TranslatorVulkan.cpp

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Author : Jamie Madill
Date : 2019-11-09 16:24:50
Hash : 3f647b1b
Message : Vulkan: Improve Bresenham line emulation. Clamps the vertex position to the subpixel grid before interpolation. This will give more correct results on systems that have less than 8 bits of subpixel accuracy. Also uses a more accurate formulation for the emulation filter in the fragment shader using dfdx and dfdy. Fixes line raster CTS tests on SwiftShader. Still does not produce spec conformant lines. Updates the public docs to indicate this. Bug: angleproject:2830 Change-Id: Ib9a268df3e7d986bd2b1348be664389fe8fc0ef2 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1826598 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Tim Van Patten <timvp@google.com>
src/compiler/translator/TranslatorVulkan.cpp
//
// Copyright 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.
//
// TranslatorVulkan:
//   A GLSL-based translator that outputs shaders that fit GL_KHR_vulkan_glsl.
//   The shaders are then fed into glslang to spit out SPIR-V (libANGLE-side).
//   See: https://www.khronos.org/registry/vulkan/specs/misc/GL_KHR_vulkan_glsl.txt
//

#include "compiler/translator/TranslatorVulkan.h"

#include "angle_gl.h"
#include "common/utilities.h"
#include "compiler/translator/BuiltinsWorkaroundGLSL.h"
#include "compiler/translator/ImmutableStringBuilder.h"
#include "compiler/translator/OutputVulkanGLSL.h"
#include "compiler/translator/StaticType.h"
#include "compiler/translator/tree_ops/NameEmbeddedUniformStructs.h"
#include "compiler/translator/tree_ops/NameNamelessUniformBuffers.h"
#include "compiler/translator/tree_ops/RewriteAtomicCounters.h"
#include "compiler/translator/tree_ops/RewriteCubeMapSamplersAs2DArray.h"
#include "compiler/translator/tree_ops/RewriteDfdy.h"
#include "compiler/translator/tree_ops/RewriteRowMajorMatrices.h"
#include "compiler/translator/tree_ops/RewriteStructSamplers.h"
#include "compiler/translator/tree_util/BuiltIn.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"
#include "compiler/translator/tree_util/RunAtTheEndOfShader.h"
#include "compiler/translator/util.h"

namespace sh
{

namespace
{
// This traverses nodes, find the struct ones and add their declarations to the sink. It also
// removes the nodes from the tree as it processes them.
class DeclareStructTypesTraverser : public TIntermTraverser
{
  public:
    explicit DeclareStructTypesTraverser(TOutputVulkanGLSL *outputVulkanGLSL)
        : TIntermTraverser(true, false, false), mOutputVulkanGLSL(outputVulkanGLSL)
    {}

    bool visitDeclaration(Visit visit, TIntermDeclaration *node) override
    {
        ASSERT(visit == PreVisit);

        if (!mInGlobalScope)
        {
            return false;
        }

        const TIntermSequence &sequence = *(node->getSequence());
        TIntermTyped *declarator        = sequence.front()->getAsTyped();
        const TType &type               = declarator->getType();

        if (type.isStructSpecifier())
        {
            const TStructure *structure = type.getStruct();

            // Embedded structs should be parsed away by now.
            ASSERT(structure->symbolType() != SymbolType::Empty);
            mOutputVulkanGLSL->writeStructType(structure);

            TIntermSymbol *symbolNode = declarator->getAsSymbolNode();
            if (symbolNode && symbolNode->variable().symbolType() == SymbolType::Empty)
            {
                // Remove the struct specifier declaration from the tree so it isn't parsed again.
                TIntermSequence emptyReplacement;
                mMultiReplacements.emplace_back(getParentNode()->getAsBlock(), node,
                                                emptyReplacement);
            }
        }

        return false;
    }

  private:
    TOutputVulkanGLSL *mOutputVulkanGLSL;
};

class DeclareDefaultUniformsTraverser : public TIntermTraverser
{
  public:
    DeclareDefaultUniformsTraverser(TInfoSinkBase *sink,
                                    ShHashFunction64 hashFunction,
                                    NameMap *nameMap)
        : TIntermTraverser(true, true, true),
          mSink(sink),
          mHashFunction(hashFunction),
          mNameMap(nameMap),
          mInDefaultUniform(false)
    {}

    bool visitDeclaration(Visit visit, TIntermDeclaration *node) override
    {
        const TIntermSequence &sequence = *(node->getSequence());

        // TODO(jmadill): Compound declarations.
        ASSERT(sequence.size() == 1);

        TIntermTyped *variable = sequence.front()->getAsTyped();
        const TType &type      = variable->getType();
        bool isUniform         = type.getQualifier() == EvqUniform && !type.isInterfaceBlock() &&
                         !IsOpaqueType(type.getBasicType());

        if (visit == PreVisit)
        {
            if (isUniform)
            {
                (*mSink) << "    " << GetTypeName(type, mHashFunction, mNameMap) << " ";
                mInDefaultUniform = true;
            }
        }
        else if (visit == InVisit)
        {
            mInDefaultUniform = isUniform;
        }
        else if (visit == PostVisit)
        {
            if (isUniform)
            {
                (*mSink) << ";\n";

