Merge pull request swiftlang#19601 from slavapestov/fewer-gsbs-2

Create fewer GenericSignatureBuilders, part 2

Author: slavapestov

include/swift/AST/GenericSignature.h

@@ -190,9 +190,10 @@ class alignas(1 << TypeAlignInBits) GenericSignature final
   Optional<ProtocolConformanceRef>
   lookupConformance(CanType depTy, ProtocolDecl *proto) const;
 
-  /// Return a vector of all generic parameters that are not subject to
-  /// a concrete same-type constraint.
-  SmallVector<GenericTypeParamType *, 2> getSubstitutableParams() const;
+  /// Iterate over all generic parameters, passing a flag to the callback
+  /// indicating if the generic parameter is canonical or not.
+  void forEachParam(
+    llvm::function_ref<void(GenericTypeParamType *, bool)> callback) const;
 
   /// Check if the generic signature makes all generic parameters
   /// concrete.

include/swift/AST/ProtocolConformance.h

@@ -415,7 +415,6 @@ class NormalProtocolConformance : public ProtocolConformance,
   {
     assert(!conformingType->hasArchetype() &&
            "ProtocolConformances should store interface types");
-    differenceAndStoreConditionalRequirements();
   }
 
   NormalProtocolConformance(Type conformingType,
@@ -428,7 +427,6 @@ class NormalProtocolConformance : public ProtocolConformance,
   {
     assert(!conformingType->hasArchetype() &&
            "ProtocolConformances should store interface types");
-    differenceAndStoreConditionalRequirements();
   }
 
   void resolveLazyInfo() const;

include/swift/AST/Witness.h

@@ -117,6 +117,15 @@ class Witness {
     return Witness(requirement);
   }
 
+  /// Create a witness for the given requirement.
+  ///
+  /// Deserialized witnesses do not have a synthetic environment.
+  static Witness forDeserialized(ValueDecl *decl,
+                                 SubstitutionMap substitutions) {
+    // TODO: It's probably a good idea to have a separate 'deserialized' bit.
+    return Witness(decl, substitutions, nullptr, SubstitutionMap());
+  }
+
   /// Create a witness that requires substitutions.
   ///
   /// \param decl The declaration for the witness.

include/swift/SIL/TypeSubstCloner.h

@@ -297,12 +297,15 @@ class TypeSubstCloner : public SILClonerWithScopes<ImplClass> {
     if (SubsMap.empty())
       return false;
 
-    for (auto ParamType : Sig->getSubstitutableParams()) {
+    bool Result = false;
+    Sig->forEachParam([&](GenericTypeParamType *ParamType, bool Canonical) {
+      if (!Canonical)
+        return;
       if (!Type(ParamType).subst(SubsMap)->isEqual(ParamType))
-        return true;
-    }
+        Result = true;
+    });
 
-    return false;
+    return Result;
   }
 
   enum { ForInlining = true };

include/swift/Serialization/ModuleFormat.h

@@ -55,7 +55,7 @@ const uint16_t VERSION_MAJOR = 0;
 /// describe what change you made. The content of this comment isn't important;
 /// it just ensures a conflict if two people change the module format.
 /// Don't worry about adhering to the 80-column limit for this line.
-const uint16_t VERSION_MINOR = 449; // Last change: serialize @_implements names
+const uint16_t VERSION_MINOR = 450; // Last change: don't serialize requirement environment
 
 using DeclIDField = BCFixed<31>;
 

lib/AST/ASTContext.cpp

@@ -4384,14 +4384,15 @@ void SubstitutionMap::Storage::Profile(
   // Profile those replacement types that corresponding to canonical generic
   // parameters within the generic signature.
   id.AddInteger(replacementTypes.size());
-  auto genericParams = genericSig->getGenericParams();
-  for (unsigned i : indices(genericParams)) {
-    auto gp = genericParams[i];
-    if (genericSig->isCanonicalTypeInContext(gp->getCanonicalType()))
+
+  unsigned i = 0;
+  genericSig->forEachParam([&](GenericTypeParamType *gp, bool canonical) {
+    if (canonical)
       id.AddPointer(replacementTypes[i].getPointer());
     else
       id.AddPointer(nullptr);
-  }
+    i++;
+  });
 
   // Conformances.
   id.AddInteger(conformances.size());

lib/AST/GenericSignature.cpp

@@ -97,45 +97,42 @@ GenericSignature::getInnermostGenericParams() const {
   return params;
 }
 
-
-SmallVector<GenericTypeParamType *, 2>
-GenericSignature::getSubstitutableParams() const {
+void GenericSignature::forEachParam(
+    llvm::function_ref<void(GenericTypeParamType *, bool)> callback) const {
   // Figure out which generic parameters are concrete or same-typed to another
-  // generic parameter.
+  // type parameter.
   auto genericParams = getGenericParams();
-  auto genericParamsAreNotSubstitutable =
-    SmallVector<bool, 4>(genericParams.size(), false);
+  auto genericParamsAreCanonical =
+    SmallVector<bool, 4>(genericParams.size(), true);
+
   for (auto req : getRequirements()) {
     if (req.getKind() != RequirementKind::SameType) continue;
 
