// slang-emit-glsl.cpp
#include "slang-emit-glsl.h"

#include "../core/slang-writer.h"

#include "slang-emit-source-writer.h"
#include "slang-ir-util.h"
#include "slang-mangled-lexer.h"

#include "slang-legalize-types.h"
#include "slang-ir-layout.h"
#include "slang/slang-ir.h"
#include "slang-ir-call-graph.h"

#include <assert.h>

namespace Slang {

void trackGLSLTargetCaps(
    GLSLExtensionTracker* extensionTracker,
    CapabilitySet const& caps);

GLSLSourceEmitter::GLSLSourceEmitter(const Desc& desc) :
    Super(desc)
{
    m_glslExtensionTracker = dynamicCast<GLSLExtensionTracker>(desc.codeGenContext->getExtensionTracker());
    SLANG_ASSERT(m_glslExtensionTracker);
}

void GLSLSourceEmitter::beforeComputeEmitActions(IRModule* module)
{
    buildEntryPointReferenceGraph(this->m_referencingEntryPoints, module);
}

SlangResult GLSLSourceEmitter::init()
{
    SLANG_RETURN_ON_FAIL(Super::init());

    // Deal with cases where a particular stage requires certain GLSL versions
    // and/or extensions.
    switch (m_entryPointStage)
    {
        case Stage::AnyHit:
        case Stage::Callable:
        case Stage::ClosestHit:
        case Stage::Intersection:
        case Stage::Miss:
        case Stage::RayGeneration:
        {
            _requireRayTracing();
            break;
        }
        case Stage::Mesh:
        case Stage::Amplification:
        {
            _requireGLSLExtension(UnownedStringSlice::fromLiteral("GL_EXT_mesh_shader"));
            _requireSPIRVVersion(SemanticVersion(1, 4));
            break;
        }
        default: break;
    }

    if (getTargetProgram()->getOptionSet().shouldUseScalarLayout())
    {
        m_glslExtensionTracker->requireExtension(
            UnownedStringSlice::fromLiteral("GL_EXT_scalar_block_layout"));
    }
    return SLANG_OK;
}

void GLSLSourceEmitter::_requireRayTracing()
{
    m_glslExtensionTracker->requireExtension(UnownedStringSlice::fromLiteral("GL_EXT_ray_tracing"));
    m_glslExtensionTracker->requireSPIRVVersion(SemanticVersion(1, 4));
    m_glslExtensionTracker->requireVersion(ProfileVersion::GLSL_460);
}

void GLSLSourceEmitter::_requireRayQuery()
{
    m_glslExtensionTracker->requireExtension(UnownedStringSlice::fromLiteral("GL_EXT_ray_query"));
    m_glslExtensionTracker->requireSPIRVVersion(SemanticVersion(1, 4)); // required due to glslang bug which enables `SPV_KHR_ray_tracing` regardless of context
    m_glslExtensionTracker->requireVersion(ProfileVersion::GLSL_460);
}

void GLSLSourceEmitter::_requireFragmentShaderBarycentric()
{
    m_glslExtensionTracker->requireExtension(UnownedStringSlice::fromLiteral("GL_EXT_fragment_shader_barycentric"));
    m_glslExtensionTracker->requireVersion(ProfileVersion::GLSL_450);
}


void GLSLSourceEmitter::_requireGLSLExtension(const UnownedStringSlice& name)
{
    m_glslExtensionTracker->requireExtension(name);
}

void GLSLSourceEmitter::_requireGLSLVersion(ProfileVersion version)
{
    if (getSourceLanguage() != SourceLanguage::GLSL)
        return;

    m_glslExtensionTracker->requireVersion(version);
}

void GLSLSourceEmitter::_requireSPIRVVersion(const SemanticVersion& version)
{
    m_glslExtensionTracker->requireSPIRVVersion(version);
}

void GLSLSourceEmitter::_requireGLSLVersion(int version)
{
    switch (version)
    {
#define CASE(NUMBER) \
    case NUMBER: _requireGLSLVersion(ProfileVersion::GLSL_##NUMBER); break
        CASE(150);
        CASE(330);
        CASE(400);
        CASE(410);
        CASE(420);
        CASE(430);
        CASE(440);
        CASE(450);
        CASE(460);

#undef CASE
    }
}

void GLSLSourceEmitter::_emitMemoryQualifierDecorations(IRInst* varDecl)
{
    if(auto collection = varDecl->findDecoration<IRMemoryQualifierSetDecoration>())
    {
        IRIntegerValue flags = collection->getMemoryQualifierBit();
        if (flags & MemoryQualifierSetModifier::Flags::kCoherent)
        {
            m_writer->emit("coherent ");
        }
        if (flags & MemoryQualifierSetModifier::Flags::kVolatile)
        {
            m_writer->emit("volatile ");
        }
        if (flags & MemoryQualifierSetModifier::Flags::kRestrict)
        {
            m_writer->emit("restrict ");
        }
        if (flags & MemoryQualifierSetModifier::Flags::kReadOnly)
        {
            m_writer->emit("readonly ");
        }
        if (flags & MemoryQualifierSetModifier::Flags::kWriteOnly)
        {
            m_writer->emit("writeonly ");
        }
    }
}

void GLSLSourceEmitter::emitMemoryQualifiers(IRInst* varDecl)
{
    _emitMemoryQualifierDecorations(varDecl);
}

void GLSLSourceEmitter::_emitGLSLStructuredBuffer(IRGlobalParam* varDecl, IRHLSLStructuredBufferTypeBase* structuredBufferType)
{
    // Shader storage buffer is an OpenGL 430 feature
    //
    // TODO: we should require either the extension or the version...
    _requireGLSLVersion(430);

