RequirementMachine: Layout requirement implied by superclass is now handled in the property map

slavapestov · slavapestov · commit be772cc74bc8 · 2022-01-05T22:41:03.000-05:00
diff --git a/lib/AST/RequirementMachine/PropertyMap.h b/lib/AST/RequirementMachine/PropertyMap.h
@@ -181,6 +181,14 @@ class PropertyMap {
   llvm::DenseMap<std::pair<unsigned, unsigned>, ProtocolConformance *>
       ConcreteConformances;
 
+  /// Superclass requirements always imply a layout requirement, and
+  /// concrete type requirements where the type is a class imply a
+  /// superclass requirement.
+  ///
+  /// Keep track of such rules to avoid wasted work from recording the
+  /// same rewrite loop more than once.
+  llvm::DenseSet<unsigned> CheckedRules;
+
   /// When a type parameter is subject to two requirements of the same
   /// kind, we have a pair of rewrite rules T.[p1] => T and T.[p2] => T.
   ///
@@ -218,6 +226,7 @@ class PropertyMap {
 private:
   void clear();
 
+  bool checkRuleOnce(unsigned ruleID);
   bool checkRulePairOnce(unsigned firstRuleID, unsigned secondRuleID);
 
   void addProperty(Term key, Symbol property, unsigned ruleID,
diff --git a/lib/AST/RequirementMachine/PropertyUnification.cpp b/lib/AST/RequirementMachine/PropertyUnification.cpp
@@ -37,6 +37,11 @@
 using namespace swift;
 using namespace rewriting;
 
+/// Returns true if we have not processed this rule before.
+bool PropertyMap::checkRuleOnce(unsigned ruleID) {
+  return CheckedRules.insert(ruleID).second;
+}
+
 /// Returns true if we have not processed this pair of rules before.
 bool PropertyMap::checkRulePairOnce(unsigned firstRuleID,
                                     unsigned secondRuleID) {
@@ -65,7 +70,7 @@ RewriteSystem::getRelation(unsigned index) const {
 }
 
 /// Given a key T, a rule (V.[p1] => V) where T == U.V, and a property [p2]
-/// where [p1] < [p2], record a rule (T.[p2] => T) that is implied by
+/// where [p1] < [p2], record a rule (T.[p2] => T) that is induced by
 /// the original rule (V.[p1] => V).
 static void recordRelation(Term key,
                            unsigned lhsRuleID,
@@ -80,7 +85,9 @@ static void recordRelation(Term key,
 
   assert(lhsProperty.isProperty());
   assert(rhsProperty.isProperty());
-  assert(lhsProperty.getKind() == rhsProperty.getKind());
+  assert(lhsProperty.getKind() == rhsProperty.getKind() ||
+         (lhsProperty.getKind() == Symbol::Kind::Superclass &&
+          rhsProperty.getKind() == Symbol::Kind::Layout));
 
   if (debug) {
     llvm::dbgs() << "%% Recording relation: ";
@@ -474,6 +481,21 @@ void PropertyMap::addProperty(
   case Symbol::Kind::Superclass: {
     // FIXME: Also handle superclass vs concrete
 
+    if (checkRuleOnce(ruleID)) {
+      // A rule (T.[superclass: C] => T) induces a rule (T.[layout: L] => T),
+      // where L is either AnyObject or _NativeObject.
+      auto superclass =
+          property.getSuperclass()->getClassOrBoundGenericClass();
+      auto layout =
+          LayoutConstraint::getLayoutConstraint(
+            superclass->getLayoutConstraintKind(),
+            Context.getASTContext());
+      auto layoutSymbol = Symbol::forLayout(layout, Context);
+
+      recordRelation(key, ruleID, layoutSymbol, System,
+                     inducedRules, debug);
+    }
+
     if (!props->Superclass) {
       props->Superclass = property;
       props->SuperclassRule = ruleID;
diff --git a/lib/AST/RequirementMachine/RequirementLowering.cpp b/lib/AST/RequirementMachine/RequirementLowering.cpp
@@ -924,25 +924,6 @@ void RuleBuilder::addRequirement(const Requirement &req,
     auto superclassSymbol = Symbol::forSuperclass(otherType, substitutions,
                                                   Context);
 
