1 files changed, 74 insertions, 0 deletions
diff --git a/gfx/angle/checkout/src/compiler/translator/tree_ops/RemoveAtomicCounterBuiltins.cpp b/gfx/angle/checkout/src/compiler/translator/tree_ops/RemoveAtomicCounterBuiltins.cpp
new file mode 100644
index 0000000000..ed0ba3fed8
--- /dev/null
+++ b/gfx/angle/checkout/src/compiler/translator/tree_ops/RemoveAtomicCounterBuiltins.cpp
@@ -0,0 +1,74 @@
+//
+// 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.
+//
+// RemoveAtomicCounterBuiltins: Remove atomic counter builtins.
+//
+
+#include "compiler/translator/tree_ops/RemoveAtomicCounterBuiltins.h"
+
+#include "compiler/translator/Compiler.h"
+#include "compiler/translator/tree_util/IntermTraverse.h"
+
+namespace sh
+{
+namespace
+{
+
+bool IsAtomicCounterDecl(const TIntermDeclaration *node)
+{
+    const TIntermSequence &sequence = *(node->getSequence());
+    TIntermTyped *variable          = sequence.front()->getAsTyped();
+    const TType &type               = variable->getType();
+    return type.getQualifier() == EvqUniform && type.isAtomicCounter();
+}
+
+// Traverser that removes all GLSL built-ins that use AtomicCounters
+// Only called when the builtins are in use, but no atomic counters have been declared
+class RemoveAtomicCounterBuiltinsTraverser : public TIntermTraverser
+{
+  public:
+    RemoveAtomicCounterBuiltinsTraverser() : TIntermTraverser(true, false, false) {}
+
+    bool visitDeclaration(Visit visit, TIntermDeclaration *node) override
+    {
+        ASSERT(visit == PreVisit);
+
+        // Active atomic counters should have been removed by RewriteAtomicCounters, and this
+        // traversal should not have been invoked
+        ASSERT(!IsAtomicCounterDecl(node));
+        return false;
+    }
+
+    bool visitAggregate(Visit visit, TIntermAggregate *node) override
+    {
+        if (node->getOp() == EOpMemoryBarrierAtomicCounter)
+        {
+            // Vulkan does not support atomic counters, so if this builtin finds its way here,
+            // we need to remove it.
+            TIntermSequence emptySequence;
+            mMultiReplacements.emplace_back(getParentNode()->getAsBlock(), node,
+                                            std::move(emptySequence));
+            return true;
+        }
+
+        // We shouldn't see any other builtins because they cannot be present without an active
+        // atomic counter, and should have been removed by RewriteAtomicCounters. If this fires,
+        // this traversal should not have been called.
+        ASSERT(!(BuiltInGroup::IsBuiltIn(node->getOp()) &&
+                 node->getFunction()->isAtomicCounterFunction()));
+
+        return false;
+    }
+};
+
+}  // anonymous namespace
+
+bool RemoveAtomicCounterBuiltins(TCompiler *compiler, TIntermBlock *root)
+{
+    RemoveAtomicCounterBuiltinsTraverser traverser;
+    root->traverse(&traverser);
+    return traverser.updateTree(compiler, root);
+}
+}  // namespace sh