[NFC][MLGO] ML Regalloc Priority Advisor

llvm/include/llvm/InitializePasses.h

 void initializePruneEHPass(PassRegistry&);
 void initializeRABasicPass(PassRegistry&);
 void initializePseudoProbeInserterPass(PassRegistry &);
 void initializeRAGreedyPass(PassRegistry&);
 void initializeReachingDefAnalysisPass(PassRegistry&);
 void initializeReassociateLegacyPassPass(PassRegistry&);
 void initializeRedundantDbgInstEliminationPass(PassRegistry&);
 void initializeRegAllocEvictionAdvisorAnalysisPass(PassRegistry &);
+void initializeRegAllocPriorityAdvisorAnalysisPass(PassRegistry &);
 void initializeRegAllocFastPass(PassRegistry&);
 void initializeRegAllocScoringPass(PassRegistry &);
 void initializeRegBankSelectPass(PassRegistry&);
 void initializeRegToMemLegacyPass(PassRegistry&);
 void initializeRegUsageInfoCollectorPass(PassRegistry&);
 void initializeRegUsageInfoPropagationPass(PassRegistry&);
 void initializeRegionInfoPassPass(PassRegistry&);
 void initializeRegionOnlyPrinterPass(PassRegistry&);

llvm/lib/Analysis/models/gen-regalloc-priority-test-model.py

+"""Generate a mock model for LLVM tests for Register Allocation.
+The generated model is not a neural net - it is just a tf.function with the
+correct input and output parameters. 
+"""
+## By construction, the mock model will always output the first liverange that can be evicted.
+
+import os
+import sys
+import tensorflow as tf
+POLICY_DECISION_LABEL = 'priority'
+POLICY_OUTPUT_SPEC = """
+[
+    {
+        "logging_name": "priority", 
+        "tensor_spec": {
+            "name": "StatefulPartitionedCall", 
+            "port": 0, 
+            "type": "float", 
+            "shape": [
+                1
+            ]
+        }
+    }
+]
+"""
+PER_LIVEINTERVAL_INT64_FEATURE_LIST = [
+    'li_size', 'stage'
+]
+PER_LIVEINTERVAL_FLOAT32_FEATURE_LIST = ['weight'
+]
+PER_LIVEINTERVAL_FEATURE_LIST = PER_LIVEINTERVAL_FLOAT32_FEATURE_LIST + \
+    PER_LIVEINTERVAL_INT64_FEATURE_LIST
+CONTEXT_FEATURE_LIST =  ('discount', 'reward', 'step_type')
+
+
+def get_input_signature():
+  """Returns (time_step_spec, action_spec) for LLVM register allocation."""
+  inputs = dict(
+      (key, tf.TensorSpec(dtype=tf.int64, shape=(), name=key))
+      for key in PER_LIVEINTERVAL_INT64_FEATURE_LIST)
+  inputs.update(
+      dict((key,
+            tf.TensorSpec(dtype=tf.float32, shape=(), name=key))
+           for key in PER_LIVEINTERVAL_FLOAT32_FEATURE_LIST))
+  inputs.update(
+      dict((key, tf.TensorSpec(dtype=tf.float32, shape=(), name=key))
+           for key in ['discount', 'reward']))
+  inputs.update(
+      dict((key, tf.TensorSpec(dtype=tf.int32, shape=(), name=key))
+           for key in ['step_type']))
+  return inputs
+
+
+def get_output_spec_path(path):
+  return os.path.join(path, 'output_spec.json')
+
+
+def build_mock_model(path):
+  """Build and save the mock model with the given signature."""
+  module = tf.Module()
+  # We have to set this useless variable in order for the TF C API to correctly
+  # intake it
+  module.var = tf.Variable(0, dtype=tf.float32)
+
+  def action(*inputs):
+    s1 = tf.reduce_sum([
+        tf.cast(inputs[0][key], tf.float32) for key in PER_LIVEINTERVAL_FEATURE_LIST
+    ],
+        axis=0)
+    s2 = tf.reduce_sum(
+        [tf.cast(inputs[0][key], tf.float32) for key in CONTEXT_FEATURE_LIST])
+    # Add a large number so s won't be 0.
+    s = s1 + s2
+    result = s + module.var
+    return {POLICY_DECISION_LABEL: result}
+  module.action = tf.function()(action)
+  action = {
+      'action': module.action.get_concrete_function(get_input_signature())
+  }
+
+  tf.saved_model.save(module, path, signatures=action)
+  output_spec_path = get_output_spec_path(path)
+  with open(output_spec_path, 'w') as f:
+    print(f'Writing output spec to {output_spec_path}.')
+    f.write(POLICY_OUTPUT_SPEC)
+
+
+def main(argv):
+  assert len(argv) == 2
+  model_path = argv[1]
+  build_mock_model(model_path)
+
+
+if __name__ == '__main__':
+  main(sys.argv)

llvm/lib/CodeGen/CMakeLists.txt

add_llvm_component_library(LLVMCodeGen
   MachineSSAUpdater.cpp
   MachineStripDebug.cpp
   MachineTraceMetrics.cpp
   MachineVerifier.cpp
   MIRFSDiscriminator.cpp
   MIRSampleProfile.cpp
   MIRYamlMapping.cpp
   MLRegallocEvictAdvisor.cpp
+  MLRegallocPriorityAdvisor.cpp
   ModuloSchedule.cpp
   MultiHazardRecognizer.cpp
   PatchableFunction.cpp
   MBFIWrapper.cpp
   MIRPrinter.cpp
   MIRPrintingPass.cpp
   MacroFusion.cpp
   NonRelocatableStringpool.cpp
add_llvm_component_library(LLVMCodeGen
   PseudoSourceValue.cpp
   RDFGraph.cpp
   RDFLiveness.cpp
   RDFRegisters.cpp
   ReachingDefAnalysis.cpp
   RegAllocBase.cpp
   RegAllocBasic.cpp
   RegAllocEvictionAdvisor.cpp
+  RegAllocPriorityAdvisor.cpp
   RegAllocFast.cpp
   RegAllocGreedy.cpp
   RegAllocPBQP.cpp
   RegAllocScore.cpp
   RegisterClassInfo.cpp
   RegisterCoalescer.cpp
   RegisterPressure.cpp
   RegisterScavenging.cpp

llvm/lib/CodeGen/MLRegallocPriorityAdvisor.cpp

+#include "AllocationOrder.h"
+#include "RegAllocGreedy.h"
+#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/MLModelRunner.h"
+#include "llvm/Analysis/ReleaseModeModelRunner.h"
+#include "llvm/Analysis/TensorSpec.h"
+#include "llvm/CodeGen/CalcSpillWeights.h"
+#include "llvm/CodeGen/LiveRegMatrix.h"
+#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineLoopInfo.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/CodeGen/RegisterClassInfo.h"
+#include "llvm/CodeGen/VirtRegMap.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/PassRegistry.h"
+#include "llvm/Support/CommandLine.h"
+
+#include "llvm/Analysis/ModelUnderTrainingRunner.h"
+#include "llvm/Analysis/NoInferenceModelRunner.h"
+
+#include "RegAllocScore.h"
+#include "llvm/Analysis/Utils/TFUtils.h"
+
+using namespace llvm;
+
+static cl::opt<std::string> TrainingLog(
+    "regalloc-prio-training-log", cl::Hidden,
+    cl::desc("Training log for the register allocator priority model"));
+
+static cl::opt<std::string> ModelUnderTraining(
+    "regalloc-prio-model", cl::Hidden,
+    cl::desc("The model being trained for register allocation priority"));
+
+namespace llvm {
+
+static const std::vector<int64_t> PerLiveRangeShape{1};
+
+#define RA_PRIORITY_FEATURES_LIST(M)                                           \
+  M(int64_t, li_size, PerLiveRangeShape, "size")                               \
+  M(int64_t, stage, PerLiveRangeShape, "stage")                                \
+  M(float, weight, PerLiveRangeShape, "weight")
+
+#define DecisionName "priority"
+
+// Named features index.
+enum FeatureIDs {
+#define _FEATURE_IDX(_, name, __, ___) name,
+  RA_PRIORITY_FEATURES_LIST(_FEATURE_IDX)
+#undef _FEATURE_IDX
+      FeatureCount
+};
+
+class MLPriorityAdvisor : public RegAllocPriorityAdvisor {
+public:
+  MLPriorityAdvisor(const MachineFunction &MF, const RAGreedy &RA,
+                    MLModelRunner *Runner);
+  void logReward(float reward) override {}
+
+protected:
+  const RegAllocPriorityAdvisor &getDefaultAdvisor() const {
+    return static_cast<const RegAllocPriorityAdvisor &>(DefaultAdvisor);
+  }
+
+  // The assumption is that if the Runner could not be constructed, we emit-ed
+  // error, and we shouldn't be asking for it here.
+  const MLModelRunner &getRunner() const { return *Runner; }
+
+  float tryFindPriority(unsigned Prio, unsigned Size, LiveRangeStage Stage,
+                        float Weight) const override;
+
+private:
+  const DefaultPriorityAdvisor DefaultAdvisor;
+  MLModelRunner *const Runner;
+};
+
+#define _DECL_FEATURES(type, name, shape, _)                                   \
+  TensorSpec::createSpec<type>(#name, shape),
+
+static const std::vector<TensorSpec> InputFeatures{
+    {RA_PRIORITY_FEATURES_LIST(_DECL_FEATURES)},
+};
+#undef _DECL_FEATURES
+
+// ===================================
+// Release (AOT) - specifics
+// ===================================
+class ReleaseModePriorityAdvisorAnalysis final
+    : public RegAllocPriorityAdvisorAnalysis {
+public:
+  ReleaseModePriorityAdvisorAnalysis()
+      : RegAllocPriorityAdvisorAnalysis(AdvisorMode::Release) {}
+  // support for isa<> and dyn_cast.
+  static bool classof(const RegAllocPriorityAdvisorAnalysis *R) {
+    return R->getAdvisorMode() == AdvisorMode::Release;
+  }
+
+private:
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    RegAllocPriorityAdvisorAnalysis::getAnalysisUsage(AU);
+  }
+
+  std::unique_ptr<RegAllocPriorityAdvisor>
+  getAdvisor(const MachineFunction &MF, const RAGreedy &RA) override {
+    if (!Runner)
+      Runner = std::make_unique<ReleaseModeModelRunner<NoopSavedModelImpl>>(
+          MF.getFunction().getContext(), InputFeatures, DecisionName);
+    return std::make_unique<MLPriorityAdvisor>(MF, RA, Runner.get());
+  }
+  std::unique_ptr<ReleaseModeModelRunner<NoopSavedModelImpl>> Runner;
+};
+
+static const TensorSpec Output =
+    TensorSpec::createSpec<float>(DecisionName, {1});
+static const TensorSpec Reward = TensorSpec::createSpec<float>("reward", {1});
+
+#define _DECL_TRAIN_FEATURES(type, name, shape, _)                             \
+  TensorSpec::createSpec<type>(std::string("action_") + #name, shape),
+
+static const std::vector<TensorSpec> TrainingInputFeatures{
+    {RA_PRIORITY_FEATURES_LIST(_DECL_TRAIN_FEATURES)
+         TensorSpec::createSpec<float>("action_discount", {1}),
+     TensorSpec::createSpec<int32_t>("action_step_type", {1}),
+     TensorSpec::createSpec<float>("action_reward", {1})}};
+#undef _DECL_TRAIN_FEATURES
+
+class DevelopmentModePriorityAdvisor : public MLPriorityAdvisor {
+public:
+  DevelopmentModePriorityAdvisor(const MachineFunction &MF, const RAGreedy &RA,
+                                 MLModelRunner *Runner, Logger *Log)
+      : MLPriorityAdvisor(MF, RA, Runner), Log(Log) {}
+
+  void logReward(float reward) override { Log->logFloatFinalReward(reward); }
+
+private:
+  float tryFindPriority(unsigned Prio, unsigned Size, LiveRangeStage Stage,
+                        float Weight) const override;
+  Logger *const Log;
+};
+
+class DevelopmentModePriorityAdvisorAnalysis final
+    : public RegAllocPriorityAdvisorAnalysis {
+public:
+  DevelopmentModePriorityAdvisorAnalysis()
+      : RegAllocPriorityAdvisorAnalysis(AdvisorMode::Development) {}
+  // support for isa<> and dyn_cast.
+  static bool classof(const RegAllocPriorityAdvisorAnalysis *R) {
+    return R->getAdvisorMode() == AdvisorMode::Development;
+  }
+
+  /// get the logger for the given function, or nullptr if we didn't collect
+  /// one. This is used to inject the score by the RegAllocScoring pass.
+  Logger *getLogger(const MachineFunction &MF) const {
+    auto I = LogMap.find(MF.getName());
+    if (I == LogMap.end())
+      return nullptr;
+    return I->second.get();
+  }
+
+private:
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    RegAllocPriorityAdvisorAnalysis::getAnalysisUsage(AU);
+  }
+
+  // Save all the logs (when requested).
+  bool doFinalization(Module &M) override {
+    if (TrainingLog.empty())
+      return false;
+    std::error_code EC;
+    auto OS = std::make_unique<raw_fd_ostream>(TrainingLog, EC);
+    if (EC) {
+      M.getContext().emitError(EC.message() + ":" + TrainingLog);
+      return false;
+    }
+    Logger::flushLogs(*OS, LogMap);
+    return false;
+  }
+
+  std::unique_ptr<RegAllocPriorityAdvisor>
+  getAdvisor(const MachineFunction &MF, const RAGreedy &RA) override {
+
+    LLVMContext &Ctx = MF.getFunction().getContext();
+    if (ModelUnderTraining.empty() && TrainingLog.empty()) {
+      Ctx.emitError("Regalloc development mode should be requested with at "
+                    "least logging enabled and/or a training model");
+      return nullptr;
+    }
+    if (!Runner) {
+      if (ModelUnderTraining.empty())
+        Runner = std::make_unique<NoInferenceModelRunner>(Ctx, InputFeatures);
+      else
+        Runner = ModelUnderTrainingRunner::createAndEnsureValid(
+            Ctx, ModelUnderTraining, DecisionName, TrainingInputFeatures);
+      if (!Runner) {
+        Ctx.emitError("Regalloc: could not set up the model runner");
+        return nullptr;
+      }
+    }
+
+    Logger *Log = nullptr;
+    if (!TrainingLog.empty()) {
+      std::vector<LoggedFeatureSpec> LFS;
+      for (const auto &FS : InputFeatures)
+        LFS.push_back({FS, None});
+      if (auto *MUTR = dyn_cast<ModelUnderTrainingRunner>(Runner.get()))
+        if (MUTR->outputLoggedFeatureSpecs().size() > 1)
+          append_range(LFS, drop_begin(MUTR->outputLoggedFeatureSpecs()));
+      // We always log the output; in particular, if we're not evaluating, we
+      // don't have an output spec json file. That's why we handle the
+      // 'normal' output separately.
+      LFS.push_back({Output, None});
+      auto I = LogMap.insert(std::make_pair(
+          MF.getFunction().getName(),
+          std::make_unique<Logger>(LFS, Reward, /*IncludeReward*/ true)));
+      assert(I.second);
+      Log = I.first->second.get();
+    }
+
+    return std::make_unique<DevelopmentModePriorityAdvisor>(MF, RA,
+                                                            Runner.get(), Log);
+  }
+
+  std::unique_ptr<MLModelRunner> Runner;
+  StringMap<std::unique_ptr<Logger>> LogMap;
+};
+
+} // namespace llvm
+
+RegAllocPriorityAdvisorAnalysis *llvm::createDevelopmentModePriorityAdvisor() {
+  return new DevelopmentModePriorityAdvisorAnalysis();
+}
+
+RegAllocPriorityAdvisorAnalysis *llvm::createReleaseModePriorityAdvisor() {
+  return new ReleaseModePriorityAdvisorAnalysis();
+}
+
+MLPriorityAdvisor::MLPriorityAdvisor(const MachineFunction &MF,
+                                     const RAGreedy &RA, MLModelRunner *Runner)
+    : RegAllocPriorityAdvisor(MF, RA), DefaultAdvisor(MF, RA),
+      Runner(std::move(Runner)) {
+  assert(this->Runner);
+}
+
+float MLPriorityAdvisor::tryFindPriority(unsigned Prio, unsigned Size,
+                                         LiveRangeStage Stage,
+                                         float Weight) const {
+  *Runner->getTensor<int64_t>(0) = static_cast<int64_t>(Size);
+  *Runner->getTensor<int64_t>(1) = static_cast<int64_t>(Stage);
+  *Runner->getTensor<float>(2) = static_cast<float>(Weight);
+
+  float Ret = Runner->evaluate<float>();
+  return Ret;
+}
+
+float DevelopmentModePriorityAdvisor::tryFindPriority(unsigned Prio,
+                                                      unsigned Size,
+                                                      LiveRangeStage Stage,
+                                                      float Weight) const {
+  float Ret = 0;
+
+  if (isa<ModelUnderTrainingRunner>(getRunner())) {
+    Ret = MLPriorityAdvisor::tryFindPriority(Prio, Size, Stage, Weight);
+  } else {
+    Ret = static_cast<float>(Prio);
+  }
+
+  if (TrainingLog.empty())
+    return Ret;
+
+  size_t CurrentFeature = 0;
+  for (; CurrentFeature < InputFeatures.size(); ++CurrentFeature) {
+    Log->logSpecifiedTensorValue(
+        CurrentFeature, reinterpret_cast<const char *>(
+                            getRunner().getTensorUntyped(CurrentFeature)));
+  }
+
+  if (auto *MUTR = dyn_cast<ModelUnderTrainingRunner>(&getRunner())) {
+    for (size_t I = 1; I < MUTR->outputLoggedFeatureSpecs().size();
+         ++I, ++CurrentFeature)
+      Log->logSpecifiedTensorValue(
+          CurrentFeature,
+          reinterpret_cast<const char *>(
+              MUTR->lastEvaluationResult()->getUntypedTensorValue(I)));
+  }
+  Log->logFloatValue(CurrentFeature, &Ret);
+
+  return Ret;
+}

