Remove invariant qualifier for input in fragment shader

src/compiler.gypi

@@ -92,6 +92,8 @@
             'compiler/translator/RecordConstantPrecision.h',
             'compiler/translator/RegenerateStructNames.cpp',
             'compiler/translator/RegenerateStructNames.h',
+            'compiler/translator/RemoveInvariantDeclaration.cpp',
+            'compiler/translator/RemoveInvariantDeclaration.h',
             'compiler/translator/RemovePow.cpp',
             'compiler/translator/RemovePow.h',
             'compiler/translator/RewriteDoWhile.cpp',

src/compiler/translator/Compiler.cpp

@@ -23,6 +23,7 @@
 #include "compiler/translator/ParseContext.h"
 #include "compiler/translator/PruneEmptyDeclarations.h"
 #include "compiler/translator/RegenerateStructNames.h"
+#include "compiler/translator/RemoveInvariantDeclaration.h"
 #include "compiler/translator/RemovePow.h"
 #include "compiler/translator/RewriteDoWhile.h"
 #include "compiler/translator/ScalarizeVecAndMatConstructorArgs.h"
@@ -91,6 +92,14 @@ bool IsGLSL130OrNewer(ShShaderOutput output)
             output == SH_GLSL_450_CORE_OUTPUT);
 }
 
+bool IsGLSL420OrNewer(ShShaderOutput output)
+{
+    return (output == SH_GLSL_420_CORE_OUTPUT ||
+            output == SH_GLSL_430_CORE_OUTPUT ||
+            output == SH_GLSL_440_CORE_OUTPUT ||
+            output == SH_GLSL_450_CORE_OUTPUT);
+}
+
 size_t GetGlobalMaxTokenSize(ShShaderSpec spec)
 {
     // WebGL defines a max token legnth of 256, while ES2 leaves max token
@@ -382,6 +391,9 @@ TIntermBlock *TCompiler::compileTreeImpl(const char *const shaderStrings[],
              (outputType == SH_GLSL_COMPATIBILITY_OUTPUT)))
             initializeGLPosition(root);
 
+        if (success && shaderType == GL_FRAGMENT_SHADER && IsGLSL420OrNewer(outputType))
+            sh::RemoveInvariantDeclaration(root);
+
         // This pass might emit short circuits so keep it before the short circuit unfolding
         if (success && (compileOptions & SH_REWRITE_DO_WHILE_LOOPS))
             RewriteDoWhile(root, getTemporaryIndex());

src/compiler/translator/Compiler.h

@@ -38,6 +38,7 @@ bool IsWebGLBasedSpec(ShShaderSpec spec);
 // Helper function to check if the shader type is GLSL.
 //
 bool IsGLSL130OrNewer(ShShaderOutput output);
+bool IsGLSL420OrNewer(ShShaderOutput output);
 
 //
 // The base class used to back handles returned to the driver.

src/compiler/translator/OutputGLSLBase.cpp

@@ -146,8 +146,9 @@ void TOutputGLSLBase::writeLayoutQualifier(const TType &type)
 
 void TOutputGLSLBase::writeVariableType(const TType &type)
 {
+    TQualifier qualifier = type.getQualifier();
     TInfoSinkBase &out = objSink();
-    if (type.isInvariant())
+    if (type.isInvariant() && qualifier != EvqFragmentIn && !IsGLSL420OrNewer(mOutput))
     {
         out << "invariant ";
     }
@@ -156,7 +157,6 @@ void TOutputGLSLBase::writeVariableType(const TType &type)
         TInterfaceBlock *interfaceBlock = type.getInterfaceBlock();
         declareInterfaceBlockLayout(interfaceBlock);
     }
-    TQualifier qualifier = type.getQualifier();
     if (qualifier != EvqTemporary && qualifier != EvqGlobal)
     {
         if (IsGLSL130OrNewer(mOutput))

src/compiler/translator/RemoveInvariantDeclaration.cpp

+//
+// Copyright (c) 2016 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.
+//
+
+#include "compiler/translator/RemoveInvariantDeclaration.h"
+
+#include "compiler/translator/IntermNode.h"
+
+namespace sh
+{
+
+namespace
+{
+
+// An AST traverser that removes invariant declaration for input in fragment shader
+// when GLSL > 4.20.
+class RemoveInvariantDeclarationTraverser : public TIntermTraverser
+{
+  public:
+    RemoveInvariantDeclarationTraverser() : TIntermTraverser(true, false, false) {}
+
+  private:
+    bool visitAggregate(Visit visit, TIntermAggregate *node) override
+    {
+        if (node->getOp() == EOpInvariantDeclaration)
+        {
+            TIntermSequence emptyReplacement;
+            mMultiReplacements.push_back(
+                NodeReplaceWithMultipleEntry(getParentNode()->getAsBlock(), node, emptyReplacement));
+            return false;
+        }
+        return true;
+    }
+};
+
+}  // anonymous namespace
+
+void RemoveInvariantDeclaration(TIntermNode *root)
+{
+    RemoveInvariantDeclarationTraverser traverser;
+    root->traverse(&traverser);
+    traverser.updateTree();
+}
+
+}  // namespace sh

src/compiler/translator/RemoveInvariantDeclaration.h

+//
+// Copyright (c) 2016 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.
+//
+
+#ifndef COMPILER_TRANSLATOR_REMOVEINVARIANTDECLARATION_H_
+#define COMPILER_TRANSLATOR_REMOVEINVARIANTDECLARATION_H_
+
+class TIntermNode;
+namespace sh
+{
+
+void RemoveInvariantDeclaration(TIntermNode *root);
+
+}  // namespace sh
+
+#endif  // COMPILER_TRANSLATOR_REMOVEINVARIANTDECLARATION_H_