    m_writer->emit("layout(");
    auto layoutTypeOp = structuredBufferType->getDataLayout()
        ? structuredBufferType->getDataLayout()->getOp()
        : kIROp_DefaultBufferLayoutType;
    switch (layoutTypeOp)
    {
    case kIROp_DefaultBufferLayoutType:
        m_writer->emit(getTargetProgram()->getOptionSet().shouldUseScalarLayout() ? "scalar" : "std430");
        break;
    case kIROp_Std430BufferLayoutType:
        m_writer->emit("std430");
        break;
    case kIROp_Std140BufferLayoutType:
        m_writer->emit("std140");
        break;
    case kIROp_ScalarBufferLayoutType:
        _requireGLSLExtension(toSlice("GL_EXT_scalar_block_layout"));
        m_writer->emit("scalar");
        break;
    default:
        m_writer->emit("std430");
        break;
    }

    bool isReadOnly = (as<IRHLSLStructuredBufferType>(structuredBufferType) != nullptr);
    auto layout = getVarLayout(varDecl);
    if (layout)
    {
        // We can use ShaderResource/DescriptorSlot interchangably here. 
       // This is possible because vk-shift-*
        const LayoutResourceKindFlags kinds = (isReadOnly ? LayoutResourceKindFlag::ShaderResource : LayoutResourceKindFlag::UnorderedAccess)
            | LayoutResourceKindFlag::DescriptorTableSlot;

        EmitVarChain chain(layout);

        const UInt index = getBindingOffsetForKinds(&chain, kinds);
        const UInt space = getBindingSpaceForKinds(&chain, kinds);

        m_writer->emit(", binding = ");
        m_writer->emit(index);
        if (space)
        {
            m_writer->emit(", set = ");
            m_writer->emit(space);
        }
    }
    
    m_writer->emit(") ");

    /*
    If the output type is a buffer, and we can determine it is only readonly we can prefix before
    buffer with 'readonly'

    The actual structuredBufferType could be

    HLSLStructuredBufferType                        - This is unambiguously read only
    HLSLRWStructuredBufferType                      - Read write
    HLSLRasterizerOrderedStructuredBufferType       - Allows read/write access
    HLSLAppendStructuredBufferType                  - Write
    HLSLConsumeStructuredBufferType                 - TODO (JS): Its possible that this can be readonly, but we currently don't support on GLSL
    */
    if (as<IRHLSLStructuredBufferType>(structuredBufferType))
    {
        m_writer->emit("readonly ");
    }

    m_writer->emit("buffer ");

    // Generate a dummy name for the block
    StringBuilder blockTypeName;
    blockTypeName << "StructuredBuffer_";
    getTypeNameHint(blockTypeName, structuredBufferType->getElementType());
    blockTypeName << "_t";
    m_writer->emit(_generateUniqueName(blockTypeName.produceString().getUnownedSlice()));

    m_writer->emit(" {\n");
    m_writer->indent();


    auto elementType = structuredBufferType->getElementType();
    emitType(elementType, "_data[]");
    m_writer->emit(";\n");

    m_writer->dedent();
    m_writer->emit("} ");

    m_writer->emit(getName(varDecl));
    emitArrayBrackets(varDecl->getDataType());

    m_writer->emit(";\n");
}

void GLSLSourceEmitter::emitSSBOHeader(IRGlobalParam* varDecl, IRType* bufferType)
{
    // TODO: A lot of this logic is copy-pasted from `emitIRStructuredBuffer_GLSL`.
    // It might be worthwhile to share the common code to avoid regressions sneaking
    // in when one or the other, but not both, gets updated.

    // Shader storage buffer is an OpenGL 430 feature
    //
    // TODO: we should require either the extension or the version...
    _requireGLSLVersion(430);

    m_writer->emit("layout(");
    IROp layoutOp = kIROp_DefaultBufferLayoutType;
    if (auto structBufferType = as<IRHLSLStructuredBufferTypeBase>(bufferType))
    {
        layoutOp = structBufferType->getDataLayout()? structBufferType->getDataLayout()->getOp() : kIROp_DefaultBufferLayoutType;
    }
    else if (auto ssboType = as<IRGLSLShaderStorageBufferType>(bufferType))
    {
        layoutOp = ssboType->getDataLayout() ? ssboType->getDataLayout()->getOp() : kIROp_DefaultBufferLayoutType;
    }

    if (layoutOp == kIROp_DefaultBufferLayoutType)
    {
        m_writer->emit(getTargetProgram()->getOptionSet().shouldUseScalarLayout() ? "scalar" : "std430");
    }
    else
    {
        switch (layoutOp)
        {
        case kIROp_DefaultBufferLayoutType:
            m_writer->emit(getTargetProgram()->getOptionSet().shouldUseScalarLayout() ? "scalar" : "std430");
            break;
        case kIROp_Std430BufferLayoutType:
            m_writer->emit("std430");
            break;
        case kIROp_Std140BufferLayoutType:
            m_writer->emit("std140");
            break;
        case kIROp_ScalarBufferLayoutType:
            _requireGLSLExtension(toSlice("GL_EXT_scalar_block_layout"));
            m_writer->emit("scalar");
            break;
        }
    }

    auto layout = getVarLayout(varDecl);
    if (layout)
    {
        // We can use ShaderResource/DescriptorSlot interchangably here.
        // This is possible because vk-shift-*
        bool isReadOnly = (as<IRHLSLByteAddressBufferType>(bufferType) != nullptr);

        const LayoutResourceKindFlags kinds = (isReadOnly ? LayoutResourceKindFlag::ShaderResource : LayoutResourceKindFlag::UnorderedAccess)
            | LayoutResourceKindFlag::DescriptorTableSlot;