llvm/lib/CodeGen/RegAllocGreedy.h

-//==- RegAllocGreedy.h ------- greedy register allocator  ----------*-C++-*-==//
-//
-// 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
-//
-//===----------------------------------------------------------------------===//
-// This file defines the RAGreedy function pass for register allocation in
-// optimized builds.
-//===----------------------------------------------------------------------===//
-
-#ifndef LLVM_CODEGEN_REGALLOCGREEDY_H_
-#define LLVM_CODEGEN_REGALLOCGREEDY_H_
-
-#include "InterferenceCache.h"
-#include "RegAllocBase.h"
-#include "RegAllocEvictionAdvisor.h"
-#include "SpillPlacement.h"
-#include "SplitKit.h"
-#include "llvm/ADT/ArrayRef.h"
-#include "llvm/ADT/BitVector.h"
-#include "llvm/ADT/DenseMap.h"
-#include "llvm/ADT/IndexedMap.h"
-#include "llvm/ADT/SetVector.h"
-#include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/StringRef.h"
-#include "llvm/Analysis/AliasAnalysis.h"
-#include "llvm/CodeGen/CalcSpillWeights.h"
-#include "llvm/CodeGen/LiveInterval.h"
-#include "llvm/CodeGen/LiveRangeEdit.h"
-#include "llvm/CodeGen/MachineFunction.h"
-#include "llvm/CodeGen/MachineFunctionPass.h"
-#include "llvm/CodeGen/RegisterClassInfo.h"
-#include "llvm/CodeGen/Spiller.h"
-#include "llvm/CodeGen/TargetRegisterInfo.h"
-#include <algorithm>
-#include <cstdint>
-#include <memory>
-#include <queue>
-#include <utility>
-
-namespace llvm {
-class AllocationOrder;
-class AnalysisUsage;
-class EdgeBundles;
-class LiveDebugVariables;
-class LiveIntervals;
-class LiveRegMatrix;
-class MachineBasicBlock;
-class MachineBlockFrequencyInfo;
-class MachineDominatorTree;
-class MachineLoop;
-class MachineLoopInfo;
-class MachineOptimizationRemarkEmitter;
-class MachineOptimizationRemarkMissed;
-class SlotIndex;
-class SlotIndexes;
-class TargetInstrInfo;
-class VirtRegMap;
-
-class LLVM_LIBRARY_VISIBILITY RAGreedy : public MachineFunctionPass,
-                                         public RegAllocBase,
-                                         private LiveRangeEdit::Delegate {
-  // Interface to eviction advisers
-public:
-  /// Track allocation stage and eviction loop prevention during allocation.
-  class ExtraRegInfo final {
-    // RegInfo - Keep additional information about each live range.
-    struct RegInfo {
-      LiveRangeStage Stage = RS_New;
-
-      // Cascade - Eviction loop prevention. See
-      // canEvictInterferenceBasedOnCost().
-      unsigned Cascade = 0;
-
-      RegInfo() = default;
-    };
-
-    IndexedMap<RegInfo, VirtReg2IndexFunctor> Info;
-    unsigned NextCascade = 1;
-
-  public:
-    ExtraRegInfo() = default;
-    ExtraRegInfo(const ExtraRegInfo &) = delete;
-
-    LiveRangeStage getStage(Register Reg) const { return Info[Reg].Stage; }
-
-    LiveRangeStage getStage(const LiveInterval &VirtReg) const {
-      return getStage(VirtReg.reg());
-    }
-
-    void setStage(Register Reg, LiveRangeStage Stage) {
-      Info.grow(Reg.id());
-      Info[Reg].Stage = Stage;
-    }
-
-    void setStage(const LiveInterval &VirtReg, LiveRangeStage Stage) {
-      setStage(VirtReg.reg(), Stage);
-    }
-
-    /// Return the current stage of the register, if present, otherwise
-    /// initialize it and return that.
-    LiveRangeStage getOrInitStage(Register Reg) {
-      Info.grow(Reg.id());
-      return getStage(Reg);
-    }
-
-    unsigned getCascade(Register Reg) const { return Info[Reg].Cascade; }
-
-    void setCascade(Register Reg, unsigned Cascade) {
-      Info.grow(Reg.id());
-      Info[Reg].Cascade = Cascade;
-    }
-
-    unsigned getOrAssignNewCascade(Register Reg) {
-      unsigned Cascade = getCascade(Reg);
-      if (!Cascade) {
-        Cascade = NextCascade++;
-        setCascade(Reg, Cascade);
-      }
-      return Cascade;
-    }
-
-    unsigned getCascadeOrCurrentNext(Register Reg) const {
-      unsigned Cascade = getCascade(Reg);
-      if (!Cascade)
-        Cascade = NextCascade;
-      return Cascade;
-    }
-
-    template <typename Iterator>
-    void setStage(Iterator Begin, Iterator End, LiveRangeStage NewStage) {
-      for (; Begin != End; ++Begin) {
-        Register Reg = *Begin;
-        Info.grow(Reg.id());
-        if (Info[Reg].Stage == RS_New)
-          Info[Reg].Stage = NewStage;
-      }
-    }
-    void LRE_DidCloneVirtReg(Register New, Register Old);
-  };
-
-  LiveRegMatrix *getInterferenceMatrix() const { return Matrix; }
-  LiveIntervals *getLiveIntervals() const { return LIS; }
-  VirtRegMap *getVirtRegMap() const { return VRM; }
-  const RegisterClassInfo &getRegClassInfo() const { return RegClassInfo; }
-  const ExtraRegInfo &getExtraInfo() const { return *ExtraInfo; }
-  size_t getQueueSize() const { return Queue.size(); }
-  // end (interface to eviction advisers)
-
-private:
-  // Convenient shortcuts.
-  using PQueue = std::priority_queue<std::pair<unsigned, unsigned>>;
-  using SmallLISet = SmallPtrSet<const LiveInterval *, 4>;
-
-  // We need to track all tentative recolorings so we can roll back any
-  // successful and unsuccessful recoloring attempts.
-  using RecoloringStack =
-      SmallVector<std::pair<const LiveInterval *, MCRegister>, 8>;
-
-  // context
-  MachineFunction *MF;
-
-  // Shortcuts to some useful interface.
-  const TargetInstrInfo *TII;
-
-  // analyses
-  SlotIndexes *Indexes;
-  MachineBlockFrequencyInfo *MBFI;
-  MachineDominatorTree *DomTree;
-  MachineLoopInfo *Loops;
-  MachineOptimizationRemarkEmitter *ORE;
-  EdgeBundles *Bundles;
-  SpillPlacement *SpillPlacer;
-  LiveDebugVariables *DebugVars;
-  AliasAnalysis *AA;
-
-  // state
-  std::unique_ptr<Spiller> SpillerInstance;
-  PQueue Queue;
-  std::unique_ptr<VirtRegAuxInfo> VRAI;
-  Optional<ExtraRegInfo> ExtraInfo;
-  std::unique_ptr<RegAllocEvictionAdvisor> EvictAdvisor;
-
-  // Enum CutOffStage to keep a track whether the register allocation failed
-  // because of the cutoffs encountered in last chance recoloring.
-  // Note: This is used as bitmask. New value should be next power of 2.
-  enum CutOffStage {
-    // No cutoffs encountered
-    CO_None = 0,
-
-    // lcr-max-depth cutoff encountered
-    CO_Depth = 1,
-
-    // lcr-max-interf cutoff encountered
-    CO_Interf = 2
-  };
-
-  uint8_t CutOffInfo;
-
-#ifndef NDEBUG
-  static const char *const StageName[];
-#endif
-
-  /// EvictionTrack - Keeps track of past evictions in order to optimize region
-  /// split decision.
-  class EvictionTrack {
-
-  public:
-    using EvictorInfo =
-        std::pair<Register /* evictor */, MCRegister /* physreg */>;
-    using EvicteeInfo = llvm::DenseMap<Register /* evictee */, EvictorInfo>;
-
-  private:
-    /// Each Vreg that has been evicted in the last stage of selectOrSplit will
-    /// be mapped to the evictor Vreg and the PhysReg it was evicted from.
-    EvicteeInfo Evictees;
-
-  public:
-    /// Clear all eviction information.
-    void clear() { Evictees.clear(); }
-
-    ///  Clear eviction information for the given evictee Vreg.
-    /// E.g. when Vreg get's a new allocation, the old eviction info is no
-    /// longer relevant.
-    /// \param Evictee The evictee Vreg for whom we want to clear collected
-    /// eviction info.
-    void clearEvicteeInfo(Register Evictee) { Evictees.erase(Evictee); }
-
-    /// Track new eviction.
-    /// The Evictor vreg has evicted the Evictee vreg from Physreg.
-    /// \param PhysReg The physical register Evictee was evicted from.
-    /// \param Evictor The evictor Vreg that evicted Evictee.
-    /// \param Evictee The evictee Vreg.
-    void addEviction(MCRegister PhysReg, Register Evictor, Register Evictee) {
-      Evictees[Evictee].first = Evictor;
-      Evictees[Evictee].second = PhysReg;
-    }
-
-    /// Return the Evictor Vreg which evicted Evictee Vreg from PhysReg.
-    /// \param Evictee The evictee vreg.
-    /// \return The Evictor vreg which evicted Evictee vreg from PhysReg. 0 if
-    /// nobody has evicted Evictee from PhysReg.
-    EvictorInfo getEvictor(Register Evictee) {
-      if (Evictees.count(Evictee)) {
-        return Evictees[Evictee];
-      }
-
-      return EvictorInfo(0, 0);
-    }
-  };
-
-  // Keeps track of past evictions in order to optimize region split decision.
-  EvictionTrack LastEvicted;
-
-  // splitting state.
-  std::unique_ptr<SplitAnalysis> SA;
-  std::unique_ptr<SplitEditor> SE;
-
-  /// Cached per-block interference maps
-  InterferenceCache IntfCache;
-
-  /// All basic blocks where the current register has uses.
-  SmallVector<SpillPlacement::BlockConstraint, 8> SplitConstraints;
-
-  /// Global live range splitting candidate info.
-  struct GlobalSplitCandidate {
-    // Register intended for assignment, or 0.
-    MCRegister PhysReg;
-
-    // SplitKit interval index for this candidate.
-    unsigned IntvIdx;
-
-    // Interference for PhysReg.
-    InterferenceCache::Cursor Intf;
-
-    // Bundles where this candidate should be live.
-    BitVector LiveBundles;
-    SmallVector<unsigned, 8> ActiveBlocks;
-
-    void reset(InterferenceCache &Cache, MCRegister Reg) {
-      PhysReg = Reg;
-      IntvIdx = 0;
-      Intf.setPhysReg(Cache, Reg);
-      LiveBundles.clear();
-      ActiveBlocks.clear();
-    }
-
-    // Set B[I] = C for every live bundle where B[I] was NoCand.
-    unsigned getBundles(SmallVectorImpl<unsigned> &B, unsigned C) {
-      unsigned Count = 0;
-      for (unsigned I : LiveBundles.set_bits())
-        if (B[I] == NoCand) {
-          B[I] = C;
-          Count++;
-        }
-      return Count;
-    }
-  };
-
-  /// Candidate info for each PhysReg in AllocationOrder.
-  /// This vector never shrinks, but grows to the size of the largest register
-  /// class.
-  SmallVector<GlobalSplitCandidate, 32> GlobalCand;
-
-  enum : unsigned { NoCand = ~0u };
-
-  /// Candidate map. Each edge bundle is assigned to a GlobalCand entry, or to
-  /// NoCand which indicates the stack interval.
-  SmallVector<unsigned, 32> BundleCand;
-
-  /// Callee-save register cost, calculated once per machine function.
-  BlockFrequency CSRCost;
-
-  /// Set of broken hints that may be reconciled later because of eviction.
-  SmallSetVector<const LiveInterval *, 8> SetOfBrokenHints;
-
-  /// The register cost values. This list will be recreated for each Machine
-  /// Function
-  ArrayRef<uint8_t> RegCosts;
-
-  /// Flags for the live range priority calculation, determined once per
-  /// machine function.
-  bool RegClassPriorityTrumpsGlobalness;
-
-public:
-  RAGreedy(const RegClassFilterFunc F = allocateAllRegClasses);
-
-  /// Return the pass name.
-  StringRef getPassName() const override { return "Greedy Register Allocator"; }
-
-  /// RAGreedy analysis usage.
-  void getAnalysisUsage(AnalysisUsage &AU) const override;
-  void releaseMemory() override;
-  Spiller &spiller() override { return *SpillerInstance; }
-  void enqueueImpl(const LiveInterval *LI) override;
-  const LiveInterval *dequeue() override;
-  MCRegister selectOrSplit(const LiveInterval &,
-                           SmallVectorImpl<Register> &) override;
-  void aboutToRemoveInterval(const LiveInterval &) override;
-
-  /// Perform register allocation.
-  bool runOnMachineFunction(MachineFunction &mf) override;
-
-  MachineFunctionProperties getRequiredProperties() const override {
-    return MachineFunctionProperties().set(
-        MachineFunctionProperties::Property::NoPHIs);
-  }
-
-  MachineFunctionProperties getClearedProperties() const override {
-    return MachineFunctionProperties().set(
-        MachineFunctionProperties::Property::IsSSA);
-  }
-
-  static char ID;
-
-private:
-  MCRegister selectOrSplitImpl(const LiveInterval &,
-                               SmallVectorImpl<Register> &, SmallVirtRegSet &,
-                               RecoloringStack &, unsigned = 0);
-
-  bool LRE_CanEraseVirtReg(Register) override;
-  void LRE_WillShrinkVirtReg(Register) override;
-  void LRE_DidCloneVirtReg(Register, Register) override;
-  void enqueue(PQueue &CurQueue, const LiveInterval *LI);
-  const LiveInterval *dequeue(PQueue &CurQueue);
-
-  BlockFrequency calcSpillCost();
-  bool addSplitConstraints(InterferenceCache::Cursor, BlockFrequency &);
-  bool addThroughConstraints(InterferenceCache::Cursor, ArrayRef<unsigned>);
-  bool growRegion(GlobalSplitCandidate &Cand);
-  bool splitCanCauseEvictionChain(Register Evictee, GlobalSplitCandidate &Cand,
-                                  unsigned BBNumber,
-                                  const AllocationOrder &Order);
-  BlockFrequency calcGlobalSplitCost(GlobalSplitCandidate &,
-                                     const AllocationOrder &Order);
-  bool calcCompactRegion(GlobalSplitCandidate &);
-  void splitAroundRegion(LiveRangeEdit &, ArrayRef<unsigned>);
-  void calcGapWeights(MCRegister, SmallVectorImpl<float> &);
-  bool canEvictInterferenceInRange(const LiveInterval &VirtReg,
-                                   MCRegister PhysReg, SlotIndex Start,
-                                   SlotIndex End, EvictionCost &MaxCost) const;
-  MCRegister getCheapestEvicteeWeight(const AllocationOrder &Order,
-                                      const LiveInterval &VirtReg,
-                                      SlotIndex Start, SlotIndex End,
-                                      float *BestEvictWeight) const;
-  void evictInterference(const LiveInterval &, MCRegister,
-                         SmallVectorImpl<Register> &);
-  bool mayRecolorAllInterferences(MCRegister PhysReg,
-                                  const LiveInterval &VirtReg,
-                                  SmallLISet &RecoloringCandidates,
-                                  const SmallVirtRegSet &FixedRegisters);
-
-  MCRegister tryAssign(const LiveInterval &, AllocationOrder &,
-                       SmallVectorImpl<Register> &, const SmallVirtRegSet &);
-  MCRegister tryEvict(const LiveInterval &, AllocationOrder &,
-                      SmallVectorImpl<Register> &, uint8_t,
-                      const SmallVirtRegSet &);
-  MCRegister tryRegionSplit(const LiveInterval &, AllocationOrder &,
-                            SmallVectorImpl<Register> &);
-  /// Calculate cost of region splitting.
-  unsigned calculateRegionSplitCost(const LiveInterval &VirtReg,
-                                    AllocationOrder &Order,
-                                    BlockFrequency &BestCost,
-                                    unsigned &NumCands, bool IgnoreCSR);
-  /// Perform region splitting.
-  unsigned doRegionSplit(const LiveInterval &VirtReg, unsigned BestCand,
-                         bool HasCompact, SmallVectorImpl<Register> &NewVRegs);
-  /// Check other options before using a callee-saved register for the first
-  /// time.
-  MCRegister tryAssignCSRFirstTime(const LiveInterval &VirtReg,
-                                   AllocationOrder &Order, MCRegister PhysReg,
-                                   uint8_t &CostPerUseLimit,
-                                   SmallVectorImpl<Register> &NewVRegs);
-  void initializeCSRCost();
-  unsigned tryBlockSplit(const LiveInterval &, AllocationOrder &,
-                         SmallVectorImpl<Register> &);
-  unsigned tryInstructionSplit(const LiveInterval &, AllocationOrder &,
-                               SmallVectorImpl<Register> &);
-  unsigned tryLocalSplit(const LiveInterval &, AllocationOrder &,
-                         SmallVectorImpl<Register> &);
-  unsigned trySplit(const LiveInterval &, AllocationOrder &,
-                    SmallVectorImpl<Register> &, const SmallVirtRegSet &);
-  unsigned tryLastChanceRecoloring(const LiveInterval &, AllocationOrder &,
-                                   SmallVectorImpl<Register> &,
-                                   SmallVirtRegSet &, RecoloringStack &,
-                                   unsigned);
-  bool tryRecoloringCandidates(PQueue &, SmallVectorImpl<Register> &,
-                               SmallVirtRegSet &, RecoloringStack &, unsigned);
-  void tryHintRecoloring(const LiveInterval &);
-  void tryHintsRecoloring();
-
-  /// Model the information carried by one end of a copy.
-  struct HintInfo {
-    /// The frequency of the copy.
-    BlockFrequency Freq;
-    /// The virtual register or physical register.
-    Register Reg;
-    /// Its currently assigned register.
-    /// In case of a physical register Reg == PhysReg.
-    MCRegister PhysReg;
-
-    HintInfo(BlockFrequency Freq, Register Reg, MCRegister PhysReg)
-        : Freq(Freq), Reg(Reg), PhysReg(PhysReg) {}
-  };
-  using HintsInfo = SmallVector<HintInfo, 4>;
-
-  BlockFrequency getBrokenHintFreq(const HintsInfo &, MCRegister);
-  void collectHintInfo(Register, HintsInfo &);
-
-  /// Greedy RA statistic to remark.
-  struct RAGreedyStats {
-    unsigned Reloads = 0;
-    unsigned FoldedReloads = 0;
-    unsigned ZeroCostFoldedReloads = 0;
-    unsigned Spills = 0;
-    unsigned FoldedSpills = 0;
-    unsigned Copies = 0;
-    float ReloadsCost = 0.0f;
-    float FoldedReloadsCost = 0.0f;
-    float SpillsCost = 0.0f;
-    float FoldedSpillsCost = 0.0f;
-    float CopiesCost = 0.0f;
-
-    bool isEmpty() {
-      return !(Reloads || FoldedReloads || Spills || FoldedSpills ||
-               ZeroCostFoldedReloads || Copies);
-    }
-
-    void add(RAGreedyStats other) {
-      Reloads += other.Reloads;
-      FoldedReloads += other.FoldedReloads;
-      ZeroCostFoldedReloads += other.ZeroCostFoldedReloads;
-      Spills += other.Spills;
-      FoldedSpills += other.FoldedSpills;
-      Copies += other.Copies;
-      ReloadsCost += other.ReloadsCost;
-      FoldedReloadsCost += other.FoldedReloadsCost;
-      SpillsCost += other.SpillsCost;
-      FoldedSpillsCost += other.FoldedSpillsCost;
-      CopiesCost += other.CopiesCost;
-    }
-
-    void report(MachineOptimizationRemarkMissed &R);
-  };
-
-  /// Compute statistic for a basic block.
-  RAGreedyStats computeStats(MachineBasicBlock &MBB);
-
-  /// Compute and report statistic through a remark.
-  RAGreedyStats reportStats(MachineLoop *L);
-
-  /// Report the statistic for each loop.
-  void reportStats();
-};
-} // namespace llvm
-#endif // #ifndef LLVM_CODEGEN_REGALLOCGREEDY_H_