                // Remove the uniform declaration from the tree so it isn't parsed again.
                TIntermSequence emptyReplacement;
                mMultiReplacements.emplace_back(getParentNode()->getAsBlock(), node,
                                                emptyReplacement);
            }

            mInDefaultUniform = false;
        }
        return true;
    }

    void visitSymbol(TIntermSymbol *symbol) override
    {
        if (mInDefaultUniform)
        {
            const ImmutableString &name = symbol->variable().name();
            ASSERT(!name.beginsWith("gl_"));
            (*mSink) << HashName(&symbol->variable(), mHashFunction, mNameMap)
                     << ArrayString(symbol->getType());
        }
    }

  private:
    TInfoSinkBase *mSink;
    ShHashFunction64 mHashFunction;
    NameMap *mNameMap;
    bool mInDefaultUniform;
};

constexpr ImmutableString kFlippedPointCoordName    = ImmutableString("flippedPointCoord");
constexpr ImmutableString kFlippedFragCoordName     = ImmutableString("flippedFragCoord");
constexpr ImmutableString kEmulatedDepthRangeParams = ImmutableString("ANGLEDepthRangeParams");
constexpr ImmutableString kUniformsBlockName        = ImmutableString("ANGLEUniformBlock");
constexpr ImmutableString kUniformsVarName          = ImmutableString("ANGLEUniforms");

constexpr const char kViewport[]             = "viewport";
constexpr const char kHalfRenderAreaHeight[] = "halfRenderAreaHeight";
constexpr const char kViewportYScale[]       = "viewportYScale";
constexpr const char kNegViewportYScale[]    = "negViewportYScale";
constexpr const char kXfbActiveUnpaused[]    = "xfbActiveUnpaused";
constexpr const char kXfbBufferOffsets[]     = "xfbBufferOffsets";
constexpr const char kAcbBufferOffsets[]     = "acbBufferOffsets";
constexpr const char kDepthRange[]           = "depthRange";

constexpr size_t kNumGraphicsDriverUniforms                                                = 8;
constexpr std::array<const char *, kNumGraphicsDriverUniforms> kGraphicsDriverUniformNames = {
    {kViewport, kHalfRenderAreaHeight, kViewportYScale, kNegViewportYScale, kXfbActiveUnpaused,
     kXfbBufferOffsets, kAcbBufferOffsets, kDepthRange}};

constexpr size_t kNumComputeDriverUniforms                                               = 1;
constexpr std::array<const char *, kNumComputeDriverUniforms> kComputeDriverUniformNames = {
    {kAcbBufferOffsets}};

size_t FindFieldIndex(const TFieldList &fieldList, const char *fieldName)
{
    for (size_t fieldIndex = 0; fieldIndex < fieldList.size(); ++fieldIndex)
    {
        if (strcmp(fieldList[fieldIndex]->name().data(), fieldName) == 0)
        {
            return fieldIndex;
        }
    }
    UNREACHABLE();
    return 0;
}

TIntermBinary *CreateDriverUniformRef(const TVariable *driverUniforms, const char *fieldName)
{
    size_t fieldIndex =
        FindFieldIndex(driverUniforms->getType().getInterfaceBlock()->fields(), fieldName);

    TIntermSymbol *angleUniformsRef = new TIntermSymbol(driverUniforms);
    TConstantUnion *uniformIndex    = new TConstantUnion;
    uniformIndex->setIConst(static_cast<int>(fieldIndex));
    TIntermConstantUnion *indexRef =
        new TIntermConstantUnion(uniformIndex, *StaticType::GetBasic<EbtInt>());
    return new TIntermBinary(EOpIndexDirectInterfaceBlock, angleUniformsRef, indexRef);
}

// Replaces a builtin variable with a version that corrects the Y coordinate.
ANGLE_NO_DISCARD bool FlipBuiltinVariable(TCompiler *compiler,
                                          TIntermBlock *root,
                                          TIntermSequence *insertSequence,
                                          TIntermTyped *viewportYScale,
                                          TSymbolTable *symbolTable,
                                          const TVariable *builtin,
                                          const ImmutableString &flippedVariableName,
                                          TIntermTyped *pivot)
{
    // Create a symbol reference to 'builtin'.
    TIntermSymbol *builtinRef = new TIntermSymbol(builtin);

    // Create a swizzle to "builtin.y"
    TVector<int> swizzleOffsetY = {1};
    TIntermSwizzle *builtinY    = new TIntermSwizzle(builtinRef, swizzleOffsetY);

    // Create a symbol reference to our new variable that will hold the modified builtin.
    const TType *type = StaticType::GetForVec<EbtFloat>(
        EvqGlobal, static_cast<unsigned char>(builtin->getType().getNominalSize()));
    TVariable *replacementVar =
        new TVariable(symbolTable, flippedVariableName, type, SymbolType::AngleInternal);
    DeclareGlobalVariable(root, replacementVar);
    TIntermSymbol *flippedBuiltinRef = new TIntermSymbol(replacementVar);

    // Use this new variable instead of 'builtin' everywhere.
    if (!ReplaceVariable(compiler, root, builtin, replacementVar))
    {
        return false;
    }

    // Create the expression "(builtin.y - pivot) * viewportYScale + pivot
    TIntermBinary *removePivot = new TIntermBinary(EOpSub, builtinY, pivot);
    TIntermBinary *inverseY    = new TIntermBinary(EOpMul, removePivot, viewportYScale);
    TIntermBinary *plusPivot   = new TIntermBinary(EOpAdd, inverseY, pivot->deepCopy());

    // Create the corrected variable and copy the value of the original builtin.
    TIntermSequence *sequence = new TIntermSequence();
    sequence->push_back(builtinRef->deepCopy());
    TIntermAggregate *aggregate = TIntermAggregate::CreateConstructor(builtin->getType(), sequence);
    TIntermBinary *assignment   = new TIntermBinary(EOpInitialize, flippedBuiltinRef, aggregate);

    // Create an assignment to the replaced variable's y.
    TIntermSwizzle *correctedY = new TIntermSwizzle(flippedBuiltinRef->deepCopy(), swizzleOffsetY);
    TIntermBinary *assignToY   = new TIntermBinary(EOpAssign, correctedY, plusPivot);