        EmitVarChain chain(layout);

        const UInt index = getBindingOffsetForKinds(&chain, kinds);
        const UInt space = getBindingSpaceForKinds(&chain, kinds);

        m_writer->emit(", binding = ");
        m_writer->emit(index);
        if (space)
        {
            m_writer->emit(", set = ");
            m_writer->emit(space);
        }
    }
    m_writer->emit(") ");

    _emitMemoryQualifierDecorations(varDecl);

    /*
    If the output type is a buffer, and we can determine it is only readonly we can prefix before
    buffer with 'readonly'

    HLSLByteAddressBufferType                   - This is unambiguously read only
    HLSLRWByteAddressBufferType                 - Read write
    HLSLRasterizerOrderedByteAddressBufferType  - Allows read/write access
    */

    if (as<IRHLSLByteAddressBufferType>(bufferType))
    {
        m_writer->emit("readonly ");
    }

    m_writer->emit("buffer ");
}

void GLSLSourceEmitter::_emitGLSLByteAddressBuffer(IRGlobalParam* varDecl, IRByteAddressBufferTypeBase* byteAddressBufferType)
{
    emitSSBOHeader(varDecl, byteAddressBufferType);

    // Generate a dummy name for the block
    m_writer->emit("_S");
    m_writer->emit(m_uniqueIDCounter++);
    m_writer->emit("\n{\n");
    m_writer->indent();

    m_writer->emit("uint _data[];\n");

    m_writer->dedent();
    m_writer->emit("} ");

    m_writer->emit(getName(varDecl));
    emitArrayBrackets(varDecl->getDataType());

    m_writer->emit(";\n");
}

void GLSLSourceEmitter::_emitGLSLSSBO(IRGlobalParam* varDecl, IRGLSLShaderStorageBufferType* ssboType)
{
    emitSSBOHeader(varDecl, ssboType);

    const auto structType = cast<IRStructType>(ssboType->getOperand(0));
    m_writer->emit(getName(structType));
    m_writer->emit("_Block");
    emitStructDeclarationsBlock(structType, true);

    m_writer->emit(getName(varDecl));
    emitArrayBrackets(varDecl->getDataType());

    m_writer->emit(";\n");
}

void GLSLSourceEmitter::_emitGLSLParameterGroup(IRGlobalParam* varDecl, IRUniformParameterGroupType* type)
{
    auto varLayout = getVarLayout(varDecl);
    SLANG_RELEASE_ASSERT(varLayout);

    EmitVarChain blockChain(varLayout);

    EmitVarChain containerChain = blockChain;
    EmitVarChain elementChain = blockChain;

    auto typeLayout = varLayout->getTypeLayout()->unwrapArray();
    if (auto parameterGroupTypeLayout = as<IRParameterGroupTypeLayout>(typeLayout))
    {
        containerChain = EmitVarChain(parameterGroupTypeLayout->getContainerVarLayout(), &blockChain);
        elementChain = EmitVarChain(parameterGroupTypeLayout->getElementVarLayout(), &blockChain);

        typeLayout = parameterGroupTypeLayout->getElementVarLayout()->getTypeLayout();
    }

    /*
    With resources backed by 'buffer' on glsl, we want to output 'readonly' if that is a good match
    for the underlying type. If uniform it's implicit it's readonly

    Here this only happens with isShaderRecord which is a 'constant buffer' (ie implicitly readonly)
    or IRGLSLShaderStorageBufferType which is read write.
    */

    {
        const LayoutResourceKindFlags kinds = LayoutResourceKindFlag::ConstantBuffer | LayoutResourceKindFlag::DescriptorTableSlot;
        _emitGLSLLayoutQualifierWithBindingKinds(LayoutResourceKind::DescriptorTableSlot, &containerChain, kinds);
    }

    _emitGLSLLayoutQualifier(LayoutResourceKind::PushConstantBuffer, &containerChain);
    bool isShaderRecord = _emitGLSLLayoutQualifier(LayoutResourceKind::ShaderRecord, &containerChain);

    if (isShaderRecord)
    {
        // TODO: A shader record in vk can be potentially read-write. Currently slang doesn't support write access
        // and readonly buffer generates SPIRV validation error.
        m_writer->emit("buffer ");
    }
    else if (as<IRGLSLShaderStorageBufferType>(type))
    {
        // Is writable
        m_writer->emit("layout(");
        m_writer->emit(getTargetProgram()->getOptionSet().shouldUseScalarLayout() ? "scalar" : "std430");
        m_writer->emit(") buffer ");
    }
    // TODO: what to do with HLSL `tbuffer` style buffers?
    else
    {
        // uniform is implicitly read only
        m_writer->emit("layout(");
        m_writer->emit(getTargetProgram()->getOptionSet().shouldUseScalarLayout() ? "scalar" : "std140");
        m_writer->emit(") uniform ");
    }

    // Generate a dummy name for the block
    m_writer->emit("_S");
    m_writer->emit(m_uniqueIDCounter++);


    auto elementType = type->getElementType();
    auto structType = as<IRStructType>(elementType);
    if (!as<IRGLSLShaderStorageBufferType>(type) && structType)
    {
        // We need to emit the fields of the struct as individual variables
        // in the constant buffer.
        //
        emitStructDeclarationsBlock(structType, true);
    }
    else
    {
        m_writer->emit("\n{\n");
        m_writer->indent();
        emitType(elementType, "_data");
        m_writer->emit(";\n");
        m_writer->dedent();
        m_writer->emit("} ");
    }

    m_writer->emit(getName(varDecl));

