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diff --git a/gfx/angle/checkout/src/compiler/translator/CallDAG.cpp b/gfx/angle/checkout/src/compiler/translator/CallDAG.cpp
new file mode 100644
index 0000000000..5d47518eba
--- /dev/null
+++ b/gfx/angle/checkout/src/compiler/translator/CallDAG.cpp
@@ -0,0 +1,316 @@
+//
+// 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: Implements a call graph DAG of functions to be re-used accross
+// analyses, allows to efficiently traverse the functions in topological
+// order.
+
+#include "compiler/translator/CallDAG.h"
+
+#include "compiler/translator/Diagnostics.h"
+#include "compiler/translator/SymbolTable.h"
+#include "compiler/translator/tree_util/IntermTraverse.h"
+
+namespace sh
+{
+
+// The CallDAGCreator does all the processing required to create the CallDAG
+// structure so that the latter contains only the necessary variables.
+class CallDAG::CallDAGCreator : public TIntermTraverser
+{
+  public:
+    CallDAGCreator(TDiagnostics *diagnostics)
+        : TIntermTraverser(true, false, false),
+          mDiagnostics(diagnostics),
+          mCurrentFunction(nullptr),
+          mCurrentIndex(0)
+    {}
+
+    InitResult assignIndices()
+    {
+        int skipped = 0;
+        for (auto &it : mFunctions)
+        {
+            // Skip unimplemented functions
+            if (it.second.definitionNode)
+            {
+                InitResult result = assignIndicesInternal(&it.second);
+                if (result != INITDAG_SUCCESS)
+                {
+                    return result;
+                }
+            }
+            else
+            {
+                skipped++;
+            }
+        }
+
+        ASSERT(mFunctions.size() == mCurrentIndex + skipped);
+        return INITDAG_SUCCESS;
+    }
+
+    void fillDataStructures(std::vector<Record> *records, std::map<int, int> *idToIndex)
+    {
+        ASSERT(records->empty());
+        ASSERT(idToIndex->empty());
+
+        records->resize(mCurrentIndex);
+
+        for (auto &it : mFunctions)
+        {
+            CreatorFunctionData &data = it.second;
+            // Skip unimplemented functions
+            if (!data.definitionNode)
+            {
+                continue;
+            }
+            ASSERT(data.index < records->size());
+            Record &record = (*records)[data.index];
+
+            record.node = data.definitionNode;
+
+            record.callees.reserve(data.callees.size());
+            for (auto &callee : data.callees)
+            {
+                record.callees.push_back(static_cast<int>(callee->index));
+            }
+
+            (*idToIndex)[it.first] = static_cast<int>(data.index);
+        }
+    }
+
+  private:
+    struct CreatorFunctionData
+    {
+        CreatorFunctionData()
+            : definitionNode(nullptr), name(""), index(0), indexAssigned(false), visiting(false)
+        {}
+
+        std::set<CreatorFunctionData *> callees;
+        TIntermFunctionDefinition *definitionNode;
+        ImmutableString name;
+        size_t index;
+        bool indexAssigned;
+        bool visiting;
+    };
+
+    bool visitFunctionDefinition(Visit visit, TIntermFunctionDefinition *node) override
+    {
+        // Create the record if need be and remember the definition node.
+        mCurrentFunction = &mFunctions[node->getFunction()->uniqueId().get()];
+        // Name will be overwritten here. If we've already traversed the prototype of this function,
+        // it should have had the same name.
+        ASSERT(mCurrentFunction->name == "" ||
+               mCurrentFunction->name == node->getFunction()->name());
+        mCurrentFunction->name           = node->getFunction()->name();
+        mCurrentFunction->definitionNode = node;
+
+        node->getBody()->traverse(this);
+        mCurrentFunction = nullptr;
+        return false;
+    }
+
+    void visitFunctionPrototype(TIntermFunctionPrototype *node) override
+    {
+        ASSERT(mCurrentFunction == nullptr);
+
+        // Function declaration, create an empty record.
+        auto &record = mFunctions[node->getFunction()->uniqueId().get()];
+        record.name  = node->getFunction()->name();
+    }
+
+    // Track functions called from another function.
+    bool visitAggregate(Visit visit, TIntermAggregate *node) override
+    {
+        if (node->getOp() == EOpCallFunctionInAST)
+        {
+            // Function call, add the callees
+            auto it = mFunctions.find(node->getFunction()->uniqueId().get());
+            ASSERT(it != mFunctions.end());
+
+            // We might be traversing the initializer of a global variable. Even though function
+            // calls in global scope are forbidden by the parser, some subsequent AST
+            // transformations can add them to emulate particular features.