llvm/lib/CodeGen/RegAllocGreedy.cpp

-//===- RegAllocGreedy.cpp - greedy register allocator ---------------------===//
-//
-// 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
-//
-//===----------------------------------------------------------------------===//
-//
-// This file defines the RAGreedy function pass for register allocation in
-// optimized builds.
-//
-//===----------------------------------------------------------------------===//
-
-#include "RegAllocGreedy.h"
-#include "AllocationOrder.h"
-#include "InterferenceCache.h"
-#include "LiveDebugVariables.h"
-#include "RegAllocBase.h"
-#include "RegAllocEvictionAdvisor.h"
-#include "SpillPlacement.h"
-#include "SplitKit.h"
-#include "llvm/ADT/ArrayRef.h"
-#include "llvm/ADT/BitVector.h"
-#include "llvm/ADT/IndexedMap.h"
-#include "llvm/ADT/SetVector.h"
-#include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/ADT/SmallSet.h"
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/ADT/StringRef.h"
-#include "llvm/Analysis/AliasAnalysis.h"
-#include "llvm/Analysis/OptimizationRemarkEmitter.h"
-#include "llvm/CodeGen/CalcSpillWeights.h"
-#include "llvm/CodeGen/EdgeBundles.h"
-#include "llvm/CodeGen/LiveInterval.h"
-#include "llvm/CodeGen/LiveIntervalUnion.h"
-#include "llvm/CodeGen/LiveIntervals.h"
-#include "llvm/CodeGen/LiveRangeEdit.h"
-#include "llvm/CodeGen/LiveRegMatrix.h"
-#include "llvm/CodeGen/LiveStacks.h"
-#include "llvm/CodeGen/MachineBasicBlock.h"
-#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
-#include "llvm/CodeGen/MachineDominators.h"
-#include "llvm/CodeGen/MachineFrameInfo.h"
-#include "llvm/CodeGen/MachineFunction.h"
-#include "llvm/CodeGen/MachineFunctionPass.h"
-#include "llvm/CodeGen/MachineInstr.h"
-#include "llvm/CodeGen/MachineLoopInfo.h"
-#include "llvm/CodeGen/MachineOperand.h"
-#include "llvm/CodeGen/MachineOptimizationRemarkEmitter.h"
-#include "llvm/CodeGen/MachineRegisterInfo.h"
-#include "llvm/CodeGen/RegAllocRegistry.h"
-#include "llvm/CodeGen/RegisterClassInfo.h"
-#include "llvm/CodeGen/SlotIndexes.h"
-#include "llvm/CodeGen/Spiller.h"
-#include "llvm/CodeGen/TargetInstrInfo.h"
-#include "llvm/CodeGen/TargetRegisterInfo.h"
-#include "llvm/CodeGen/TargetSubtargetInfo.h"
-#include "llvm/CodeGen/VirtRegMap.h"
-#include "llvm/IR/DebugInfoMetadata.h"
-#include "llvm/IR/Function.h"
-#include "llvm/IR/LLVMContext.h"
-#include "llvm/InitializePasses.h"
-#include "llvm/MC/MCRegisterInfo.h"
-#include "llvm/Pass.h"
-#include "llvm/Support/BlockFrequency.h"
-#include "llvm/Support/BranchProbability.h"
-#include "llvm/Support/CommandLine.h"
-#include "llvm/Support/Debug.h"
-#include "llvm/Support/MathExtras.h"
-#include "llvm/Support/Timer.h"
-#include "llvm/Support/raw_ostream.h"
-#include <algorithm>
-#include <cassert>
-#include <cstdint>
-#include <utility>
-
-using namespace llvm;
-
-#define DEBUG_TYPE "regalloc"
-
-STATISTIC(NumGlobalSplits, "Number of split global live ranges");
-STATISTIC(NumLocalSplits,  "Number of split local live ranges");
-STATISTIC(NumEvicted,      "Number of interferences evicted");
-
-static cl::opt<SplitEditor::ComplementSpillMode> SplitSpillMode(
-    "split-spill-mode", cl::Hidden,
-    cl::desc("Spill mode for splitting live ranges"),
-    cl::values(clEnumValN(SplitEditor::SM_Partition, "default", "Default"),
-               clEnumValN(SplitEditor::SM_Size, "size", "Optimize for size"),
-               clEnumValN(SplitEditor::SM_Speed, "speed", "Optimize for speed")),
-    cl::init(SplitEditor::SM_Speed));
-
-static cl::opt<unsigned>
-LastChanceRecoloringMaxDepth("lcr-max-depth", cl::Hidden,
-                             cl::desc("Last chance recoloring max depth"),
-                             cl::init(5));
-
-static cl::opt<unsigned> LastChanceRecoloringMaxInterference(
-    "lcr-max-interf", cl::Hidden,
-    cl::desc("Last chance recoloring maximum number of considered"
-             " interference at a time"),
-    cl::init(8));
-
-static cl::opt<bool> ExhaustiveSearch(
-    "exhaustive-register-search", cl::NotHidden,
-    cl::desc("Exhaustive Search for registers bypassing the depth "
-             "and interference cutoffs of last chance recoloring"),
-    cl::Hidden);
-
-static cl::opt<bool> EnableDeferredSpilling(
-    "enable-deferred-spilling", cl::Hidden,
-    cl::desc("Instead of spilling a variable right away, defer the actual "
-             "code insertion to the end of the allocation. That way the "
-             "allocator might still find a suitable coloring for this "
-             "variable because of other evicted variables."),
-    cl::init(false));
-
-// FIXME: Find a good default for this flag and remove the flag.
-static cl::opt<unsigned>
-CSRFirstTimeCost("regalloc-csr-first-time-cost",
-              cl::desc("Cost for first time use of callee-saved register."),
-              cl::init(0), cl::Hidden);
-
-static cl::opt<unsigned long> GrowRegionComplexityBudget(
-    "grow-region-complexity-budget",
-    cl::desc("growRegion() does not scale with the number of BB edges, so "
-             "limit its budget and bail out once we reach the limit."),
-    cl::init(10000), cl::Hidden);
-
-static cl::opt<bool> GreedyRegClassPriorityTrumpsGlobalness(
-    "greedy-regclass-priority-trumps-globalness",
-    cl::desc("Change the greedy register allocator's live range priority "
-             "calculation to make the AllocationPriority of the register class "
-             "more important then whether the range is global"),
-    cl::Hidden);
-
-static RegisterRegAlloc greedyRegAlloc("greedy", "greedy register allocator",
-                                       createGreedyRegisterAllocator);
-
-char RAGreedy::ID = 0;
-char &llvm::RAGreedyID = RAGreedy::ID;
-
-INITIALIZE_PASS_BEGIN(RAGreedy, "greedy",
-                "Greedy Register Allocator", false, false)
-INITIALIZE_PASS_DEPENDENCY(LiveDebugVariables)
-INITIALIZE_PASS_DEPENDENCY(SlotIndexes)
-INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
-INITIALIZE_PASS_DEPENDENCY(RegisterCoalescer)
-INITIALIZE_PASS_DEPENDENCY(MachineScheduler)
-INITIALIZE_PASS_DEPENDENCY(LiveStacks)
-INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
-INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
-INITIALIZE_PASS_DEPENDENCY(VirtRegMap)
-INITIALIZE_PASS_DEPENDENCY(LiveRegMatrix)
-INITIALIZE_PASS_DEPENDENCY(EdgeBundles)
-INITIALIZE_PASS_DEPENDENCY(SpillPlacement)
-INITIALIZE_PASS_DEPENDENCY(MachineOptimizationRemarkEmitterPass)
-INITIALIZE_PASS_DEPENDENCY(RegAllocEvictionAdvisorAnalysis)
-INITIALIZE_PASS_END(RAGreedy, "greedy",
-                "Greedy Register Allocator", false, false)
-
-#ifndef NDEBUG
-const char *const RAGreedy::StageName[] = {
-    "RS_New",
-    "RS_Assign",
-    "RS_Split",
-    "RS_Split2",
-    "RS_Spill",
-    "RS_Memory",
-    "RS_Done"
-};
-#endif
-
-// Hysteresis to use when comparing floats.
-// This helps stabilize decisions based on float comparisons.
-const float Hysteresis = (2007 / 2048.0f); // 0.97998046875
-
-FunctionPass* llvm::createGreedyRegisterAllocator() {
-  return new RAGreedy();
-}
-
-namespace llvm {
-FunctionPass* createGreedyRegisterAllocator(
-  std::function<bool(const TargetRegisterInfo &TRI,
-                     const TargetRegisterClass &RC)> Ftor);
-
-}
-
-FunctionPass* llvm::createGreedyRegisterAllocator(
-  std::function<bool(const TargetRegisterInfo &TRI,
-                     const TargetRegisterClass &RC)> Ftor) {
-  return new RAGreedy(Ftor);
-}
-
-RAGreedy::RAGreedy(RegClassFilterFunc F):
-  MachineFunctionPass(ID),
-  RegAllocBase(F) {
-}
-
-void RAGreedy::getAnalysisUsage(AnalysisUsage &AU) const {
-  AU.setPreservesCFG();
-  AU.addRequired<MachineBlockFrequencyInfo>();
-  AU.addPreserved<MachineBlockFrequencyInfo>();
-  AU.addRequired<AAResultsWrapperPass>();
-  AU.addPreserved<AAResultsWrapperPass>();
-  AU.addRequired<LiveIntervals>();
-  AU.addPreserved<LiveIntervals>();
-  AU.addRequired<SlotIndexes>();
-  AU.addPreserved<SlotIndexes>();
-  AU.addRequired<LiveDebugVariables>();
-  AU.addPreserved<LiveDebugVariables>();
-  AU.addRequired<LiveStacks>();
-  AU.addPreserved<LiveStacks>();
-  AU.addRequired<MachineDominatorTree>();
-  AU.addPreserved<MachineDominatorTree>();
-  AU.addRequired<MachineLoopInfo>();
-  AU.addPreserved<MachineLoopInfo>();
-  AU.addRequired<VirtRegMap>();
-  AU.addPreserved<VirtRegMap>();
-  AU.addRequired<LiveRegMatrix>();
-  AU.addPreserved<LiveRegMatrix>();
-  AU.addRequired<EdgeBundles>();
-  AU.addRequired<SpillPlacement>();
-  AU.addRequired<MachineOptimizationRemarkEmitterPass>();
-  AU.addRequired<RegAllocEvictionAdvisorAnalysis>();
-  MachineFunctionPass::getAnalysisUsage(AU);
-}
-
-//===----------------------------------------------------------------------===//
-//                     LiveRangeEdit delegate methods
-//===----------------------------------------------------------------------===//
-
-bool RAGreedy::LRE_CanEraseVirtReg(Register VirtReg) {
-  LiveInterval &LI = LIS->getInterval(VirtReg);
-  if (VRM->hasPhys(VirtReg)) {
-    Matrix->unassign(LI);
-    aboutToRemoveInterval(LI);
-    return true;
-  }
-  // Unassigned virtreg is probably in the priority queue.
-  // RegAllocBase will erase it after dequeueing.
-  // Nonetheless, clear the live-range so that the debug
-  // dump will show the right state for that VirtReg.
-  LI.clear();
-  return false;
-}
-
-void RAGreedy::LRE_WillShrinkVirtReg(Register VirtReg) {
-  if (!VRM->hasPhys(VirtReg))
-    return;
-
-  // Register is assigned, put it back on the queue for reassignment.
-  LiveInterval &LI = LIS->getInterval(VirtReg);
-  Matrix->unassign(LI);
-  RegAllocBase::enqueue(&LI);
-}
-
-void RAGreedy::LRE_DidCloneVirtReg(Register New, Register Old) {
-  ExtraInfo->LRE_DidCloneVirtReg(New, Old);
-}
-
-void RAGreedy::ExtraRegInfo::LRE_DidCloneVirtReg(Register New, Register Old) {
-  // Cloning a register we haven't even heard about yet?  Just ignore it.
-  if (!Info.inBounds(Old))
-    return;
-
-  // LRE may clone a virtual register because dead code elimination causes it to
-  // be split into connected components. The new components are much smaller
-  // than the original, so they should get a new chance at being assigned.
-  // same stage as the parent.
-  Info[Old].Stage = RS_Assign;
-  Info.grow(New.id());
-  Info[New] = Info[Old];
-}
-
-void RAGreedy::releaseMemory() {
-  SpillerInstance.reset();
-  GlobalCand.clear();
-}
-
-void RAGreedy::enqueueImpl(const LiveInterval *LI) { enqueue(Queue, LI); }
-
-void RAGreedy::enqueue(PQueue &CurQueue, const LiveInterval *LI) {
-  // Prioritize live ranges by size, assigning larger ranges first.
-  // The queue holds (size, reg) pairs.
-  const unsigned Size = LI->getSize();
-  const Register Reg = LI->reg();
-  assert(Reg.isVirtual() && "Can only enqueue virtual registers");
-  unsigned Prio;
-
-  auto Stage = ExtraInfo->getOrInitStage(Reg);
-  if (Stage == RS_New) {
-    Stage = RS_Assign;
-    ExtraInfo->setStage(Reg, Stage);
-  }
-  if (Stage == RS_Split) {
-    // Unsplit ranges that couldn't be allocated immediately are deferred until
-    // everything else has been allocated.
-    Prio = Size;
-  } else if (Stage == RS_Memory) {
-    // Memory operand should be considered last.
-    // Change the priority such that Memory operand are assigned in
-    // the reverse order that they came in.
-    // TODO: Make this a member variable and probably do something about hints.
-    static unsigned MemOp = 0;
-    Prio = MemOp++;
-  } else {
-    // Giant live ranges fall back to the global assignment heuristic, which
-    // prevents excessive spilling in pathological cases.
-    bool ReverseLocal = TRI->reverseLocalAssignment();
-    const TargetRegisterClass &RC = *MRI->getRegClass(Reg);
-    bool ForceGlobal =
-        !ReverseLocal && (Size / SlotIndex::InstrDist) >
-                             (2 * RegClassInfo.getNumAllocatableRegs(&RC));
-    unsigned GlobalBit = 0;
-
-    if (Stage == RS_Assign && !ForceGlobal && !LI->empty() &&
-        LIS->intervalIsInOneMBB(*LI)) {
-      // Allocate original local ranges in linear instruction order. Since they
-      // are singly defined, this produces optimal coloring in the absence of
-      // global interference and other constraints.
-      if (!ReverseLocal)
-        Prio = LI->beginIndex().getInstrDistance(Indexes->getLastIndex());
-      else {
-        // Allocating bottom up may allow many short LRGs to be assigned first
-        // to one of the cheap registers. This could be much faster for very
-        // large blocks on targets with many physical registers.
-        Prio = Indexes->getZeroIndex().getInstrDistance(LI->endIndex());
-      }
-    } else {
-      // Allocate global and split ranges in long->short order. Long ranges that
-      // don't fit should be spilled (or split) ASAP so they don't create
-      // interference.  Mark a bit to prioritize global above local ranges.
-      Prio = Size;
-      GlobalBit = 1;
-    }
-    if (RegClassPriorityTrumpsGlobalness)
-      Prio |= RC.AllocationPriority << 25 | GlobalBit << 24;
-    else
-      Prio |= GlobalBit << 29 | RC.AllocationPriority << 24;
-
-    // Mark a higher bit to prioritize global and local above RS_Split.
-    Prio |= (1u << 31);
-
-    // Boost ranges that have a physical register hint.
-    if (VRM->hasKnownPreference(Reg))
-      Prio |= (1u << 30);
-  }
-  // The virtual register number is a tie breaker for same-sized ranges.
-  // Give lower vreg numbers higher priority to assign them first.
-  CurQueue.push(std::make_pair(Prio, ~Reg));
-}
-
-const LiveInterval *RAGreedy::dequeue() { return dequeue(Queue); }
-
-const LiveInterval *RAGreedy::dequeue(PQueue &CurQueue) {
-  if (CurQueue.empty())
-    return nullptr;
-  LiveInterval *LI = &LIS->getInterval(~CurQueue.top().second);
-  CurQueue.pop();
-  return LI;
-}
-
-//===----------------------------------------------------------------------===//
-//                            Direct Assignment
-//===----------------------------------------------------------------------===//
-
-/// tryAssign - Try to assign VirtReg to an available register.
-MCRegister RAGreedy::tryAssign(const LiveInterval &VirtReg,
-                               AllocationOrder &Order,
-                               SmallVectorImpl<Register> &NewVRegs,
-                               const SmallVirtRegSet &FixedRegisters) {
-  MCRegister PhysReg;
-  for (auto I = Order.begin(), E = Order.end(); I != E && !PhysReg; ++I) {
-    assert(*I);
-    if (!Matrix->checkInterference(VirtReg, *I)) {
-      if (I.isHint())
-        return *I;
-      else
-        PhysReg = *I;
-    }
-  }
-  if (!PhysReg.isValid())
-    return PhysReg;
-
-  // PhysReg is available, but there may be a better choice.
-
-  // If we missed a simple hint, try to cheaply evict interference from the
-  // preferred register.
-  if (Register Hint = MRI->getSimpleHint(VirtReg.reg()))
-    if (Order.isHint(Hint)) {
-      MCRegister PhysHint = Hint.asMCReg();
-      LLVM_DEBUG(dbgs() << "missed hint " << printReg(PhysHint, TRI) << '\n');
-
-      if (EvictAdvisor->canEvictHintInterference(VirtReg, PhysHint,
-                                                 FixedRegisters)) {
-        evictInterference(VirtReg, PhysHint, NewVRegs);
-        return PhysHint;
-      }
-      // Record the missed hint, we may be able to recover
-      // at the end if the surrounding allocation changed.
-      SetOfBrokenHints.insert(&VirtReg);
-    }
-
-  // Try to evict interference from a cheaper alternative.
-  uint8_t Cost = RegCosts[PhysReg];
-
-  // Most registers have 0 additional cost.
-  if (!Cost)
-    return PhysReg;
-
-  LLVM_DEBUG(dbgs() << printReg(PhysReg, TRI) << " is available at cost "
-                    << (unsigned)Cost << '\n');
-  MCRegister CheapReg = tryEvict(VirtReg, Order, NewVRegs, Cost, FixedRegisters);
-  return CheapReg ? CheapReg : PhysReg;
-}
-
-//===----------------------------------------------------------------------===//
-//                         Interference eviction
-//===----------------------------------------------------------------------===//
-
-Register RegAllocEvictionAdvisor::canReassign(const LiveInterval &VirtReg,
-                                              Register PrevReg) const {
-  auto Order =
-      AllocationOrder::create(VirtReg.reg(), *VRM, RegClassInfo, Matrix);
-  MCRegister PhysReg;
-  for (auto I = Order.begin(), E = Order.end(); I != E && !PhysReg; ++I) {
-    if ((*I).id() == PrevReg.id())
-      continue;
-
-    MCRegUnitIterator Units(*I, TRI);
-    for (; Units.isValid(); ++Units) {
-      // Instantiate a "subquery", not to be confused with the Queries array.
-      LiveIntervalUnion::Query subQ(VirtReg, Matrix->getLiveUnions()[*Units]);
-      if (subQ.checkInterference())
-        break;
-    }
-    // If no units have interference, break out with the current PhysReg.
-    if (!Units.isValid())
-      PhysReg = *I;
-  }
-  if (PhysReg)
-    LLVM_DEBUG(dbgs() << "can reassign: " << VirtReg << " from "
-                      << printReg(PrevReg, TRI) << " to "
-                      << printReg(PhysReg, TRI) << '\n');
-  return PhysReg;
-}
-
-/// Return true if all interferences between VirtReg and PhysReg between
-/// Start and End can be evicted.
-///
-/// \param VirtReg Live range that is about to be assigned.
-/// \param PhysReg Desired register for assignment.
-/// \param Start   Start of range to look for interferences.
-/// \param End     End of range to look for interferences.
-/// \param MaxCost Only look for cheaper candidates and update with new cost
-///                when returning true.
-/// \return True when interference can be evicted cheaper than MaxCost.
-bool RAGreedy::canEvictInterferenceInRange(const LiveInterval &VirtReg,
-                                           MCRegister PhysReg, SlotIndex Start,
-                                           SlotIndex End,
-                                           EvictionCost &MaxCost) const {
-  EvictionCost Cost;
-
-  for (MCRegUnitIterator Units(PhysReg, TRI); Units.isValid(); ++Units) {
-    LiveIntervalUnion::Query &Q = Matrix->query(VirtReg, *Units);
-
-    // Check if any interfering live range is heavier than MaxWeight.
-    for (const LiveInterval *Intf : reverse(Q.interferingVRegs())) {
-      // Check if interference overlast the segment in interest.
-      if (!Intf->overlaps(Start, End))
-        continue;
-
-      // Never evict spill products. They cannot split or spill.
-      if (ExtraInfo->getStage(*Intf) == RS_Done)
-        return false;
-
-      // Would this break a satisfied hint?
-      bool BreaksHint = VRM->hasPreferredPhys(Intf->reg());
-      // Update eviction cost.
-      Cost.BrokenHints += BreaksHint;
-      Cost.MaxWeight = std::max(Cost.MaxWeight, Intf->weight());
-      // Abort if this would be too expensive.
-      if (!(Cost < MaxCost))
-        return false;
-    }
-  }
-
-  if (Cost.MaxWeight == 0)
-    return false;
-
-  MaxCost = Cost;
-  return true;
-}
-
-/// Return the physical register that will be best
-/// candidate for eviction by a local split interval that will be created
-/// between Start and End.
-///
-/// \param Order            The allocation order
-/// \param VirtReg          Live range that is about to be assigned.
-/// \param Start            Start of range to look for interferences
-/// \param End              End of range to look for interferences
-/// \param BestEvictweight  The eviction cost of that eviction
-/// \return The PhysReg which is the best candidate for eviction and the
-/// eviction cost in BestEvictweight
-MCRegister RAGreedy::getCheapestEvicteeWeight(const AllocationOrder &Order,
-                                              const LiveInterval &VirtReg,
-                                              SlotIndex Start, SlotIndex End,
-                                              float *BestEvictweight) const {
-  EvictionCost BestEvictCost;
-  BestEvictCost.setMax();
-  BestEvictCost.MaxWeight = VirtReg.weight();
-  MCRegister BestEvicteePhys;
-
-  // Go over all physical registers and find the best candidate for eviction
-  for (MCRegister PhysReg : Order.getOrder()) {
-
-    if (!canEvictInterferenceInRange(VirtReg, PhysReg, Start, End,
-                                     BestEvictCost))
-      continue;
-
-    // Best so far.
-    BestEvicteePhys = PhysReg;
-  }
-  *BestEvictweight = BestEvictCost.MaxWeight;
-  return BestEvicteePhys;
-}
-
-/// evictInterference - Evict any interferring registers that prevent VirtReg
-/// from being assigned to Physreg. This assumes that canEvictInterference
-/// returned true.
-void RAGreedy::evictInterference(const LiveInterval &VirtReg,
-                                 MCRegister PhysReg,
-                                 SmallVectorImpl<Register> &NewVRegs) {
-  // Make sure that VirtReg has a cascade number, and assign that cascade
-  // number to every evicted register. These live ranges than then only be
-  // evicted by a newer cascade, preventing infinite loops.
-  unsigned Cascade = ExtraInfo->getOrAssignNewCascade(VirtReg.reg());
-
-  LLVM_DEBUG(dbgs() << "evicting " << printReg(PhysReg, TRI)
-                    << " interference: Cascade " << Cascade << '\n');
-
-  // Collect all interfering virtregs first.
-  SmallVector<const LiveInterval *, 8> Intfs;
-  for (MCRegUnitIterator Units(PhysReg, TRI); Units.isValid(); ++Units) {
-    LiveIntervalUnion::Query &Q = Matrix->query(VirtReg, *Units);
-    // We usually have the interfering VRegs cached so collectInterferingVRegs()
-    // should be fast, we may need to recalculate if when different physregs
-    // overlap the same register unit so we had different SubRanges queried