    // If the underlying variable was an array (or array of arrays, etc.)
    // we need to emit all those array brackets here.
    emitArrayBrackets(varDecl->getDataType());

    m_writer->emit(";\n");
}

void GLSLSourceEmitter::_emitGLSLImageFormatModifier(IRInst* var, IRTextureType* resourceType)
{
    // If the user specified a format manually, using `[format(...)]`,
    // then we will respect that format and emit a matching `layout` modifier.
    //
    if (auto formatDecoration = var->findDecoration<IRFormatDecoration>())
    {
        auto format = formatDecoration->getFormat();
        if (format == ImageFormat::unknown)
        {
            // If the user explicitly opts out of having a format, then
            // the output shader will require the extension to support
            // load/store from format-less images.
            //
            // TODO: We should have a validation somewhere in the compiler
            // that atomic operations are only allowed on images with
            // explicit formats (and then only on specific formats).
            // This is really an argument that format should be part of
            // the image *type* (with a "base type" for images with
            // unknown format).
            //
            _requireGLSLExtension(UnownedStringSlice::fromLiteral("GL_EXT_shader_image_load_formatted"));
        }
        else
        {
            auto formatInfo = getImageFormatInfo(format);
            if (formatInfo.scalarType == SLANG_SCALAR_TYPE_UINT64 || formatInfo.scalarType == SLANG_SCALAR_TYPE_INT64)
            {
                _requireGLSLExtension(UnownedStringSlice::fromLiteral("GL_EXT_shader_image_int64"));
            }
            // If there is an explicit format specified, then we
            // should emit a `layout` modifier using the GLSL name
            // for the format.
            //
            m_writer->emit("layout(");
            m_writer->emit(getGLSLNameForImageFormat(format));
            m_writer->emit(")\n");
        }

        // No matter what, if an explicit `[format(...)]` was given,
        // then we don't need to emit anything else.
        //
        return;
    }


    // When no explicit format is specified, we need to either
    // emit the image as having an unknown format, or else infer
    // a format from the type.
    //
    // For now our default behavior is to infer (so that unmodified
    // HLSL input is more likely to generate valid SPIR-V that
    // runs anywhere), but we provide a flag to opt into
    // treating images without explicit formats as having
    // unknown format.
    //
    if (getCodeGenContext()->getUseUnknownImageFormatAsDefault())
    {
        _requireGLSLExtension(UnownedStringSlice::fromLiteral("GL_EXT_shader_image_load_formatted"));
        return;
    }

    // At this point we have a resource type like `RWTexture2D<X>`
    // and we want to infer a reasonable format from the element
    // type `X` that was specified.
    //
    // E.g., if `X` is `float` then we can infer a format like `r32f`,
    // and so forth. The catch of course is that it is possible to
    // specify a shader parameter with a type like `RWTexture2D<float4>` but
    // provide an image at runtime with a format like `rgba8`, so
    // this inference is never guaranteed to give perfect results.
    //
    // If users don't like our inferred result, they need to use a
    // `[format(...)]` attribute to manually specify what they want.
    //
    // TODO: We should consider whether we can expand the space of
    // allowed types for `X` in `RWTexture2D<X>` to include special
    // pseudo-types that act just like, e.g., `float4`, but come
    // with attached/implied format information.
    //
    auto elementType = resourceType->getElementType();
    Int vectorWidth = 1;
    if (auto elementVecType = as<IRVectorType>(elementType))
    {
        if (auto intLitVal = as<IRIntLit>(elementVecType->getElementCount()))
        {
            vectorWidth = (Int)intLitVal->getValue();
        }
        else
        {
            vectorWidth = 0;
        }
        elementType = elementVecType->getElementType();
    }
    if (auto elementBasicType = as<IRBasicType>(elementType))
    {
        m_writer->emit("layout(");
        switch (vectorWidth)
        {
            default: m_writer->emit("rgba");  break;

            case 3:
            {
                // TODO: GLSL doesn't support 3-component formats so for now we are going to
                // default to rgba
                //
                // The SPIR-V spec (https://www.khronos.org/registry/spir-v/specs/unified1/SPIRV.pdf)
                // section 3.11 on Image Formats it does not list rgbf32.
                //
                // It seems SPIR-V can support having an image with an unknown-at-compile-time
                // format, so long as the underlying API supports it. Ideally this would mean that we can
                // just drop all these qualifiers when emitting GLSL for Vulkan targets.
                //
                // This raises the question of what to do more long term. For Vulkan hopefully we can just
                // drop the layout. For OpenGL targets it would seem reasonable to have well-defined rules
                // for inferring the format (and just document that 3-component formats map to 4-component formats,
                // but that shouldn't matter because the API wouldn't let the user allocate those 3-component formats anyway),
                // and add an attribute for specifying the format manually if you really want to override our
                // inference (e.g., to specify r11fg11fb10f).

                m_writer->emit("rgba");
                //Emit("rgb");
                break;
            }

            case 2:  m_writer->emit("rg");    break;
            case 1:  m_writer->emit("r");     break;
        }
        switch (elementBasicType->getBaseType())
        {
            default:
            case BaseType::Float:   m_writer->emit("32f");  break;
            case BaseType::Half:    m_writer->emit("16f");  break;
            case BaseType::UInt:    m_writer->emit("32ui"); break;
            case BaseType::Int:     m_writer->emit("32i"); break;
            case BaseType::Int8:    m_writer->emit("8i"); break;
            case BaseType::Int16:   m_writer->emit("16i"); break;
            case BaseType::Int64:   m_writer->emit("64i"); break;
            case BaseType::IntPtr:  m_writer->emit("64i"); break;
            case BaseType::UInt8:   m_writer->emit("8ui"); break;
            case BaseType::UInt16:  m_writer->emit("16ui"); break;
            case BaseType::UInt64:  m_writer->emit("64ui"); break;
            case BaseType::UIntPtr: m_writer->emit("64ui"); break;

