Vulkan: dFdy is incorrect when the framebuffer is flipped

To account for framebuffer flipping, `dFdy()` expressions
must be changed to:

    dFdy() * ANGLEUniforms.viewportYScale

Bug: angleproject:3487
Test: dEQP-GLES3.functional.shaders.derivate.dfdy.*
Change-Id: I38f25ba37fb8c5ae61cee5ac911df88ec4a93fef
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1678404
Commit-Queue: Tim Van Patten <timvp@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>

src/compiler.gni

@@ -154,6 +154,8 @@ angle_translator_sources = [
   "src/compiler/translator/tree_ops/RemoveUnreferencedVariables.h",
   "src/compiler/translator/tree_ops/RewriteAtomicFunctionExpressions.cpp",
   "src/compiler/translator/tree_ops/RewriteAtomicFunctionExpressions.h",
+  "src/compiler/translator/tree_ops/RewriteDfdy.cpp",
+  "src/compiler/translator/tree_ops/RewriteDfdy.h",
   "src/compiler/translator/tree_ops/RewriteDoWhile.cpp",
   "src/compiler/translator/tree_ops/RewriteDoWhile.h",
   "src/compiler/translator/tree_ops/RewriteExpressionsWithShaderStorageBlock.cpp",
@@ -183,6 +185,8 @@ angle_translator_sources = [
   "src/compiler/translator/tree_ops/VectorizeVectorScalarArithmetic.cpp",
   "src/compiler/translator/tree_ops/VectorizeVectorScalarArithmetic.h",
   "src/compiler/translator/tree_util/BuiltIn_autogen.h",
+  "src/compiler/translator/tree_util/FindFunction.cpp",
+  "src/compiler/translator/tree_util/FindFunction.h",
   "src/compiler/translator/tree_util/FindMain.cpp",
   "src/compiler/translator/tree_util/FindMain.h",
   "src/compiler/translator/tree_util/FindSymbolNode.cpp",

src/compiler/translator/TranslatorVulkan.cpp

@@ -17,8 +17,10 @@
 #include "compiler/translator/OutputVulkanGLSL.h"
 #include "compiler/translator/StaticType.h"
 #include "compiler/translator/tree_ops/NameEmbeddedUniformStructs.h"
+#include "compiler/translator/tree_ops/RewriteDfdy.h"
 #include "compiler/translator/tree_ops/RewriteStructSamplers.h"
 #include "compiler/translator/tree_util/BuiltIn_autogen.h"
+#include "compiler/translator/tree_util/FindFunction.h"
 #include "compiler/translator/tree_util/FindMain.h"
 #include "compiler/translator/tree_util/IntermNode_util.h"
 #include "compiler/translator/tree_util/ReplaceVariable.h"
@@ -388,12 +390,13 @@ const TVariable *AddDriverUniformsToShader(TIntermBlock *root, TSymbolTable *sym
     TIntermSymbol *driverUniformsDeclarator = new TIntermSymbol(driverUniformsVar);
     driverUniformsDecl->appendDeclarator(driverUniformsDeclarator);
 
-    // Insert the declarations before Main.
+    // Insert the declarations before first function, since functions before main() may refer to
+    // these values.
     TIntermSequence *insertSequence = new TIntermSequence;
     insertSequence->push_back(driverUniformsDecl);
 
-    size_t mainIndex = FindMainIndex(root);
+    size_t firstFunctionIndex = FindFirstFunctionDefinitionIndex(root);
-    root->insertChildNodes(mainIndex, *insertSequence);
+    root->insertChildNodes(firstFunctionIndex, *insertSequence);
 
     return driverUniformsVar;
 }
@@ -766,6 +769,11 @@ void TranslatorVulkan::translate(TIntermBlock *root,
             InsertFragCoordCorrection(root, GetMainSequence(root), &getSymbolTable(),
                                       driverUniforms);
         }
+
+        {
+            TIntermBinary *viewportYScale = CreateDriverUniformRef(driverUniforms, kViewportYScale);
+            RewriteDfdy(root, getSymbolTable(), getShaderVersion(), viewportYScale);
+        }
     }
     else
     {

