1 files changed, 100 insertions, 0 deletions
diff --git a/gfx/angle/checkout/src/compiler/translator/ValidateBarrierFunctionCall.cpp b/gfx/angle/checkout/src/compiler/translator/ValidateBarrierFunctionCall.cpp
new file mode 100644
index 0000000000..c36406ea59
--- /dev/null
+++ b/gfx/angle/checkout/src/compiler/translator/ValidateBarrierFunctionCall.cpp
@@ -0,0 +1,100 @@
+//
+// Copyright 2020 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.
+//
+// ValidateBarrierFunctionCalls:
+//   Runs compilation checks related to the "barrier built-in function.
+
+#include "compiler/translator/ValidateBarrierFunctionCall.h"
+
+#include "compiler/translator/Diagnostics.h"
+#include "compiler/translator/SymbolTable.h"
+#include "compiler/translator/tree_util/IntermTraverse.h"
+
+namespace sh
+{
+namespace
+{
+class Traverser : public TIntermTraverser
+{
+  public:
+    Traverser(TDiagnostics *diagnostics)
+        : TIntermTraverser(true, false, true), mDiagnostics(diagnostics)
+    {}
+
+    bool visitFunctionDefinition(Visit visit, TIntermFunctionDefinition *node) override
+    {
+        if (!node->getFunction()->isMain())
+        {
+            return false;
+        }
+
+        mInMain = visit == PreVisit;
+        return true;
+    }
+
+    bool visitBranch(Visit visit, TIntermBranch *branch) override
+    {
+        if (branch->getFlowOp() == EOpReturn)
+        {
+            mSeenReturn = true;
+        }
+
+        return true;
+    }
+
+    bool visitAggregate(Visit visit, TIntermAggregate *node) override
+    {
+        if (node->getOp() != EOpBarrierTCS)
+        {
+            return true;
+        }
+
+        if (mSeenReturn)
+        {
+            mDiagnostics->error(node->getLine(),
+                                "barrier() may not be called at any point after a return statement "
+                                "in the function main().",
+                                "barrier");
+            mValid = false;
+            return false;
+        }
+
+        // TODO(anglebug.com/5557): Determine if we should check loops as well.
+        if (mBranchCount > 0)
+        {
+            mDiagnostics->error(
+                node->getLine(),
+                "barrier() may not be called in potentially divergent flow control.", "barrier");
+            mValid = false;
+            return false;
+        }
+
+        return true;
+    }
+
+    bool visitIfElse(Visit visit, TIntermIfElse *node) override
+    {
+        mBranchCount += ((visit == PreVisit) ? 1 : -1);
+        return true;
+    }
+
+    bool valid() const { return mValid; }
+
+  private:
+    TDiagnostics *mDiagnostics = nullptr;
+    bool mInMain               = false;
+    bool mSeenReturn           = false;
+    bool mValid                = true;
+    uint32_t mBranchCount      = 0;
+};
+}  // anonymous namespace
+
+bool ValidateBarrierFunctionCall(TIntermBlock *root, TDiagnostics *diagnostics)
+{
+    Traverser traverser(diagnostics);
+    root->traverse(&traverser);
+    return traverser.valid();
+}
+}  // namespace sh