    // Add this assigment at the beginning of the main function
    insertSequence->insert(insertSequence->begin(), assignToY);
    insertSequence->insert(insertSequence->begin(), assignment);

    return compiler->validateAST(root);
}

TIntermSequence *GetMainSequence(TIntermBlock *root)
{
    TIntermFunctionDefinition *main = FindMain(root);
    return main->getBody()->getSequence();
}

// Declares a new variable to replace gl_DepthRange, its values are fed from a driver uniform.
ANGLE_NO_DISCARD bool ReplaceGLDepthRangeWithDriverUniform(TCompiler *compiler,
                                                           TIntermBlock *root,
                                                           const TVariable *driverUniforms,
                                                           TSymbolTable *symbolTable)
{
    // Create a symbol reference to "gl_DepthRange"
    const TVariable *depthRangeVar = static_cast<const TVariable *>(
        symbolTable->findBuiltIn(ImmutableString("gl_DepthRange"), 0));

    // ANGLEUniforms.depthRange
    TIntermBinary *angleEmulatedDepthRangeRef = CreateDriverUniformRef(driverUniforms, kDepthRange);

    // Use this variable instead of gl_DepthRange everywhere.
    return ReplaceVariableWithTyped(compiler, root, depthRangeVar, angleEmulatedDepthRangeRef);
}

// This operation performs the viewport depth translation needed by Vulkan. In GL the viewport
// transformation is slightly different - see the GL 2.0 spec section "2.12.1 Controlling the
// Viewport". In Vulkan the corresponding spec section is currently "23.4. Coordinate
// Transformations".
// The equations reduce to an expression:
//
//     z_vk = 0.5 * (w_gl + z_gl)
//
// where z_vk is the depth output of a Vulkan vertex shader and z_gl is the same for GL.
ANGLE_NO_DISCARD bool AppendVertexShaderDepthCorrectionToMain(TCompiler *compiler,
                                                              TIntermBlock *root,
                                                              TSymbolTable *symbolTable)
{
    // Create a symbol reference to "gl_Position"
    const TVariable *position  = BuiltInVariable::gl_Position();
    TIntermSymbol *positionRef = new TIntermSymbol(position);

    // Create a swizzle to "gl_Position.z"
    TVector<int> swizzleOffsetZ = {2};
    TIntermSwizzle *positionZ   = new TIntermSwizzle(positionRef, swizzleOffsetZ);

    // Create a constant "0.5"
    TIntermConstantUnion *oneHalf = CreateFloatNode(0.5f);

    // Create a swizzle to "gl_Position.w"
    TVector<int> swizzleOffsetW = {3};
    TIntermSwizzle *positionW   = new TIntermSwizzle(positionRef->deepCopy(), swizzleOffsetW);

    // Create the expression "(gl_Position.z + gl_Position.w) * 0.5".
    TIntermBinary *zPlusW = new TIntermBinary(EOpAdd, positionZ->deepCopy(), positionW->deepCopy());
    TIntermBinary *halfZPlusW = new TIntermBinary(EOpMul, zPlusW, oneHalf->deepCopy());

    // Create the assignment "gl_Position.z = (gl_Position.z + gl_Position.w) * 0.5"
    TIntermTyped *positionZLHS = positionZ->deepCopy();
    TIntermBinary *assignment  = new TIntermBinary(TOperator::EOpAssign, positionZLHS, halfZPlusW);

    // Append the assignment as a statement at the end of the shader.
    return RunAtTheEndOfShader(compiler, root, assignment, symbolTable);
}

ANGLE_NO_DISCARD bool AppendVertexShaderTransformFeedbackOutputToMain(TCompiler *compiler,
                                                                      TIntermBlock *root,
                                                                      TSymbolTable *symbolTable)
{
    TVariable *xfbPlaceholder = new TVariable(symbolTable, ImmutableString("@@ XFB-OUT @@"),
                                              new TType(), SymbolType::AngleInternal);

    // Append the assignment as a statement at the end of the shader.
    return RunAtTheEndOfShader(compiler, root, new TIntermSymbol(xfbPlaceholder), symbolTable);
}

// The Add*DriverUniformsToShader operation adds an internal uniform block to a shader. The driver
// block is used to implement Vulkan-specific features and workarounds. Returns the driver uniforms
// variable.
//
// There are Graphics and Compute variations as they require different uniforms.
const TVariable *AddGraphicsDriverUniformsToShader(TIntermBlock *root, TSymbolTable *symbolTable)
{
    // Init the depth range type.
    TFieldList *depthRangeParamsFields = new TFieldList();
    depthRangeParamsFields->push_back(new TField(new TType(EbtFloat, EbpHigh, EvqGlobal, 1, 1),
                                                 ImmutableString("near"), TSourceLoc(),
                                                 SymbolType::AngleInternal));
    depthRangeParamsFields->push_back(new TField(new TType(EbtFloat, EbpHigh, EvqGlobal, 1, 1),
                                                 ImmutableString("far"), TSourceLoc(),
                                                 SymbolType::AngleInternal));
    depthRangeParamsFields->push_back(new TField(new TType(EbtFloat, EbpHigh, EvqGlobal, 1, 1),
                                                 ImmutableString("diff"), TSourceLoc(),
                                                 SymbolType::AngleInternal));
    depthRangeParamsFields->push_back(new TField(new TType(EbtFloat, EbpHigh, EvqGlobal, 1, 1),
                                                 ImmutableString("dummyPacker"), TSourceLoc(),
                                                 SymbolType::AngleInternal));
    TStructure *emulatedDepthRangeParams = new TStructure(
        symbolTable, kEmulatedDepthRangeParams, depthRangeParamsFields, SymbolType::AngleInternal);
    TType *emulatedDepthRangeType = new TType(emulatedDepthRangeParams, false);