-    {
-      // Build the symbol [layout: L].
-      auto layout =
-        LayoutConstraint::getLayoutConstraint(
-          otherType->getClassOrBoundGenericClass()->getLayoutConstraintKind(),
-          Context.getASTContext());
-      auto layoutSymbol = Symbol::forLayout(layout, Context);
-
-      MutableTerm layoutSubjectTerm;
-      layoutSubjectTerm.add(superclassSymbol);
-
-      MutableTerm layoutConstraintTerm = layoutSubjectTerm;
-      layoutConstraintTerm.add(layoutSymbol);
-
-      // Add the rule [superclass: C<X, Y>].[layout: L] => [superclass: C<X, Y>].
-      PermanentRules.emplace_back(layoutConstraintTerm,
-                                  layoutSubjectTerm);
-    }
-
     // Build the term T.[superclass: C<X, Y>].
     constraintTerm = subjectTerm;
     constraintTerm.add(superclassSymbol);
diff --git a/test/Generics/generic_objc_superclass.swift b/test/Generics/generic_objc_superclass.swift
@@ -13,7 +13,6 @@ func foo<T : Generic<U>, U>(_: T, _: U) {
 
 // CHECK-LABEL: Requirement machine for <τ_0_0, τ_0_1 where τ_0_0 : Generic<τ_0_1>>
 // CHECK-NEXT: Rewrite system: {
-// CHECK-NEXT: - [superclass: Generic<τ_0_0> with <τ_0_1>].[layout: AnyObject] => [superclass: Generic<τ_0_0> with <τ_0_1>] [permanent]
 // CHECK-NEXT: - τ_0_0.[superclass: Generic<τ_0_0> with <τ_0_1>] => τ_0_0
 // CHECK-NEXT: - τ_0_0.[layout: AnyObject] => τ_0_0
 // CHECK-NEXT: }
diff --git a/test/Generics/unify_superclass_types_1.swift b/test/Generics/unify_superclass_types_1.swift
@@ -16,14 +16,12 @@ extension P where Self : Derived {
 // CHECK-LABEL: Requirement machine for <τ_0_0 where τ_0_0 : Derived, τ_0_0 : P>
 // CHECK-NEXT: Rewrite system: {
 // CHECK-NEXT: - [P].[P] => [P] [permanent]
-// CHECK-NEXT: - [superclass: Base].[layout: _NativeClass] => [superclass: Base] [permanent]
-// CHECK-NEXT: - [superclass: Derived].[layout: _NativeClass] => [superclass: Derived] [permanent]
 // CHECK-NEXT: - [P].[superclass: Base] => [P]
 // CHECK-NEXT: - τ_0_0.[superclass: Derived] => τ_0_0
 // CHECK-NEXT: - τ_0_0.[P] => τ_0_0
+// CHECK-NEXT: - τ_0_0.[superclass: Base] => τ_0_0
 // CHECK-NEXT: - [P].[layout: _NativeClass] => [P]
 // CHECK-NEXT: - τ_0_0.[layout: _NativeClass] => τ_0_0
-// CHECK-NEXT: - τ_0_0.[superclass: Base] => τ_0_0
 // CHECK-NEXT: }
 // CHECK-NEXT: Rewrite loops: {
 // CHECK:      }
diff --git a/test/Generics/unify_superclass_types_2.swift b/test/Generics/unify_superclass_types_2.swift
@@ -31,10 +31,12 @@ func unifySuperclassTest<T : P1 & P2>(_: T) {
 // CHECK-LABEL: Requirement machine for <τ_0_0 where τ_0_0 : P1, τ_0_0 : P2>
 // CHECK-NEXT: Rewrite system: {
 // CHECK:      - τ_0_0.[P1&P2:X].[superclass: Generic<τ_0_0, String, τ_0_1> with <τ_0_0.[P2:A2], τ_0_0.[P2:B2]>] => τ_0_0.[P1&P2:X]