-    // against it.
-    ArrayRef<const LiveInterval *> IVR = Q.interferingVRegs();
-    Intfs.append(IVR.begin(), IVR.end());
-  }
-
-  // Evict them second. This will invalidate the queries.
-  for (const LiveInterval *Intf : Intfs) {
-    // The same VirtReg may be present in multiple RegUnits. Skip duplicates.
-    if (!VRM->hasPhys(Intf->reg()))
-      continue;
-
-    LastEvicted.addEviction(PhysReg, VirtReg.reg(), Intf->reg());
-
-    Matrix->unassign(*Intf);
-    assert((ExtraInfo->getCascade(Intf->reg()) < Cascade ||
-            VirtReg.isSpillable() < Intf->isSpillable()) &&
-           "Cannot decrease cascade number, illegal eviction");
-    ExtraInfo->setCascade(Intf->reg(), Cascade);
-    ++NumEvicted;
-    NewVRegs.push_back(Intf->reg());
-  }
-}
-
-/// Returns true if the given \p PhysReg is a callee saved register and has not
-/// been used for allocation yet.
-bool RegAllocEvictionAdvisor::isUnusedCalleeSavedReg(MCRegister PhysReg) const {
-  MCRegister CSR = RegClassInfo.getLastCalleeSavedAlias(PhysReg);
-  if (!CSR)
-    return false;
-
-  return !Matrix->isPhysRegUsed(PhysReg);
-}
-
-Optional<unsigned>
-RegAllocEvictionAdvisor::getOrderLimit(const LiveInterval &VirtReg,
-                                       const AllocationOrder &Order,
-                                       unsigned CostPerUseLimit) const {
-  unsigned OrderLimit = Order.getOrder().size();
-
-  if (CostPerUseLimit < uint8_t(~0u)) {
-    // Check of any registers in RC are below CostPerUseLimit.
-    const TargetRegisterClass *RC = MRI->getRegClass(VirtReg.reg());
-    uint8_t MinCost = RegClassInfo.getMinCost(RC);
-    if (MinCost >= CostPerUseLimit) {
-      LLVM_DEBUG(dbgs() << TRI->getRegClassName(RC) << " minimum cost = "
-                        << MinCost << ", no cheaper registers to be found.\n");
-      return None;
-    }
-
-    // It is normal for register classes to have a long tail of registers with
-    // the same cost. We don't need to look at them if they're too expensive.
-    if (RegCosts[Order.getOrder().back()] >= CostPerUseLimit) {
-      OrderLimit = RegClassInfo.getLastCostChange(RC);
-      LLVM_DEBUG(dbgs() << "Only trying the first " << OrderLimit
-                        << " regs.\n");
-    }
-  }
-  return OrderLimit;
-}
-
-bool RegAllocEvictionAdvisor::canAllocatePhysReg(unsigned CostPerUseLimit,
-                                                 MCRegister PhysReg) const {
-  if (RegCosts[PhysReg] >= CostPerUseLimit)
-    return false;
-  // The first use of a callee-saved register in a function has cost 1.
-  // Don't start using a CSR when the CostPerUseLimit is low.
-  if (CostPerUseLimit == 1 && isUnusedCalleeSavedReg(PhysReg)) {
-    LLVM_DEBUG(
-        dbgs() << printReg(PhysReg, TRI) << " would clobber CSR "
-               << printReg(RegClassInfo.getLastCalleeSavedAlias(PhysReg), TRI)
-               << '\n');
-    return false;
-  }
-  return true;
-}
-
-/// tryEvict - Try to evict all interferences for a physreg.
-/// @param  VirtReg Currently unassigned virtual register.
-/// @param  Order   Physregs to try.
-/// @return         Physreg to assign VirtReg, or 0.
-MCRegister RAGreedy::tryEvict(const LiveInterval &VirtReg,
-                              AllocationOrder &Order,
-                              SmallVectorImpl<Register> &NewVRegs,
-                              uint8_t CostPerUseLimit,
-                              const SmallVirtRegSet &FixedRegisters) {
-  NamedRegionTimer T("evict", "Evict", TimerGroupName, TimerGroupDescription,
-                     TimePassesIsEnabled);
-
-  MCRegister BestPhys = EvictAdvisor->tryFindEvictionCandidate(
-      VirtReg, Order, CostPerUseLimit, FixedRegisters);
-  if (BestPhys.isValid())
-    evictInterference(VirtReg, BestPhys, NewVRegs);
-  return BestPhys;
-}
-
-//===----------------------------------------------------------------------===//
-//                              Region Splitting
-//===----------------------------------------------------------------------===//
-
-/// addSplitConstraints - Fill out the SplitConstraints vector based on the
-/// interference pattern in Physreg and its aliases. Add the constraints to
-/// SpillPlacement and return the static cost of this split in Cost, assuming
-/// that all preferences in SplitConstraints are met.
-/// Return false if there are no bundles with positive bias.
-bool RAGreedy::addSplitConstraints(InterferenceCache::Cursor Intf,
-                                   BlockFrequency &Cost) {
-  ArrayRef<SplitAnalysis::BlockInfo> UseBlocks = SA->getUseBlocks();
-
-  // Reset interference dependent info.
-  SplitConstraints.resize(UseBlocks.size());
-  BlockFrequency StaticCost = 0;
-  for (unsigned I = 0; I != UseBlocks.size(); ++I) {
-    const SplitAnalysis::BlockInfo &BI = UseBlocks[I];
-    SpillPlacement::BlockConstraint &BC = SplitConstraints[I];
-
-    BC.Number = BI.MBB->getNumber();
-    Intf.moveToBlock(BC.Number);
-    BC.Entry = BI.LiveIn ? SpillPlacement::PrefReg : SpillPlacement::DontCare;
-    BC.Exit = (BI.LiveOut &&
-               !LIS->getInstructionFromIndex(BI.LastInstr)->isImplicitDef())
-                  ? SpillPlacement::PrefReg
-                  : SpillPlacement::DontCare;
-    BC.ChangesValue = BI.FirstDef.isValid();
-
-    if (!Intf.hasInterference())
-      continue;
-
-    // Number of spill code instructions to insert.
-    unsigned Ins = 0;
-
-    // Interference for the live-in value.
-    if (BI.LiveIn) {
-      if (Intf.first() <= Indexes->getMBBStartIdx(BC.Number)) {
-        BC.Entry = SpillPlacement::MustSpill;
-        ++Ins;
-      } else if (Intf.first() < BI.FirstInstr) {
-        BC.Entry = SpillPlacement::PrefSpill;
-        ++Ins;
-      } else if (Intf.first() < BI.LastInstr) {
-        ++Ins;
-      }
-
-      // Abort if the spill cannot be inserted at the MBB' start
-      if (((BC.Entry == SpillPlacement::MustSpill) ||
-           (BC.Entry == SpillPlacement::PrefSpill)) &&
-          SlotIndex::isEarlierInstr(BI.FirstInstr,
-                                    SA->getFirstSplitPoint(BC.Number)))
-        return false;
-    }
-
-    // Interference for the live-out value.
-    if (BI.LiveOut) {
-      if (Intf.last() >= SA->getLastSplitPoint(BC.Number)) {
-        BC.Exit = SpillPlacement::MustSpill;
-        ++Ins;
-      } else if (Intf.last() > BI.LastInstr) {
-        BC.Exit = SpillPlacement::PrefSpill;
-        ++Ins;
-      } else if (Intf.last() > BI.FirstInstr) {
-        ++Ins;
-      }
-    }
-
-    // Accumulate the total frequency of inserted spill code.
-    while (Ins--)
-      StaticCost += SpillPlacer->getBlockFrequency(BC.Number);
-  }
-  Cost = StaticCost;
-
-  // Add constraints for use-blocks. Note that these are the only constraints
-  // that may add a positive bias, it is downhill from here.
-  SpillPlacer->addConstraints(SplitConstraints);
-  return SpillPlacer->scanActiveBundles();
-}
-
-/// addThroughConstraints - Add constraints and links to SpillPlacer from the
-/// live-through blocks in Blocks.
-bool RAGreedy::addThroughConstraints(InterferenceCache::Cursor Intf,
-                                     ArrayRef<unsigned> Blocks) {
-  const unsigned GroupSize = 8;
-  SpillPlacement::BlockConstraint BCS[GroupSize];
-  unsigned TBS[GroupSize];
-  unsigned B = 0, T = 0;
-
-  for (unsigned Number : Blocks) {
-    Intf.moveToBlock(Number);
-
-    if (!Intf.hasInterference()) {
-      assert(T < GroupSize && "Array overflow");
-      TBS[T] = Number;
-      if (++T == GroupSize) {
-        SpillPlacer->addLinks(makeArrayRef(TBS, T));
-        T = 0;
-      }
-      continue;
-    }
-
-    assert(B < GroupSize && "Array overflow");
-    BCS[B].Number = Number;
-
-    // Abort if the spill cannot be inserted at the MBB' start
-    MachineBasicBlock *MBB = MF->getBlockNumbered(Number);
-    auto FirstNonDebugInstr = MBB->getFirstNonDebugInstr();
-    if (FirstNonDebugInstr != MBB->end() &&
-        SlotIndex::isEarlierInstr(LIS->getInstructionIndex(*FirstNonDebugInstr),
-                                  SA->getFirstSplitPoint(Number)))
-      return false;
-    // Interference for the live-in value.
-    if (Intf.first() <= Indexes->getMBBStartIdx(Number))
-      BCS[B].Entry = SpillPlacement::MustSpill;
-    else
-      BCS[B].Entry = SpillPlacement::PrefSpill;
-
-    // Interference for the live-out value.
-    if (Intf.last() >= SA->getLastSplitPoint(Number))
-      BCS[B].Exit = SpillPlacement::MustSpill;
-    else
-      BCS[B].Exit = SpillPlacement::PrefSpill;
-
-    if (++B == GroupSize) {
-      SpillPlacer->addConstraints(makeArrayRef(BCS, B));
-      B = 0;
-    }
-  }
-
-  SpillPlacer->addConstraints(makeArrayRef(BCS, B));
-  SpillPlacer->addLinks(makeArrayRef(TBS, T));
-  return true;
-}
-
-bool RAGreedy::growRegion(GlobalSplitCandidate &Cand) {
-  // Keep track of through blocks that have not been added to SpillPlacer.
-  BitVector Todo = SA->getThroughBlocks();
-  SmallVectorImpl<unsigned> &ActiveBlocks = Cand.ActiveBlocks;
-  unsigned AddedTo = 0;
-#ifndef NDEBUG
-  unsigned Visited = 0;
-#endif
-
-  unsigned long Budget = GrowRegionComplexityBudget;
-  while (true) {
-    ArrayRef<unsigned> NewBundles = SpillPlacer->getRecentPositive();
-    // Find new through blocks in the periphery of PrefRegBundles.
-    for (unsigned Bundle : NewBundles) {
-      // Look at all blocks connected to Bundle in the full graph.
-      ArrayRef<unsigned> Blocks = Bundles->getBlocks(Bundle);
-      // Limit compilation time by bailing out after we use all our budget.
-      if (Blocks.size() >= Budget)
-        return false;
-      Budget -= Blocks.size();
-      for (unsigned Block : Blocks) {
-        if (!Todo.test(Block))
-          continue;
-        Todo.reset(Block);
-        // This is a new through block. Add it to SpillPlacer later.
-        ActiveBlocks.push_back(Block);
-#ifndef NDEBUG
-        ++Visited;
-#endif
-      }
-    }
-    // Any new blocks to add?
-    if (ActiveBlocks.size() == AddedTo)
-      break;
-
-    // Compute through constraints from the interference, or assume that all
-    // through blocks prefer spilling when forming compact regions.
-    auto NewBlocks = makeArrayRef(ActiveBlocks).slice(AddedTo);
-    if (Cand.PhysReg) {
-      if (!addThroughConstraints(Cand.Intf, NewBlocks))
-        return false;
-    } else
-      // Provide a strong negative bias on through blocks to prevent unwanted
-      // liveness on loop backedges.
-      SpillPlacer->addPrefSpill(NewBlocks, /* Strong= */ true);
-    AddedTo = ActiveBlocks.size();
-
-    // Perhaps iterating can enable more bundles?
-    SpillPlacer->iterate();
-  }
-  LLVM_DEBUG(dbgs() << ", v=" << Visited);
-  return true;
-}
-
-/// calcCompactRegion - Compute the set of edge bundles that should be live
-/// when splitting the current live range into compact regions.  Compact
-/// regions can be computed without looking at interference.  They are the
-/// regions formed by removing all the live-through blocks from the live range.
-///
-/// Returns false if the current live range is already compact, or if the
-/// compact regions would form single block regions anyway.
-bool RAGreedy::calcCompactRegion(GlobalSplitCandidate &Cand) {
-  // Without any through blocks, the live range is already compact.
-  if (!SA->getNumThroughBlocks())
-    return false;
-
-  // Compact regions don't correspond to any physreg.
-  Cand.reset(IntfCache, MCRegister::NoRegister);
-
-  LLVM_DEBUG(dbgs() << "Compact region bundles");
-
-  // Use the spill placer to determine the live bundles. GrowRegion pretends
-  // that all the through blocks have interference when PhysReg is unset.
-  SpillPlacer->prepare(Cand.LiveBundles);
-
-  // The static split cost will be zero since Cand.Intf reports no interference.
-  BlockFrequency Cost;
-  if (!addSplitConstraints(Cand.Intf, Cost)) {
-    LLVM_DEBUG(dbgs() << ", none.\n");
-    return false;
-  }
-
-  if (!growRegion(Cand)) {
-    LLVM_DEBUG(dbgs() << ", cannot spill all interferences.\n");
-    return false;
-  }
-
-  SpillPlacer->finish();
-
-  if (!Cand.LiveBundles.any()) {
-    LLVM_DEBUG(dbgs() << ", none.\n");
-    return false;
-  }
-
-  LLVM_DEBUG({
-    for (int I : Cand.LiveBundles.set_bits())
-      dbgs() << " EB#" << I;
-    dbgs() << ".\n";
-  });
-  return true;
-}
-
-/// calcSpillCost - Compute how expensive it would be to split the live range in
-/// SA around all use blocks instead of forming bundle regions.
-BlockFrequency RAGreedy::calcSpillCost() {
-  BlockFrequency Cost = 0;
-  ArrayRef<SplitAnalysis::BlockInfo> UseBlocks = SA->getUseBlocks();
-  for (const SplitAnalysis::BlockInfo &BI : UseBlocks) {
-    unsigned Number = BI.MBB->getNumber();
-    // We normally only need one spill instruction - a load or a store.
-    Cost += SpillPlacer->getBlockFrequency(Number);
-
-    // Unless the value is redefined in the block.
-    if (BI.LiveIn && BI.LiveOut && BI.FirstDef)
-      Cost += SpillPlacer->getBlockFrequency(Number);
-  }
-  return Cost;
-}
-
-/// Check if splitting Evictee will create a local split interval in
-/// basic block number BBNumber that may cause a bad eviction chain. This is
-/// intended to prevent bad eviction sequences like:
-/// movl  %ebp, 8(%esp)           # 4-byte Spill
-/// movl  %ecx, %ebp
-/// movl  %ebx, %ecx
-/// movl  %edi, %ebx
-/// movl  %edx, %edi
-/// cltd
-/// idivl %esi
-/// movl  %edi, %edx
-/// movl  %ebx, %edi
-/// movl  %ecx, %ebx
-/// movl  %ebp, %ecx
-/// movl  16(%esp), %ebp          # 4 - byte Reload
-///
-/// Such sequences are created in 2 scenarios:
-///
-/// Scenario #1:
-/// %0 is evicted from physreg0 by %1.
-/// Evictee %0 is intended for region splitting with split candidate
-/// physreg0 (the reg %0 was evicted from).
-/// Region splitting creates a local interval because of interference with the
-/// evictor %1 (normally region splitting creates 2 interval, the "by reg"
-/// and "by stack" intervals and local interval created when interference
-/// occurs).
-/// One of the split intervals ends up evicting %2 from physreg1.
-/// Evictee %2 is intended for region splitting with split candidate
-/// physreg1.
-/// One of the split intervals ends up evicting %3 from physreg2, etc.
-///
-/// Scenario #2
-/// %0 is evicted from physreg0 by %1.
-/// %2 is evicted from physreg2 by %3 etc.
-/// Evictee %0 is intended for region splitting with split candidate
-/// physreg1.
-/// Region splitting creates a local interval because of interference with the
-/// evictor %1.
-/// One of the split intervals ends up evicting back original evictor %1
-/// from physreg0 (the reg %0 was evicted from).
-/// Another evictee %2 is intended for region splitting with split candidate
-/// physreg1.
-/// One of the split intervals ends up evicting %3 from physreg2, etc.
-///
-/// \param Evictee  The register considered to be split.
-/// \param Cand     The split candidate that determines the physical register
-///                 we are splitting for and the interferences.
-/// \param BBNumber The number of a BB for which the region split process will
-///                 create a local split interval.
-/// \param Order    The physical registers that may get evicted by a split
-///                 artifact of Evictee.
-/// \return True if splitting Evictee may cause a bad eviction chain, false
-/// otherwise.
-bool RAGreedy::splitCanCauseEvictionChain(Register Evictee,
-                                          GlobalSplitCandidate &Cand,
-                                          unsigned BBNumber,
-                                          const AllocationOrder &Order) {
-  EvictionTrack::EvictorInfo VregEvictorInfo = LastEvicted.getEvictor(Evictee);
-  unsigned Evictor = VregEvictorInfo.first;
-  MCRegister PhysReg = VregEvictorInfo.second;
-
-  // No actual evictor.
-  if (!Evictor || !PhysReg)
-    return false;
-
-  float MaxWeight = 0;
-  MCRegister FutureEvictedPhysReg =
-      getCheapestEvicteeWeight(Order, LIS->getInterval(Evictee),
-                               Cand.Intf.first(), Cand.Intf.last(), &MaxWeight);
-
-  // The bad eviction chain occurs when either the split candidate is the
-  // evicting reg or one of the split artifact will evict the evicting reg.
-  if ((PhysReg != Cand.PhysReg) && (PhysReg != FutureEvictedPhysReg))
-    return false;
-
-  Cand.Intf.moveToBlock(BBNumber);
-
-  // Check to see if the Evictor contains interference (with Evictee) in the
-  // given BB. If so, this interference caused the eviction of Evictee from
-  // PhysReg. This suggest that we will create a local interval during the
-  // region split to avoid this interference This local interval may cause a bad
-  // eviction chain.
-  if (!LIS->hasInterval(Evictor))
-    return false;
-  LiveInterval &EvictorLI = LIS->getInterval(Evictor);
-  if (EvictorLI.FindSegmentContaining(Cand.Intf.first()) == EvictorLI.end())
-    return false;
-
-  // Now, check to see if the local interval we will create is going to be
-  // expensive enough to evict somebody If so, this may cause a bad eviction
-  // chain.
-  float splitArtifactWeight =
-      VRAI->futureWeight(LIS->getInterval(Evictee),
-                         Cand.Intf.first().getPrevIndex(), Cand.Intf.last());
-  if (splitArtifactWeight >= 0 && splitArtifactWeight < MaxWeight)
-    return false;
-
-  return true;
-}
-
-/// calcGlobalSplitCost - Return the global split cost of following the split
-/// pattern in LiveBundles. This cost should be added to the local cost of the
-/// interference pattern in SplitConstraints.
-///
-BlockFrequency RAGreedy::calcGlobalSplitCost(GlobalSplitCandidate &Cand,
-                                             const AllocationOrder &Order) {
-  BlockFrequency GlobalCost = 0;
-  const BitVector &LiveBundles = Cand.LiveBundles;
-  ArrayRef<SplitAnalysis::BlockInfo> UseBlocks = SA->getUseBlocks();
-  for (unsigned I = 0; I != UseBlocks.size(); ++I) {
-    const SplitAnalysis::BlockInfo &BI = UseBlocks[I];
-    SpillPlacement::BlockConstraint &BC = SplitConstraints[I];
-    bool RegIn  = LiveBundles[Bundles->getBundle(BC.Number, false)];
-    bool RegOut = LiveBundles[Bundles->getBundle(BC.Number, true)];
-    unsigned Ins = 0;
-
-    Cand.Intf.moveToBlock(BC.Number);
-
-    if (BI.LiveIn)
-      Ins += RegIn != (BC.Entry == SpillPlacement::PrefReg);
-    if (BI.LiveOut)
-      Ins += RegOut != (BC.Exit == SpillPlacement::PrefReg);
-    while (Ins--)
-      GlobalCost += SpillPlacer->getBlockFrequency(BC.Number);
-  }
-
-  for (unsigned Number : Cand.ActiveBlocks) {
-    bool RegIn  = LiveBundles[Bundles->getBundle(Number, false)];
-    bool RegOut = LiveBundles[Bundles->getBundle(Number, true)];
-    if (!RegIn && !RegOut)
-      continue;
-    if (RegIn && RegOut) {
-      // We need double spill code if this block has interference.
-      Cand.Intf.moveToBlock(Number);
-      if (Cand.Intf.hasInterference()) {
-        GlobalCost += SpillPlacer->getBlockFrequency(Number);
-        GlobalCost += SpillPlacer->getBlockFrequency(Number);
-      }
-      continue;
-    }
-    // live-in / stack-out or stack-in live-out.
-    GlobalCost += SpillPlacer->getBlockFrequency(Number);
-  }
-  return GlobalCost;
-}
-
-/// splitAroundRegion - Split the current live range around the regions
-/// determined by BundleCand and GlobalCand.
-///
-/// Before calling this function, GlobalCand and BundleCand must be initialized
-/// so each bundle is assigned to a valid candidate, or NoCand for the
-/// stack-bound bundles.  The shared SA/SE SplitAnalysis and SplitEditor
-/// objects must be initialized for the current live range, and intervals
-/// created for the used candidates.
-///
-/// @param LREdit    The LiveRangeEdit object handling the current split.
-/// @param UsedCands List of used GlobalCand entries. Every BundleCand value
-///                  must appear in this list.
-void RAGreedy::splitAroundRegion(LiveRangeEdit &LREdit,
-                                 ArrayRef<unsigned> UsedCands) {
-  // These are the intervals created for new global ranges. We may create more
-  // intervals for local ranges.
-  const unsigned NumGlobalIntvs = LREdit.size();
-  LLVM_DEBUG(dbgs() << "splitAroundRegion with " << NumGlobalIntvs
-                    << " globals.\n");
-  assert(NumGlobalIntvs && "No global intervals configured");
-
-  // Isolate even single instructions when dealing with a proper sub-class.
-  // That guarantees register class inflation for the stack interval because it
-  // is all copies.
-  Register Reg = SA->getParent().reg();
-  bool SingleInstrs = RegClassInfo.isProperSubClass(MRI->getRegClass(Reg));
-
-  // First handle all the blocks with uses.
-  ArrayRef<SplitAnalysis::BlockInfo> UseBlocks = SA->getUseBlocks();
-  for (const SplitAnalysis::BlockInfo &BI : UseBlocks) {
-    unsigned Number = BI.MBB->getNumber();
-    unsigned IntvIn = 0, IntvOut = 0;
-    SlotIndex IntfIn, IntfOut;
-    if (BI.LiveIn) {
-      unsigned CandIn = BundleCand[Bundles->getBundle(Number, false)];
-      if (CandIn != NoCand) {
-        GlobalSplitCandidate &Cand = GlobalCand[CandIn];
-        IntvIn = Cand.IntvIdx;
-        Cand.Intf.moveToBlock(Number);
-        IntfIn = Cand.Intf.first();
-      }
-    }
-    if (BI.LiveOut) {
-      unsigned CandOut = BundleCand[Bundles->getBundle(Number, true)];
-      if (CandOut != NoCand) {
-        GlobalSplitCandidate &Cand = GlobalCand[CandOut];
-        IntvOut = Cand.IntvIdx;
-        Cand.Intf.moveToBlock(Number);
-        IntfOut = Cand.Intf.last();
-      }
-    }
-
-    // Create separate intervals for isolated blocks with multiple uses.
-    if (!IntvIn && !IntvOut) {
