Sema: Remove DependentComponentSplitterStep

Author: slavapestov

include/swift/Sema/ConstraintGraph.h

@@ -338,12 +338,6 @@ class ConstraintGraph {
     /// The constraints in this component.
     TinyPtrVector<Constraint *> constraints;
 
-    /// The set of components that this component depends on, such that
-    /// the partial solutions of the those components need to be available
-    /// before this component can be solved.
-    ///
-    SmallVector<unsigned, 2> dependencies;
-
   public:
     Component(unsigned solutionIndex) : solutionIndex(solutionIndex) { }
 
@@ -359,11 +353,6 @@ class ConstraintGraph {
       return constraints;
     }
 
-    /// Records a component which this component depends on.
-    void recordDependency(const Component &component);
-
-    ArrayRef<unsigned> getDependencies() const { return dependencies; }
-
     unsigned getNumDisjunctions() const { return numDisjunctions; }
   };
 

lib/Sema/CSStep.cpp

@@ -126,7 +126,6 @@ void SplitterStep::computeFollowupSteps(
   // Take the orphaned constraints, because they'll go into a component now.
   OrphanedConstraints = CG.takeOrphanedConstraints();
 
-  IncludeInMergedResults.resize(numComponents, true);
   Components.resize(numComponents);
   PartialSolutions = std::unique_ptr<SmallVector<Solution, 4>[]>(
       new SmallVector<Solution, 4>[numComponents]);
@@ -135,26 +134,9 @@ void SplitterStep::computeFollowupSteps(
   for (unsigned i : indices(components)) {
     unsigned solutionIndex = components[i].solutionIndex;
 
-    // If there are no dependencies, build a normal component step.
-    if (components[i].getDependencies().empty()) {
-      steps.push_back(std::make_unique<ComponentStep>(
-          CS, solutionIndex, &Components[i], std::move(components[i]),
-          PartialSolutions[solutionIndex]));
-      continue;
-    }
-
-    // Note that the partial results from any dependencies of this component
-    // need not be included in the final merged results, because they'll
-    // already be part of the partial results for this component.
-    for (auto dependsOn : components[i].getDependencies()) {
-      IncludeInMergedResults[dependsOn] = false;
-    }
-
-    // Otherwise, build a dependent component "splitter" step, which
-    // handles all combinations of incoming partial solutions.
-    steps.push_back(std::make_unique<DependentComponentSplitterStep>(
-        CS, &Components[i], solutionIndex, std::move(components[i]),
-        llvm::MutableArrayRef(PartialSolutions.get(), numComponents)));
+    steps.push_back(std::make_unique<ComponentStep>(
+        CS, solutionIndex, &Components[i], std::move(components[i]),
+        PartialSolutions[solutionIndex]));
   }
 
   assert(CS.InactiveConstraints.empty() && "Missed a constraint");
@@ -223,8 +205,7 @@ bool SplitterStep::mergePartialSolutions() const {
   SmallVector<unsigned, 2> countsVec;
   countsVec.reserve(numComponents);
   for (unsigned idx : range(numComponents)) {
-    countsVec.push_back(
-        IncludeInMergedResults[idx] ? PartialSolutions[idx].size() : 1);
+    countsVec.push_back(PartialSolutions[idx].size());
   }
 
   // Produce all combinations of partial solutions.
@@ -237,9 +218,6 @@ bool SplitterStep::mergePartialSolutions() const {
     // solutions.
     ConstraintSystem::SolverScope scope(CS);
     for (unsigned i : range(numComponents)) {
-      if (!IncludeInMergedResults[i])
-        continue;
-
       CS.replaySolution(PartialSolutions[i][indices[i]]);
     }
 
@@ -271,77 +249,15 @@ bool SplitterStep::mergePartialSolutions() const {
   return anySolutions;
 }
 
