1 files changed, 220 insertions, 0 deletions
diff --git a/contrib/llvm-project/llvm/lib/CodeGen/MacroFusion.cpp b/contrib/llvm-project/llvm/lib/CodeGen/MacroFusion.cpp
new file mode 100644
index 000000000000..5bd6ca0978a4
--- /dev/null
+++ b/contrib/llvm-project/llvm/lib/CodeGen/MacroFusion.cpp
@@ -0,0 +1,220 @@
+//===- MacroFusion.cpp - Macro Fusion -------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+/// \file This file contains the implementation of the DAG scheduling mutation
+/// to pair instructions back to back.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/MacroFusion.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/CodeGen/ScheduleDAG.h"
+#include "llvm/CodeGen/ScheduleDAGInstrs.h"
+#include "llvm/CodeGen/ScheduleDAGMutation.h"
+#include "llvm/CodeGen/TargetInstrInfo.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+
+#define DEBUG_TYPE "machine-scheduler"
+
+STATISTIC(NumFused, "Number of instr pairs fused");
+
+using namespace llvm;
+
+static cl::opt<bool> EnableMacroFusion("misched-fusion", cl::Hidden,
+  cl::desc("Enable scheduling for macro fusion."), cl::init(true));
+
+static bool isHazard(const SDep &Dep) {
+  return Dep.getKind() == SDep::Anti || Dep.getKind() == SDep::Output;
+}
+
+static SUnit *getPredClusterSU(const SUnit &SU) {
+  for (const SDep &SI : SU.Preds)
+    if (SI.isCluster())
+      return SI.getSUnit();
+
+  return nullptr;
+}
+
+bool llvm::hasLessThanNumFused(const SUnit &SU, unsigned FuseLimit) {
+  unsigned Num = 1;
+  const SUnit *CurrentSU = &SU;
+  while ((CurrentSU = getPredClusterSU(*CurrentSU)) && Num < FuseLimit) Num ++;
+  return Num < FuseLimit;
+}
+
+bool llvm::fuseInstructionPair(ScheduleDAGInstrs &DAG, SUnit &FirstSU,
+                               SUnit &SecondSU) {
+  // Check that neither instr is already paired with another along the edge
+  // between them.
+  for (SDep &SI : FirstSU.Succs)
+    if (SI.isCluster())
+      return false;
+
+  for (SDep &SI : SecondSU.Preds)
+    if (SI.isCluster())
+      return false;
+  // Though the reachability checks above could be made more generic,
+  // perhaps as part of ScheduleDAGInstrs::addEdge(), since such edges are valid,
+  // the extra computation cost makes it less interesting in general cases.
+
+  // Create a single weak edge between the adjacent instrs. The only effect is
+  // to cause bottom-up scheduling to heavily prioritize the clustered instrs.
+  if (!DAG.addEdge(&SecondSU, SDep(&FirstSU, SDep::Cluster)))
+    return false;
+
+  // TODO - If we want to chain more than two instructions, we need to create
+  // artifical edges to make dependencies from the FirstSU also dependent
+  // on other chained instructions, and other chained instructions also
+  // dependent on the dependencies of the SecondSU, to prevent them from being
+  // scheduled into these chained instructions.
+  assert(hasLessThanNumFused(FirstSU, 2) &&
+         "Currently we only support chaining together two instructions");
+
+  // Adjust the latency between both instrs.
+  for (SDep &SI : FirstSU.Succs)
+    if (SI.getSUnit() == &SecondSU)
+      SI.setLatency(0);
+
+  for (SDep &SI : SecondSU.Preds)
+    if (SI.getSUnit() == &FirstSU)
+      SI.setLatency(0);
+
+  LLVM_DEBUG(
+      dbgs() << "Macro fuse: "; DAG.dumpNodeName(FirstSU); dbgs() << " - ";
+      DAG.dumpNodeName(SecondSU); dbgs() << " /  ";
+      dbgs() << DAG.TII->getName(FirstSU.getInstr()->getOpcode()) << " - "
+             << DAG.TII->getName(SecondSU.getInstr()->getOpcode()) << '\n';);
+
+  // Make data dependencies from the FirstSU also dependent on the SecondSU to
+  // prevent them from being scheduled between the FirstSU and the SecondSU.
+  if (&SecondSU != &DAG.ExitSU)
+    for (const SDep &SI : FirstSU.Succs) {
+      SUnit *SU = SI.getSUnit();
+      if (SI.isWeak() || isHazard(SI) ||
+          SU == &DAG.ExitSU || SU == &SecondSU || SU->isPred(&SecondSU))
+        continue;
+      LLVM_DEBUG(dbgs() << "  Bind "; DAG.dumpNodeName(SecondSU);
+                 dbgs() << " - "; DAG.dumpNodeName(*SU); dbgs() << '\n';);
+      DAG.addEdge(SU, SDep(&SecondSU, SDep::Artificial));
+    }
+
+  // Make the FirstSU also dependent on the dependencies of the SecondSU to
+  // prevent them from being scheduled between the FirstSU and the SecondSU.
