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diff --git a/gfx/angle/checkout/src/compiler/translator/CallDAG.h b/gfx/angle/checkout/src/compiler/translator/CallDAG.h
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+//
+// Copyright 2002 The ANGLE Project Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+
+// CallDAG.h: Defines a call graph DAG of functions to be re-used accross
+// analyses, allows to efficiently traverse the functions in topological
+// order.
+
+#ifndef COMPILER_TRANSLATOR_CALLDAG_H_
+#define COMPILER_TRANSLATOR_CALLDAG_H_
+
+#include <map>
+
+#include "compiler/translator/IntermNode.h"
+
+namespace sh
+{
+
+// The translator needs to analyze the the graph of the function calls
+// to run checks and analyses; since in GLSL recursion is not allowed
+// that graph is a DAG.
+// This class is used to precompute that function call DAG so that it
+// can be reused by multiple analyses.
+//
+// It stores a vector of function records, with one record per defined function.
+// Records are accessed by index but a function symbol id can be converted
+// to the index of the corresponding record. The records contain the AST node
+// of the function definition and the indices of the function's callees.
+//
+// In addition, records are in reverse topological order: a function F being
+// called by a function G will have index index(F) < index(G), that way
+// depth-first analysis becomes analysis in the order of indices.
+
+class CallDAG : angle::NonCopyable
+{
+  public:
+    CallDAG();
+    ~CallDAG();
+
+    struct Record
+    {
+        TIntermFunctionDefinition *node;  // Guaranteed to be non-null.
+        std::vector<int> callees;
+    };
+
+    enum InitResult
+    {
+        INITDAG_SUCCESS,
+        INITDAG_RECURSION,
+        INITDAG_UNDEFINED,
+    };
+
+    // Returns INITDAG_SUCCESS if it was able to create the DAG, otherwise prints
+    // the initialization error in diagnostics, if present.
+    InitResult init(TIntermNode *root, TDiagnostics *diagnostics);
+
+    // Returns InvalidIndex if the function wasn't found
+    size_t findIndex(const TSymbolUniqueId &id) const;
+
+    const Record &getRecordFromIndex(size_t index) const;
+    size_t size() const;
+    void clear();
+
+    const static size_t InvalidIndex;
+
+  private:
+    std::vector<Record> mRecords;
+    std::map<int, int> mFunctionIdToIndex;
+
+    class CallDAGCreator;
+};
+
+}  // namespace sh
+
+#endif  // COMPILER_TRANSLATOR_CALLDAG_H_