     GenericTypeParamType *gp;
     if (auto secondGP = req.getSecondType()->getAs<GenericTypeParamType>()) {
-      // If two generic parameters are same-typed, then the left-hand one
-      // is canonical.
+      // If two generic parameters are same-typed, then the right-hand one
+      // is non-canonical.
+      assert(req.getFirstType()->is<GenericTypeParamType>());
       gp = secondGP;
     } else {
-      // If an associated type is same-typed, it doesn't constrain the generic
-      // parameter itself.
-      if (req.getSecondType()->isTypeParameter()) continue;
-
-      // Otherwise, the generic parameter is concrete.
+      // Otherwise, the right-hand side is an associated type or concrete type,
+      // and the left-hand one is non-canonical.
       gp = req.getFirstType()->getAs<GenericTypeParamType>();
       if (!gp) continue;
+
+      // If an associated type is same-typed, it doesn't constrain the generic
+      // parameter itself. That is, if T == U.Foo, then T is canonical, whereas
+      // U.Foo is not.
+      if (req.getSecondType()->isTypeParameter()) continue;
     }
 
     unsigned index = GenericParamKey(gp).findIndexIn(genericParams);
-    genericParamsAreNotSubstitutable[index] = true;
+    genericParamsAreCanonical[index] = false;
   }
 
-  // Collect the generic parameters that are substitutable.
-  SmallVector<GenericTypeParamType *, 2> result;
-  for (auto index : indices(genericParams)) {
-    auto gp = genericParams[index];
-    if (!genericParamsAreNotSubstitutable[index])
-      result.push_back(gp);
-  }
-
-  return result;
+  // Call the callback with each parameter and the result of the above analysis.
+  for (auto index : indices(genericParams))
+    callback(genericParams[index], genericParamsAreCanonical[index]);
 }
 
 bool GenericSignature::areAllParamsConcrete() const {

lib/AST/ProtocolConformance.cpp

@@ -886,7 +886,6 @@ SpecializedProtocolConformance::SpecializedProtocolConformance(
     GenericSubstitutions(substitutions)
 {
   assert(genericConformance->getKind() != ProtocolConformanceKind::Specialized);
-  computeConditionalRequirements();
 }
 
 void SpecializedProtocolConformance::computeConditionalRequirements() const {

lib/AST/SubstitutionMap.cpp

@@ -200,18 +200,19 @@ SubstitutionMap SubstitutionMap::get(GenericSignature *genericSig,
   // Form the replacement types.
   SmallVector<Type, 4> replacementTypes;
   replacementTypes.reserve(genericSig->getGenericParams().size());
-  for (auto gp : genericSig->getGenericParams()) {
+
+  genericSig->forEachParam([&](GenericTypeParamType *gp, bool canonical) {
     // Don't eagerly form replacements for non-canonical generic parameters.
-    if (!genericSig->isCanonicalTypeInContext(gp->getCanonicalType())) {
+    if (!canonical) {
       replacementTypes.push_back(Type());
-      continue;
+      return;
     }
 
     // Record the replacement.
     Type replacement = Type(gp).subst(subs, lookupConformance,
                                       SubstFlags::UseErrorType);
     replacementTypes.push_back(replacement);
-  }
+  });
 
   // Form the stored conformances.
   SmallVector<ProtocolConformanceRef, 4> conformances;
@@ -318,6 +319,20 @@ SubstitutionMap::lookupConformance(CanType type, ProtocolDecl *proto) const {
   if (!type->isTypeParameter())
     return None;
 
+  auto genericSig = getGenericSignature();
+
+  // Fast path
+  unsigned index = 0;
+  for (auto reqt : genericSig->getRequirements()) {
+    if (reqt.getKind() == RequirementKind::Conformance) {
+      if (reqt.getFirstType()->isEqual(type) &&
+          reqt.getSecondType()->isEqual(proto->getDeclaredType()))
+        return getConformances()[index];
+
+      index++;
+    }
+  }
+
   // Retrieve the starting conformance from the conformance map.
   auto getInitialConformance =
     [&](Type type, ProtocolDecl *proto) -> Optional<ProtocolConformanceRef> {
@@ -338,8 +353,6 @@ SubstitutionMap::lookupConformance(CanType type, ProtocolDecl *proto) const {
       return None;
     };
 
-  auto genericSig = getGenericSignature();
-
   // If the type doesn't conform to this protocol, the result isn't formed
   // from these requirements.
   if (!genericSig->conformsToProtocol(type, proto)) {

lib/IRGen/GenMeta.cpp

@@ -313,15 +313,15 @@ namespace {
       GenericSignature *sig = asImpl().getGenericSignature();
       assert(sig);
       auto canSig = sig->getCanonicalSignature();
-      
-      for (auto param : canSig->getGenericParams()) {
+
+      canSig->forEachParam([&](GenericTypeParamType *param, bool canonical) {
         // Currently, there are only type parameters. The parameter is a key
         // argument if it's canonical in its generic context.
         asImpl().addGenericParameter(GenericParamKind::Type,
-                 /*key argument*/ canSig->isCanonicalTypeInContext(param),
-                 /*extra argument*/ false);
-      }
-      
+                                     /*key argument*/ canonical,
+                                     /*extra argument*/ false);
+      });
+
       // Pad the structure up to four bytes for the following requirements.
       unsigned padding = (unsigned) -canSig->getGenericParams().size() & 3;
       for (unsigned i = 0; i < padding; ++i)