+  if (&FirstSU != &DAG.EntrySU) {
+    for (const SDep &SI : SecondSU.Preds) {
+      SUnit *SU = SI.getSUnit();
+      if (SI.isWeak() || isHazard(SI) || &FirstSU == SU || FirstSU.isSucc(SU))
+        continue;
+      LLVM_DEBUG(dbgs() << "  Bind "; DAG.dumpNodeName(*SU); dbgs() << " - ";
+                 DAG.dumpNodeName(FirstSU); dbgs() << '\n';);
+      DAG.addEdge(&FirstSU, SDep(SU, SDep::Artificial));
+    }
+    // ExitSU comes last by design, which acts like an implicit dependency
+    // between ExitSU and any bottom root in the graph. We should transfer
+    // this to FirstSU as well.
+    if (&SecondSU == &DAG.ExitSU) {
+      for (SUnit &SU : DAG.SUnits) {
+        if (SU.Succs.empty())
+          DAG.addEdge(&FirstSU, SDep(&SU, SDep::Artificial));
+      }
+    }
+  }
+
+  ++NumFused;
+  return true;
+}
+
+namespace {
+
+/// Post-process the DAG to create cluster edges between instrs that may
+/// be fused by the processor into a single operation.
+class MacroFusion : public ScheduleDAGMutation {
+  std::vector<MacroFusionPredTy> Predicates;
+  bool FuseBlock;
+  bool scheduleAdjacentImpl(ScheduleDAGInstrs &DAG, SUnit &AnchorSU);
+
+public:
+  MacroFusion(ArrayRef<MacroFusionPredTy> Predicates, bool FuseBlock)
+      : Predicates(Predicates.begin(), Predicates.end()), FuseBlock(FuseBlock) {
+  }
+
+  void apply(ScheduleDAGInstrs *DAGInstrs) override;
+
+  bool shouldScheduleAdjacent(const TargetInstrInfo &TII,
+                              const TargetSubtargetInfo &STI,
+                              const MachineInstr *FirstMI,
+                              const MachineInstr &SecondMI);
+};
+
+} // end anonymous namespace
+
+bool MacroFusion::shouldScheduleAdjacent(const TargetInstrInfo &TII,
+                                         const TargetSubtargetInfo &STI,
+                                         const MachineInstr *FirstMI,
+                                         const MachineInstr &SecondMI) {
+  return llvm::any_of(Predicates, [&](MacroFusionPredTy Predicate) {
+    return Predicate(TII, STI, FirstMI, SecondMI);
+  });
+}
+
+void MacroFusion::apply(ScheduleDAGInstrs *DAG) {
+  if (FuseBlock)
+    // For each of the SUnits in the scheduling block, try to fuse the instr in
+    // it with one in its predecessors.
+    for (SUnit &ISU : DAG->SUnits)
+        scheduleAdjacentImpl(*DAG, ISU);
+
+  if (DAG->ExitSU.getInstr())
+    // Try to fuse the instr in the ExitSU with one in its predecessors.
+    scheduleAdjacentImpl(*DAG, DAG->ExitSU);
+}
+
+/// Implement the fusion of instr pairs in the scheduling DAG,
+/// anchored at the instr in AnchorSU..
+bool MacroFusion::scheduleAdjacentImpl(ScheduleDAGInstrs &DAG, SUnit &AnchorSU) {
+  const MachineInstr &AnchorMI = *AnchorSU.getInstr();
+  const TargetInstrInfo &TII = *DAG.TII;
+  const TargetSubtargetInfo &ST = DAG.MF.getSubtarget();
+
+  // Check if the anchor instr may be fused.
+  if (!shouldScheduleAdjacent(TII, ST, nullptr, AnchorMI))
+    return false;
+
+  // Explorer for fusion candidates among the dependencies of the anchor instr.
+  for (SDep &Dep : AnchorSU.Preds) {
+    // Ignore dependencies other than data or strong ordering.
+    if (Dep.isWeak() || isHazard(Dep))
+      continue;
+
+    SUnit &DepSU = *Dep.getSUnit();
+    if (DepSU.isBoundaryNode())
+      continue;
+
+    // Only chain two instructions together at most.
+    const MachineInstr *DepMI = DepSU.getInstr();
+    if (!hasLessThanNumFused(DepSU, 2) ||
+        !shouldScheduleAdjacent(TII, ST, DepMI, AnchorMI))
+      continue;
+
+    if (fuseInstructionPair(DAG, DepSU, AnchorSU))
+      return true;
+  }
+
+  return false;
+}
+
+std::unique_ptr<ScheduleDAGMutation>
+llvm::createMacroFusionDAGMutation(ArrayRef<MacroFusionPredTy> Predicates,
+                                   bool BranchOnly) {
+  if (EnableMacroFusion)
+    return std::make_unique<MacroFusion>(Predicates, !BranchOnly);
+  return nullptr;
+}