-      LLVM_DEBUG(dbgs() << printMBBReference(*BI.MBB) << " isolated.\n");
-      if (SA->shouldSplitSingleBlock(BI, SingleInstrs))
-        SE->splitSingleBlock(BI);
-      continue;
-    }
-
-    if (IntvIn && IntvOut)
-      SE->splitLiveThroughBlock(Number, IntvIn, IntfIn, IntvOut, IntfOut);
-    else if (IntvIn)
-      SE->splitRegInBlock(BI, IntvIn, IntfIn);
-    else
-      SE->splitRegOutBlock(BI, IntvOut, IntfOut);
-  }
-
-  // Handle live-through blocks. The relevant live-through blocks are stored in
-  // the ActiveBlocks list with each candidate. We need to filter out
-  // duplicates.
-  BitVector Todo = SA->getThroughBlocks();
-  for (unsigned UsedCand : UsedCands) {
-    ArrayRef<unsigned> Blocks = GlobalCand[UsedCand].ActiveBlocks;
-    for (unsigned Number : Blocks) {
-      if (!Todo.test(Number))
-        continue;
-      Todo.reset(Number);
-
-      unsigned IntvIn = 0, IntvOut = 0;
-      SlotIndex IntfIn, IntfOut;
-
-      unsigned CandIn = BundleCand[Bundles->getBundle(Number, false)];
-      if (CandIn != NoCand) {
-        GlobalSplitCandidate &Cand = GlobalCand[CandIn];
-        IntvIn = Cand.IntvIdx;
-        Cand.Intf.moveToBlock(Number);
-        IntfIn = Cand.Intf.first();
-      }
-
-      unsigned CandOut = BundleCand[Bundles->getBundle(Number, true)];
-      if (CandOut != NoCand) {
-        GlobalSplitCandidate &Cand = GlobalCand[CandOut];
-        IntvOut = Cand.IntvIdx;
-        Cand.Intf.moveToBlock(Number);
-        IntfOut = Cand.Intf.last();
-      }
-      if (!IntvIn && !IntvOut)
-        continue;
-      SE->splitLiveThroughBlock(Number, IntvIn, IntfIn, IntvOut, IntfOut);
-    }
-  }
-
-  ++NumGlobalSplits;
-
-  SmallVector<unsigned, 8> IntvMap;
-  SE->finish(&IntvMap);
-  DebugVars->splitRegister(Reg, LREdit.regs(), *LIS);
-
-  unsigned OrigBlocks = SA->getNumLiveBlocks();
-
-  // Sort out the new intervals created by splitting. We get four kinds:
-  // - Remainder intervals should not be split again.
-  // - Candidate intervals can be assigned to Cand.PhysReg.
-  // - Block-local splits are candidates for local splitting.
-  // - DCE leftovers should go back on the queue.
-  for (unsigned I = 0, E = LREdit.size(); I != E; ++I) {
-    const LiveInterval &Reg = LIS->getInterval(LREdit.get(I));
-
-    // Ignore old intervals from DCE.
-    if (ExtraInfo->getOrInitStage(Reg.reg()) != RS_New)
-      continue;
-
-    // Remainder interval. Don't try splitting again, spill if it doesn't
-    // allocate.
-    if (IntvMap[I] == 0) {
-      ExtraInfo->setStage(Reg, RS_Spill);
-      continue;
-    }
-
-    // Global intervals. Allow repeated splitting as long as the number of live
-    // blocks is strictly decreasing.
-    if (IntvMap[I] < NumGlobalIntvs) {
-      if (SA->countLiveBlocks(&Reg) >= OrigBlocks) {
-        LLVM_DEBUG(dbgs() << "Main interval covers the same " << OrigBlocks
-                          << " blocks as original.\n");
-        // Don't allow repeated splitting as a safe guard against looping.
-        ExtraInfo->setStage(Reg, RS_Split2);
-      }
-      continue;
-    }
-
-    // Other intervals are treated as new. This includes local intervals created
-    // for blocks with multiple uses, and anything created by DCE.
-  }
-
-  if (VerifyEnabled)
-    MF->verify(this, "After splitting live range around region");
-}
-
-MCRegister RAGreedy::tryRegionSplit(const LiveInterval &VirtReg,
-                                    AllocationOrder &Order,
-                                    SmallVectorImpl<Register> &NewVRegs) {
-  if (!TRI->shouldRegionSplitForVirtReg(*MF, VirtReg))
-    return MCRegister::NoRegister;
-  unsigned NumCands = 0;
-  BlockFrequency SpillCost = calcSpillCost();
-  BlockFrequency BestCost;
-
-  // Check if we can split this live range around a compact region.
-  bool HasCompact = calcCompactRegion(GlobalCand.front());
-  if (HasCompact) {
-    // Yes, keep GlobalCand[0] as the compact region candidate.
-    NumCands = 1;
-    BestCost = BlockFrequency::getMaxFrequency();
-  } else {
-    // No benefit from the compact region, our fallback will be per-block
-    // splitting. Make sure we find a solution that is cheaper than spilling.
-    BestCost = SpillCost;
-    LLVM_DEBUG(dbgs() << "Cost of isolating all blocks = ";
-               MBFI->printBlockFreq(dbgs(), BestCost) << '\n');
-  }
-
-  unsigned BestCand = calculateRegionSplitCost(VirtReg, Order, BestCost,
-                                               NumCands, false /*IgnoreCSR*/);
-
-  // No solutions found, fall back to single block splitting.
-  if (!HasCompact && BestCand == NoCand)
-    return MCRegister::NoRegister;
-
-  return doRegionSplit(VirtReg, BestCand, HasCompact, NewVRegs);
-}
-
-unsigned RAGreedy::calculateRegionSplitCost(const LiveInterval &VirtReg,
-                                            AllocationOrder &Order,
-                                            BlockFrequency &BestCost,
-                                            unsigned &NumCands,
-                                            bool IgnoreCSR) {
-  unsigned BestCand = NoCand;
-  for (MCPhysReg PhysReg : Order) {
-    assert(PhysReg);
-    if (IgnoreCSR && EvictAdvisor->isUnusedCalleeSavedReg(PhysReg))
-      continue;
-
-    // Discard bad candidates before we run out of interference cache cursors.
-    // This will only affect register classes with a lot of registers (>32).
-    if (NumCands == IntfCache.getMaxCursors()) {
-      unsigned WorstCount = ~0u;
-      unsigned Worst = 0;
-      for (unsigned CandIndex = 0; CandIndex != NumCands; ++CandIndex) {
-        if (CandIndex == BestCand || !GlobalCand[CandIndex].PhysReg)
-          continue;
-        unsigned Count = GlobalCand[CandIndex].LiveBundles.count();
-        if (Count < WorstCount) {
-          Worst = CandIndex;
-          WorstCount = Count;
-        }
-      }
-      --NumCands;
-      GlobalCand[Worst] = GlobalCand[NumCands];
-      if (BestCand == NumCands)
-        BestCand = Worst;
-    }
-
-    if (GlobalCand.size() <= NumCands)
-      GlobalCand.resize(NumCands+1);
-    GlobalSplitCandidate &Cand = GlobalCand[NumCands];
-    Cand.reset(IntfCache, PhysReg);
-
-    SpillPlacer->prepare(Cand.LiveBundles);
-    BlockFrequency Cost;
-    if (!addSplitConstraints(Cand.Intf, Cost)) {
-      LLVM_DEBUG(dbgs() << printReg(PhysReg, TRI) << "\tno positive bundles\n");
-      continue;
-    }
-    LLVM_DEBUG(dbgs() << printReg(PhysReg, TRI) << "\tstatic = ";
-               MBFI->printBlockFreq(dbgs(), Cost));
-    if (Cost >= BestCost) {
-      LLVM_DEBUG({
-        if (BestCand == NoCand)
-          dbgs() << " worse than no bundles\n";
-        else
-          dbgs() << " worse than "
-                 << printReg(GlobalCand[BestCand].PhysReg, TRI) << '\n';
-      });
-      continue;
-    }
-    if (!growRegion(Cand)) {
-      LLVM_DEBUG(dbgs() << ", cannot spill all interferences.\n");
-      continue;
-    }
-
-    SpillPlacer->finish();
-
-    // No live bundles, defer to splitSingleBlocks().
-    if (!Cand.LiveBundles.any()) {
-      LLVM_DEBUG(dbgs() << " no bundles.\n");
-      continue;
-    }
-
-    Cost += calcGlobalSplitCost(Cand, Order);
-    LLVM_DEBUG({
-      dbgs() << ", total = ";
-      MBFI->printBlockFreq(dbgs(), Cost) << " with bundles";
-      for (int I : Cand.LiveBundles.set_bits())
-        dbgs() << " EB#" << I;
-      dbgs() << ".\n";
-    });
-    if (Cost < BestCost) {
-      BestCand = NumCands;
-      BestCost = Cost;
-    }
-    ++NumCands;
-  }
-
-  return BestCand;
-}
-
-unsigned RAGreedy::doRegionSplit(const LiveInterval &VirtReg, unsigned BestCand,
-                                 bool HasCompact,
-                                 SmallVectorImpl<Register> &NewVRegs) {
-  SmallVector<unsigned, 8> UsedCands;
-  // Prepare split editor.
-  LiveRangeEdit LREdit(&VirtReg, NewVRegs, *MF, *LIS, VRM, this, &DeadRemats);
-  SE->reset(LREdit, SplitSpillMode);
-
-  // Assign all edge bundles to the preferred candidate, or NoCand.
-  BundleCand.assign(Bundles->getNumBundles(), NoCand);
-
-  // Assign bundles for the best candidate region.
-  if (BestCand != NoCand) {
-    GlobalSplitCandidate &Cand = GlobalCand[BestCand];
-    if (unsigned B = Cand.getBundles(BundleCand, BestCand)) {
-      UsedCands.push_back(BestCand);
-      Cand.IntvIdx = SE->openIntv();
-      LLVM_DEBUG(dbgs() << "Split for " << printReg(Cand.PhysReg, TRI) << " in "
-                        << B << " bundles, intv " << Cand.IntvIdx << ".\n");
-      (void)B;
-    }
-  }
-
-  // Assign bundles for the compact region.
-  if (HasCompact) {
-    GlobalSplitCandidate &Cand = GlobalCand.front();
-    assert(!Cand.PhysReg && "Compact region has no physreg");
-    if (unsigned B = Cand.getBundles(BundleCand, 0)) {
-      UsedCands.push_back(0);
-      Cand.IntvIdx = SE->openIntv();
-      LLVM_DEBUG(dbgs() << "Split for compact region in " << B
-                        << " bundles, intv " << Cand.IntvIdx << ".\n");
-      (void)B;
-    }
-  }
-
-  splitAroundRegion(LREdit, UsedCands);
-  return 0;
-}
-
-//===----------------------------------------------------------------------===//
-//                            Per-Block Splitting
-//===----------------------------------------------------------------------===//
-
-/// tryBlockSplit - Split a global live range around every block with uses. This
-/// creates a lot of local live ranges, that will be split by tryLocalSplit if
-/// they don't allocate.
-unsigned RAGreedy::tryBlockSplit(const LiveInterval &VirtReg,
-                                 AllocationOrder &Order,
-                                 SmallVectorImpl<Register> &NewVRegs) {
-  assert(&SA->getParent() == &VirtReg && "Live range wasn't analyzed");
-  Register Reg = VirtReg.reg();
-  bool SingleInstrs = RegClassInfo.isProperSubClass(MRI->getRegClass(Reg));
-  LiveRangeEdit LREdit(&VirtReg, NewVRegs, *MF, *LIS, VRM, this, &DeadRemats);
-  SE->reset(LREdit, SplitSpillMode);
-  ArrayRef<SplitAnalysis::BlockInfo> UseBlocks = SA->getUseBlocks();
-  for (const SplitAnalysis::BlockInfo &BI : UseBlocks) {
-    if (SA->shouldSplitSingleBlock(BI, SingleInstrs))
-      SE->splitSingleBlock(BI);
-  }
-  // No blocks were split.
-  if (LREdit.empty())
-    return 0;
-
-  // We did split for some blocks.
-  SmallVector<unsigned, 8> IntvMap;
-  SE->finish(&IntvMap);
-
-  // Tell LiveDebugVariables about the new ranges.
-  DebugVars->splitRegister(Reg, LREdit.regs(), *LIS);
-
-  // Sort out the new intervals created by splitting. The remainder interval
-  // goes straight to spilling, the new local ranges get to stay RS_New.
-  for (unsigned I = 0, E = LREdit.size(); I != E; ++I) {
-    const LiveInterval &LI = LIS->getInterval(LREdit.get(I));
-    if (ExtraInfo->getOrInitStage(LI.reg()) == RS_New && IntvMap[I] == 0)
-      ExtraInfo->setStage(LI, RS_Spill);
-  }
-
-  if (VerifyEnabled)
-    MF->verify(this, "After splitting live range around basic blocks");
-  return 0;
-}
-
-//===----------------------------------------------------------------------===//
-//                         Per-Instruction Splitting
-//===----------------------------------------------------------------------===//
-
-/// Get the number of allocatable registers that match the constraints of \p Reg
-/// on \p MI and that are also in \p SuperRC.
-static unsigned getNumAllocatableRegsForConstraints(
-    const MachineInstr *MI, Register Reg, const TargetRegisterClass *SuperRC,
-    const TargetInstrInfo *TII, const TargetRegisterInfo *TRI,
-    const RegisterClassInfo &RCI) {
-  assert(SuperRC && "Invalid register class");
-
-  const TargetRegisterClass *ConstrainedRC =
-      MI->getRegClassConstraintEffectForVReg(Reg, SuperRC, TII, TRI,
-                                             /* ExploreBundle */ true);
-  if (!ConstrainedRC)
-    return 0;
-  return RCI.getNumAllocatableRegs(ConstrainedRC);
-}
-
-/// tryInstructionSplit - Split a live range around individual instructions.
-/// This is normally not worthwhile since the spiller is doing essentially the
-/// same thing. However, when the live range is in a constrained register
-/// class, it may help to insert copies such that parts of the live range can
-/// be moved to a larger register class.
-///
-/// This is similar to spilling to a larger register class.
-unsigned RAGreedy::tryInstructionSplit(const LiveInterval &VirtReg,
-                                       AllocationOrder &Order,
-                                       SmallVectorImpl<Register> &NewVRegs) {
-  const TargetRegisterClass *CurRC = MRI->getRegClass(VirtReg.reg());
-  // There is no point to this if there are no larger sub-classes.
-  if (!RegClassInfo.isProperSubClass(CurRC))
-    return 0;
-
-  // Always enable split spill mode, since we're effectively spilling to a
-  // register.
-  LiveRangeEdit LREdit(&VirtReg, NewVRegs, *MF, *LIS, VRM, this, &DeadRemats);
-  SE->reset(LREdit, SplitEditor::SM_Size);
-
-  ArrayRef<SlotIndex> Uses = SA->getUseSlots();
-  if (Uses.size() <= 1)
-    return 0;
-
-  LLVM_DEBUG(dbgs() << "Split around " << Uses.size()
-                    << " individual instrs.\n");
-
-  const TargetRegisterClass *SuperRC =
-      TRI->getLargestLegalSuperClass(CurRC, *MF);
-  unsigned SuperRCNumAllocatableRegs =
-      RegClassInfo.getNumAllocatableRegs(SuperRC);
-  // Split around every non-copy instruction if this split will relax
-  // the constraints on the virtual register.
-  // Otherwise, splitting just inserts uncoalescable copies that do not help
-  // the allocation.
-  for (const SlotIndex Use : Uses) {
-    if (const MachineInstr *MI = Indexes->getInstructionFromIndex(Use))
-      if (MI->isFullCopy() ||
-          SuperRCNumAllocatableRegs ==
-              getNumAllocatableRegsForConstraints(MI, VirtReg.reg(), SuperRC,
-                                                  TII, TRI, RegClassInfo)) {
-        LLVM_DEBUG(dbgs() << "    skip:\t" << Use << '\t' << *MI);
-        continue;
-      }
-    SE->openIntv();
-    SlotIndex SegStart = SE->enterIntvBefore(Use);
-    SlotIndex SegStop = SE->leaveIntvAfter(Use);
-    SE->useIntv(SegStart, SegStop);
-  }
-
-  if (LREdit.empty()) {
-    LLVM_DEBUG(dbgs() << "All uses were copies.\n");
-    return 0;
-  }
-
-  SmallVector<unsigned, 8> IntvMap;
-  SE->finish(&IntvMap);
-  DebugVars->splitRegister(VirtReg.reg(), LREdit.regs(), *LIS);
-  // Assign all new registers to RS_Spill. This was the last chance.
-  ExtraInfo->setStage(LREdit.begin(), LREdit.end(), RS_Spill);
-  return 0;
-}
-
-//===----------------------------------------------------------------------===//
-//                             Local Splitting
-//===----------------------------------------------------------------------===//
-
-/// calcGapWeights - Compute the maximum spill weight that needs to be evicted
-/// in order to use PhysReg between two entries in SA->UseSlots.
-///
-/// GapWeight[I] represents the gap between UseSlots[I] and UseSlots[I + 1].
-///
-void RAGreedy::calcGapWeights(MCRegister PhysReg,
-                              SmallVectorImpl<float> &GapWeight) {
-  assert(SA->getUseBlocks().size() == 1 && "Not a local interval");
-  const SplitAnalysis::BlockInfo &BI = SA->getUseBlocks().front();
-  ArrayRef<SlotIndex> Uses = SA->getUseSlots();
-  const unsigned NumGaps = Uses.size()-1;
-
-  // Start and end points for the interference check.
-  SlotIndex StartIdx =
-    BI.LiveIn ? BI.FirstInstr.getBaseIndex() : BI.FirstInstr;
-  SlotIndex StopIdx =
-    BI.LiveOut ? BI.LastInstr.getBoundaryIndex() : BI.LastInstr;
-
-  GapWeight.assign(NumGaps, 0.0f);
-
-  // Add interference from each overlapping register.
-  for (MCRegUnitIterator Units(PhysReg, TRI); Units.isValid(); ++Units) {
-    if (!Matrix->query(const_cast<LiveInterval&>(SA->getParent()), *Units)
-          .checkInterference())
-      continue;
-
-    // We know that VirtReg is a continuous interval from FirstInstr to
-    // LastInstr, so we don't need InterferenceQuery.
-    //
-    // Interference that overlaps an instruction is counted in both gaps
-    // surrounding the instruction. The exception is interference before
-    // StartIdx and after StopIdx.
-    //
-    LiveIntervalUnion::SegmentIter IntI =
-      Matrix->getLiveUnions()[*Units] .find(StartIdx);
-    for (unsigned Gap = 0; IntI.valid() && IntI.start() < StopIdx; ++IntI) {
-      // Skip the gaps before IntI.
-      while (Uses[Gap+1].getBoundaryIndex() < IntI.start())
-        if (++Gap == NumGaps)
-          break;
-      if (Gap == NumGaps)
-        break;
-
-      // Update the gaps covered by IntI.
-      const float weight = IntI.value()->weight();
-      for (; Gap != NumGaps; ++Gap) {
-        GapWeight[Gap] = std::max(GapWeight[Gap], weight);
-        if (Uses[Gap+1].getBaseIndex() >= IntI.stop())
-          break;
-      }
-      if (Gap == NumGaps)
-        break;
-    }
-  }
-
-  // Add fixed interference.
-  for (MCRegUnitIterator Units(PhysReg, TRI); Units.isValid(); ++Units) {
-    const LiveRange &LR = LIS->getRegUnit(*Units);
-    LiveRange::const_iterator I = LR.find(StartIdx);
-    LiveRange::const_iterator E = LR.end();
-
-    // Same loop as above. Mark any overlapped gaps as HUGE_VALF.
-    for (unsigned Gap = 0; I != E && I->start < StopIdx; ++I) {
-      while (Uses[Gap+1].getBoundaryIndex() < I->start)
-        if (++Gap == NumGaps)
-          break;
-      if (Gap == NumGaps)
-        break;
-
-      for (; Gap != NumGaps; ++Gap) {
-        GapWeight[Gap] = huge_valf;
-        if (Uses[Gap+1].getBaseIndex() >= I->end)
-          break;
-      }
-      if (Gap == NumGaps)
-        break;
-    }
-  }
-}
-
-/// tryLocalSplit - Try to split VirtReg into smaller intervals inside its only
-/// basic block.
-///
-unsigned RAGreedy::tryLocalSplit(const LiveInterval &VirtReg,
-                                 AllocationOrder &Order,
-                                 SmallVectorImpl<Register> &NewVRegs) {
-  // TODO: the function currently only handles a single UseBlock; it should be
-  // possible to generalize.
-  if (SA->getUseBlocks().size() != 1)
-    return 0;
-
-  const SplitAnalysis::BlockInfo &BI = SA->getUseBlocks().front();
-
-  // Note that it is possible to have an interval that is live-in or live-out
-  // while only covering a single block - A phi-def can use undef values from
-  // predecessors, and the block could be a single-block loop.
-  // We don't bother doing anything clever about such a case, we simply assume
-  // that the interval is continuous from FirstInstr to LastInstr. We should
-  // make sure that we don't do anything illegal to such an interval, though.
-
-  ArrayRef<SlotIndex> Uses = SA->getUseSlots();
-  if (Uses.size() <= 2)
-    return 0;
-  const unsigned NumGaps = Uses.size()-1;
-
-  LLVM_DEBUG({
-    dbgs() << "tryLocalSplit: ";
-    for (const auto &Use : Uses)
-      dbgs() << ' ' << Use;
-    dbgs() << '\n';
-  });
-
-  // If VirtReg is live across any register mask operands, compute a list of
-  // gaps with register masks.
-  SmallVector<unsigned, 8> RegMaskGaps;
-  if (Matrix->checkRegMaskInterference(VirtReg)) {
-    // Get regmask slots for the whole block.
-    ArrayRef<SlotIndex> RMS = LIS->getRegMaskSlotsInBlock(BI.MBB->getNumber());
-    LLVM_DEBUG(dbgs() << RMS.size() << " regmasks in block:");
-    // Constrain to VirtReg's live range.
-    unsigned RI =
-        llvm::lower_bound(RMS, Uses.front().getRegSlot()) - RMS.begin();
-    unsigned RE = RMS.size();
-    for (unsigned I = 0; I != NumGaps && RI != RE; ++I) {
-      // Look for Uses[I] <= RMS <= Uses[I + 1].
-      assert(!SlotIndex::isEarlierInstr(RMS[RI], Uses[I]));
-      if (SlotIndex::isEarlierInstr(Uses[I + 1], RMS[RI]))
-        continue;
-      // Skip a regmask on the same instruction as the last use. It doesn't
-      // overlap the live range.
-      if (SlotIndex::isSameInstr(Uses[I + 1], RMS[RI]) && I + 1 == NumGaps)
-        break;
-      LLVM_DEBUG(dbgs() << ' ' << RMS[RI] << ':' << Uses[I] << '-'
-                        << Uses[I + 1]);
-      RegMaskGaps.push_back(I);
-      // Advance ri to the next gap. A regmask on one of the uses counts in
-      // both gaps.
-      while (RI != RE && SlotIndex::isEarlierInstr(RMS[RI], Uses[I + 1]))
-        ++RI;
-    }
-    LLVM_DEBUG(dbgs() << '\n');
-  }
-
-  // Since we allow local split results to be split again, there is a risk of
-  // creating infinite loops. It is tempting to require that the new live
-  // ranges have less instructions than the original. That would guarantee
-  // convergence, but it is too strict. A live range with 3 instructions can be
-  // split 2+3 (including the COPY), and we want to allow that.
-  //
-  // Instead we use these rules:
-  //
-  // 1. Allow any split for ranges with getStage() < RS_Split2. (Except for the
-  //    noop split, of course).
-  // 2. Require progress be made for ranges with getStage() == RS_Split2. All
-  //    the new ranges must have fewer instructions than before the split.
-  // 3. New ranges with the same number of instructions are marked RS_Split2,
-  //    smaller ranges are marked RS_New.
-  //
-  // These rules allow a 3 -> 2+3 split once, which we need. They also prevent
-  // excessive splitting and infinite loops.
-  //
-  bool ProgressRequired = ExtraInfo->getStage(VirtReg) >= RS_Split2;
-
-  // Best split candidate.
-  unsigned BestBefore = NumGaps;
-  unsigned BestAfter = 0;
-  float BestDiff = 0;
-
-  const float blockFreq =
-    SpillPlacer->getBlockFrequency(BI.MBB->getNumber()).getFrequency() *
-    (1.0f / MBFI->getEntryFreq());
-  SmallVector<float, 8> GapWeight;
-
-  for (MCPhysReg PhysReg : Order) {
-    assert(PhysReg);
-    // Keep track of the largest spill weight that would need to be evicted in