+            if (mCurrentFunction)
+            {
+                mCurrentFunction->callees.insert(&it->second);
+            }
+        }
+        return true;
+    }
+
+    // Recursively assigns indices to a sub DAG
+    InitResult assignIndicesInternal(CreatorFunctionData *root)
+    {
+        // Iterative implementation of the index assignment algorithm. A recursive version
+        // would be prettier but since the CallDAG creation runs before the limiting of the
+        // call depth, we might get stack overflows (computation of the call depth uses the
+        // CallDAG).
+
+        ASSERT(root);
+
+        if (root->indexAssigned)
+        {
+            return INITDAG_SUCCESS;
+        }
+
+        // If we didn't have to detect recursion, functionsToProcess could be a simple queue
+        // in which we add the function being processed's callees. However in order to detect
+        // recursion we need to know which functions we are currently visiting. For that reason
+        // functionsToProcess will look like a concatenation of segments of the form
+        // [F visiting = true, subset of F callees with visiting = false] and the following
+        // segment (if any) will be start with a callee of F.
+        // This way we can remember when we started visiting a function, to put visiting back
+        // to false.
+        TVector<CreatorFunctionData *> functionsToProcess;
+        functionsToProcess.push_back(root);
+
+        InitResult result = INITDAG_SUCCESS;
+
+        std::stringstream errorStream = sh::InitializeStream<std::stringstream>();
+
+        while (!functionsToProcess.empty())
+        {
+            CreatorFunctionData *function = functionsToProcess.back();
+
+            if (function->visiting)
+            {
+                function->visiting      = false;
+                function->index         = mCurrentIndex++;
+                function->indexAssigned = true;
+
+                functionsToProcess.pop_back();
+                continue;
+            }
+
+            if (!function->definitionNode)
+            {
+                errorStream << "Undefined function '" << function->name
+                            << "()' used in the following call chain:";
+                result = INITDAG_UNDEFINED;
+                break;
+            }
+
+            if (function->indexAssigned)
+            {
+                functionsToProcess.pop_back();
+                continue;
+            }
+
+            function->visiting = true;
+
+            for (auto callee : function->callees)
+            {
+                functionsToProcess.push_back(callee);
+
+                // Check if the callee is already being visited after pushing it so that it appears
+                // in the chain printed in the info log.
+                if (callee->visiting)
+                {
+                    errorStream << "Recursive function call in the following call chain:";
+                    result = INITDAG_RECURSION;
+                    break;
+                }
+            }
+
+            if (result != INITDAG_SUCCESS)
+            {
+                break;
+            }
+        }
+
+        // The call chain is made of the function we were visiting when the error was detected.
+        if (result != INITDAG_SUCCESS)
+        {
+            bool first = true;
+            for (auto function : functionsToProcess)
+            {
+                if (function->visiting)
+                {
+                    if (!first)
+                    {
+                        errorStream << " -> ";
+                    }
+                    errorStream << function->name << ")";
+                    first = false;
+                }
+            }
+            if (mDiagnostics)
+            {
+                std::string errorStr = errorStream.str();
+                mDiagnostics->globalError(errorStr.c_str());
+            }
+        }
+
+        return result;
+    }
+
+    TDiagnostics *mDiagnostics;
+
+    std::map<int, CreatorFunctionData> mFunctions;
+    CreatorFunctionData *mCurrentFunction;
+    size_t mCurrentIndex;
+};
+
+// CallDAG
+
+CallDAG::CallDAG() {}
+
+CallDAG::~CallDAG() {}
+
+const size_t CallDAG::InvalidIndex = std::numeric_limits<size_t>::max();
+
+size_t CallDAG::findIndex(const TSymbolUniqueId &id) const
+{
+    auto it = mFunctionIdToIndex.find(id.get());
+
+    if (it == mFunctionIdToIndex.end())
+    {
+        return InvalidIndex;
+    }
+    else
+    {
+        return it->second;
+    }
+}
+
+const CallDAG::Record &CallDAG::getRecordFromIndex(size_t index) const
+{
+    ASSERT(index != InvalidIndex && index < mRecords.size());
+    return mRecords[index];
+}
+
+size_t CallDAG::size() const
+{
+    return mRecords.size();
+}
+
+void CallDAG::clear()
+{
+    mRecords.clear();
+    mFunctionIdToIndex.clear();
+}
+
+CallDAG::InitResult CallDAG::init(TIntermNode *root, TDiagnostics *diagnostics)
+{
+    CallDAGCreator creator(diagnostics);
+
+    // Creates the mapping of functions to callees
+    root->traverse(&creator);
+
+    // Does the topological sort and detects recursions
+    InitResult result = creator.assignIndices();
+    if (result != INITDAG_SUCCESS)
+    {
+        return result;
+    }
+
+    creator.fillDataStructures(&mRecords, &mFunctionIdToIndex);
+    return INITDAG_SUCCESS;
+}
+
+}  // namespace sh