SkSL performance improvements

src/sksl/ir/SkSLSymbolTable.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
  
 #ifndef SKSL_SYMBOLTABLE
 #define SKSL_SYMBOLTABLE
 
 #include <memory>
 #include <unordered_map>
+#include <vector>
 #include "SkSLErrorReporter.h"
 #include "SkSLSymbol.h"
-#include "SkSLUnresolvedFunction.h"
 
 namespace SkSL {
 
+struct FunctionDeclaration;
+
 /**
  * Maps identifiers to symbols. Functions, in particular, are mapped to either FunctionDeclaration
  * or UnresolvedFunction depending on whether they are overloaded or not.
  */
 class SymbolTable {
 public:
     SymbolTable(ErrorReporter& errorReporter)
     : fErrorReporter(errorReporter) {}
 
     SymbolTable(std::shared_ptr<SymbolTable> parent, ErrorReporter& errorReporter)
     : fParent(parent)
     , fErrorReporter(errorReporter) {}
 
-    std::shared_ptr<Symbol> operator[](const std::string& name);
+    const Symbol* operator[](const std::string& name);
 
-    void add(const std::string& name, std::shared_ptr<Symbol> symbol);
+    void add(const std::string& name, std::unique_ptr<Symbol> symbol);
+
+    void addWithoutOwnership(const std::string& name, const Symbol* symbol);
+
+    Symbol* takeOwnership(Symbol* s);
 
     const std::shared_ptr<SymbolTable> fParent;
 
 private:
-    static std::vector<std::shared_ptr<FunctionDeclaration>> GetFunctions(
-                                                                  const std::shared_ptr<Symbol>& s);
+    static std::vector<const FunctionDeclaration*> GetFunctions(const Symbol& s);
 
-    std::unordered_map<std::string, std::shared_ptr<Symbol>> fSymbols;
+    std::vector<std::unique_ptr<Symbol>> fOwnedPointers;
+
+    std::unordered_map<std::string, const Symbol*> fSymbols;
 
     ErrorReporter& fErrorReporter;
 };
 
 } // namespace
 
 #endif