    // Declare a global depth range variable.
    TVariable *depthRangeVar =
        new TVariable(symbolTable->nextUniqueId(), kEmptyImmutableString, SymbolType::Empty,
                      TExtension::UNDEFINED, emulatedDepthRangeType);

    DeclareGlobalVariable(root, depthRangeVar);

    // This field list mirrors the structure of GraphicsDriverUniforms in ContextVk.cpp.
    TFieldList *driverFieldList = new TFieldList;

    const std::array<TType *, kNumGraphicsDriverUniforms> kDriverUniformTypes = {{
        new TType(EbtFloat, 4),
        new TType(EbtFloat),
        new TType(EbtFloat),
        new TType(EbtFloat),
        new TType(EbtUInt),
        new TType(EbtInt, 4),
        new TType(EbtUInt, 4),
        emulatedDepthRangeType,
    }};

    for (size_t uniformIndex = 0; uniformIndex < kNumGraphicsDriverUniforms; ++uniformIndex)
    {
        TField *driverUniformField =
            new TField(kDriverUniformTypes[uniformIndex],
                       ImmutableString(kGraphicsDriverUniformNames[uniformIndex]), TSourceLoc(),
                       SymbolType::AngleInternal);
        driverFieldList->push_back(driverUniformField);
    }

    // Define a driver uniform block "ANGLEUniformBlock" with instance name "ANGLEUniforms".
    return DeclareInterfaceBlock(root, symbolTable, driverFieldList, EvqUniform,
                                 TMemoryQualifier::Create(), 0, kUniformsBlockName,
                                 kUniformsVarName);
}

const TVariable *AddComputeDriverUniformsToShader(TIntermBlock *root, TSymbolTable *symbolTable)
{
    // This field list mirrors the structure of ComputeDriverUniforms in ContextVk.cpp.
    TFieldList *driverFieldList = new TFieldList;

    const std::array<TType *, kNumComputeDriverUniforms> kDriverUniformTypes = {{
        new TType(EbtUInt, 4),
    }};

    for (size_t uniformIndex = 0; uniformIndex < kNumComputeDriverUniforms; ++uniformIndex)
    {
        TField *driverUniformField =
            new TField(kDriverUniformTypes[uniformIndex],
                       ImmutableString(kComputeDriverUniformNames[uniformIndex]), TSourceLoc(),
                       SymbolType::AngleInternal);
        driverFieldList->push_back(driverUniformField);
    }

    // Define a driver uniform block "ANGLEUniformBlock" with instance name "ANGLEUniforms".
    return DeclareInterfaceBlock(root, symbolTable, driverFieldList, EvqUniform,
                                 TMemoryQualifier::Create(), 0, kUniformsBlockName,
                                 kUniformsVarName);
}

TIntermPreprocessorDirective *GenerateLineRasterIfDef()
{
    return new TIntermPreprocessorDirective(
        PreprocessorDirective::Ifdef, ImmutableString("ANGLE_ENABLE_LINE_SEGMENT_RASTERIZATION"));
}

TIntermPreprocessorDirective *GenerateEndIf()
{
    return new TIntermPreprocessorDirective(PreprocessorDirective::Endif, kEmptyImmutableString);
}

TVariable *AddANGLEPositionVaryingDeclaration(TIntermBlock *root,
                                              TSymbolTable *symbolTable,
                                              TQualifier qualifier)
{
    TIntermSequence *insertSequence = new TIntermSequence;

    insertSequence->push_back(GenerateLineRasterIfDef());

    // Define a driver varying vec2 "ANGLEPosition".
    TType *varyingType               = new TType(EbtFloat, EbpMedium, qualifier, 2);
    TVariable *varyingVar            = new TVariable(symbolTable, ImmutableString("ANGLEPosition"),
                                          varyingType, SymbolType::AngleInternal);
    TIntermSymbol *varyingDeclarator = new TIntermSymbol(varyingVar);
    TIntermDeclaration *varyingDecl  = new TIntermDeclaration;
    varyingDecl->appendDeclarator(varyingDeclarator);
    insertSequence->push_back(varyingDecl);

    insertSequence->push_back(GenerateEndIf());

    // Insert the declarations before Main.
    size_t mainIndex = FindMainIndex(root);
    root->insertChildNodes(mainIndex, *insertSequence);

    return varyingVar;
}

ANGLE_NO_DISCARD bool AddBresenhamEmulationVS(TCompiler *compiler,
                                              TIntermBlock *root,
                                              TSymbolTable *symbolTable,
                                              const TVariable *driverUniforms)
{
    TVariable *anglePosition = AddANGLEPositionVaryingDeclaration(root, symbolTable, EvqVaryingOut);

    // Clamp position to subpixel grid.
    // Do perspective divide (get normalized device coords)
    // "vec2 ndc = gl_Position.xy / gl_Position.w"
    const TType *vec2Type        = StaticType::GetBasic<EbtFloat, 2>();
    TIntermBinary *viewportRef   = CreateDriverUniformRef(driverUniforms, kViewport);
    TIntermSymbol *glPos         = new TIntermSymbol(BuiltInVariable::gl_Position());
    TIntermSwizzle *glPosXY      = CreateSwizzle(glPos, 0, 1);
    TIntermSwizzle *glPosW       = CreateSwizzle(glPos->deepCopy(), 3);
    TVariable *ndc               = CreateTempVariable(symbolTable, vec2Type);
    TIntermBinary *noPerspective = new TIntermBinary(EOpDiv, glPosXY, glPosW);
    TIntermDeclaration *ndcDecl  = CreateTempInitDeclarationNode(ndc, noPerspective);