                // TODO: Here are formats that are available in GLSL,
                // but that are not handled by the above cases.
                //
                // r11f_g11f_b10f
                //
                // rgba16
                // rgb10_a2
                // rgba8
                // rg16
                // rg8
                // r16
                // r8
                //
                // rgba16_snorm
                // rgba8_snorm
                // rg16_snorm
                // rg8_snorm
                // r16_snorm
                // r8_snorm
                //
                // rgb10_a2ui
        }
        m_writer->emit(")\n");
    }
}

bool GLSLSourceEmitter::_emitGLSLLayoutQualifierWithBindingKinds(LayoutResourceKind kind, EmitVarChain* chain, LayoutResourceKindFlags bindingKinds)
{
    if (!chain)
        return false;

    UInt index, space; 
    auto varLayout = chain->varLayout;

    // If bindingKinds are set, we use that for binding lookup
    if (bindingKinds != 0)
    {
        if (!varLayout->usesResourceFromKinds(bindingKinds))
        {
            return false;
        }

        index = getBindingOffsetForKinds(chain, bindingKinds);
        space = getBindingSpaceForKinds(chain, bindingKinds);
    }
    else
    {
        // Otherwise we just use kind
        if (!varLayout->usesResourceKind(kind))
        {
            return false;
        }
        
        index = getBindingOffset(chain, kind);
        space = getBindingSpace(chain, kind);
    }

    switch (kind)
    {
        case LayoutResourceKind::Uniform:
        {
            // Explicit offsets require a GLSL extension (which
            // is not universally supported, it seems) or a new
            // enough GLSL version (which we don't want to
            // universally require), so for right now we
            // won't actually output explicit offsets for uniform
            // shader parameters.
            //
            // TODO: We should fix this so that we skip any
            // extra work for parameters that are laid out as
            // expected by the default rules, but do *something*
            // for parameters that need non-default layout.
            //
            // Using the `GL_ARB_enhanced_layouts` feature is one
            // option, but we should also be able to do some
            // things by introducing padding into the declaration
            // (padding insertion would probably be best done at
            // the IR level).
            bool useExplicitOffsets = false;
            if (useExplicitOffsets)
            {
                _requireGLSLExtension(UnownedStringSlice::fromLiteral("GL_ARB_enhanced_layouts"));

                m_writer->emit("layout(offset = ");
                m_writer->emit(index);
                m_writer->emit(")\n");
            }
        }
        break;

        case LayoutResourceKind::VaryingInput:
        case LayoutResourceKind::VaryingOutput:
            m_writer->emit("layout(location = ");
            m_writer->emit(index);
            if (space)
            {
                m_writer->emit(", index = ");
                m_writer->emit(space);
            }
            m_writer->emit(")\n");
            break;

        case LayoutResourceKind::SpecializationConstant:
            m_writer->emit("layout(constant_id = ");
            m_writer->emit(index);
            m_writer->emit(")\n");
            break;

        case LayoutResourceKind::ConstantBuffer:
        case LayoutResourceKind::ShaderResource:
        case LayoutResourceKind::UnorderedAccess:
        case LayoutResourceKind::SamplerState:

        case LayoutResourceKind::DescriptorTableSlot:
            m_writer->emit("layout(binding = ");
            m_writer->emit(index);
            if (space)
            {
                m_writer->emit(", set = ");
                m_writer->emit(space);
            }
            m_writer->emit(")\n");
            break;

        case LayoutResourceKind::PushConstantBuffer:
            m_writer->emit("layout(push_constant)\n");
            break;
        case LayoutResourceKind::ShaderRecord:
            m_writer->emit("layout(shaderRecordEXT)\n");
            break;

        case LayoutResourceKind::InputAttachmentIndex:
            m_writer->emit("layout(input_attachment_index = ");
            m_writer->emit(index);
            m_writer->emit(")\n");
            break;
    }
    return true;
}

void GLSLSourceEmitter::_emitGLSLLayoutQualifiers(IRVarLayout* layout, EmitVarChain* inChain, LayoutResourceKind filter)
{
    if (!layout) return;

    switch (getSourceLanguage())
    {
        default:
            return;

        case SourceLanguage::GLSL:
            break;
    }

    EmitVarChain chain(layout, inChain);

    for (auto info : layout->getOffsetAttrs())
    {
        // Skip info that doesn't match our filter
        if (filter != LayoutResourceKind::None
            && filter != info->getResourceKind())
        {
            continue;
        }

        _emitGLSLLayoutQualifier(info->getResourceKind(), &chain);
    }
}

void GLSLSourceEmitter::_emitGLSLSubpassInputType(IRSubpassInputType* type)
{
    _emitGLSLTypePrefix(type->getElementType(), true);
    m_writer->emit("subpassInput");
    if (type->isMultisample())
    {
        m_writer->emit("MS");
    }
}

void GLSLSourceEmitter::_emitGLSLTextureOrTextureSamplerType(IRTextureTypeBase*  type, char const* baseName)
{
    if (type->getElementType()->getOp() == kIROp_HalfType)
    {
        // Texture access is always as float types if half is specified

