1 files changed, 209 insertions, 0 deletions
diff --git a/gfx/angle/checkout/src/compiler/translator/tree_ops/RemoveInactiveInterfaceVariables.cpp b/gfx/angle/checkout/src/compiler/translator/tree_ops/RemoveInactiveInterfaceVariables.cpp
new file mode 100644
index 0000000000..a5e20ebcb0
--- /dev/null
+++ b/gfx/angle/checkout/src/compiler/translator/tree_ops/RemoveInactiveInterfaceVariables.cpp
@@ -0,0 +1,209 @@
+//
+// Copyright 2019 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.
+//
+// RemoveInactiveInterfaceVariables.h:
+//  Drop shader interface variable declarations for those that are inactive.
+//
+
+#include "compiler/translator/tree_ops/RemoveInactiveInterfaceVariables.h"
+
+#include "compiler/translator/SymbolTable.h"
+#include "compiler/translator/tree_util/IntermTraverse.h"
+#include "compiler/translator/util.h"
+
+namespace sh
+{
+
+namespace
+{
+
+// Traverser that removes all declarations that correspond to inactive variables.
+class RemoveInactiveInterfaceVariablesTraverser : public TIntermTraverser
+{
+  public:
+    RemoveInactiveInterfaceVariablesTraverser(
+        TSymbolTable *symbolTable,
+        const std::vector<sh::ShaderVariable> &attributes,
+        const std::vector<sh::ShaderVariable> &inputVaryings,
+        const std::vector<sh::ShaderVariable> &outputVariables,
+        const std::vector<sh::ShaderVariable> &uniforms,
+        const std::vector<sh::InterfaceBlock> &interfaceBlocks,
+        bool removeFragmentOutputs);
+
+    bool visitDeclaration(Visit visit, TIntermDeclaration *node) override;
+    bool visitBinary(Visit visit, TIntermBinary *node) override;
+
+  private:
+    const std::vector<sh::ShaderVariable> &mAttributes;
+    const std::vector<sh::ShaderVariable> &mInputVaryings;
+    const std::vector<sh::ShaderVariable> &mOutputVariables;
+    const std::vector<sh::ShaderVariable> &mUniforms;
+    const std::vector<sh::InterfaceBlock> &mInterfaceBlocks;
+    bool mRemoveFragmentOutputs;
+};
+
+RemoveInactiveInterfaceVariablesTraverser::RemoveInactiveInterfaceVariablesTraverser(
+    TSymbolTable *symbolTable,
+    const std::vector<sh::ShaderVariable> &attributes,
+    const std::vector<sh::ShaderVariable> &inputVaryings,
+    const std::vector<sh::ShaderVariable> &outputVariables,
+    const std::vector<sh::ShaderVariable> &uniforms,
+    const std::vector<sh::InterfaceBlock> &interfaceBlocks,
+    bool removeFragmentOutputs)
+    : TIntermTraverser(true, false, false, symbolTable),
+      mAttributes(attributes),
+      mInputVaryings(inputVaryings),
+      mOutputVariables(outputVariables),
+      mUniforms(uniforms),
+      mInterfaceBlocks(interfaceBlocks),
+      mRemoveFragmentOutputs(removeFragmentOutputs)
+{}
+
+template <typename Variable>
+bool IsVariableActive(const std::vector<Variable> &mVars, const ImmutableString &name)
+{
+    for (const Variable &var : mVars)
+    {
+        if (name == var.name)
+        {
+            return var.active;
+        }
+    }
+    UNREACHABLE();
+    return true;
+}
+
+bool RemoveInactiveInterfaceVariablesTraverser::visitDeclaration(Visit visit,
+                                                                 TIntermDeclaration *node)
+{
+    // SeparateDeclarations should have already been run.
+    ASSERT(node->getSequence()->size() == 1u);
+
+    TIntermTyped *declarator = node->getSequence()->front()->getAsTyped();
+    ASSERT(declarator);
+
+    TIntermSymbol *asSymbol = declarator->getAsSymbolNode();
+    if (!asSymbol)
+    {
+        return false;
+    }
+
+    const TType &type = declarator->getType();
+
+    // Remove all shader interface variables except outputs, i.e. uniforms, interface blocks and
+    // inputs.
+    //
+    // Imagine a situation where the VS doesn't write to a varying but the FS reads from it.  This
+    // is allowed, though the value of the varying is undefined.  If the varying is removed here,
+    // the situation is changed to VS not declaring the varying, but the FS reading from it, which
+    // is not allowed.  That's why inactive shader outputs are not removed.