    // Convert NDC to window coordinates. According to Vulkan spec.
    // "vec2 window = 0.5 * viewport.wh * (ndc + 1) + viewport.xy"
    TIntermBinary *ndcPlusOne =
        new TIntermBinary(EOpAdd, CreateTempSymbolNode(ndc), CreateFloatNode(1.0f));
    TIntermSwizzle *viewportZW = CreateSwizzle(viewportRef, 2, 3);
    TIntermBinary *ndcViewport = new TIntermBinary(EOpMul, viewportZW, ndcPlusOne);
    TIntermBinary *ndcViewportHalf =
        new TIntermBinary(EOpVectorTimesScalar, ndcViewport, CreateFloatNode(0.5f));
    TIntermSwizzle *viewportXY     = CreateSwizzle(viewportRef->deepCopy(), 0, 1);
    TIntermBinary *ndcToWindow     = new TIntermBinary(EOpAdd, ndcViewportHalf, viewportXY);
    TVariable *windowCoords        = CreateTempVariable(symbolTable, vec2Type);
    TIntermDeclaration *windowDecl = CreateTempInitDeclarationNode(windowCoords, ndcToWindow);

    // Clamp to subpixel grid.
    // "vec2 clamped = round(window * 2^{subpixelBits}) / 2^{subpixelBits}"
    int subpixelBits                    = compiler->getResources().SubPixelBits;
    TIntermConstantUnion *scaleConstant = CreateFloatNode(static_cast<float>(1 << subpixelBits));
    TIntermBinary *windowScaled =
        new TIntermBinary(EOpVectorTimesScalar, CreateTempSymbolNode(windowCoords), scaleConstant);
    TIntermUnary *windowRounded = new TIntermUnary(EOpRound, windowScaled, nullptr);
    TIntermBinary *windowRoundedBack =
        new TIntermBinary(EOpDiv, windowRounded, scaleConstant->deepCopy());
    TVariable *clampedWindowCoords = CreateTempVariable(symbolTable, vec2Type);
    TIntermDeclaration *clampedDecl =
        CreateTempInitDeclarationNode(clampedWindowCoords, windowRoundedBack);

    // Set varying.
    // "ANGLEPosition = 2 * (clamped - viewport.xy) / viewport.wh - 1"
    TIntermBinary *clampedOffset = new TIntermBinary(
        EOpSub, CreateTempSymbolNode(clampedWindowCoords), viewportXY->deepCopy());
    TIntermBinary *clampedOff2x =
        new TIntermBinary(EOpVectorTimesScalar, clampedOffset, CreateFloatNode(2.0f));
    TIntermBinary *clampedDivided = new TIntermBinary(EOpDiv, clampedOff2x, viewportZW->deepCopy());
    TIntermBinary *clampedNDC    = new TIntermBinary(EOpSub, clampedDivided, CreateFloatNode(1.0f));
    TIntermSymbol *varyingRef    = new TIntermSymbol(anglePosition);
    TIntermBinary *varyingAssign = new TIntermBinary(EOpAssign, varyingRef, clampedNDC);

    // Ensure the statements run at the end of the main() function.
    TIntermFunctionDefinition *main = FindMain(root);
    TIntermBlock *mainBody          = main->getBody();
    mainBody->appendStatement(GenerateLineRasterIfDef());
    mainBody->appendStatement(ndcDecl);
    mainBody->appendStatement(windowDecl);
    mainBody->appendStatement(clampedDecl);
    mainBody->appendStatement(varyingAssign);
    mainBody->appendStatement(GenerateEndIf());
    return compiler->validateAST(root);
}

ANGLE_NO_DISCARD bool InsertFragCoordCorrection(TCompiler *compiler,
                                                TIntermBlock *root,
                                                TIntermSequence *insertSequence,
                                                TSymbolTable *symbolTable,
                                                const TVariable *driverUniforms)
{
    TIntermBinary *viewportYScale = CreateDriverUniformRef(driverUniforms, kViewportYScale);
    TIntermBinary *pivot          = CreateDriverUniformRef(driverUniforms, kHalfRenderAreaHeight);
    return FlipBuiltinVariable(compiler, root, insertSequence, viewportYScale, symbolTable,
                               BuiltInVariable::gl_FragCoord(), kFlippedFragCoordName, pivot);
}

// This block adds OpenGL line segment rasterization emulation behind #ifdef guards.
// OpenGL's simple rasterization algorithm is a strict subset of the pixels generated by the Vulkan
// algorithm. Thus we can implement a shader patch that rejects pixels if they would not be
// generated by the OpenGL algorithm. OpenGL's algorithm is similar to Bresenham's line algorithm.
// It is implemented for each pixel by testing if the line segment crosses a small diamond inside
// the pixel. See the OpenGL ES 2.0 spec section "3.4.1 Basic Line Segment Rasterization". Also
// see the Vulkan spec section "24.6.1. Basic Line Segment Rasterization":
// https://khronos.org/registry/vulkan/specs/1.0/html/vkspec.html#primsrast-lines-basic
//
// Using trigonometric math and the fact that we know the size of the diamond we can derive a
// formula to test if the line segment crosses the pixel center. gl_FragCoord is used along with an
// internal position varying to determine the inputs to the formula.
//
// The implementation of the test is similar to the following pseudocode:
//
// void main()
// {
//    vec2 p  = (((((ANGLEPosition.xy) * 0.5) + 0.5) * viewport.zw) + viewport.xy);
//    vec2 d  = dFdx(p) + dFdy(p);
//    vec2 f  = gl_FragCoord.xy;
//    vec2 p_ = p.yx;
//    vec2 d_ = d.yx;
//    vec2 f_ = f.yx;
//
//    vec2 i = abs(p - f + (d / d_) * (f_ - p_));
//
//    if (i.x > (0.5 + e) && i.y > (0.5 + e))
//        discard;
//     <otherwise run fragment shader main>
// }
//
// Note this emulation can not provide fully correct rasterization. See the docs more more info.

