Use array for the cache.

Author: David Ungar

include/swift/AST/ASTContext.h

@@ -943,7 +943,7 @@ class ASTContext final {
   }
 
   /// Logically, there is a separate cache for each SourceFile.
-  llvm::SmallVectorImpl<Type> &getDefaultTypeRequestCache(SourceFile *);
+  Type &getDefaultTypeRequestCache(SourceFile *, KnownProtocolKind);
 
 private:
   friend Decl;

include/swift/AST/TypeCheckRequests.h

@@ -361,7 +361,7 @@ class DefaultTypeRequest
   static bool getPerformLocalLookup(KnownProtocolKind);
   TypeChecker &getTypeChecker() const;
   SourceFile *getSourceFile() const;
-  llvm::SmallVectorImpl<Type> &getCache() const;
+  Type &getCache() const;
   bool isDependencyMissing(Type result) const;
 };
 

lib/AST/ASTContext.cpp

@@ -293,7 +293,7 @@ FOR_KNOWN_FOUNDATION_TYPES(CACHE_FOUNDATION_DECL)
   /// Caches of default types for DefaultTypeRequest.
   /// Used to be instance variables in the TypeChecker.
   /// There is a logically separate cache for each SourceFile.
-  llvm::DenseMap<SourceFile *, llvm::SmallVector<Type, NumKnownProtocols>>
+  llvm::DenseMap<SourceFile *, std::array<Type, NumKnownProtocols>>
       DefaultTypeRequestCaches;
 
   /// Structure that captures data that is segregated into different
@@ -5080,7 +5080,7 @@ LayoutConstraint LayoutConstraint::getLayoutConstraint(LayoutConstraintKind Kind
   return LayoutConstraint(New);
 }
 
-llvm::SmallVectorImpl<Type> &
-ASTContext::getDefaultTypeRequestCache(SourceFile *SF) {
-  return getImpl().DefaultTypeRequestCaches[SF];
+Type &
+ASTContext::getDefaultTypeRequestCache(SourceFile *SF, KnownProtocolKind kind) {
+  return getImpl().DefaultTypeRequestCaches[SF][size_t(kind)];
 }

lib/AST/TypeCheckRequests.cpp

@@ -456,20 +456,19 @@ SourceFile *DefaultTypeRequest::getSourceFile() const {
   return getDeclContext()->getParentSourceFile();
 }
 
-llvm::SmallVectorImpl<Type> &DefaultTypeRequest::getCache() const {
+Type &DefaultTypeRequest::getCache() const {
   return getDeclContext()->getASTContext().getDefaultTypeRequestCache(
-      getSourceFile());
+      getSourceFile(), getKnownProtocolKind());
 }
 
 Optional<Type> DefaultTypeRequest::getCachedResult() const {
-  auto const &cache = getCache();
-  Type result = cache[size_t(getKnownProtocolKind())];
-  if (!result)
+  auto const &cachedType = getCache();
+  if (!cachedType)
     return None;
-  assert(!isDependencyMissing(result) &&
+  assert(!isDependencyMissing(cachedType) &&
          "Since the cache is now cached by SourceFile, the dependency should "
          "have been recorded when it was looked up.");
-  return result;
+  return cachedType;
 }
 
 bool DefaultTypeRequest::isDependencyMissing(Type result) const {
@@ -482,8 +481,7 @@ bool DefaultTypeRequest::isDependencyMissing(Type result) const {
 }
 
 void DefaultTypeRequest::cacheResult(Type value) const {
-  auto &cache = getCache();
-  cache[size_t(getKnownProtocolKind())] = value;
+  getCache() = value;
 }
 
 const char *