added basic dataflow analysis to skslc

src/sksl/SkSLCompiler.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_COMPILER
 #define SKSL_COMPILER
 
+#include <set>
 #include <vector>
 #include "ir/SkSLProgram.h"
 #include "ir/SkSLSymbolTable.h"
+#include "SkSLCFGGenerator.h"
 #include "SkSLContext.h"
 #include "SkSLErrorReporter.h"
 #include "SkSLGLSLCodeGenerator.h"
 
 #define SK_FRAGCOLOR_BUILTIN 10001
 
 namespace SkSL {
 
 class IRGenerator;
 
@@ skipping 21 matching lines @@
     
     bool toGLSL(Program::Kind kind, const std::string& text, GLCaps caps, std::string* out);
 
     void error(Position position, std::string msg) override;
 
     std::string errorText();
 
     void writeErrorCount();
 
 private:
+    void addDefinition(const Expression* lvalue, const Expression* expr,
+                       std::unordered_map<const Variable*, const Expression*>* definitions);
+ 
+    void addDefinitions(const BasicBlock::Node& node, 
+                        std::unordered_map<const Variable*, const Expression*>* definitions);
+
+    void scanCFG(CFG* cfg, BlockId block, std::set<BlockId>* workList);
+
+    void scanCFG(const FunctionDefinition& f);
 
     void internalConvertProgram(std::string text,
                                 Modifiers::Flag* defaultPrecision,
                                 std::vector<std::unique_ptr<ProgramElement>>* result);
 
     std::shared_ptr<SymbolTable> fTypes;
     IRGenerator* fIRGenerator;
     std::string fSkiaVertText; // FIXME store parsed version instead
 
     Context fContext;
     int fErrorCount;
     std::string fErrorText;
 };
 
 } // namespace
 
 #endif