ANGLE_NO_DISCARD bool AddBresenhamEmulationFS(TCompiler *compiler,
                                              TInfoSinkBase &sink,
                                              TIntermBlock *root,
                                              TSymbolTable *symbolTable,
                                              const TVariable *driverUniforms,
                                              bool usesFragCoord)
{
    TVariable *anglePosition = AddANGLEPositionVaryingDeclaration(root, symbolTable, EvqVaryingIn);
    const TType *vec2Type    = StaticType::GetBasic<EbtFloat, 2>();
    TIntermBinary *viewportRef = CreateDriverUniformRef(driverUniforms, kViewport);

    // vec2 p = ((ANGLEPosition * 0.5) + 0.5) * viewport.zw + viewport.xy
    TIntermSwizzle *viewportXY    = CreateSwizzle(viewportRef->deepCopy(), 0, 1);
    TIntermSwizzle *viewportZW    = CreateSwizzle(viewportRef, 2, 3);
    TIntermSymbol *position       = new TIntermSymbol(anglePosition);
    TIntermConstantUnion *oneHalf = CreateFloatNode(0.5f);
    TIntermBinary *halfPosition   = new TIntermBinary(EOpVectorTimesScalar, position, oneHalf);
    TIntermBinary *offsetHalfPosition =
        new TIntermBinary(EOpAdd, halfPosition, oneHalf->deepCopy());
    TIntermBinary *scaledPosition = new TIntermBinary(EOpMul, offsetHalfPosition, viewportZW);
    TIntermBinary *windowPosition = new TIntermBinary(EOpAdd, scaledPosition, viewportXY);
    TVariable *p                  = CreateTempVariable(symbolTable, vec2Type);
    TIntermDeclaration *pDecl     = CreateTempInitDeclarationNode(p, windowPosition);

    // vec2 d = dFdx(p) + dFdy(p)
    TIntermUnary *dfdx        = new TIntermUnary(EOpDFdx, new TIntermSymbol(p), nullptr);
    TIntermUnary *dfdy        = new TIntermUnary(EOpDFdy, new TIntermSymbol(p), nullptr);
    TIntermBinary *dfsum      = new TIntermBinary(EOpAdd, dfdx, dfdy);
    TVariable *d              = CreateTempVariable(symbolTable, vec2Type);
    TIntermDeclaration *dDecl = CreateTempInitDeclarationNode(d, dfsum);

    // vec2 f = gl_FragCoord.xy
    const TVariable *fragCoord  = BuiltInVariable::gl_FragCoord();
    TIntermSwizzle *fragCoordXY = CreateSwizzle(new TIntermSymbol(fragCoord), 0, 1);
    TVariable *f                = CreateTempVariable(symbolTable, vec2Type);
    TIntermDeclaration *fDecl   = CreateTempInitDeclarationNode(f, fragCoordXY);

    // vec2 p_ = p.yx
    TIntermSwizzle *pyx        = CreateSwizzle(new TIntermSymbol(p), 1, 0);
    TVariable *p_              = CreateTempVariable(symbolTable, vec2Type);
    TIntermDeclaration *p_decl = CreateTempInitDeclarationNode(p_, pyx);

    // vec2 d_ = d.yx
    TIntermSwizzle *dyx        = CreateSwizzle(new TIntermSymbol(d), 1, 0);
    TVariable *d_              = CreateTempVariable(symbolTable, vec2Type);
    TIntermDeclaration *d_decl = CreateTempInitDeclarationNode(d_, dyx);

    // vec2 f_ = f.yx
    TIntermSwizzle *fyx        = CreateSwizzle(new TIntermSymbol(f), 1, 0);
    TVariable *f_              = CreateTempVariable(symbolTable, vec2Type);
    TIntermDeclaration *f_decl = CreateTempInitDeclarationNode(f_, fyx);

    // vec2 i = abs(p - f + (d/d_) * (f_ - p_))
    TIntermBinary *dd   = new TIntermBinary(EOpDiv, new TIntermSymbol(d), new TIntermSymbol(d_));
    TIntermBinary *fp   = new TIntermBinary(EOpSub, new TIntermSymbol(f_), new TIntermSymbol(p_));
    TIntermBinary *ddfp = new TIntermBinary(EOpMul, dd, fp);
    TIntermBinary *pf   = new TIntermBinary(EOpSub, new TIntermSymbol(p), new TIntermSymbol(f));
    TIntermBinary *expr = new TIntermBinary(EOpAdd, pf, ddfp);
    TIntermUnary *absd  = new TIntermUnary(EOpAbs, expr, nullptr);
    TVariable *i        = CreateTempVariable(symbolTable, vec2Type);
    TIntermDeclaration *iDecl = CreateTempInitDeclarationNode(i, absd);

    // Using a small epsilon value ensures that we don't suffer from numerical instability when
    // lines are exactly vertical or horizontal.
    static constexpr float kEpsilon   = 0.0001f;
    static constexpr float kThreshold = 0.5 + kEpsilon;
    TIntermConstantUnion *threshold   = CreateFloatNode(kThreshold);

    // if (i.x > (0.5 + e) && i.y > (0.5 + e))
    TIntermSwizzle *ix     = CreateSwizzle(new TIntermSymbol(i), 0);
    TIntermBinary *checkX  = new TIntermBinary(EOpGreaterThan, ix, threshold);
    TIntermSwizzle *iy     = CreateSwizzle(new TIntermSymbol(i), 1);
    TIntermBinary *checkY  = new TIntermBinary(EOpGreaterThan, iy, threshold->deepCopy());
    TIntermBinary *checkXY = new TIntermBinary(EOpLogicalAnd, checkX, checkY);

