())
+      L = Parent;
+  }
+  return L;
+}
+
+bool loopContainsBoth(const MachineLoopInfo *LI, const MachineBasicBlock *BB1,
+                      const MachineBasicBlock *BB2) {
+  const MachineLoop *L1 = getOutermostLoop(LI, BB1);
+  const MachineLoop *L2 = getOutermostLoop(LI, BB2);
+  return L1 != nullptr && L1 == L2;
+}
+
+} // namespace
+
+namespace llvm {
+
+bool isSccLiveAt(llvm::MachineBasicBlock *MBB,
----------------
arsenm wrote:

This function shouldn't be added. It's reinventing physical register liveness tracking for the 100th time in LLVM. Either directly use LiveIntervals, or for fuzzier usage MBB::computeRegisterLiveness, or use tracking in LiveRegUnits in passes with post-RA physreg tracking 

https://github.com/llvm/llvm-project/pull/136631