    }
    else
    {
        _emitGLSLTypePrefix(type->getElementType(), true);
    }

    m_writer->emit(baseName);
    switch (type->GetBaseShape())
    {
        case SLANG_TEXTURE_1D:		m_writer->emit("1D");		break;
        case SLANG_TEXTURE_2D:		m_writer->emit("2D");		break;
        case SLANG_TEXTURE_3D:		m_writer->emit("3D");		break;
        case SLANG_TEXTURE_CUBE:	m_writer->emit("Cube");	    break;
        case SLANG_TEXTURE_BUFFER:	m_writer->emit("Buffer");	break;
        default:
            SLANG_DIAGNOSE_UNEXPECTED(getSink(), SourceLoc(), "unhandled resource shape");
            break;
    }

    if (type->isMultisample())
    {
        m_writer->emit("MS");
    }
    if (type->isArray())
    {
        m_writer->emit("Array");
    }
    if (type->isShadow())
    {
        m_writer->emit("Shadow");
    }
}

void GLSLSourceEmitter::_emitGLSLTypePrefix(IRType* type, bool promoteHalfToFloat)
{
    type = dropNormAttributes(type);

    switch (type->getOp())
    {
        case kIROp_FloatType:
            // no prefix
            break;

        case kIROp_Int8Type:    m_writer->emit("i8");     break;
        case kIROp_Int16Type:   m_writer->emit("i16");    break;
        case kIROp_IntType:     m_writer->emit("i");      break;
        case kIROp_Int64Type:
        {
            _requireBaseType(BaseType::Int64);
            m_writer->emit("i64");
            break;
        }
        case kIROp_IntPtrType:   
        {
#if SLANG_PTR_IS_64
            _requireBaseType(BaseType::Int64);
            m_writer->emit("i64");
#else
            m_writer->emit("i");
#endif
            break;
        }

        case kIROp_UInt8Type:   m_writer->emit("u8");     break;
        case kIROp_UInt16Type:  m_writer->emit("u16");    break;
        case kIROp_UIntType:    m_writer->emit("u");      break;

        case kIROp_UInt64Type:
        {
            _requireBaseType(BaseType::UInt64);
            m_writer->emit("u64");
            break;
        }
        case kIROp_UIntPtrType:
        {
#if SLANG_PTR_IS_64
            _requireBaseType(BaseType::Int64);
            m_writer->emit("u64");
#else
            m_writer->emit("u");
#endif
            break;
        }
        case kIROp_BoolType:    m_writer->emit("b");		break;

        case kIROp_HalfType:
        {
            _requireBaseType(BaseType::Half);
            if (promoteHalfToFloat)
            {
                // no prefix
            }
            else
            {
                m_writer->emit("f16");
            }
            break;
        }
        case kIROp_DoubleType:  m_writer->emit("d");		break;

        case kIROp_VectorType:
            _emitGLSLTypePrefix(cast<IRVectorType>(type)->getElementType(), promoteHalfToFloat);
            break;

        case kIROp_MatrixType:
            _emitGLSLTypePrefix(cast<IRMatrixType>(type)->getElementType(), promoteHalfToFloat);
            break;

        default:
            SLANG_DIAGNOSE_UNEXPECTED(getSink(), SourceLoc(), "unhandled GLSL type prefix");
            break;
    }
}

void GLSLSourceEmitter::_maybeEmitGLSLBuiltin(IRGlobalParam* var, UnownedStringSlice name)
{
    // It's important for us to redeclare these mesh output builtins with an
    // explicit array size to allow indexing into them with a variable
    // according to the rules of GLSL.
    if(name == "gl_MeshPrimitivesEXT" || name == "gl_MeshVerticesEXT")
    {
        // GLSL doesn't allow us to specify the struct outside the block
        // declaration, so we snoop the underlying struct type here and emit
        // that inline.

        auto paramGroupType = as<IRGLSLOutputParameterGroupType>(var->getFullType());
        SLANG_ASSERT(paramGroupType && "Mesh shader builtin output was not a parameter group");
        auto arrayType = as<IRArrayTypeBase>(paramGroupType->getOperand(0));
        SLANG_ASSERT(paramGroupType && "Mesh shader builtin output was not an array");
        auto elementType = as<IRStructType>(arrayType->getElementType());
        SLANG_ASSERT(paramGroupType && "Mesh shader builtin output was not an array of structs");
        auto elementTypeNameOp = composeGetters<IRStringLit>(
            elementType,
            &IRInst::findDecoration<IRTargetIntrinsicDecoration>,
            &IRTargetIntrinsicDecoration::getDefinitionOperand);
        SLANG_ASSERT(elementTypeNameOp && "Mesh shader builtin output element type wasn't named");
        auto elementTypeName = elementTypeNameOp->getStringSlice();

        // // It would be nice to use emitVarModifiers here, however with
        // // LRK::BuiltinVaryingOutput this is going to add an illegal location
        // // layout qualifier.
        // auto layout = getVarLayout(var);
        // SLANG_ASSERT(layout && "Mesh shader builtin output has no layout");
        // SLANG_ASSERT(layout->usesResourceKind(LayoutResourceKind::VaryingOutput));
        // emitVarModifiers(layout, var, arrayType);
        emitMeshShaderModifiers(var);
        m_writer->emit("out");
        m_writer->emit(" ");
        m_writer->emit(elementTypeName);
        emitStructDeclarationsBlock(elementType, false);
        m_writer->emit(" ");
        m_writer->emit(name);
        emitArrayBrackets(arrayType);
        m_writer->emit(";\n\n");
    }
    else if(name == "gl_PrimitivePointIndicesEXT"
            || name == "gl_PrimitiveLineIndicesEXT"
            || name == "gl_PrimitiveTriangleIndicesEXT")
    {
        // GLSL has some specific requirements about how these are declared,
        // Do it manually here to avoid `emitGlobalParam` emitting
        // decorations/layout we are not allowed to output.
        auto varType = composeGetters<IRType>(
                var,
                &IRGlobalParam::getDataType,
                &IROutTypeBase::getValueType);
        SLANG_ASSERT(varType && "Indices mesh output dind't have an 'out' type");

        m_writer->emit("out ");
        emitType(varType, getName(var));
        m_writer->emit(";\n\n");
    }
    else if (name == "gl_ClipDistance")
    {
        // Is this an output? We do not need to define input.
        auto varType = var->getDataType();
        if (auto outType = as<IROutType>(varType))
        {
            varType = outType->getValueType();
            m_writer->emit("out ");
            emitType(varType, getName(var));
            m_writer->emit(";\n\n");
        }
    }
    else if (name == "gl_ShadingRateEXT")
    {
        _requireGLSLExtension(toSlice("GL_EXT_fragment_shading_rate"));
    }
    else if (name == "gl_PrimitiveShadingRateEXT")
    {
        _requireGLSLExtension(toSlice("GL_EXT_fragment_shading_rate_primitive"));
    }
}