src/compiler/translator/tree_ops/RewriteDfdy.cpp

@@ -0,0 +1,89 @@
+//
+// 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.
+//
+// Implementation of dFdy viewport transformation.
+// See header for more info.
+
+#include "compiler/translator/tree_ops/RewriteDfdy.h"
+
+#include "common/angleutils.h"
+#include "compiler/translator/SymbolTable.h"
+#include "compiler/translator/tree_util/IntermNode_util.h"
+#include "compiler/translator/tree_util/IntermTraverse.h"
+
+namespace sh
+{
+
+namespace
+{
+
+class Traverser : public TIntermTraverser
+{
+  public:
+    static void Apply(TIntermNode *root,
+                      const TSymbolTable &symbolTable,
+                      TIntermBinary *viewportYScale);
+
+  private:
+    Traverser(TIntermBinary *viewportYScale, TSymbolTable *symbolTable);
+    bool visitUnary(Visit visit, TIntermUnary *node) override;
+
+    TIntermBinary *mViewportYScale = nullptr;
+};
+
+Traverser::Traverser(TIntermBinary *viewportYScale, TSymbolTable *symbolTable)
+    : TIntermTraverser(true, false, false, symbolTable), mViewportYScale(viewportYScale)
+{}
+
+// static
+void Traverser::Apply(TIntermNode *root,
+                      const TSymbolTable &symbolTable,
+                      TIntermBinary *viewportYScale)
+{
+    TSymbolTable *pSymbolTable = const_cast<TSymbolTable *>(&symbolTable);
+    Traverser traverser(viewportYScale, pSymbolTable);
+    root->traverse(&traverser);
+    traverser.updateTree();
+}
+
+bool Traverser::visitUnary(Visit visit, TIntermUnary *node)
+{
+    // Decide if the node represents a call to dFdy()
+    if (node->getOp() != EOpDFdy)
+    {
+        return true;
+    }
+
+    // Copy the dFdy node so we can replace it with the corrected value
+    TIntermUnary *newDfdy = node->deepCopy()->getAsUnaryNode();
+
+    size_t objectSize    = node->getType().getObjectSize();
+    TOperator multiplyOp = (objectSize == 1) ? EOpMul : EOpVectorTimesScalar;
+
+    // Correct dFdy()'s value:
+    // (dFdy() * ANGLEUniforms.viewportYScale)
+    TIntermBinary *correctedDfdy = new TIntermBinary(multiplyOp, newDfdy, mViewportYScale);
+
+    // Replace the old dFdy node with the new node that contains the corrected value
+    queueReplacement(correctedDfdy, OriginalNode::IS_DROPPED);
+
+    return true;
+}
+
+}  // anonymous namespace
+
+void RewriteDfdy(TIntermNode *root,
+                 const TSymbolTable &symbolTable,
+                 int shaderVersion,
+                 TIntermBinary *viewportYScale)
+{
+    // dFdy is only valid in GLSL 3.0 and later.
+    if (shaderVersion < 300)
+        return;
+
+    Traverser::Apply(root, symbolTable, viewportYScale);
+}
+
+}  // namespace sh

src/compiler/translator/tree_ops/RewriteDfdy.h

@@ -0,0 +1,30 @@
+//
+// 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.
+//
+// This mutating tree traversal flips the output of dFdy() to account for framebuffer flipping.
+//
+// From: dFdy(p)
+// To:   (dFdy(p) * viewportYScale)
+//
+// See http://anglebug.com/3487
+
+#ifndef COMPILER_TRANSLATOR_TREEOPS_FLIP_DFDY_H_
+#define COMPILER_TRANSLATOR_TREEOPS_FLIP_DFDY_H_
+
+class TIntermNode;
+class TIntermBinary;
+class TSymbolTable;
+
+namespace sh
+{
+
+void RewriteDfdy(TIntermNode *root,
+                 const TSymbolTable &symbolTable,
+                 int shaderVersion,
+                 TIntermBinary *viewportYScale);
+
+}  // namespace sh
+
+#endif  // COMPILER_TRANSLATOR_TREEOPS_FLIP_DFDY_H_

src/compiler/translator/tree_util/FindFunction.cpp

@@ -0,0 +1,32 @@
+//
+// 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.
+//
+
+// FindFunction.cpp: Find functions.
+
+#include "compiler/translator/tree_util/FindFunction.h"
+
+#include "compiler/translator/IntermNode.h"
+#include "compiler/translator/Symbol.h"
+
+namespace sh
+{
+
+size_t FindFirstFunctionDefinitionIndex(TIntermBlock *root)
+{
+    const TIntermSequence &sequence = *root->getSequence();
+    for (size_t index = 0; index < sequence.size(); ++index)
+    {
+        TIntermNode *node                       = sequence[index];
+        TIntermFunctionDefinition *nodeFunction = node->getAsFunctionDefinition();
+        if (nodeFunction != nullptr)
+        {
+            return index;
+        }
+    }
+    return std::numeric_limits<size_t>::max();
+}
+
+}  // namespace sh

src/compiler/translator/tree_util/FindFunction.h

@@ -0,0 +1,21 @@
+//
+// 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.
+//
+
+// FindFunction.h: Adds functions to find functions
+
+#ifndef COMPILER_TRANSLATOR_TREEUTIL_FINDFUNCTION_H_
+#define COMPILER_TRANSLATOR_TREEUTIL_FINDFUNCTION_H_
+
+#include <cstddef>
+
+namespace sh
+{
+class TIntermBlock;
+
+size_t FindFirstFunctionDefinitionIndex(TIntermBlock *root);
+}  // namespace sh
+
+#endif  // COMPILER_TRANSLATOR_TREEUTIL_FINDFUNCTION_H_

src/tests/deqp_support/deqp_gles3_test_expectations.txt

@@ -660,7 +660,6 @@
 3219 VULKAN : dEQP-GLES3.functional.negative_api.shader.link_program = FAIL
 3219 VULKAN : dEQP-GLES3.functional.negative_api.shader.use_program = FAIL
 3443 VULKAN : dEQP-GLES3.functional.ubo.random.basic_arrays.10 = FAIL
-3487 VULKAN : dEQP-GLES3.functional.shaders.derivate.dfdy.* = FAIL
 
 // New vertex attribute formats:
 3193 VULKAN : dEQP-GLES3.functional.vertex_arrays.single_attribute.*.int2_10_10_10.* = SKIP