[Constraint graph] Move constraint uniquing into gatherConstraints().

DougGregor · DougGregor · commit 692dfed39b83 · 2019-09-03T15:04:03.000-07:00
Simplify the interface to gatherConstraints() by performing the uniquing within the function itself and returning only the resulting (uniqued) vector of constraints. (cherry picked from commit 8355f3d)
diff --git a/lib/Sema/CSBindings.cpp b/lib/Sema/CSBindings.cpp
@@ -209,14 +209,14 @@ bool ConstraintSystem::PotentialBindings::isViable(
 static bool hasNilLiteralConstraint(TypeVariableType *typeVar,
                                     ConstraintSystem &CS) {
   // Look for a literal-conformance constraint on the type variable.
-  llvm::SetVector<Constraint *> constraints;
-  CS.getConstraintGraph().gatherConstraints(
-      typeVar, constraints, ConstraintGraph::GatheringKind::EquivalenceClass,
-      [](Constraint *constraint) -> bool {
-        return constraint->getKind() == ConstraintKind::LiteralConformsTo &&
-               constraint->getProtocol()->isSpecificProtocol(
-                   KnownProtocolKind::ExpressibleByNilLiteral);
-      });
+  auto constraints =
+      CS.getConstraintGraph().gatherConstraints(
+          typeVar, ConstraintGraph::GatheringKind::EquivalenceClass,
+          [](Constraint *constraint) -> bool {
+            return constraint->getKind() == ConstraintKind::LiteralConformsTo &&
+                   constraint->getProtocol()->isSpecificProtocol(
+                       KnownProtocolKind::ExpressibleByNilLiteral);
+          });
 
   for (auto constraint : constraints)
     if (CS.simplifyType(constraint->getFirstType())->isEqual(typeVar))
@@ -392,9 +392,9 @@ ConstraintSystem::getPotentialBindings(TypeVariableType *typeVar) {
   }
 
   // Gather the constraints associated with this type variable.
-  llvm::SetVector<Constraint *> constraints;
-  getConstraintGraph().gatherConstraints(
-      typeVar, constraints, ConstraintGraph::GatheringKind::EquivalenceClass);
+  auto constraints =
+      getConstraintGraph().gatherConstraints(
+          typeVar, ConstraintGraph::GatheringKind::EquivalenceClass);
 
   PotentialBindings result(typeVar);
 
diff --git a/lib/Sema/CSDiag.cpp b/lib/Sema/CSDiag.cpp
@@ -7319,9 +7319,8 @@ bool FailureDiagnosis::diagnoseAmbiguousGenericParameters() {
     // because type B would have no constraints associated with it.
     unsigned numConstraints = 0;
     {
-      llvm::SetVector<Constraint *> constraints;
-      CS.getConstraintGraph().gatherConstraints(
-          tv, constraints, ConstraintGraph::GatheringKind::EquivalenceClass,
+      auto constraints = CS.getConstraintGraph().gatherConstraints(
+          tv, ConstraintGraph::GatheringKind::EquivalenceClass,
           [&](Constraint *constraint) -> bool {
             // We are not interested in ConformsTo constraints because
             // we can't derive any concrete type information from them.
diff --git a/lib/Sema/CSGen.cpp b/lib/Sema/CSGen.cpp
@@ -532,9 +532,8 @@ namespace {
 
     llvm::SmallSetVector<ProtocolDecl *, 2> literalProtos;
     if (auto argTypeVar = argTy->getAs<TypeVariableType>()) {
-      llvm::SetVector<Constraint *> constraints;
-      CS.getConstraintGraph().gatherConstraints(
-          argTypeVar, constraints,
+      auto constraints = CS.getConstraintGraph().gatherConstraints(
+          argTypeVar,
           ConstraintGraph::GatheringKind::EquivalenceClass,
           [](Constraint *constraint) {
             return constraint->getKind() == ConstraintKind::LiteralConformsTo;
diff --git a/lib/Sema/CSSimplify.cpp b/lib/Sema/CSSimplify.cpp
@@ -6930,9 +6930,8 @@ ConstraintSystem::addKeyPathApplicationRootConstraint(Type root, ConstraintLocat
   if (!typeVar)
     return;
 
-  llvm::SetVector<Constraint *> constraints;
-  CG.gatherConstraints(
-      typeVar, constraints, ConstraintGraph::GatheringKind::EquivalenceClass,
+  auto constraints = CG.gatherConstraints(
+      typeVar, ConstraintGraph::GatheringKind::EquivalenceClass,
       [&keyPathExpr](Constraint *constraint) -> bool {
         return constraint->getKind() == ConstraintKind::KeyPath &&
                constraint->getLocator()->getAnchor() == keyPathExpr;
diff --git a/lib/Sema/CSSolver.cpp b/lib/Sema/CSSolver.cpp
@@ -1494,9 +1494,8 @@ static Constraint *selectBestBindingDisjunction(
     if (!firstBindDisjunction)
       firstBindDisjunction = disjunction;
 