    // discard
    TIntermBranch *discard     = new TIntermBranch(EOpKill, nullptr);
    TIntermBlock *discardBlock = new TIntermBlock;
    discardBlock->appendStatement(discard);
    TIntermIfElse *ifStatement = new TIntermIfElse(checkXY, discardBlock, nullptr);

    // Ensure the line raster code runs at the beginning of main().
    TIntermFunctionDefinition *main = FindMain(root);
    TIntermSequence *mainSequence   = main->getBody()->getSequence();
    ASSERT(mainSequence);

    std::array<TIntermNode *, 9> nodes = {
        {pDecl, dDecl, fDecl, p_decl, d_decl, f_decl, iDecl, ifStatement, GenerateEndIf()}};
    mainSequence->insert(mainSequence->begin(), nodes.begin(), nodes.end());

    // If the shader does not use frag coord, we should insert it inside the ifdef.
    if (!usesFragCoord)
    {
        if (!InsertFragCoordCorrection(compiler, root, mainSequence, symbolTable, driverUniforms))
        {
            return false;
        }
    }

    mainSequence->insert(mainSequence->begin(), GenerateLineRasterIfDef());
    return compiler->validateAST(root);
}

}  // anonymous namespace

TranslatorVulkan::TranslatorVulkan(sh::GLenum type, ShShaderSpec spec)
    : TCompiler(type, spec, SH_GLSL_450_CORE_OUTPUT)
{}

bool TranslatorVulkan::translateImpl(TIntermBlock *root,
                                     ShCompileOptions compileOptions,
                                     PerformanceDiagnostics * /*perfDiagnostics*/,
                                     const TVariable **driverUniformsOut,
                                     TOutputVulkanGLSL *outputGLSL)
{
    TInfoSinkBase &sink = getInfoSink().obj;

    if (getShaderType() == GL_VERTEX_SHADER)
    {
        if (!ShaderBuiltinsWorkaround(this, root, &getSymbolTable(), compileOptions))
        {
            return false;
        }
    }

    sink << "#version 450 core\n";

    // Write out default uniforms into a uniform block assigned to a specific set/binding.
    int defaultUniformCount           = 0;
    int aggregateTypesUsedForUniforms = 0;
    int atomicCounterCount            = 0;
    for (const auto &uniform : getUniforms())
    {
        if (!uniform.isBuiltIn() && uniform.staticUse && !gl::IsOpaqueType(uniform.type))
        {
            ++defaultUniformCount;
        }

        if (uniform.isStruct() || uniform.isArrayOfArrays())
        {
            ++aggregateTypesUsedForUniforms;
        }

        if (gl::IsAtomicCounterType(uniform.type))
        {
            ++atomicCounterCount;
        }
    }

    // TODO(lucferron): Refactor this function to do fewer tree traversals.
    // http://anglebug.com/2461
    if (aggregateTypesUsedForUniforms > 0)
    {
        if (!NameEmbeddedStructUniforms(this, root, &getSymbolTable()))
        {
            return false;
        }

        bool rewriteStructSamplersResult;
        int removedUniformsCount;

        if (compileOptions & SH_USE_OLD_REWRITE_STRUCT_SAMPLERS)
        {
            rewriteStructSamplersResult =
                RewriteStructSamplersOld(this, root, &getSymbolTable(), &removedUniformsCount);
        }
        else
        {
            rewriteStructSamplersResult =
                RewriteStructSamplers(this, root, &getSymbolTable(), &removedUniformsCount);
        }

        if (!rewriteStructSamplersResult)
        {
            return false;
        }
        defaultUniformCount -= removedUniformsCount;

        // We must declare the struct types before using them.
        DeclareStructTypesTraverser structTypesTraverser(outputGLSL);
        root->traverse(&structTypesTraverser);
        if (!structTypesTraverser.updateTree(this, root))
        {
            return false;
        }
    }

    // Rewrite samplerCubes as sampler2DArrays.  This must be done after rewriting struct samplers
    // as it doesn't expect that.
    if (compileOptions & SH_EMULATE_SEAMFUL_CUBE_MAP_SAMPLING)
    {
        if (!RewriteCubeMapSamplersAs2DArray(this, root, &getSymbolTable(),
                                             getShaderType() == GL_FRAGMENT_SHADER))
        {
            return false;
        }
    }

    if (getShaderVersion() >= 300)
    {
        // Make sure every uniform buffer variable has a name.  The following transformation relies
        // on this.
        if (!NameNamelessUniformBuffers(this, root, &getSymbolTable()))
        {
            return false;
        }

        // In GLES3+, matrices can be declared row- or column-major.  Transform all to column-major
        // as interface block field layout qualifiers are not allowed.  This should be done after
        // samplers are taken out of structs (as structs could be rewritten), but before uniforms
        // are collected in a uniform buffer as they are handled especially.
        if (!RewriteRowMajorMatrices(this, root, &getSymbolTable()))
        {
            return false;
        }
    }

    if (defaultUniformCount > 0)
    {
        sink << "\n@@ LAYOUT-defaultUniforms(std140) @@ uniform defaultUniforms\n{\n";

        DeclareDefaultUniformsTraverser defaultTraverser(&sink, getHashFunction(), &getNameMap());
        root->traverse(&defaultTraverser);
        if (!defaultTraverser.updateTree(this, root))
        {
            return false;
        }

        sink << "};\n";
    }

    const TVariable *driverUniforms;
    if (getShaderType() == GL_COMPUTE_SHADER)
    {
        driverUniforms = AddComputeDriverUniformsToShader(root, &getSymbolTable());
    }
    else
    {
        driverUniforms = AddGraphicsDriverUniformsToShader(root, &getSymbolTable());
    }

    if (atomicCounterCount > 0)
    {
        // ANGLEUniforms.acbBufferOffsets
        const TIntermBinary *acbBufferOffsets =
            CreateDriverUniformRef(driverUniforms, kAcbBufferOffsets);

        if (!RewriteAtomicCounters(this, root, &getSymbolTable(), acbBufferOffsets))
        {
            return false;
        }
    }

    if (getShaderType() != GL_COMPUTE_SHADER)
    {
        if (!ReplaceGLDepthRangeWithDriverUniform(this, root, driverUniforms, &getSymbolTable()))
        {
            return false;
        }
    }

