initial checkin of SkSL compiler

src/sksl/ir/SkSLVariable.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_VARIABLE
+#define SKSL_VARIABLE
+
+#include "SkSLModifiers.h"
+#include "SkSLPosition.h"
+#include "SkSLSymbol.h"
+#include "SkSLType.h"
+
+namespace SkSL {
+
+/**
+ * Represents a variable, whether local, global, or a function parameter. This represents the
+ * variable itself (the storage location), which is shared between all VariableReferences which
+ * read or write that storage location.
+ */
+struct Variable : public Symbol {
+    enum Storage {
+        kGlobal_Storage,
+        kLocal_Storage,
+        kParameter_Storage
+    };
+
+    Variable(Position position, Modifiers modifiers, std::string name, std::shared_ptr<Type> type,
+             Storage storage)
+    : INHERITED(position, kVariable_Kind, std::move(name))
+    , fModifiers(modifiers)
+    , fType(type)
+    , fStorage(storage)
+    , fIsReadFrom(false)
+    , fIsWrittenTo(false) {}
+
+    virtual std::string description() const override {
+        return fModifiers.description() + fType->fName + " " + fName;
+    }
+
+    const Modifiers fModifiers;
+    const std::string fValue;
+    const std::shared_ptr<Type> fType;
+    const Storage fStorage;
+
+    mutable bool fIsReadFrom;
+    mutable bool fIsWrittenTo;
+
+    typedef Symbol INHERITED;
+};
+
+} // namespace SkSL
+
+namespace std {
+    template <>
+        struct hash<SkSL::Variable> {
+        public :
+        size_t operator()(const SkSL::Variable &var) const{
+            return hash<std::string>()(var.fName) ^ hash<std::string>()(var.fType->description());
+        }
+    };
+} // namespace std
+
+#endif