-    // order to make use of PhysReg between UseSlots[I] and UseSlots[I + 1].
-    calcGapWeights(PhysReg, GapWeight);
-
-    // Remove any gaps with regmask clobbers.
-    if (Matrix->checkRegMaskInterference(VirtReg, PhysReg))
-      for (unsigned I = 0, E = RegMaskGaps.size(); I != E; ++I)
-        GapWeight[RegMaskGaps[I]] = huge_valf;
-
-    // Try to find the best sequence of gaps to close.
-    // The new spill weight must be larger than any gap interference.
-
-    // We will split before Uses[SplitBefore] and after Uses[SplitAfter].
-    unsigned SplitBefore = 0, SplitAfter = 1;
-
-    // MaxGap should always be max(GapWeight[SplitBefore..SplitAfter-1]).
-    // It is the spill weight that needs to be evicted.
-    float MaxGap = GapWeight[0];
-
-    while (true) {
-      // Live before/after split?
-      const bool LiveBefore = SplitBefore != 0 || BI.LiveIn;
-      const bool LiveAfter = SplitAfter != NumGaps || BI.LiveOut;
-
-      LLVM_DEBUG(dbgs() << printReg(PhysReg, TRI) << ' ' << Uses[SplitBefore]
-                        << '-' << Uses[SplitAfter] << " I=" << MaxGap);
-
-      // Stop before the interval gets so big we wouldn't be making progress.
-      if (!LiveBefore && !LiveAfter) {
-        LLVM_DEBUG(dbgs() << " all\n");
-        break;
-      }
-      // Should the interval be extended or shrunk?
-      bool Shrink = true;
-
-      // How many gaps would the new range have?
-      unsigned NewGaps = LiveBefore + SplitAfter - SplitBefore + LiveAfter;
-
-      // Legally, without causing looping?
-      bool Legal = !ProgressRequired || NewGaps < NumGaps;
-
-      if (Legal && MaxGap < huge_valf) {
-        // Estimate the new spill weight. Each instruction reads or writes the
-        // register. Conservatively assume there are no read-modify-write
-        // instructions.
-        //
-        // Try to guess the size of the new interval.
-        const float EstWeight = normalizeSpillWeight(
-            blockFreq * (NewGaps + 1),
-            Uses[SplitBefore].distance(Uses[SplitAfter]) +
-                (LiveBefore + LiveAfter) * SlotIndex::InstrDist,
-            1);
-        // Would this split be possible to allocate?
-        // Never allocate all gaps, we wouldn't be making progress.
-        LLVM_DEBUG(dbgs() << " w=" << EstWeight);
-        if (EstWeight * Hysteresis >= MaxGap) {
-          Shrink = false;
-          float Diff = EstWeight - MaxGap;
-          if (Diff > BestDiff) {
-            LLVM_DEBUG(dbgs() << " (best)");
-            BestDiff = Hysteresis * Diff;
-            BestBefore = SplitBefore;
-            BestAfter = SplitAfter;
-          }
-        }
-      }
-
-      // Try to shrink.
-      if (Shrink) {
-        if (++SplitBefore < SplitAfter) {
-          LLVM_DEBUG(dbgs() << " shrink\n");
-          // Recompute the max when necessary.
-          if (GapWeight[SplitBefore - 1] >= MaxGap) {
-            MaxGap = GapWeight[SplitBefore];
-            for (unsigned I = SplitBefore + 1; I != SplitAfter; ++I)
-              MaxGap = std::max(MaxGap, GapWeight[I]);
-          }
-          continue;
-        }
-        MaxGap = 0;
-      }
-
-      // Try to extend the interval.
-      if (SplitAfter >= NumGaps) {
-        LLVM_DEBUG(dbgs() << " end\n");
-        break;
-      }
-
-      LLVM_DEBUG(dbgs() << " extend\n");
-      MaxGap = std::max(MaxGap, GapWeight[SplitAfter++]);
-    }
-  }
-
-  // Didn't find any candidates?
-  if (BestBefore == NumGaps)
-    return 0;
-
-  LLVM_DEBUG(dbgs() << "Best local split range: " << Uses[BestBefore] << '-'
-                    << Uses[BestAfter] << ", " << BestDiff << ", "
-                    << (BestAfter - BestBefore + 1) << " instrs\n");
-
-  LiveRangeEdit LREdit(&VirtReg, NewVRegs, *MF, *LIS, VRM, this, &DeadRemats);
-  SE->reset(LREdit);
-
-  SE->openIntv();
-  SlotIndex SegStart = SE->enterIntvBefore(Uses[BestBefore]);
-  SlotIndex SegStop  = SE->leaveIntvAfter(Uses[BestAfter]);
-  SE->useIntv(SegStart, SegStop);
-  SmallVector<unsigned, 8> IntvMap;
-  SE->finish(&IntvMap);
-  DebugVars->splitRegister(VirtReg.reg(), LREdit.regs(), *LIS);
-  // If the new range has the same number of instructions as before, mark it as
-  // RS_Split2 so the next split will be forced to make progress. Otherwise,
-  // leave the new intervals as RS_New so they can compete.
-  bool LiveBefore = BestBefore != 0 || BI.LiveIn;
-  bool LiveAfter = BestAfter != NumGaps || BI.LiveOut;
-  unsigned NewGaps = LiveBefore + BestAfter - BestBefore + LiveAfter;
-  if (NewGaps >= NumGaps) {
-    LLVM_DEBUG(dbgs() << "Tagging non-progress ranges:");
-    assert(!ProgressRequired && "Didn't make progress when it was required.");
-    for (unsigned I = 0, E = IntvMap.size(); I != E; ++I)
-      if (IntvMap[I] == 1) {
-        ExtraInfo->setStage(LIS->getInterval(LREdit.get(I)), RS_Split2);
-        LLVM_DEBUG(dbgs() << ' ' << printReg(LREdit.get(I)));
-      }
-    LLVM_DEBUG(dbgs() << '\n');
-  }
-  ++NumLocalSplits;
-
-  return 0;
-}
-
-//===----------------------------------------------------------------------===//
-//                          Live Range Splitting
-//===----------------------------------------------------------------------===//
-
-/// trySplit - Try to split VirtReg or one of its interferences, making it
-/// assignable.
-/// @return Physreg when VirtReg may be assigned and/or new NewVRegs.
-unsigned RAGreedy::trySplit(const LiveInterval &VirtReg, AllocationOrder &Order,
-                            SmallVectorImpl<Register> &NewVRegs,
-                            const SmallVirtRegSet &FixedRegisters) {
-  // Ranges must be Split2 or less.
-  if (ExtraInfo->getStage(VirtReg) >= RS_Spill)
-    return 0;
-
-  // Local intervals are handled separately.
-  if (LIS->intervalIsInOneMBB(VirtReg)) {
-    NamedRegionTimer T("local_split", "Local Splitting", TimerGroupName,
-                       TimerGroupDescription, TimePassesIsEnabled);
-    SA->analyze(&VirtReg);
-    Register PhysReg = tryLocalSplit(VirtReg, Order, NewVRegs);
-    if (PhysReg || !NewVRegs.empty())
-      return PhysReg;
-    return tryInstructionSplit(VirtReg, Order, NewVRegs);
-  }
-
-  NamedRegionTimer T("global_split", "Global Splitting", TimerGroupName,
-                     TimerGroupDescription, TimePassesIsEnabled);
-
-  SA->analyze(&VirtReg);
-
-  // First try to split around a region spanning multiple blocks. RS_Split2
-  // ranges already made dubious progress with region splitting, so they go
-  // straight to single block splitting.
-  if (ExtraInfo->getStage(VirtReg) < RS_Split2) {
-    MCRegister PhysReg = tryRegionSplit(VirtReg, Order, NewVRegs);
-    if (PhysReg || !NewVRegs.empty())
-      return PhysReg;
-  }
-
-  // Then isolate blocks.
-  return tryBlockSplit(VirtReg, Order, NewVRegs);
-}
-
-//===----------------------------------------------------------------------===//
-//                          Last Chance Recoloring
-//===----------------------------------------------------------------------===//
-
-/// Return true if \p reg has any tied def operand.
-static bool hasTiedDef(MachineRegisterInfo *MRI, unsigned reg) {
-  for (const MachineOperand &MO : MRI->def_operands(reg))
-    if (MO.isTied())
-      return true;
-
-  return false;
-}
-
-/// Return true if the existing assignment of \p Intf overlaps, but is not the
-/// same, as \p PhysReg.
-static bool assignedRegPartiallyOverlaps(const TargetRegisterInfo &TRI,
-                                         const VirtRegMap &VRM,
-                                         MCRegister PhysReg,
-                                         const LiveInterval &Intf) {
-  MCRegister AssignedReg = VRM.getPhys(Intf.reg());
-  if (PhysReg == AssignedReg)
-    return false;
-  return TRI.regsOverlap(PhysReg, AssignedReg);
-}
-
-/// mayRecolorAllInterferences - Check if the virtual registers that
-/// interfere with \p VirtReg on \p PhysReg (or one of its aliases) may be
-/// recolored to free \p PhysReg.
-/// When true is returned, \p RecoloringCandidates has been augmented with all
-/// the live intervals that need to be recolored in order to free \p PhysReg
-/// for \p VirtReg.
-/// \p FixedRegisters contains all the virtual registers that cannot be
-/// recolored.
-bool RAGreedy::mayRecolorAllInterferences(
-    MCRegister PhysReg, const LiveInterval &VirtReg,
-    SmallLISet &RecoloringCandidates, const SmallVirtRegSet &FixedRegisters) {
-  const TargetRegisterClass *CurRC = MRI->getRegClass(VirtReg.reg());
-
-  for (MCRegUnitIterator Units(PhysReg, TRI); Units.isValid(); ++Units) {
-    LiveIntervalUnion::Query &Q = Matrix->query(VirtReg, *Units);
-    // If there is LastChanceRecoloringMaxInterference or more interferences,
-    // chances are one would not be recolorable.
-    if (Q.interferingVRegs(LastChanceRecoloringMaxInterference).size() >=
-            LastChanceRecoloringMaxInterference &&
-        !ExhaustiveSearch) {
-      LLVM_DEBUG(dbgs() << "Early abort: too many interferences.\n");
-      CutOffInfo |= CO_Interf;
-      return false;
-    }
-    for (const LiveInterval *Intf : reverse(Q.interferingVRegs())) {
-      // If Intf is done and sits on the same register class as VirtReg, it
-      // would not be recolorable as it is in the same state as
-      // VirtReg. However there are at least two exceptions.
-      //
-      // If VirtReg has tied defs and Intf doesn't, then
-      // there is still a point in examining if it can be recolorable.
-      //
-      // Additionally, if the register class has overlapping tuple members, it
-      // may still be recolorable using a different tuple. This is more likely
-      // if the existing assignment aliases with the candidate.
-      //
-      if (((ExtraInfo->getStage(*Intf) == RS_Done &&
-            MRI->getRegClass(Intf->reg()) == CurRC &&
-            !assignedRegPartiallyOverlaps(*TRI, *VRM, PhysReg, *Intf)) &&
-           !(hasTiedDef(MRI, VirtReg.reg()) &&
-             !hasTiedDef(MRI, Intf->reg()))) ||
-          FixedRegisters.count(Intf->reg())) {
-        LLVM_DEBUG(
-            dbgs() << "Early abort: the interference is not recolorable.\n");
-        return false;
-      }
-      RecoloringCandidates.insert(Intf);
-    }
-  }
-  return true;
-}
-
-/// tryLastChanceRecoloring - Try to assign a color to \p VirtReg by recoloring
-/// its interferences.
-/// Last chance recoloring chooses a color for \p VirtReg and recolors every
-/// virtual register that was using it. The recoloring process may recursively
-/// use the last chance recoloring. Therefore, when a virtual register has been
-/// assigned a color by this mechanism, it is marked as Fixed, i.e., it cannot
-/// be last-chance-recolored again during this recoloring "session".
-/// E.g.,
-/// Let
-/// vA can use {R1, R2    }
-/// vB can use {    R2, R3}
-/// vC can use {R1        }
-/// Where vA, vB, and vC cannot be split anymore (they are reloads for
-/// instance) and they all interfere.
-///
-/// vA is assigned R1
-/// vB is assigned R2
-/// vC tries to evict vA but vA is already done.
-/// Regular register allocation fails.
-///
-/// Last chance recoloring kicks in:
-/// vC does as if vA was evicted => vC uses R1.
-/// vC is marked as fixed.
-/// vA needs to find a color.
-/// None are available.
-/// vA cannot evict vC: vC is a fixed virtual register now.
-/// vA does as if vB was evicted => vA uses R2.
-/// vB needs to find a color.
-/// R3 is available.
-/// Recoloring => vC = R1, vA = R2, vB = R3
-///
-/// \p Order defines the preferred allocation order for \p VirtReg.
-/// \p NewRegs will contain any new virtual register that have been created
-/// (split, spill) during the process and that must be assigned.
-/// \p FixedRegisters contains all the virtual registers that cannot be
-/// recolored.
-///
-/// \p RecolorStack tracks the original assignments of successfully recolored
-/// registers.
-///
-/// \p Depth gives the current depth of the last chance recoloring.
-/// \return a physical register that can be used for VirtReg or ~0u if none
-/// exists.
-unsigned RAGreedy::tryLastChanceRecoloring(const LiveInterval &VirtReg,
-                                           AllocationOrder &Order,
-                                           SmallVectorImpl<Register> &NewVRegs,
-                                           SmallVirtRegSet &FixedRegisters,
-                                           RecoloringStack &RecolorStack,
-                                           unsigned Depth) {
-  if (!TRI->shouldUseLastChanceRecoloringForVirtReg(*MF, VirtReg))
-    return ~0u;
-
-  LLVM_DEBUG(dbgs() << "Try last chance recoloring for " << VirtReg << '\n');
-
-  const ssize_t EntryStackSize = RecolorStack.size();
-
-  // Ranges must be Done.
-  assert((ExtraInfo->getStage(VirtReg) >= RS_Done || !VirtReg.isSpillable()) &&
-         "Last chance recoloring should really be last chance");
-  // Set the max depth to LastChanceRecoloringMaxDepth.
-  // We may want to reconsider that if we end up with a too large search space
-  // for target with hundreds of registers.
-  // Indeed, in that case we may want to cut the search space earlier.
-  if (Depth >= LastChanceRecoloringMaxDepth && !ExhaustiveSearch) {
-    LLVM_DEBUG(dbgs() << "Abort because max depth has been reached.\n");
-    CutOffInfo |= CO_Depth;
-    return ~0u;
-  }
-
-  // Set of Live intervals that will need to be recolored.
-  SmallLISet RecoloringCandidates;
-
-  // Mark VirtReg as fixed, i.e., it will not be recolored pass this point in
-  // this recoloring "session".
-  assert(!FixedRegisters.count(VirtReg.reg()));
-  FixedRegisters.insert(VirtReg.reg());
-  SmallVector<Register, 4> CurrentNewVRegs;
-
-  for (MCRegister PhysReg : Order) {
-    assert(PhysReg.isValid());
-    LLVM_DEBUG(dbgs() << "Try to assign: " << VirtReg << " to "
-                      << printReg(PhysReg, TRI) << '\n');
-    RecoloringCandidates.clear();
-    CurrentNewVRegs.clear();
-
-    // It is only possible to recolor virtual register interference.
-    if (Matrix->checkInterference(VirtReg, PhysReg) >
-        LiveRegMatrix::IK_VirtReg) {
-      LLVM_DEBUG(
-          dbgs() << "Some interferences are not with virtual registers.\n");
-
-      continue;
-    }
-
-    // Early give up on this PhysReg if it is obvious we cannot recolor all
-    // the interferences.
-    if (!mayRecolorAllInterferences(PhysReg, VirtReg, RecoloringCandidates,
-                                    FixedRegisters)) {
-      LLVM_DEBUG(dbgs() << "Some interferences cannot be recolored.\n");
-      continue;
-    }
-
-    // RecoloringCandidates contains all the virtual registers that interfere
-    // with VirtReg on PhysReg (or one of its aliases). Enqueue them for
-    // recoloring and perform the actual recoloring.
-    PQueue RecoloringQueue;
-    for (const LiveInterval *RC : RecoloringCandidates) {
-      Register ItVirtReg = RC->reg();
-      enqueue(RecoloringQueue, RC);
-      assert(VRM->hasPhys(ItVirtReg) &&
-             "Interferences are supposed to be with allocated variables");
-
-      // Record the current allocation.
-      RecolorStack.push_back(std::make_pair(RC, VRM->getPhys(ItVirtReg)));
-
-      // unset the related struct.
-      Matrix->unassign(*RC);
-    }
-
-    // Do as if VirtReg was assigned to PhysReg so that the underlying
-    // recoloring has the right information about the interferes and
-    // available colors.
-    Matrix->assign(VirtReg, PhysReg);
-
-    // Save the current recoloring state.
-    // If we cannot recolor all the interferences, we will have to start again
-    // at this point for the next physical register.
-    SmallVirtRegSet SaveFixedRegisters(FixedRegisters);
-    if (tryRecoloringCandidates(RecoloringQueue, CurrentNewVRegs,
-                                FixedRegisters, RecolorStack, Depth)) {
-      // Push the queued vregs into the main queue.
-      for (Register NewVReg : CurrentNewVRegs)
-        NewVRegs.push_back(NewVReg);
-      // Do not mess up with the global assignment process.
-      // I.e., VirtReg must be unassigned.
-      Matrix->unassign(VirtReg);
-      return PhysReg;
-    }
-
-    LLVM_DEBUG(dbgs() << "Fail to assign: " << VirtReg << " to "
-                      << printReg(PhysReg, TRI) << '\n');
-
-    // The recoloring attempt failed, undo the changes.
-    FixedRegisters = SaveFixedRegisters;
-    Matrix->unassign(VirtReg);
-
-    // For a newly created vreg which is also in RecoloringCandidates,
-    // don't add it to NewVRegs because its physical register will be restored
-    // below. Other vregs in CurrentNewVRegs are created by calling
-    // selectOrSplit and should be added into NewVRegs.
-    for (Register &R : CurrentNewVRegs) {
-      if (RecoloringCandidates.count(&LIS->getInterval(R)))
-        continue;
-      NewVRegs.push_back(R);
-    }
-
-    // Roll back our unsuccessful recoloring. Also roll back any successful
-    // recolorings in any recursive recoloring attempts, since it's possible
-    // they would have introduced conflicts with assignments we will be
-    // restoring further up the stack. Perform all unassignments prior to
-    // reassigning, since sub-recolorings may have conflicted with the registers
-    // we are going to restore to their original assignments.
-    for (ssize_t I = RecolorStack.size() - 1; I >= EntryStackSize; --I) {
-      const LiveInterval *LI;
-      MCRegister PhysReg;
-      std::tie(LI, PhysReg) = RecolorStack[I];
-
-      if (VRM->hasPhys(LI->reg()))
-        Matrix->unassign(*LI);
-    }
-
-    for (size_t I = EntryStackSize; I != RecolorStack.size(); ++I) {
-      const LiveInterval *LI;
-      MCRegister PhysReg;
-      std::tie(LI, PhysReg) = RecolorStack[I];
-      Matrix->assign(*LI, PhysReg);
-    }
-
-    // Pop the stack of recoloring attempts.
-    RecolorStack.resize(EntryStackSize);
-  }
-
-  // Last chance recoloring did not worked either, give up.
-  return ~0u;
-}
-
-/// tryRecoloringCandidates - Try to assign a new color to every register
-/// in \RecoloringQueue.
-/// \p NewRegs will contain any new virtual register created during the
-/// recoloring process.
-/// \p FixedRegisters[in/out] contains all the registers that have been
-/// recolored.
-/// \return true if all virtual registers in RecoloringQueue were successfully
-/// recolored, false otherwise.
-bool RAGreedy::tryRecoloringCandidates(PQueue &RecoloringQueue,
-                                       SmallVectorImpl<Register> &NewVRegs,
-                                       SmallVirtRegSet &FixedRegisters,
-                                       RecoloringStack &RecolorStack,
-                                       unsigned Depth) {
-  while (!RecoloringQueue.empty()) {
-    const LiveInterval *LI = dequeue(RecoloringQueue);
-    LLVM_DEBUG(dbgs() << "Try to recolor: " << *LI << '\n');
-    MCRegister PhysReg = selectOrSplitImpl(*LI, NewVRegs, FixedRegisters,
-                                           RecolorStack, Depth + 1);
-    // When splitting happens, the live-range may actually be empty.
-    // In that case, this is okay to continue the recoloring even
-    // if we did not find an alternative color for it. Indeed,
-    // there will not be anything to color for LI in the end.
-    if (PhysReg == ~0u || (!PhysReg && !LI->empty()))
-      return false;
-
-    if (!PhysReg) {
-      assert(LI->empty() && "Only empty live-range do not require a register");
-      LLVM_DEBUG(dbgs() << "Recoloring of " << *LI
-                        << " succeeded. Empty LI.\n");
-      continue;
-    }
-    LLVM_DEBUG(dbgs() << "Recoloring of " << *LI
-                      << " succeeded with: " << printReg(PhysReg, TRI) << '\n');
-
-    Matrix->assign(*LI, PhysReg);
-    FixedRegisters.insert(LI->reg());
-  }
-  return true;
-}
-
-//===----------------------------------------------------------------------===//
-//                            Main Entry Point
-//===----------------------------------------------------------------------===//
-
-MCRegister RAGreedy::selectOrSplit(const LiveInterval &VirtReg,
-                                   SmallVectorImpl<Register> &NewVRegs) {
-  CutOffInfo = CO_None;
-  LLVMContext &Ctx = MF->getFunction().getContext();
-  SmallVirtRegSet FixedRegisters;
-  RecoloringStack RecolorStack;
-  MCRegister Reg =
-      selectOrSplitImpl(VirtReg, NewVRegs, FixedRegisters, RecolorStack);
-  if (Reg == ~0U && (CutOffInfo != CO_None)) {
-    uint8_t CutOffEncountered = CutOffInfo & (CO_Depth | CO_Interf);
-    if (CutOffEncountered == CO_Depth)
-      Ctx.emitError("register allocation failed: maximum depth for recoloring "
-                    "reached. Use -fexhaustive-register-search to skip "
-                    "cutoffs");
-    else if (CutOffEncountered == CO_Interf)
-      Ctx.emitError("register allocation failed: maximum interference for "
-                    "recoloring reached. Use -fexhaustive-register-search "
-                    "to skip cutoffs");
-    else if (CutOffEncountered == (CO_Depth | CO_Interf))
-      Ctx.emitError("register allocation failed: maximum interference and "
-                    "depth for recoloring reached. Use "
-                    "-fexhaustive-register-search to skip cutoffs");
-  }
-  return Reg;
-}
-
-/// Using a CSR for the first time has a cost because it causes push|pop
-/// to be added to prologue|epilogue. Splitting a cold section of the live
-/// range can have lower cost than using the CSR for the first time;
-/// Spilling a live range in the cold path can have lower cost than using
-/// the CSR for the first time. Returns the physical register if we decide