    // Declare gl_FragColor and glFragData as webgl_FragColor and webgl_FragData
    // if it's core profile shaders and they are used.
    if (getShaderType() == GL_FRAGMENT_SHADER)
    {
        bool usesPointCoord = false;
        bool usesFragCoord  = false;

        // Search for the gl_PointCoord usage, if its used, we need to flip the y coordinate.
        for (const ShaderVariable &inputVarying : mInputVaryings)
        {
            if (!inputVarying.isBuiltIn())
            {
                continue;
            }

            if (inputVarying.name == "gl_PointCoord")
            {
                usesPointCoord = true;
                break;
            }

            if (inputVarying.name == "gl_FragCoord")
            {
                usesFragCoord = true;
                break;
            }
        }

        if (!AddBresenhamEmulationFS(this, sink, root, &getSymbolTable(), driverUniforms,
                                     usesFragCoord))
        {
            return false;
        }

        bool hasGLFragColor = false;
        bool hasGLFragData  = false;

        for (const ShaderVariable &outputVar : mOutputVariables)
        {
            if (outputVar.name == "gl_FragColor")
            {
                ASSERT(!hasGLFragColor);
                hasGLFragColor = true;
                continue;
            }
            else if (outputVar.name == "gl_FragData")
            {
                ASSERT(!hasGLFragData);
                hasGLFragData = true;
                continue;
            }
        }
        ASSERT(!(hasGLFragColor && hasGLFragData));
        if (hasGLFragColor)
        {
            sink << "layout(location = 0) out vec4 webgl_FragColor;\n";
        }
        if (hasGLFragData)
        {
            sink << "layout(location = 0) out vec4 webgl_FragData[gl_MaxDrawBuffers];\n";
        }

        if (usesPointCoord)
        {
            TIntermBinary *viewportYScale =
                CreateDriverUniformRef(driverUniforms, kNegViewportYScale);
            TIntermConstantUnion *pivot = CreateFloatNode(0.5f);
            if (!FlipBuiltinVariable(this, root, GetMainSequence(root), viewportYScale,
                                     &getSymbolTable(), BuiltInVariable::gl_PointCoord(),
                                     kFlippedPointCoordName, pivot))
            {
                return false;
            }
        }

        if (usesFragCoord)
        {
            if (!InsertFragCoordCorrection(this, root, GetMainSequence(root), &getSymbolTable(),
                                           driverUniforms))
            {
                return false;
            }
        }

        {
            TIntermBinary *viewportYScale = CreateDriverUniformRef(driverUniforms, kViewportYScale);
            if (!RewriteDfdy(this, root, getSymbolTable(), getShaderVersion(), viewportYScale))
            {
                return false;
            }
        }
    }
    else if (getShaderType() == GL_VERTEX_SHADER)
    {
        if (!AddBresenhamEmulationVS(this, root, &getSymbolTable(), driverUniforms))
        {
            return false;
        }

        // Add a macro to declare transform feedback buffers.
        sink << "@@ XFB-DECL @@\n\n";

        // Append a macro for transform feedback substitution prior to modifying depth.
        if (!AppendVertexShaderTransformFeedbackOutputToMain(this, root, &getSymbolTable()))
        {
            return false;
        }

        // Append depth range translation to main.
        if (!AppendVertexShaderDepthCorrectionToMain(this, root, &getSymbolTable()))
        {
            return false;
        }
    }
    else if (getShaderType() == GL_GEOMETRY_SHADER)
    {
        WriteGeometryShaderLayoutQualifiers(
            sink, getGeometryShaderInputPrimitiveType(), getGeometryShaderInvocations(),
            getGeometryShaderOutputPrimitiveType(), getGeometryShaderMaxVertices());
    }
    else
    {
        ASSERT(getShaderType() == GL_COMPUTE_SHADER);
        EmitWorkGroupSizeGLSL(*this, sink);
    }

    if (!validateAST(root))
    {
        return false;
    }

    if (driverUniformsOut)
    {
        *driverUniformsOut = driverUniforms;
    }

    return true;
}

bool TranslatorVulkan::translate(TIntermBlock *root,
                                 ShCompileOptions compileOptions,
                                 PerformanceDiagnostics *perfDiagnostics)
{

    TInfoSinkBase &sink = getInfoSink().obj;
    TOutputVulkanGLSL outputGLSL(sink, getArrayIndexClampingStrategy(), getHashFunction(),
                                 getNameMap(), &getSymbolTable(), getShaderType(),
                                 getShaderVersion(), getOutputType(), compileOptions);

    if (!translateImpl(root, compileOptions, perfDiagnostics, nullptr, &outputGLSL))
    {
        return false;
    }

    // Write translated shader.
    root->traverse(&outputGLSL);

    return true;
}

bool TranslatorVulkan::shouldFlattenPragmaStdglInvariantAll()
{
    // Not necessary.
    return false;
}

TIntermBinary *TranslatorVulkan::getDriverUniformNegViewportYScaleRef(
    const TVariable *driverUniforms) const
{
    return CreateDriverUniformRef(driverUniforms, kNegViewportYScale);
}

}  // namespace sh
kc3-lang/angle/src/compiler/translator/TranslatorVulkan.cpp

Commit

kc3-lang/angle /src/compiler/translator/TranslatorVulkan.cpp