-// CHECK-NEXT: - τ_0_0.[P1&P2:X].[layout: _NativeClass] => τ_0_0.[P1&P2:X]
 // CHECK-NEXT: - τ_0_0.[P1&P2:X].[superclass: Generic<Int, τ_0_0, τ_0_1> with <τ_0_0.[P1:A1], τ_0_0.[P1:B1]>] => τ_0_0.[P1&P2:X]
 // CHECK-NEXT: - τ_0_0.X => τ_0_0.[P1&P2:X]
 // CHECK-NEXT: - τ_0_0.[P2:X] => τ_0_0.[P1&P2:X]
+// CHECK-NEXT: - [P1:X].[layout: _NativeClass] => [P1:X]
+// CHECK-NEXT: - [P2:X].[layout: _NativeClass] => [P2:X]
+// CHECK-NEXT: - τ_0_0.[P1&P2:X].[layout: _NativeClass] => τ_0_0.[P1&P2:X]
 // CHECK-NEXT: - τ_0_0.[P2:A2].[concrete: Int] => τ_0_0.[P2:A2]
 // CHECK-NEXT: - τ_0_0.[P1:A1].[concrete: String] => τ_0_0.[P1:A1]
 // CHECK-NEXT: - τ_0_0.[P2:B2] => τ_0_0.[P1:B1]
diff --git a/test/Generics/unify_superclass_types_3.swift b/test/Generics/unify_superclass_types_3.swift
@@ -33,10 +33,12 @@ func unifySuperclassTest<T : P1 & P2>(_: T) {
 // CHECK-LABEL: Requirement machine for <τ_0_0 where τ_0_0 : P1, τ_0_0 : P2>
 // CHECK-NEXT: Rewrite system: {
 // CHECK:      - τ_0_0.[P1&P2:X].[superclass: Generic<τ_0_0, String, τ_0_1> with <τ_0_0.[P2:A2], τ_0_0.[P2:B2]>] => τ_0_0.[P1&P2:X]
-// CHECK-NEXT: - τ_0_0.[P1&P2:X].[layout: _NativeClass] => τ_0_0.[P1&P2:X]
 // CHECK-NEXT: - τ_0_0.[P1&P2:X].[superclass: Derived<τ_0_0, τ_0_1> with <τ_0_0.[P1:A1], τ_0_0.[P1:B1]>] => τ_0_0.[P1&P2:X]
 // CHECK-NEXT: - τ_0_0.X => τ_0_0.[P1&P2:X]
 // CHECK-NEXT: - τ_0_0.[P2:X] => τ_0_0.[P1&P2:X]
+// CHECK-NEXT: - [P1:X].[layout: _NativeClass] => [P1:X]
+// CHECK-NEXT: - [P2:X].[layout: _NativeClass] => [P2:X]
+// CHECK-NEXT: - τ_0_0.[P1&P2:X].[layout: _NativeClass] => τ_0_0.[P1&P2:X]
 // CHECK-NEXT: - τ_0_0.[P2:A2].[concrete: Int] => τ_0_0.[P2:A2]
 // CHECK-NEXT: - τ_0_0.[P1:A1].[concrete: String] => τ_0_0.[P1:A1]
 // CHECK-NEXT: - τ_0_0.[P2:B2] => τ_0_0.[P1:B1]
diff --git a/test/Generics/unify_superclass_types_4.swift b/test/Generics/unify_superclass_types_4.swift
@@ -36,10 +36,12 @@ func unifySuperclassTest<T : P1 & P2>(_: T) {
 // CHECK-LABEL: Requirement machine for <τ_0_0 where τ_0_0 : P1, τ_0_0 : P2>
 // CHECK-NEXT: Rewrite system: {
 // CHECK:      - τ_0_0.[P1&P2:X].[superclass: Derived<τ_0_0> with <τ_0_0.[P2:A2]>] => τ_0_0.[P1&P2:X]
-// CHECK-NEXT: - τ_0_0.[P1&P2:X].[layout: _NativeClass] => τ_0_0.[P1&P2:X]
 // CHECK-NEXT: - τ_0_0.[P1&P2:X].[superclass: Base<τ_0_0> with <τ_0_0.[P1:A1]>] => τ_0_0.[P1&P2:X]
 // CHECK-NEXT: - τ_0_0.X => τ_0_0.[P1&P2:X]
 // CHECK-NEXT: - τ_0_0.[P2:X] => τ_0_0.[P1&P2:X]
+// CHECK-NEXT: - [P1:X].[layout: _NativeClass] => [P1:X]
+// CHECK-NEXT: - [P2:X].[layout: _NativeClass] => [P2:X]
+// CHECK-NEXT: - τ_0_0.[P1&P2:X].[layout: _NativeClass] => τ_0_0.[P1&P2:X]
 // CHECK-NEXT: - τ_0_0.[P2:A2].[Q:T] => τ_0_0.[P1:A1]
 // CHECK-NEXT: }
 // CHECK-NEXT: Rewrite loops: {