void GLSLSourceEmitter::_requireBaseType(BaseType baseType)
{
    m_glslExtensionTracker->requireBaseTypeExtension(baseType);
}

void GLSLSourceEmitter::_maybeEmitGLSLFlatModifier(IRType* valueType)
{
    auto tt = valueType;
    if (auto vecType = as<IRVectorType>(tt))
        tt = vecType->getElementType();
    if (auto vecType = as<IRMatrixType>(tt))
        tt = vecType->getElementType();

    switch (tt->getOp())
    {
        default:
            break;

        case kIROp_IntType:
        case kIROp_UIntType:
        case kIROp_UInt64Type:
            m_writer->emit("flat ");
            break;
    }
}

void GLSLSourceEmitter::emitLoopControlDecorationImpl(IRLoopControlDecoration* decl)
{
    if (decl->getMode() == kIRLoopControl_Unroll)
    {
        // https://github.com/KhronosGroup/GLSL/blob/master/extensions/ext/GL_EXT_control_flow_attributes.txt
        m_glslExtensionTracker->requireExtension(UnownedStringSlice::fromLiteral("GL_EXT_control_flow_attributes"));
        m_writer->emit("[[unroll]]\n");
    }
    else if (decl->getMode() == kIRLoopControl_Loop)
    {
        m_glslExtensionTracker->requireExtension(UnownedStringSlice::fromLiteral("GL_EXT_control_flow_attributes"));
        m_writer->emit("[[dont_unroll]]\n");
    }
}

void GLSLSourceEmitter::_emitSpecialFloatImpl(IRType* type, const char* valueExpr)
{
    if( type->getOp() != kIROp_FloatType )
    {
        emitType(type);
    }
    m_writer->emit("(");
    m_writer->emit(valueExpr);
    m_writer->emit(")");
}

void GLSLSourceEmitter::emitSimpleValueImpl(IRInst* inst)
{
    switch (inst->getOp())
    {
        case kIROp_IntLit:
        {
            auto litInst = static_cast<IRConstant*>(inst);

            IRBasicType* type = as<IRBasicType>(inst->getDataType());
            if (type)
            {
                switch (type->getBaseType())
                {
                    default:

                    case BaseType::Int8:
                    {
                        emitType(type);
                        m_writer->emit("(");
                        m_writer->emit(int8_t(litInst->value.intVal));
                        m_writer->emit(")");
                        return;
                    }
                    case BaseType::Int16:
                    {
                        m_writer->emit(int16_t(litInst->value.intVal));
                        m_writer->emit("S");
                        return;
                    }
                    case BaseType::Int:
                    {
                        m_writer->emit(int32_t(litInst->value.intVal));
                        return;
                    }
                    case BaseType::UInt8:
                    {
                        emitType(type);
                        m_writer->emit("(");
                        m_writer->emit(UInt(uint8_t(litInst->value.intVal)));
                        m_writer->emit("U)");
                        return;
                    }
                    case BaseType::UInt16:
                    {
                        m_writer->emit(UInt(uint16_t(litInst->value.intVal)));
                        m_writer->emit("US");
                        return;
                    }
                    case BaseType::UInt:
                    {
                        m_writer->emit(UInt(uint32_t(litInst->value.intVal)));
                        m_writer->emit("U");
                        return;
                    }
                    case BaseType::IntPtr:
                    case BaseType::Int64:
                    {
                        m_writer->emitInt64(int64_t(litInst->value.intVal));
                        m_writer->emit("L");
                        return;
                    }
                    case BaseType::UIntPtr:
                    case BaseType::UInt64:
                    {
                        SLANG_COMPILE_TIME_ASSERT(sizeof(litInst->value.intVal) >= sizeof(uint64_t));
                        m_writer->emitUInt64(uint64_t(litInst->value.intVal));
                        m_writer->emit("UL");
                        return;
                    }

                }
            }
            break;
        }
        case kIROp_FloatLit:
        {
            IRConstant* constantInst = static_cast<IRConstant*>(inst);

            auto type = constantInst->getDataType();
            IRConstant::FloatKind kind = constantInst->getFloatKind();

            switch (kind)
            {
                case IRConstant::FloatKind::Nan:
                {
                    _emitSpecialFloatImpl(type, "0.0 / 0.0");
                    return;
                }
                case IRConstant::FloatKind::PositiveInfinity:
                {
                    _emitSpecialFloatImpl(type, "1.0 / 0.0");
                    return;
                }
                case IRConstant::FloatKind::NegativeInfinity:
                {
                    _emitSpecialFloatImpl(type, "-1.0 / 0.0");
                    return;
                }
                default:
                {
                    m_writer->emit(((IRConstant*) inst)->value.floatVal);
                    switch( type->getOp() )
                    {
                    case kIROp_HalfType:
                        m_writer->emit("HF");
                        break;
                    case kIROp_DoubleType:
                        m_writer->emit("LF");
                        break;
                    default:
                        break;
                    }

                    return;
                }
            }
            break;
        }

        default: break;
    }

    Super::emitSimpleValueImpl(inst);
}


void GLSLSourceEmitter::emitParameterGroupImpl(IRGlobalParam* varDecl, IRUniformParameterGroupType* type)
{
    _emitGLSLParameterGroup(varDecl, type);
}

