1 files changed, 141 insertions, 0 deletions
diff --git a/gfx/angle/checkout/src/compiler/translator/tree_ops/RewriteDfdy.cpp b/gfx/angle/checkout/src/compiler/translator/tree_ops/RewriteDfdy.cpp
new file mode 100644
index 0000000000..1a2aabf7dc
--- /dev/null
+++ b/gfx/angle/checkout/src/compiler/translator/tree_ops/RewriteDfdy.cpp
@@ -0,0 +1,141 @@
+//
+// 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/TranslatorVulkan.h"
+#include "compiler/translator/tree_util/DriverUniform.h"
+#include "compiler/translator/tree_util/IntermNode_util.h"
+#include "compiler/translator/tree_util/IntermTraverse.h"
+#include "compiler/translator/tree_util/SpecializationConstant.h"
+
+namespace sh
+{
+
+namespace
+{
+
+class Traverser : public TIntermTraverser
+{
+  public:
+    Traverser(TSymbolTable *symbolTable, SpecConst *specConst, const DriverUniform *driverUniforms);
+
+  private:
+    bool visitAggregate(Visit visit, TIntermAggregate *node) override;
+
+    SpecConst *mSpecConst                = nullptr;
+    const DriverUniform *mDriverUniforms = nullptr;
+};
+
+Traverser::Traverser(TSymbolTable *symbolTable,
+                     SpecConst *specConst,
+                     const DriverUniform *driverUniforms)
+    : TIntermTraverser(true, false, false, symbolTable),
+      mSpecConst(specConst),
+      mDriverUniforms(driverUniforms)
+{}
+
+bool Traverser::visitAggregate(Visit visit, TIntermAggregate *node)
+{
+    // Decide if the node represents a call to dFdx() or dFdy()
+    if (node->getOp() != EOpDFdx && node->getOp() != EOpDFdy)
+    {
+        return true;
+    }
+
+    const bool isDFdx = node->getOp() == EOpDFdx;
+
+    // Two transformations are done on dFdx and dFdy:
+    //
+    // - If pre-rotation is applied, dFdx and dFdy may need to swap their axis based on the degree
+    //   of rotation.  dFdx becomes dFdy if rotation is 90 or 270 degrees.  Similarly, dFdy becomes
+    //   dFdx.
+    // - The result is potentially negated.  This could be due to viewport y-flip or pre-rotation.
+    //
+    // Accordingly, there are two variables controlling the above transformations:
+    //
+    // - Rotation: A vec2 that is either (0, 1) or (1, 0).  dFdx and dFdy are replaced with:
+    //
+    //       dFdx * Rotation.x + dFdy * Rotation.y
+    //
+    // - Scale: A vec2 with -1 or 1 for either x or y components.  The previous result is multiplied
+    //   by this.
+    //
+    // Together, the above operations account for the combinations of 4 possible rotations and
+    // y-flip.
+
+    // Get the results of dFdx(operand) and dFdy(operand), and multiply them by the swizzles
+    TIntermTyped *operand = node->getChildNode(0)->getAsTyped();
+
+    TIntermTyped *dFdx = CreateBuiltInUnaryFunctionCallNode("dFdx", operand, *mSymbolTable, 300);
+    TIntermTyped *dFdy =
+        CreateBuiltInUnaryFunctionCallNode("dFdy", operand->deepCopy(), *mSymbolTable, 300);
+
+    // Get rotation multiplier
+    TIntermTyped *swapXY = mSpecConst->getSwapXY();
+    if (swapXY == nullptr)
+    {
+        swapXY = mDriverUniforms->getSwapXY();
+    }
+
+    TIntermTyped *swapXMultiplier = MakeSwapXMultiplier(swapXY);
+    TIntermTyped *swapYMultiplier = MakeSwapYMultiplier(swapXY->deepCopy());
+
+    // Get flip multiplier
+    TIntermTyped *flipXY = mDriverUniforms->getFlipXY(mSymbolTable, DriverUniformFlip::Fragment);
+
+    // Multiply the flip and rotation multipliers
+    TIntermTyped *xMultiplier =
+        new TIntermBinary(EOpMul, isDFdx ? swapXMultiplier : swapYMultiplier,
+                          (new TIntermSwizzle(flipXY->deepCopy(), {0}))->fold(nullptr));
+    TIntermTyped *yMultiplier =
+        new TIntermBinary(EOpMul, isDFdx ? swapYMultiplier : swapXMultiplier,
+                          (new TIntermSwizzle(flipXY->deepCopy(), {1}))->fold(nullptr));
+
+    const TOperator mulOp            = dFdx->getType().isVector() ? EOpVectorTimesScalar : EOpMul;
+    TIntermTyped *rotatedFlippedDfdx = new TIntermBinary(mulOp, dFdx, xMultiplier);
+    TIntermTyped *rotatedFlippedDfdy = new TIntermBinary(mulOp, dFdy, yMultiplier);
+
+    // Sum them together into the result
+    TIntermBinary *rotatedFlippedResult =
+        new TIntermBinary(EOpAdd, rotatedFlippedDfdx, rotatedFlippedDfdy);
+
+    // Replace the old dFdx() or dFdy() node with the new node that contains the corrected value
+    //
+    // Note the following bugs (anglebug.com/7346):
+    //
+    // - Side effects of operand are duplicated with the above
+    // - If the direct child of this node is itself dFdx/y, its queueReplacement will not be
+    //   effective as the parent is also replaced.
+    queueReplacement(rotatedFlippedResult, OriginalNode::IS_DROPPED);
+
+    return true;
+}
+}  // anonymous namespace
+
+bool RewriteDfdy(TCompiler *compiler,
+                 TIntermBlock *root,
+                 TSymbolTable *symbolTable,
+                 int shaderVersion,
+                 SpecConst *specConst,
+                 const DriverUniform *driverUniforms)
+{
+    // dFdx/dFdy is only valid in GLSL 3.0 and later.
+    if (shaderVersion < 300)
+    {
+        return true;
+    }
+
+    Traverser traverser(symbolTable, specConst, driverUniforms);
+    root->traverse(&traverser);
+    return traverser.updateTree(compiler, root);
+}
+
+}  // namespace sh