-/// to use the CSR; otherwise return 0.
-MCRegister RAGreedy::tryAssignCSRFirstTime(
-    const LiveInterval &VirtReg, AllocationOrder &Order, MCRegister PhysReg,
-    uint8_t &CostPerUseLimit, SmallVectorImpl<Register> &NewVRegs) {
-  if (ExtraInfo->getStage(VirtReg) == RS_Spill && VirtReg.isSpillable()) {
-    // We choose spill over using the CSR for the first time if the spill cost
-    // is lower than CSRCost.
-    SA->analyze(&VirtReg);
-    if (calcSpillCost() >= CSRCost)
-      return PhysReg;
-
-    // We are going to spill, set CostPerUseLimit to 1 to make sure that
-    // we will not use a callee-saved register in tryEvict.
-    CostPerUseLimit = 1;
-    return 0;
-  }
-  if (ExtraInfo->getStage(VirtReg) < RS_Split) {
-    // We choose pre-splitting over using the CSR for the first time if
-    // the cost of splitting is lower than CSRCost.
-    SA->analyze(&VirtReg);
-    unsigned NumCands = 0;
-    BlockFrequency BestCost = CSRCost; // Don't modify CSRCost.
-    unsigned BestCand = calculateRegionSplitCost(VirtReg, Order, BestCost,
-                                                 NumCands, true /*IgnoreCSR*/);
-    if (BestCand == NoCand)
-      // Use the CSR if we can't find a region split below CSRCost.
-      return PhysReg;
-
-    // Perform the actual pre-splitting.
-    doRegionSplit(VirtReg, BestCand, false/*HasCompact*/, NewVRegs);
-    return 0;
-  }
-  return PhysReg;
-}
-
-void RAGreedy::aboutToRemoveInterval(const LiveInterval &LI) {
-  // Do not keep invalid information around.
-  SetOfBrokenHints.remove(&LI);
-}
-
-void RAGreedy::initializeCSRCost() {
-  // We use the larger one out of the command-line option and the value report
-  // by TRI.
-  CSRCost = BlockFrequency(
-      std::max((unsigned)CSRFirstTimeCost, TRI->getCSRFirstUseCost()));
-  if (!CSRCost.getFrequency())
-    return;
-
-  // Raw cost is relative to Entry == 2^14; scale it appropriately.
-  uint64_t ActualEntry = MBFI->getEntryFreq();
-  if (!ActualEntry) {
-    CSRCost = 0;
-    return;
-  }
-  uint64_t FixedEntry = 1 << 14;
-  if (ActualEntry < FixedEntry)
-    CSRCost *= BranchProbability(ActualEntry, FixedEntry);
-  else if (ActualEntry <= UINT32_MAX)
-    // Invert the fraction and divide.
-    CSRCost /= BranchProbability(FixedEntry, ActualEntry);
-  else
-    // Can't use BranchProbability in general, since it takes 32-bit numbers.
-    CSRCost = CSRCost.getFrequency() * (ActualEntry / FixedEntry);
-}
-
-/// Collect the hint info for \p Reg.
-/// The results are stored into \p Out.
-/// \p Out is not cleared before being populated.
-void RAGreedy::collectHintInfo(Register Reg, HintsInfo &Out) {
-  for (const MachineInstr &Instr : MRI->reg_nodbg_instructions(Reg)) {
-    if (!Instr.isFullCopy())
-      continue;
-    // Look for the other end of the copy.
-    Register OtherReg = Instr.getOperand(0).getReg();
-    if (OtherReg == Reg) {
-      OtherReg = Instr.getOperand(1).getReg();
-      if (OtherReg == Reg)
-        continue;
-    }
-    // Get the current assignment.
-    MCRegister OtherPhysReg =
-        OtherReg.isPhysical() ? OtherReg.asMCReg() : VRM->getPhys(OtherReg);
-    // Push the collected information.
-    Out.push_back(HintInfo(MBFI->getBlockFreq(Instr.getParent()), OtherReg,
-                           OtherPhysReg));
-  }
-}
-
-/// Using the given \p List, compute the cost of the broken hints if
-/// \p PhysReg was used.
-/// \return The cost of \p List for \p PhysReg.
-BlockFrequency RAGreedy::getBrokenHintFreq(const HintsInfo &List,
-                                           MCRegister PhysReg) {
-  BlockFrequency Cost = 0;
-  for (const HintInfo &Info : List) {
-    if (Info.PhysReg != PhysReg)
-      Cost += Info.Freq;
-  }
-  return Cost;
-}
-
-/// Using the register assigned to \p VirtReg, try to recolor
-/// all the live ranges that are copy-related with \p VirtReg.
-/// The recoloring is then propagated to all the live-ranges that have
-/// been recolored and so on, until no more copies can be coalesced or
-/// it is not profitable.
-/// For a given live range, profitability is determined by the sum of the
-/// frequencies of the non-identity copies it would introduce with the old
-/// and new register.
-void RAGreedy::tryHintRecoloring(const LiveInterval &VirtReg) {
-  // We have a broken hint, check if it is possible to fix it by
-  // reusing PhysReg for the copy-related live-ranges. Indeed, we evicted
-  // some register and PhysReg may be available for the other live-ranges.
-  SmallSet<Register, 4> Visited;
-  SmallVector<unsigned, 2> RecoloringCandidates;
-  HintsInfo Info;
-  Register Reg = VirtReg.reg();
-  MCRegister PhysReg = VRM->getPhys(Reg);
-  // Start the recoloring algorithm from the input live-interval, then
-  // it will propagate to the ones that are copy-related with it.
-  Visited.insert(Reg);
-  RecoloringCandidates.push_back(Reg);
-
-  LLVM_DEBUG(dbgs() << "Trying to reconcile hints for: " << printReg(Reg, TRI)
-                    << '(' << printReg(PhysReg, TRI) << ")\n");
-
-  do {
-    Reg = RecoloringCandidates.pop_back_val();
-
-    // We cannot recolor physical register.
-    if (Register::isPhysicalRegister(Reg))
-      continue;
-
-    // This may be a skipped class
-    if (!VRM->hasPhys(Reg)) {
-      assert(!ShouldAllocateClass(*TRI, *MRI->getRegClass(Reg)) &&
-             "We have an unallocated variable which should have been handled");
-      continue;
-    }
-
-    // Get the live interval mapped with this virtual register to be able
-    // to check for the interference with the new color.
-    LiveInterval &LI = LIS->getInterval(Reg);
-    MCRegister CurrPhys = VRM->getPhys(Reg);
-    // Check that the new color matches the register class constraints and
-    // that it is free for this live range.
-    if (CurrPhys != PhysReg && (!MRI->getRegClass(Reg)->contains(PhysReg) ||
-                                Matrix->checkInterference(LI, PhysReg)))
-      continue;
-
-    LLVM_DEBUG(dbgs() << printReg(Reg, TRI) << '(' << printReg(CurrPhys, TRI)
-                      << ") is recolorable.\n");
-
-    // Gather the hint info.
-    Info.clear();
-    collectHintInfo(Reg, Info);
-    // Check if recoloring the live-range will increase the cost of the
-    // non-identity copies.
-    if (CurrPhys != PhysReg) {
-      LLVM_DEBUG(dbgs() << "Checking profitability:\n");
-      BlockFrequency OldCopiesCost = getBrokenHintFreq(Info, CurrPhys);
-      BlockFrequency NewCopiesCost = getBrokenHintFreq(Info, PhysReg);
-      LLVM_DEBUG(dbgs() << "Old Cost: " << OldCopiesCost.getFrequency()
-                        << "\nNew Cost: " << NewCopiesCost.getFrequency()
-                        << '\n');
-      if (OldCopiesCost < NewCopiesCost) {
-        LLVM_DEBUG(dbgs() << "=> Not profitable.\n");
-        continue;
-      }
-      // At this point, the cost is either cheaper or equal. If it is
-      // equal, we consider this is profitable because it may expose
-      // more recoloring opportunities.
-      LLVM_DEBUG(dbgs() << "=> Profitable.\n");
-      // Recolor the live-range.
-      Matrix->unassign(LI);
-      Matrix->assign(LI, PhysReg);
-    }
-    // Push all copy-related live-ranges to keep reconciling the broken
-    // hints.
-    for (const HintInfo &HI : Info) {
-      if (Visited.insert(HI.Reg).second)
-        RecoloringCandidates.push_back(HI.Reg);
-    }
-  } while (!RecoloringCandidates.empty());
-}
-
-/// Try to recolor broken hints.
-/// Broken hints may be repaired by recoloring when an evicted variable
-/// freed up a register for a larger live-range.
-/// Consider the following example:
-/// BB1:
-///   a =
-///   b =
-/// BB2:
-///   ...
-///   = b
-///   = a
-/// Let us assume b gets split:
-/// BB1:
-///   a =
-///   b =
-/// BB2:
-///   c = b
-///   ...
-///   d = c
-///   = d
-///   = a
-/// Because of how the allocation work, b, c, and d may be assigned different
-/// colors. Now, if a gets evicted later:
-/// BB1:
-///   a =
-///   st a, SpillSlot
-///   b =
-/// BB2:
-///   c = b
-///   ...
-///   d = c
-///   = d
-///   e = ld SpillSlot
-///   = e
-/// This is likely that we can assign the same register for b, c, and d,
-/// getting rid of 2 copies.
-void RAGreedy::tryHintsRecoloring() {
-  for (const LiveInterval *LI : SetOfBrokenHints) {
-    assert(Register::isVirtualRegister(LI->reg()) &&
-           "Recoloring is possible only for virtual registers");
-    // Some dead defs may be around (e.g., because of debug uses).
-    // Ignore those.
-    if (!VRM->hasPhys(LI->reg()))
-      continue;
-    tryHintRecoloring(*LI);
-  }
-}
-
-MCRegister RAGreedy::selectOrSplitImpl(const LiveInterval &VirtReg,
-                                       SmallVectorImpl<Register> &NewVRegs,
-                                       SmallVirtRegSet &FixedRegisters,
-                                       RecoloringStack &RecolorStack,
-                                       unsigned Depth) {
-  uint8_t CostPerUseLimit = uint8_t(~0u);
-  // First try assigning a free register.
-  auto Order =
-      AllocationOrder::create(VirtReg.reg(), *VRM, RegClassInfo, Matrix);
-  if (MCRegister PhysReg =
-          tryAssign(VirtReg, Order, NewVRegs, FixedRegisters)) {
-    // If VirtReg got an assignment, the eviction info is no longer relevant.
-    LastEvicted.clearEvicteeInfo(VirtReg.reg());
-    // When NewVRegs is not empty, we may have made decisions such as evicting
-    // a virtual register, go with the earlier decisions and use the physical
-    // register.
-    if (CSRCost.getFrequency() &&
-        EvictAdvisor->isUnusedCalleeSavedReg(PhysReg) && NewVRegs.empty()) {
-      MCRegister CSRReg = tryAssignCSRFirstTime(VirtReg, Order, PhysReg,
-                                                CostPerUseLimit, NewVRegs);
-      if (CSRReg || !NewVRegs.empty())
-        // Return now if we decide to use a CSR or create new vregs due to
-        // pre-splitting.
-        return CSRReg;
-    } else
-      return PhysReg;
-  }
-
-  LiveRangeStage Stage = ExtraInfo->getStage(VirtReg);
-  LLVM_DEBUG(dbgs() << StageName[Stage] << " Cascade "
-                    << ExtraInfo->getCascade(VirtReg.reg()) << '\n');
-
-  // Try to evict a less worthy live range, but only for ranges from the primary
-  // queue. The RS_Split ranges already failed to do this, and they should not
-  // get a second chance until they have been split.
-  if (Stage != RS_Split)
-    if (Register PhysReg =
-            tryEvict(VirtReg, Order, NewVRegs, CostPerUseLimit,
-                     FixedRegisters)) {
-      Register Hint = MRI->getSimpleHint(VirtReg.reg());
-      // If VirtReg has a hint and that hint is broken record this
-      // virtual register as a recoloring candidate for broken hint.
-      // Indeed, since we evicted a variable in its neighborhood it is
-      // likely we can at least partially recolor some of the
-      // copy-related live-ranges.
-      if (Hint && Hint != PhysReg)
-        SetOfBrokenHints.insert(&VirtReg);
-      // If VirtReg eviction someone, the eviction info for it as an evictee is
-      // no longer relevant.
-      LastEvicted.clearEvicteeInfo(VirtReg.reg());
-      return PhysReg;
-    }
-
-  assert((NewVRegs.empty() || Depth) && "Cannot append to existing NewVRegs");
-
-  // The first time we see a live range, don't try to split or spill.
-  // Wait until the second time, when all smaller ranges have been allocated.
-  // This gives a better picture of the interference to split around.
-  if (Stage < RS_Split) {
-    ExtraInfo->setStage(VirtReg, RS_Split);
-    LLVM_DEBUG(dbgs() << "wait for second round\n");
-    NewVRegs.push_back(VirtReg.reg());
-    return 0;
-  }
-
-  if (Stage < RS_Spill) {
-    // Try splitting VirtReg or interferences.
-    unsigned NewVRegSizeBefore = NewVRegs.size();
-    Register PhysReg = trySplit(VirtReg, Order, NewVRegs, FixedRegisters);
-    if (PhysReg || (NewVRegs.size() - NewVRegSizeBefore)) {
-      // If VirtReg got split, the eviction info is no longer relevant.
-      LastEvicted.clearEvicteeInfo(VirtReg.reg());
-      return PhysReg;
-    }
-  }
-
-  // If we couldn't allocate a register from spilling, there is probably some
-  // invalid inline assembly. The base class will report it.
-  if (Stage >= RS_Done || !VirtReg.isSpillable()) {
-    return tryLastChanceRecoloring(VirtReg, Order, NewVRegs, FixedRegisters,
-                                   RecolorStack, Depth);
-  }
-
-  // Finally spill VirtReg itself.
-  if ((EnableDeferredSpilling ||
-       TRI->shouldUseDeferredSpillingForVirtReg(*MF, VirtReg)) &&
-      ExtraInfo->getStage(VirtReg) < RS_Memory) {
-    // TODO: This is experimental and in particular, we do not model
-    // the live range splitting done by spilling correctly.
-    // We would need a deep integration with the spiller to do the
-    // right thing here. Anyway, that is still good for early testing.
-    ExtraInfo->setStage(VirtReg, RS_Memory);
-    LLVM_DEBUG(dbgs() << "Do as if this register is in memory\n");
-    NewVRegs.push_back(VirtReg.reg());
-  } else {
-    NamedRegionTimer T("spill", "Spiller", TimerGroupName,
-                       TimerGroupDescription, TimePassesIsEnabled);
-    LiveRangeEdit LRE(&VirtReg, NewVRegs, *MF, *LIS, VRM, this, &DeadRemats);
-    spiller().spill(LRE);
-    ExtraInfo->setStage(NewVRegs.begin(), NewVRegs.end(), RS_Done);
-
-    // Tell LiveDebugVariables about the new ranges. Ranges not being covered by
-    // the new regs are kept in LDV (still mapping to the old register), until
-    // we rewrite spilled locations in LDV at a later stage.
-    DebugVars->splitRegister(VirtReg.reg(), LRE.regs(), *LIS);
-
-    if (VerifyEnabled)
-      MF->verify(this, "After spilling");
-  }
-
-  // The live virtual register requesting allocation was spilled, so tell
-  // the caller not to allocate anything during this round.
-  return 0;
-}
-
-void RAGreedy::RAGreedyStats::report(MachineOptimizationRemarkMissed &R) {
-  using namespace ore;
-  if (Spills) {
-    R << NV("NumSpills", Spills) << " spills ";
-    R << NV("TotalSpillsCost", SpillsCost) << " total spills cost ";
-  }
-  if (FoldedSpills) {
-    R << NV("NumFoldedSpills", FoldedSpills) << " folded spills ";
-    R << NV("TotalFoldedSpillsCost", FoldedSpillsCost)
-      << " total folded spills cost ";
-  }
-  if (Reloads) {
-    R << NV("NumReloads", Reloads) << " reloads ";
-    R << NV("TotalReloadsCost", ReloadsCost) << " total reloads cost ";
-  }
-  if (FoldedReloads) {
-    R << NV("NumFoldedReloads", FoldedReloads) << " folded reloads ";
-    R << NV("TotalFoldedReloadsCost", FoldedReloadsCost)
-      << " total folded reloads cost ";
-  }
-  if (ZeroCostFoldedReloads)
-    R << NV("NumZeroCostFoldedReloads", ZeroCostFoldedReloads)
-      << " zero cost folded reloads ";
-  if (Copies) {
-    R << NV("NumVRCopies", Copies) << " virtual registers copies ";
-    R << NV("TotalCopiesCost", CopiesCost) << " total copies cost ";
-  }
-}
-
-RAGreedy::RAGreedyStats RAGreedy::computeStats(MachineBasicBlock &MBB) {
-  RAGreedyStats Stats;
-  const MachineFrameInfo &MFI = MF->getFrameInfo();
-  int FI;
-
-  auto isSpillSlotAccess = [&MFI](const MachineMemOperand *A) {
-    return MFI.isSpillSlotObjectIndex(cast<FixedStackPseudoSourceValue>(
-        A->getPseudoValue())->getFrameIndex());
-  };
-  auto isPatchpointInstr = [](const MachineInstr &MI) {
-    return MI.getOpcode() == TargetOpcode::PATCHPOINT ||
-           MI.getOpcode() == TargetOpcode::STACKMAP ||
-           MI.getOpcode() == TargetOpcode::STATEPOINT;
-  };
-  for (MachineInstr &MI : MBB) {
-    if (MI.isCopy()) {
-      MachineOperand &Dest = MI.getOperand(0);
-      MachineOperand &Src = MI.getOperand(1);
-      if (Dest.isReg() && Src.isReg() && Dest.getReg().isVirtual() &&
-          Src.getReg().isVirtual())
-        ++Stats.Copies;
-      continue;
-    }
-
-    SmallVector<const MachineMemOperand *, 2> Accesses;
-    if (TII->isLoadFromStackSlot(MI, FI) && MFI.isSpillSlotObjectIndex(FI)) {
-      ++Stats.Reloads;
-      continue;
-    }
-    if (TII->isStoreToStackSlot(MI, FI) && MFI.isSpillSlotObjectIndex(FI)) {
-      ++Stats.Spills;
-      continue;
-    }
-    if (TII->hasLoadFromStackSlot(MI, Accesses) &&
-        llvm::any_of(Accesses, isSpillSlotAccess)) {
-      if (!isPatchpointInstr(MI)) {
-        Stats.FoldedReloads += Accesses.size();
-        continue;
-      }
-      // For statepoint there may be folded and zero cost folded stack reloads.
-      std::pair<unsigned, unsigned> NonZeroCostRange =
-          TII->getPatchpointUnfoldableRange(MI);
-      SmallSet<unsigned, 16> FoldedReloads;
-      SmallSet<unsigned, 16> ZeroCostFoldedReloads;
-      for (unsigned Idx = 0, E = MI.getNumOperands(); Idx < E; ++Idx) {
-        MachineOperand &MO = MI.getOperand(Idx);
-        if (!MO.isFI() || !MFI.isSpillSlotObjectIndex(MO.getIndex()))
-          continue;
-        if (Idx >= NonZeroCostRange.first && Idx < NonZeroCostRange.second)
-          FoldedReloads.insert(MO.getIndex());
-        else
-          ZeroCostFoldedReloads.insert(MO.getIndex());
-      }
-      // If stack slot is used in folded reload it is not zero cost then.
-      for (unsigned Slot : FoldedReloads)
-        ZeroCostFoldedReloads.erase(Slot);
-      Stats.FoldedReloads += FoldedReloads.size();
-      Stats.ZeroCostFoldedReloads += ZeroCostFoldedReloads.size();
-      continue;
-    }
-    Accesses.clear();
-    if (TII->hasStoreToStackSlot(MI, Accesses) &&
-        llvm::any_of(Accesses, isSpillSlotAccess)) {
-      Stats.FoldedSpills += Accesses.size();
-    }
-  }
-  // Set cost of collected statistic by multiplication to relative frequency of
-  // this basic block.
-  float RelFreq = MBFI->getBlockFreqRelativeToEntryBlock(&MBB);
-  Stats.ReloadsCost = RelFreq * Stats.Reloads;
-  Stats.FoldedReloadsCost = RelFreq * Stats.FoldedReloads;
-  Stats.SpillsCost = RelFreq * Stats.Spills;
-  Stats.FoldedSpillsCost = RelFreq * Stats.FoldedSpills;
-  Stats.CopiesCost = RelFreq * Stats.Copies;
-  return Stats;
-}
-
-RAGreedy::RAGreedyStats RAGreedy::reportStats(MachineLoop *L) {
-  RAGreedyStats Stats;
-
-  // Sum up the spill and reloads in subloops.
-  for (MachineLoop *SubLoop : *L)
-    Stats.add(reportStats(SubLoop));
-
-  for (MachineBasicBlock *MBB : L->getBlocks())
-    // Handle blocks that were not included in subloops.
-    if (Loops->getLoopFor(MBB) == L)
-      Stats.add(computeStats(*MBB));
-
-  if (!Stats.isEmpty()) {
-    using namespace ore;
-
-    ORE->emit([&]() {
-      MachineOptimizationRemarkMissed R(DEBUG_TYPE, "LoopSpillReloadCopies",
-                                        L->getStartLoc(), L->getHeader());
-      Stats.report(R);
-      R << "generated in loop";
-      return R;
-    });
-  }
-  return Stats;
-}
-
-void RAGreedy::reportStats() {
-  if (!ORE->allowExtraAnalysis(DEBUG_TYPE))
-    return;
-  RAGreedyStats Stats;
-  for (MachineLoop *L : *Loops)
-    Stats.add(reportStats(L));
-  // Process non-loop blocks.
-  for (MachineBasicBlock &MBB : *MF)
-    if (!Loops->getLoopFor(&MBB))
-      Stats.add(computeStats(MBB));
-  if (!Stats.isEmpty()) {
-    using namespace ore;
-
-    ORE->emit([&]() {
-      DebugLoc Loc;
-      if (auto *SP = MF->getFunction().getSubprogram())
-        Loc = DILocation::get(SP->getContext(), SP->getLine(), 1, SP);
-      MachineOptimizationRemarkMissed R(DEBUG_TYPE, "SpillReloadCopies", Loc,
-                                        &MF->front());
-      Stats.report(R);
-      R << "generated in function";
-      return R;
-    });
-  }
-}
-
-bool RAGreedy::runOnMachineFunction(MachineFunction &mf) {
-  LLVM_DEBUG(dbgs() << "********** GREEDY REGISTER ALLOCATION **********\n"
-                    << "********** Function: " << mf.getName() << '\n');
-
-  MF = &mf;
-  TII = MF->getSubtarget().getInstrInfo();
-
-  if (VerifyEnabled)
-    MF->verify(this, "Before greedy register allocator");
-
-  RegAllocBase::init(getAnalysis<VirtRegMap>(),
-                     getAnalysis<LiveIntervals>(),
-                     getAnalysis<LiveRegMatrix>());
-  Indexes = &getAnalysis<SlotIndexes>();
-  MBFI = &getAnalysis<MachineBlockFrequencyInfo>();
-  DomTree = &getAnalysis<MachineDominatorTree>();
-  ORE = &getAnalysis<MachineOptimizationRemarkEmitterPass>().getORE();
-  Loops = &getAnalysis<MachineLoopInfo>();
-  Bundles = &getAnalysis<EdgeBundles>();
-  SpillPlacer = &getAnalysis<SpillPlacement>();
-  DebugVars = &getAnalysis<LiveDebugVariables>();
-  AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
-
-  initializeCSRCost();
-
-  RegCosts = TRI->getRegisterCosts(*MF);
-  RegClassPriorityTrumpsGlobalness =
-      GreedyRegClassPriorityTrumpsGlobalness.getNumOccurrences()
-          ? GreedyRegClassPriorityTrumpsGlobalness
-          : TRI->regClassPriorityTrumpsGlobalness(*MF);
-
-  ExtraInfo.emplace();
-  EvictAdvisor =
-      getAnalysis<RegAllocEvictionAdvisorAnalysis>().getAdvisor(*MF, *this);
-
-  VRAI = std::make_unique<VirtRegAuxInfo>(*MF, *LIS, *VRM, *Loops, *MBFI);
-  SpillerInstance.reset(createInlineSpiller(*this, *MF, *VRM, *VRAI));
-
-  VRAI->calculateSpillWeightsAndHints();
-
-  LLVM_DEBUG(LIS->dump());
-
-  SA.reset(new SplitAnalysis(*VRM, *LIS, *Loops));
-  SE.reset(new SplitEditor(*SA, *AA, *LIS, *VRM, *DomTree, *MBFI, *VRAI));
-
-  IntfCache.init(MF, Matrix->getLiveUnions(), Indexes, LIS, TRI);
-  GlobalCand.resize(32);  // This will grow as needed.
-  SetOfBrokenHints.clear();
-  LastEvicted.clear();
-
-  allocatePhysRegs();
-  tryHintsRecoloring();
-
-  if (VerifyEnabled)
-    MF->verify(this, "Before post optimization");
-  postOptimization();
-  reportStats();
-
-  releaseMemory();
-  return true;
-}