+    //
+    // Inactive fragment shader outputs can be removed though, as there is no next stage.
+    bool removeDeclaration     = false;
+    const TQualifier qualifier = type.getQualifier();
+
+    if (type.isInterfaceBlock())
+    {
+        // When a member has an explicit location, interface block should not be removed.
+        // If the member or interface would be removed, GetProgramResource could not return the
+        // location.
+        if (!IsShaderIoBlock(type.getQualifier()) && type.getQualifier() != EvqPatchIn &&
+            type.getQualifier() != EvqPatchOut)
+        {
+            removeDeclaration =
+                !IsVariableActive(mInterfaceBlocks, type.getInterfaceBlock()->name());
+        }
+    }
+    else if (qualifier == EvqUniform)
+    {
+        removeDeclaration = !IsVariableActive(mUniforms, asSymbol->getName());
+    }
+    else if (qualifier == EvqAttribute || qualifier == EvqVertexIn)
+    {
+        removeDeclaration = !IsVariableActive(mAttributes, asSymbol->getName());
+    }
+    else if (IsShaderIn(qualifier))
+    {
+        removeDeclaration = !IsVariableActive(mInputVaryings, asSymbol->getName());
+    }
+    else if (qualifier == EvqFragmentOut)
+    {
+        removeDeclaration =
+            !IsVariableActive(mOutputVariables, asSymbol->getName()) && mRemoveFragmentOutputs;
+    }
+
+    if (removeDeclaration)
+    {
+        TIntermSequence replacement;
+
+        // If the declaration was of a struct, keep the struct declaration itself.
+        if (type.isStructSpecifier())
+        {
+            TType *structSpecifierType      = new TType(type.getStruct(), true);
+            TVariable *emptyVariable        = new TVariable(mSymbolTable, kEmptyImmutableString,
+                                                            structSpecifierType, SymbolType::Empty);
+            TIntermDeclaration *declaration = new TIntermDeclaration();
+            declaration->appendDeclarator(new TIntermSymbol(emptyVariable));
+            replacement.push_back(declaration);
+        }
+
+        mMultiReplacements.emplace_back(getParentNode()->getAsBlock(), node,
+                                        std::move(replacement));
+    }
+
+    return false;
+}
+
+bool RemoveInactiveInterfaceVariablesTraverser::visitBinary(Visit visit, TIntermBinary *node)
+{
+    // Remove any code that initOutputVariables might have added corresponding to inactive
+    // output variables.  This code is always in the form of `variable = ...;`.
+    if (node->getOp() != EOpAssign)
+    {
+        // Don't recurse, won't find the initialization nested in another expression.
+        return false;
+    }
+
+    // Get the symbol being initialized, and check if it's an inactive output.  If it is, this must
+    // necessarily be initialization code that ANGLE has added (and wasn't there in the original
+    // shader; if it was, the symbol wouldn't have been inactive).
+    TIntermSymbol *symbol = node->getLeft()->getAsSymbolNode();
+    if (symbol == nullptr)
+    {
+        return false;
+    }
+
+    const TQualifier qualifier = symbol->getType().getQualifier();
+    if (qualifier != EvqFragmentOut || IsVariableActive(mOutputVariables, symbol->getName()))
+    {
+        return false;
+    }
+
+    // Drop the initialization code.
+    TIntermSequence replacement;
+    mMultiReplacements.emplace_back(getParentNode()->getAsBlock(), node, std::move(replacement));
+    return false;
+}
+
+}  // namespace
+
+bool RemoveInactiveInterfaceVariables(TCompiler *compiler,
+                                      TIntermBlock *root,
+                                      TSymbolTable *symbolTable,
+                                      const std::vector<sh::ShaderVariable> &attributes,
+                                      const std::vector<sh::ShaderVariable> &inputVaryings,
+                                      const std::vector<sh::ShaderVariable> &outputVariables,
+                                      const std::vector<sh::ShaderVariable> &uniforms,
+                                      const std::vector<sh::InterfaceBlock> &interfaceBlocks,
+                                      bool removeFragmentOutputs)
+{
+    RemoveInactiveInterfaceVariablesTraverser traverser(symbolTable, attributes, inputVaryings,
+                                                        outputVariables, uniforms, interfaceBlocks,
+                                                        removeFragmentOutputs);
+    root->traverse(&traverser);
+    return traverser.updateTree(compiler, root);
+}
+
+}  // namespace sh