-    llvm::SetVector<Constraint *> constraints;
-    cs.getConstraintGraph().gatherConstraints(
-        typeVar, constraints, ConstraintGraph::GatheringKind::EquivalenceClass,
+    auto constraints = cs.getConstraintGraph().gatherConstraints(
+        typeVar, ConstraintGraph::GatheringKind::EquivalenceClass,
         [](Constraint *constraint) {
           return constraint->getKind() == ConstraintKind::Conversion;
         });
@@ -1551,9 +1550,8 @@ void ConstraintSystem::ArgumentInfoCollector::walk(Type argType) {
 
     visited.insert(rep);
 
-    llvm::SetVector<Constraint *> constraints;
-    CS.getConstraintGraph().gatherConstraints(
-        rep, constraints, ConstraintGraph::GatheringKind::EquivalenceClass);
+    auto constraints = CS.getConstraintGraph().gatherConstraints(
+        rep, ConstraintGraph::GatheringKind::EquivalenceClass);
 
     for (auto *constraint : constraints) {
       switch (constraint->getKind()) {
@@ -1747,9 +1745,8 @@ Constraint *ConstraintSystem::getUnboundBindOverloadDisjunction(
   while (visitedVars.insert(rep).second) {
     // Look for a disjunction that binds this type variable to an overload set.
     TypeVariableType *optionalObjectTypeVar = nullptr;
-    llvm::SetVector<Constraint *> disjunctions;
-    getConstraintGraph().gatherConstraints(
-        rep, disjunctions, ConstraintGraph::GatheringKind::EquivalenceClass,
+    auto disjunctions = getConstraintGraph().gatherConstraints(
+        rep, ConstraintGraph::GatheringKind::EquivalenceClass,
         [this, rep, &optionalObjectTypeVar](Constraint *match) {
           // If we have an "optional object of" constraint where the right-hand
           // side is this type variable, we may need to follow that type
@@ -1850,9 +1847,8 @@ void ConstraintSystem::sortDesignatedTypes(
     SmallVectorImpl<NominalTypeDecl *> &nominalTypes,
     Constraint *bindOverload) {
   auto *tyvar = bindOverload->getFirstType()->castTo<TypeVariableType>();
-  llvm::SetVector<Constraint *> applicableFns;
-  getConstraintGraph().gatherConstraints(
-      tyvar, applicableFns, ConstraintGraph::GatheringKind::EquivalenceClass,
+  auto applicableFns = getConstraintGraph().gatherConstraints(
+      tyvar, ConstraintGraph::GatheringKind::EquivalenceClass,
       [](Constraint *match) {
         return match->getKind() == ConstraintKind::ApplicableFunction;
       });
@@ -2266,21 +2262,21 @@ void DisjunctionChoice::propagateConversionInfo(ConstraintSystem &cs) const {
     return;
 
   auto conversionType = bindings.Bindings[0].BindingType;
-  llvm::SetVector<Constraint *> constraints;
-  cs.CG.gatherConstraints(typeVar, constraints,
-                          ConstraintGraph::GatheringKind::EquivalenceClass,
-                          [](Constraint *constraint) -> bool {
-                            switch (constraint->getKind()) {
-                            case ConstraintKind::Conversion:
-                            case ConstraintKind::Defaultable:
-                            case ConstraintKind::ConformsTo:
-                            case ConstraintKind::LiteralConformsTo:
-                              return false;
-
-                            default:
-                              return true;
-                            }
-                          });
+  auto constraints = cs.CG.gatherConstraints(
+      typeVar,
+      ConstraintGraph::GatheringKind::EquivalenceClass,
+      [](Constraint *constraint) -> bool {
+        switch (constraint->getKind()) {
+        case ConstraintKind::Conversion:
+        case ConstraintKind::Defaultable:
+        case ConstraintKind::ConformsTo:
+        case ConstraintKind::LiteralConformsTo:
+          return false;
+
+        default:
+          return true;
+        }
+      });
 
   if (constraints.empty())
     cs.addConstraint(ConstraintKind::Bind, typeVar, conversionType,
diff --git a/lib/Sema/ConstraintGraph.cpp b/lib/Sema/ConstraintGraph.cpp
@@ -373,15 +373,14 @@ void ConstraintGraph::unbindTypeVariable(TypeVariableType *typeVar, Type fixed){
   }
 }
 
