Reduce the Stack Size of ConstraintSystem

The ConstraintSystem class is on the order of 1000s of bytes in size on
the stacka nd is causing issues with dispatch's 64k stack limit.

This changes most Small data types which store data on the stack to non
small heap based data types.

Author: gmittert

lib/Sema/CSSolver.cpp

@@ -245,7 +245,8 @@ void ConstraintSystem::applySolution(const Solution &solution) {
   }
 
   // Register the defaulted type variables.
-  DefaultedConstraints.append(solution.DefaultedConstraints.begin(),
+  DefaultedConstraints.insert(DefaultedConstraints.end(),
+                              solution.DefaultedConstraints.begin(),
                               solution.DefaultedConstraints.end());
 
   // Add the node types back.
@@ -339,6 +340,12 @@ bool ConstraintSystem::simplify(bool ContinueAfterFailures) {
 
 namespace {
 
+template<typename T>
+void truncate(std::vector<T> &vec, unsigned newSize) {
+  assert(newSize <= vec.size() && "Not a truncation!");
+  vec.erase(vec.begin() + newSize, vec.end());
+}
+
 /// Truncate the given small vector to the given new size.
 template<typename T>
 void truncate(SmallVectorImpl<T> &vec, unsigned newSize) {

lib/Sema/CSStep.cpp

@@ -99,8 +99,8 @@ void SplitterStep::computeFollowupSteps(
   // FIXME: We're seeding typeVars with TypeVariables so that the
   // connected-components algorithm only considers those type variables within
   // our component. There are clearly better ways to do this.
-  SmallVector<TypeVariableType *, 16> typeVars(CS.TypeVariables);
-  SmallVector<unsigned, 16> components;
+  std::vector<TypeVariableType *> typeVars(CS.TypeVariables);
+  std::vector<unsigned> components;
   unsigned numComponents = CG.computeConnectedComponents(typeVars, components);
   if (numComponents < 2) {
     componentSteps.push_back(llvm::make_unique<ComponentStep>(

lib/Sema/CSStep.h

@@ -291,7 +291,7 @@ class ComponentStep final : public SolverStep {
     ConstraintSystem &CS;
     ConstraintSystem::SolverScope *SolverScope;
 
-    SmallVector<TypeVariableType *, 16> TypeVars;
+    std::vector<TypeVariableType *> TypeVars;
     ConstraintSystem::SolverScope *PrevPartialScope = nullptr;
 
     // The component this scope is associated with.
@@ -336,7 +336,7 @@ class ComponentStep final : public SolverStep {
   std::unique_ptr<Scope> ComponentScope = nullptr;
 
   /// Type variables and constraints "in scope" of this step.
-  SmallVector<TypeVariableType *, 16> TypeVars;
+  std::vector<TypeVariableType *> TypeVars;
   /// Constraints "in scope" of this step.
   ConstraintList *Constraints;
 

lib/Sema/ConstraintGraph.cpp

@@ -528,7 +528,7 @@ void ConstraintGraph::gatherConstraints(
 static void connectedComponentsDFS(ConstraintGraph &cg,
                                    ConstraintGraphNode &node,
                                    unsigned component,
-                                   SmallVectorImpl<unsigned> &components) {
+                                   std::vector<unsigned> &components) {
   // Local function that recurses on the given set of type variables.
   auto visitAdjacencies = [&](ArrayRef<TypeVariableType *> typeVars) {
     for (auto adj : typeVars) {
@@ -562,8 +562,8 @@ static void connectedComponentsDFS(ConstraintGraph &cg,
 }
 
 unsigned ConstraintGraph::computeConnectedComponents(
-           SmallVectorImpl<TypeVariableType *> &typeVars,
-           SmallVectorImpl<unsigned> &components) {
+           std::vector<TypeVariableType *> &typeVars,
+           std::vector<unsigned> &components) {
   // Track those type variables that the caller cares about.
   llvm::SmallPtrSet<TypeVariableType *, 4> typeVarSubset(typeVars.begin(),
                                                          typeVars.end());
@@ -871,9 +871,9 @@ void ConstraintGraph::dump() {
 }
 
 void ConstraintGraph::printConnectedComponents(llvm::raw_ostream &out) {
-  SmallVector<TypeVariableType *, 16> typeVars;
-  typeVars.append(TypeVariables.begin(), TypeVariables.end());
-  SmallVector<unsigned, 16> components;
+  std::vector<TypeVariableType *> typeVars;
+  typeVars.insert(typeVars.end(), TypeVariables.begin(), TypeVariables.end());
+  std::vector<unsigned> components;
   unsigned numComponents = computeConnectedComponents(typeVars, components);
   for (unsigned component = 0; component != numComponents; ++component) {
     out.indent(2);

lib/Sema/ConstraintGraph.h

@@ -249,8 +249,8 @@ class ConstraintGraph {
   /// one component for each of the constraints produced by
   /// \c getOrphanedConstraints().
   unsigned computeConnectedComponents(
-             SmallVectorImpl<TypeVariableType *> &typeVars,
-             SmallVectorImpl<unsigned> &components);
+             std::vector<TypeVariableType *> &typeVars,
+             std::vector<unsigned> &components);
 
   /// Retrieve the set of "orphaned" constraints, which are known to the
   /// constraint graph but have no type variables to anchor them.