llvm/lib/CodeGen/RegAllocPriorityAdvisor.h

+#include "llvm/Pass.h"
+
+namespace llvm {
+
+class MachineFunction;
+class RAGreedy;
+
+class RegAllocPriorityAdvisor {
+public:
+  RegAllocPriorityAdvisor(const RegAllocPriorityAdvisor &) = delete;
+  RegAllocPriorityAdvisor(RegAllocPriorityAdvisor &&) = delete;
+  virtual ~RegAllocPriorityAdvisor() = default;
+
+  virtual float tryFindPriority(unsigned Prio, unsigned Size,
+                                LiveRangeStage Stage, float Weight) const = 0;
+  virtual void logReward(float reward) = 0;
+
+protected:
+  RegAllocPriorityAdvisor(const MachineFunction &MF, const RAGreedy &RA);
+
+  const MachineFunction &MF;
+  const RAGreedy &RA;
+};
+
+class RegAllocPriorityAdvisorAnalysis : public ImmutablePass {
+public:
+  enum class AdvisorMode : int { Default, Release, Development };
+
+  RegAllocPriorityAdvisorAnalysis(AdvisorMode Mode)
+      : ImmutablePass(ID), Mode(Mode){};
+  static char ID;
+
+  /// Get an advisor for the given context (i.e. machine function, etc)
+  virtual std::unique_ptr<RegAllocPriorityAdvisor>
+  getAdvisor(const MachineFunction &MF, const RAGreedy &RA) = 0;
+  AdvisorMode getAdvisorMode() const { return Mode; }
+
+protected:
+  // This analysis preserves everything, and subclasses may have additional
+  // requirements.
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.setPreservesAll();
+  }
+
+private:
+  StringRef getPassName() const override;
+  const AdvisorMode Mode;
+};
+
+template <> Pass *callDefaultCtor<RegAllocPriorityAdvisorAnalysis>();
+
+RegAllocPriorityAdvisorAnalysis *createReleaseModePriorityAdvisor();
+
+RegAllocPriorityAdvisorAnalysis *createDevelopmentModePriorityAdvisor();
+
+class DefaultPriorityAdvisor : public RegAllocPriorityAdvisor {
+public:
+  DefaultPriorityAdvisor(const MachineFunction &MF, const RAGreedy &RA)
+      : RegAllocPriorityAdvisor(MF, RA) {}
+
+  void logReward(float reward) override{};
+
+private:
+  float tryFindPriority(unsigned Prio, unsigned Size, LiveRangeStage Stage,
+                        float Weight) const override;
+};
+} // namespace llvm
 No newline at end of file

llvm/lib/CodeGen/RegAllocPriorityAdvisor.cpp

+#include "RegAllocGreedy.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+
+using namespace llvm;
+
+static cl::opt<RegAllocPriorityAdvisorAnalysis::AdvisorMode> Mode(
+    "regalloc-prio-enable-advisor", cl::Hidden,
+    cl::init(RegAllocPriorityAdvisorAnalysis::AdvisorMode::Default),
+    cl::desc("Enable regalloc advisor mode"),
+    cl::values(
+        clEnumValN(RegAllocPriorityAdvisorAnalysis::AdvisorMode::Default,
+                   "default", "Default"),
+        clEnumValN(RegAllocPriorityAdvisorAnalysis::AdvisorMode::Release,
+                   "release", "precompiled"),
+        clEnumValN(RegAllocPriorityAdvisorAnalysis::AdvisorMode::Development,
+                   "development", "for training")));
+
+char RegAllocPriorityAdvisorAnalysis::ID = 0;
+INITIALIZE_PASS(RegAllocPriorityAdvisorAnalysis, "regalloc-prio",
+                "RegAllocPriorityAdvisorAnalysis", false, true)
+
+namespace {
+class DefaultPriorityAdvisorAnalysis final
+    : public RegAllocPriorityAdvisorAnalysis {
+public:
+  DefaultPriorityAdvisorAnalysis(bool NotAsRequested)
+      : RegAllocPriorityAdvisorAnalysis(AdvisorMode::Default),
+        NotAsRequested(NotAsRequested) {}
+
+  // support for isa<> and dyn_cast.
+  static bool classof(const RegAllocPriorityAdvisorAnalysis *R) {
+    return R->getAdvisorMode() == AdvisorMode::Default;
+  }
+
+private:
+  std::unique_ptr<RegAllocPriorityAdvisor>
+  getAdvisor(const MachineFunction &MF, const RAGreedy &RA) override {
+    return std::make_unique<DefaultPriorityAdvisor>(MF, RA);
+  }
+  bool doInitialization(Module &M) override {
+    if (NotAsRequested)
+      M.getContext().emitError("Requested regalloc priority advisor analysis "
+                               "could be created. Using default");
+    return RegAllocPriorityAdvisorAnalysis::doInitialization(M);
+  }
+  const bool NotAsRequested;
+};
+} // namespace
+
+template <> Pass *llvm::callDefaultCtor<RegAllocPriorityAdvisorAnalysis>() {
+  Pass *Ret = nullptr;
+  switch (Mode) {
+  case RegAllocPriorityAdvisorAnalysis::AdvisorMode::Default:
+    Ret = new DefaultPriorityAdvisorAnalysis(/*NotAsRequested*/ false);
+    break;
+  case RegAllocPriorityAdvisorAnalysis::AdvisorMode::Development:
+#if defined(LLVM_HAVE_TF_API)
+    Ret = createDevelopmentModePriorityAdvisor();
+#endif
+    break;
+  case RegAllocPriorityAdvisorAnalysis::AdvisorMode::Release:
+#if defined(LLVM_HAVE_TF_AOT)
+    Ret = createReleaseModePriorityAdvisor();
+#endif
+    break;
+  }
+  if (Ret)
+    return Ret;
+  return new DefaultPriorityAdvisorAnalysis(/*NotAsRequested*/ true);
+}
+
+StringRef RegAllocPriorityAdvisorAnalysis::getPassName() const {
+  switch (getAdvisorMode()) {
+  case AdvisorMode::Default:
+    return "Default Regalloc Priority Advisor";
+  case AdvisorMode::Release:
+    return "Release mode Regalloc Priority Advisor";
+  case AdvisorMode::Development:
+    return "Development mode Regalloc Priority Advisor";
+  }
+  llvm_unreachable("Unknown advisor kind");
+}
+
+RegAllocPriorityAdvisor::RegAllocPriorityAdvisor(const MachineFunction &MF,
+                                                 const RAGreedy &RA)
+    : MF(MF), RA(RA) {}
+
+float DefaultPriorityAdvisor::tryFindPriority(unsigned Prio, unsigned Size,
+                                              LiveRangeStage Stage,
+                                              float Weight) const {
+  return static_cast<float>(Prio);
+}
 No newline at end of file

llvm/test/CodeGen/MLRegalloc/Inputs/reference-prio-log-noml.txt

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+ feature {  float_list {  value: 0  }  }
+ feature {  float_list {  value: 0  }  }
+ feature {  float_list {  value: 0  }  }
+ feature {  float_list {  value: 0  }  }
+ feature {  float_list {  value: 0  }  }
+ feature {  float_list {  value: 0  }  }
+ feature {  float_list {  value: 0  }  }
+ feature {  float_list {  value: 0  }  }  }  } } "
+ }
+}

llvm/test/CodeGen/MLRegalloc/dev-mode-prio-logging.ll

+; REQUIRES: have_tf_api
+; REQUIRES: x86_64-linux
+;
+; Check that we log correctly, both with a learned policy, and the default policy
+;
+; RUN: llc -mtriple=x86_64-linux-unknown -regalloc=greedy -regalloc-prio-enable-advisor=development \
+; RUN:   -regalloc-prio-training-log=%t1 -tfutils-text-log < %S/Inputs/input.ll
+; RUN: sed -i 's/ \+/ /g' %t1
+; RUN: sed -i 's/\\n key:/\n key:/g' %t1
+; RUN: sed -i 's/\\n feature/\n feature/g' %t1
+; RUN: sed -i 's/\\n/ /g' %t1
+; RUN: FileCheck --input-file %t1 %s --check-prefixes=CHECK,NOML
+; RUN: diff %t1 %S/Inputs/reference-prio-log-noml.txt
+
+; RUN: rm -rf %t && mkdir %t
+; RUN: %python %S/../../../lib/Analysis/models/gen-regalloc-priority-test-model.py %t
+; RUN: llc -mtriple=x86_64-linux-unknown -regalloc=greedy -regalloc-prio-enable-advisor=development \
+; RUN:   -regalloc-prio-training-log=%t2 -tfutils-text-log -regalloc-prio-model=%t < %S/Inputs/input.ll
+; RUN: sed -i 's/ \+/ /g' %t2
+; RUN: sed -i 's/\\n key:/\n key:/g' %t2
+; RUN: sed -i 's/\\n feature/\n feature/g' %t2
+; RUN: sed -i 's/\\n/ /g' %t2
+; RUN: FileCheck --input-file %t2 %s --check-prefixes=CHECK,ML
+
+; CHECK-NOT: nan
+; CHECK-LABEL: key: \"priority\"
+; NOML-NEXT: feature {  float_list {  value: 2.68435814e+09  }  }
+; ML-NEXT: feature {  float_list {  value: 3551  }  }
+; CHECK-LABEL: key: \"reward\"
+