-StepResult DependentComponentSplitterStep::take(bool prevFailed) {
-  // "split" is considered a failure if previous step failed,
-  // or there is a failure recorded by constraint system, or
-  // system can't be simplified.
-  if (prevFailed || CS.getFailedConstraint() || CS.simplify())
-    return done(/*isSuccess=*/false);
-
-  // Figure out the sets of partial solutions that this component depends on.
-  SmallVector<const SmallVector<Solution, 4> *, 2> dependsOnSets;
-  for (auto index : Component.getDependencies()) {
-    dependsOnSets.push_back(&AllPartialSolutions[index]);
-  }
-
-  // Produce all combinations of partial solutions for the inputs.
-  SmallVector<std::unique_ptr<SolverStep>, 4> followup;
-  SmallVector<unsigned, 2> indices(Component.getDependencies().size(), 0);
-  auto dependsOnSetsRef = llvm::ArrayRef(dependsOnSets);
-  do {
-    // Form the set of input partial solutions.
-    SmallVector<const Solution *, 2> dependsOnSolutions;
-    for (auto index : swift::indices(indices)) {
-      dependsOnSolutions.push_back(&(*dependsOnSets[index])[indices[index]]);
-    }
-    ContextualSolutions.push_back(std::make_unique<SmallVector<Solution, 2>>());
-
-    followup.push_back(std::make_unique<ComponentStep>(
-        CS, Index, Constraints, Component, std::move(dependsOnSolutions),
-        *ContextualSolutions.back()));
-  } while (nextCombination(dependsOnSetsRef, indices));
-
-  /// Wait until all of the component steps are done.
-  return suspend(followup);
-}
-
-StepResult DependentComponentSplitterStep::resume(bool prevFailed) {
-  for (auto &ComponentStepSolutions : ContextualSolutions) {
-    Solutions.append(std::make_move_iterator(ComponentStepSolutions->begin()),
-                     std::make_move_iterator(ComponentStepSolutions->end()));
-  }
-  return done(/*isSuccess=*/!Solutions.empty());
-}
-
-void DependentComponentSplitterStep::print(llvm::raw_ostream &Out) {
-  Out << "DependentComponentSplitterStep for dependencies on [";
-  interleave(
-      Component.getDependencies(), [&](unsigned index) { Out << index; },
-      [&] { Out << ", "; });
-  Out << "]\n";
-}
-
 StepResult ComponentStep::take(bool prevFailed) {
   // One of the previous components created by "split"
   // failed, it means that we can't solve this component.
-  if ((prevFailed && DependsOnPartialSolutions.empty()) ||
-      CS.isTooComplex(Solutions) || CS.worseThanBestSolution())
+  if (prevFailed || CS.isTooComplex(Solutions) || CS.worseThanBestSolution())
     return done(/*isSuccess=*/false);
 
   // Setup active scope, only if previous component didn't fail.
   setupScope();
 
-  // If there are any dependent partial solutions to compose, do so now.
-  if (!DependsOnPartialSolutions.empty()) {
-    for (auto partial : DependsOnPartialSolutions) {
-      CS.replaySolution(*partial);
-    }
-
-    // Simplify again.
-    if (CS.failedConstraint || CS.simplify())
-      return done(/*isSuccess=*/false);
-  }
-
   /// Try to figure out what this step is going to be,
   /// after the scope has been established.
   SmallString<64> potentialBindings;

lib/Sema/CSStep.h

@@ -240,10 +240,6 @@ class SplitterStep final : public SolverStep {
 
   SmallVector<Constraint *, 4> OrphanedConstraints;
 
-  /// Whether to include the partial results of this component in the final
-  /// merged results.
-  SmallVector<bool, 4> IncludeInMergedResults;
-
 public:
   SplitterStep(ConstraintSystem &cs, SmallVectorImpl<Solution> &solutions)
       : SolverStep(cs, solutions) {}
@@ -269,56 +265,6 @@ class SplitterStep final : public SolverStep {
   bool mergePartialSolutions() const;
 };
 