lib/Sema/ConstraintSystem.cpp

@@ -2329,7 +2329,7 @@ size_t Solution::getTotalMemory() const {
          llvm::capacity_in_bytes(Fixes) + DisjunctionChoices.getMemorySize() +
          OpenedTypes.getMemorySize() + OpenedExistentialTypes.getMemorySize() +
          (DefaultedConstraints.size() * sizeof(void *)) +
-         llvm::capacity_in_bytes(Conformances);
+         Conformances.size() * sizeof(std::pair<ConstraintLocator *, ProtocolConformanceRef>);
 }
 
 DeclName OverloadChoice::getName() const {

lib/Sema/ConstraintSystem.h

@@ -591,14 +591,14 @@ class Solution {
   ConstraintSystem &getConstraintSystem() const { return *constraintSystem; }
 
   /// The set of type bindings.
-  llvm::SmallDenseMap<TypeVariableType *, Type> typeBindings;
+  llvm::DenseMap<TypeVariableType *, Type> typeBindings;
 
   /// The set of overload choices along with their types.
-  llvm::SmallDenseMap<ConstraintLocator *, SelectedOverload> overloadChoices;
+  llvm::DenseMap<ConstraintLocator *, SelectedOverload> overloadChoices;
 
   /// The set of constraint restrictions used to arrive at this restriction,
   /// which informs constraint application.
-  llvm::SmallDenseMap<std::pair<CanType, CanType>, ConversionRestrictionKind>
+  llvm::DenseMap<std::pair<CanType, CanType>, ConversionRestrictionKind>
     ConstraintRestrictions;
 
   /// The list of fixes that need to be applied to the initial expression
@@ -610,22 +610,22 @@ class Solution {
 
   /// The set of disjunction choices used to arrive at this solution,
   /// which informs constraint application.
-  llvm::SmallDenseMap<ConstraintLocator *, unsigned> DisjunctionChoices;
+  llvm::DenseMap<ConstraintLocator *, unsigned> DisjunctionChoices;
 
   /// The set of opened types for a given locator.
-  llvm::SmallDenseMap<ConstraintLocator *, ArrayRef<OpenedType>> OpenedTypes;
+  llvm::DenseMap<ConstraintLocator *, ArrayRef<OpenedType>> OpenedTypes;
 
   /// The opened existential type for a given locator.
-  llvm::SmallDenseMap<ConstraintLocator *, OpenedArchetypeType *>
+  llvm::DenseMap<ConstraintLocator *, OpenedArchetypeType *>
     OpenedExistentialTypes;
 
   /// The locators of \c Defaultable constraints whose defaults were used.
-  llvm::SmallPtrSet<ConstraintLocator *, 8> DefaultedConstraints;
+  llvm::SmallPtrSet<ConstraintLocator *, 2> DefaultedConstraints;
 
   /// The node -> type mappings introduced by this solution.
   llvm::SmallVector<std::pair<TypedNode, Type>, 8> addedNodeTypes;
 
-  llvm::SmallVector<std::pair<ConstraintLocator *, ProtocolConformanceRef>, 8>
+  std::vector<std::pair<ConstraintLocator *, ProtocolConformanceRef>>
       Conformances;
 
   /// The set of closures that have been transformed by a function builder.
@@ -1042,7 +1042,7 @@ class ConstraintSystem {
   /// solution it represents.
   Score CurrentScore;
 
-  SmallVector<TypeVariableType *, 16> TypeVariables;
+  std::vector<TypeVariableType *> TypeVariables;
 
   /// Maps expressions to types for choosing a favored overload
   /// type in a disjunction constraint.
@@ -1075,7 +1075,7 @@ class ConstraintSystem {
   /// there are multiple ways in which one type could convert to another, e.g.,
   /// given class types A and B, the solver might choose either a superclass
   /// conversion or a user-defined conversion.
-  SmallVector<std::tuple<Type, Type, ConversionRestrictionKind>, 32>
+  std::vector<std::tuple<Type, Type, ConversionRestrictionKind>>
       ConstraintRestrictions;
 
   /// The set of fixes applied to make the solution work.
@@ -1085,7 +1085,7 @@ class ConstraintSystem {
 
   /// The set of remembered disjunction choices used to reach
   /// the current constraint system.
-  SmallVector<std::pair<ConstraintLocator*, unsigned>, 32>
+  std::vector<std::pair<ConstraintLocator*, unsigned>>
       DisjunctionChoices;
 
   /// The worklist of "active" constraints that should be revisited
@@ -1112,7 +1112,7 @@ class ConstraintSystem {
   /// The node -> type mappings introduced by generating constraints.
   llvm::SmallVector<std::pair<TypedNode, Type>, 8> addedNodeTypes;
 
-  SmallVector<std::pair<ConstraintLocator *, ProtocolConformanceRef>, 8>
+  std::vector<std::pair<ConstraintLocator *, ProtocolConformanceRef>>
       CheckedConformances;
 
   /// The set of closures that have been transformed by a function builder.
@@ -1121,7 +1121,7 @@ class ConstraintSystem {
 
 public:
   /// The locators of \c Defaultable constraints whose defaults were used.
-  SmallVector<ConstraintLocator *, 8> DefaultedConstraints;
+  std::vector<ConstraintLocator *> DefaultedConstraints;
 
   /// A cache that stores the @dynamicCallable required methods implemented by
   /// types.