initial checkin of SkSL compiler

src/sksl/ir/SkSLFunctionCall.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_FUNCTIONCALL
+#define SKSL_FUNCTIONCALL
+
+#include "SkSLExpression.h"
+#include "SkSLFunctionDeclaration.h"
+
+namespace SkSL {
+
+/**
+ * A function invocation.
+ */
+struct FunctionCall : public Expression {
+    FunctionCall(Position position, std::shared_ptr<FunctionDeclaration> function,

[dogben, 2016/06/22 17:43:57]

Checking my understanding: Reading the GLSL spec, it sounds like functions can
only be called by name. Even the "subroutine" thing looks like a function
declaration. So, things like "(b ? f1 : f2)(arg1, arg2)" are not allowed.
Correct?

[ethannicholas, 2016/06/24 21:23:10]

Correct.

+                 std::vector<std::unique_ptr<Expression>> parameters)

[dogben, 2016/06/22 17:43:57]

nit: s/parameters/arguments/g

+    : INHERITED(position, kFunctionCall_Kind, function->fReturnType)
+    , fFunction(function)

[dogben, 2016/06/22 17:43:57]

nit: std::move

+    , fParameters(std::move(parameters)) {}
+
+    virtual std::string description() const override {

[dogben, 2016/06/22 17:43:57]

nit: remove virtual

+        std::string result = fFunction->fName + "(";
+        std::string separator = "";
+        for (size_t i = 0; i < fParameters.size(); i++) {
+            result += separator;
+            result += fParameters[i]->description();
+            separator = ", ";
+        }
+        result += ")";
+        return result;
+    }
+
+    const std::shared_ptr<FunctionDeclaration> fFunction;
+    const std::vector<std::unique_ptr<Expression>> fParameters;
+
+    typedef Expression INHERITED;
+};
+
+} // namespace
+
+#endif