-/// `DependentComponentSplitterStep` is responsible for composing the partial
-/// solutions from other components (on which this component depends) into
-/// the inputs based on which we can solve a particular component.
-class DependentComponentSplitterStep final : public SolverStep {
-  /// Constraints "in scope" of this step.
-  ConstraintList *Constraints;
-
-  /// Index into the parent splitter step.
-  unsigned Index;
-
-  /// The component that has dependencies.
-  ConstraintGraph::Component Component;
-
-  /// Array containing all of the partial solutions for the parent split.
-  MutableArrayRef<SmallVector<Solution, 4>> AllPartialSolutions;
-
-  /// The solutions computed the \c ComponentSteps created for each partial
-  /// solution combinations. Will be merged into the final \c Solutions vector
-  /// in \c resume.
-  std::vector<std::unique_ptr<SmallVector<Solution, 2>>> ContextualSolutions;
-
-  /// Take all of the constraints in this component and put them into
-  /// \c Constraints.
-  void injectConstraints() {
-    for (auto constraint : Component.getConstraints()) {
-      Constraints->erase(constraint);
-      Constraints->push_back(constraint);
-    }
-  }
-
-public:
-  DependentComponentSplitterStep(
-      ConstraintSystem &cs,
-      ConstraintList *constraints,
-      unsigned index,
-      ConstraintGraph::Component &&component,
-      MutableArrayRef<SmallVector<Solution, 4>> allPartialSolutions)
-    : SolverStep(cs, allPartialSolutions[index]), Constraints(constraints),
-      Index(index), Component(std::move(component)),
-      AllPartialSolutions(allPartialSolutions) {
-    assert(!Component.getDependencies().empty() && "Should use ComponentStep");
-    injectConstraints();
-  }
-
-  StepResult take(bool prevFailed) override;
-  StepResult resume(bool prevFailed) override;
-
-  void print(llvm::raw_ostream &Out) override;
-};
-
 
 /// `ComponentStep` represents a set of type variables and related
 /// constraints which could be solved independently. It's further
@@ -381,10 +327,6 @@ class ComponentStep final : public SolverStep {
   /// Constraints "in scope" of this step.
   ConstraintList *Constraints;
 
-  /// The set of partial solutions that should be composed before evaluating
-  /// this component.
-  SmallVector<const Solution *, 2> DependsOnPartialSolutions;
-
   /// Constraint which doesn't have any free type variables associated
   /// with it, which makes it disconnected in the graph.
   Constraint *OrphanedConstraint = nullptr;
@@ -419,8 +361,6 @@ class ComponentStep final : public SolverStep {
       constraints->erase(constraint);
       Constraints->push_back(constraint);
     }
-
-    assert(component.getDependencies().empty());
   }
 
   /// Create a component step that composes existing partial solutions before
@@ -429,15 +369,11 @@ class ComponentStep final : public SolverStep {
       ConstraintSystem &cs, unsigned index,
       ConstraintList *constraints,
       const ConstraintGraph::Component &component,
-      llvm::SmallVectorImpl<const Solution *> &&dependsOnPartialSolutions,
       SmallVectorImpl<Solution> &solutions)
         : SolverStep(cs, solutions), Index(index), IsSingle(false),
           OriginalScore(getCurrentScore()), OriginalBestScore(getBestScore()),
-          Constraints(constraints),
-          DependsOnPartialSolutions(std::move(dependsOnPartialSolutions)) {
+          Constraints(constraints) {
     TypeVars = component.typeVars;
-    assert(DependsOnPartialSolutions.size() ==
-           component.getDependencies().size());
 
     for (auto constraint : component.getConstraints()) {
       constraints->erase(constraint);

lib/Sema/ConstraintGraph.cpp

@@ -865,10 +865,6 @@ void ConstraintGraph::Component::addConstraint(Constraint *constraint) {
   constraints.push_back(constraint);
 }
 
-void ConstraintGraph::Component::recordDependency(const Component &component) {
-  dependencies.push_back(component.solutionIndex);
-}
-
 SmallVector<ConstraintGraph::Component, 1>
 ConstraintGraph::computeConnectedComponents(
            ArrayRef<TypeVariableType *> typeVars) {
@@ -1122,20 +1118,6 @@ void ConstraintGraph::printConnectedComponents(
                [&] {
                  out << ' ';
                });
-
-    auto dependencies = component.getDependencies();
-    if (dependencies.empty())
-      continue;
-
-    SmallVector<unsigned, 4> indices{dependencies.begin(), dependencies.end()};
-    // Sort dependencies so output is stable.
-    llvm::sort(indices);
-
-    // Print all of the one-way components.
-    out << " depends on ";
-    llvm::interleave(
-        indices, [&out](unsigned index) { out << index; },
-        [&out] { out << ", "; });
   }
 }