-void ConstraintGraph::gatherConstraints(
-    TypeVariableType *typeVar, llvm::SetVector<Constraint *> &constraints,
-    GatheringKind kind,
+llvm::TinyPtrVector<Constraint *> ConstraintGraph::gatherConstraints(
+    TypeVariableType *typeVar, GatheringKind kind,
     llvm::function_ref<bool(Constraint *)> acceptConstraint) {
-  auto &reprNode = (*this)[CS.getRepresentative(typeVar)];
-  auto equivClass = reprNode.getEquivalenceClass();
-  llvm::SmallPtrSet<TypeVariableType *, 4> typeVars;
+  llvm::TinyPtrVector<Constraint *> constraints;
 
   /// Add constraints for the given adjacent type variable.
+  llvm::SmallPtrSet<TypeVariableType *, 4> typeVars;
+  llvm::SmallPtrSet<Constraint *, 4> visitedConstraints;
   auto addAdjacentConstraints = [&](TypeVariableType *adjTypeVar) {
     auto adjTypeVarsToVisit =
         (*this)[CS.getRepresentative(adjTypeVar)].getEquivalenceClass();
@@ -390,17 +389,23 @@ void ConstraintGraph::gatherConstraints(
         continue;
 
       for (auto constraint : (*this)[adjTypeVarEquiv].getConstraints()) {
+        if (!visitedConstraints.insert(constraint).second)
+          continue;
+
         if (acceptConstraint(constraint))
-          constraints.insert(constraint);
+          constraints.push_back(constraint);
       }
     }
   };
 
+  auto &reprNode = (*this)[CS.getRepresentative(typeVar)];
+  auto equivClass = reprNode.getEquivalenceClass();
   for (auto typeVar : equivClass) {
     auto &node = (*this)[typeVar];
     for (auto constraint : node.getConstraints()) {
-      if (acceptConstraint(constraint))
-        constraints.insert(constraint);
+      if (visitedConstraints.insert(constraint).second &&
+          acceptConstraint(constraint))
+        constraints.push_back(constraint);
 
       // If we want all mentions, visit type variables within each of our
       // constraints.
@@ -417,6 +422,8 @@ void ConstraintGraph::gatherConstraints(
       addAdjacentConstraints(adjTypeVar);
     }
   }
+
+  return constraints;
 }
 
 #pragma mark Algorithms
diff --git a/lib/Sema/ConstraintGraph.h b/lib/Sema/ConstraintGraph.h
@@ -188,9 +188,8 @@ class ConstraintGraph {
   /// Gather the set of constraints that involve the given type variable,
   /// i.e., those constraints that will be affected when the type variable
   /// gets merged or bound to a fixed type.
-  void
+  llvm::TinyPtrVector<Constraint *>
   gatherConstraints(TypeVariableType *typeVar,
-                    llvm::SetVector<Constraint *> &constraints,
                     GatheringKind kind,
                     llvm::function_ref<bool(Constraint *)> acceptConstraint =
                         [](Constraint *constraint) { return true; });
diff --git a/lib/Sema/ConstraintSystem.cpp b/lib/Sema/ConstraintSystem.cpp
@@ -205,9 +205,8 @@ void ConstraintSystem::assignFixedType(TypeVariableType *typeVar, Type type,
 void ConstraintSystem::addTypeVariableConstraintsToWorkList(
        TypeVariableType *typeVar) {
   // Gather the constraints affected by a change to this type variable.
-  llvm::SetVector<Constraint *> inactiveConstraints;
-  CG.gatherConstraints(
-      typeVar, inactiveConstraints, ConstraintGraph::GatheringKind::AllMentions,
+  auto inactiveConstraints = CG.gatherConstraints(
+      typeVar, ConstraintGraph::GatheringKind::AllMentions,
       [](Constraint *constraint) { return !constraint->isActive(); });
 
   // Add any constraints that aren't already active to the worklist.
@@ -2020,13 +2019,13 @@ void ConstraintSystem::resolveOverload(ConstraintLocator *locator,
         increaseScore(SK_KeyPathSubscript);
 
         auto dynamicResultTy = boundType->castTo<TypeVariableType>();
-        llvm::SetVector<Constraint *> constraints;
-        CG.gatherConstraints(dynamicResultTy, constraints,
-                             ConstraintGraph::GatheringKind::EquivalenceClass,
-                             [](Constraint *constraint) {
-                               return constraint->getKind() ==
-                                      ConstraintKind::ApplicableFunction;
-                             });
+        auto constraints = CG.gatherConstraints(
+            dynamicResultTy,
+            ConstraintGraph::GatheringKind::EquivalenceClass,
+            [](Constraint *constraint) {
+              return constraint->getKind() ==
+                     ConstraintKind::ApplicableFunction;
+            });
 
         assert(constraints.size() == 1);
         auto *applicableFn = constraints.front();