void GLSLSourceEmitter::emitEntryPointAttributesImpl(IRFunc* irFunc, IREntryPointDecoration* entryPointDecor)
{
    SLANG_ASSERT(entryPointDecor);

    auto profile = entryPointDecor->getProfile();
    auto stage = profile.getStage();

    auto emitLocalSizeLayout = [&]()
      {
          Int sizeAlongAxis[kThreadGroupAxisCount];
          getComputeThreadGroupSize(irFunc, sizeAlongAxis);

          m_writer->emit("layout(");
          char const* axes[] = { "x", "y", "z" };
          for (int ii = 0; ii < kThreadGroupAxisCount; ++ii)
          {
              if (ii != 0) m_writer->emit(", ");
              m_writer->emit("local_size_");
              m_writer->emit(axes[ii]);
              m_writer->emit(" = ");
              m_writer->emit(sizeAlongAxis[ii]);
          }
          m_writer->emit(") in;\n");
      };

    switch (stage)
    {
        case Stage::Compute:
        {
            emitLocalSizeLayout();
        }
        break;
        case Stage::Geometry:
        {
            if (auto decor = irFunc->findDecoration<IRMaxVertexCountDecoration>())
            {
                auto count = getIntVal(decor->getCount());
                m_writer->emit("layout(max_vertices = ");
                m_writer->emit(Int(count));
                m_writer->emit(") out;\n");
            }

            if (auto decor = irFunc->findDecoration<IRInstanceDecoration>())
            {
                auto count = getIntVal(decor->getCount());
                m_writer->emit("layout(invocations = ");
                m_writer->emit(Int(count));
                m_writer->emit(") in;\n");
            }

            // These decorations were moved from the parameters to the entry point by ir-glsl-legalize.
            // The actual parameters have become potentially multiple global parameters.
            if (auto decor = irFunc->findDecoration<IRGeometryInputPrimitiveTypeDecoration>())
            {
                switch (decor->getOp())
                {
                    case kIROp_TriangleInputPrimitiveTypeDecoration:       m_writer->emit("layout(triangles) in;\n"); break;
                    case kIROp_LineInputPrimitiveTypeDecoration:           m_writer->emit("layout(lines) in;\n"); break;
                    case kIROp_LineAdjInputPrimitiveTypeDecoration:        m_writer->emit("layout(lines_adjacency) in;\n"); break;
                    case kIROp_PointInputPrimitiveTypeDecoration:          m_writer->emit("layout(points) in;\n"); break;
                    case kIROp_TriangleAdjInputPrimitiveTypeDecoration:    m_writer->emit("layout(triangles_adjacency) in;\n"); break;
                    default:
                    {
                        SLANG_ASSERT(!"Unknown primitive type");
                    }
                }
            }

            if (auto decor = irFunc->findDecoration<IRStreamOutputTypeDecoration>())
            {
                IRType* type = decor->getStreamType();

                switch (type->getOp())
                {
                    case kIROp_HLSLPointStreamType:     m_writer->emit("layout(points) out;\n"); break;
                    case kIROp_HLSLLineStreamType:      m_writer->emit("layout(line_strip) out;\n"); break;
                    case kIROp_HLSLTriangleStreamType:  m_writer->emit("layout(triangle_strip) out;\n"); break;
                    default: SLANG_ASSERT(!"Unknown stream out type");
                }
            }
        }
        break;
        case Stage::Pixel:
        {
            if (irFunc->findDecoration<IREarlyDepthStencilDecoration>())
            {
                // https://www.khronos.org/opengl/wiki/Early_Fragment_Test
                m_writer->emit("layout(early_fragment_tests) in;\n");
            }
            break;
        }
        case Stage::Mesh:
        {
            emitLocalSizeLayout();
            if (auto decor = irFunc->findDecoration<IRVerticesDecoration>())
            {
                m_writer->emit("layout(max_vertices = ");
                m_writer->emit(decor->getMaxSize()->getValue());
                m_writer->emit(") out;\n");
            }
            if (auto decor = irFunc->findDecoration<IRPrimitivesDecoration>())
            {
                m_writer->emit("layout(max_primitives = ");
                m_writer->emit(decor->getMaxSize()->getValue());
                m_writer->emit(") out;\n");
            }
            if (auto decor = irFunc->findDecoration<IROutputTopologyDecoration>())
            {
                // TODO: Ellie validate here/elsewhere, what's allowed here is
                // different from the tesselator
                // The naming here is plural, so add an 's'
                m_writer->emit("layout(");
                m_writer->emit(decor->getTopology()->getStringSlice());
                m_writer->emit("s) out;\n");
            }
        }
        break;
        case Stage::Amplification:
        {
            emitLocalSizeLayout();
        }
        break;
        // TODO: There are other stages that will need this kind of handling.
        default:
            break;
    }
}

void GLSLSourceEmitter::_emitGLSLPerVertexVaryingFragmentInput(IRGlobalParam* param, IRType* type)
{
    // Note: The logic here is almost identical to the default
    // emit logic for global shader parameters. The main difference
    // is that we emit a parameter of type `X` as an array of
    // type `X[3]` to account for the per-vertex-ness of the
    // parameter.
    //

        // Need to emit appropriate modifiers here.

    // We expect/require all shader parameters to
    // have some kind of layout information associated with them.
    //
    auto layout = getVarLayout(param);
    SLANG_ASSERT(layout);

    emitVarModifiers(layout, param, type);

    emitRateQualifiersAndAddressSpace(param);

    auto name = getName(param);
    StringSliceLoc nameAndLoc(name.getUnownedSlice());
    NameDeclaratorInfo nameDeclarator(&nameAndLoc);

    LiteralSizedArrayDeclaratorInfo arrayDeclarator(&nameDeclarator, 3);

    // Note: We are invoking `_emitType` here directly because there
    // is no overload of `emitType` that works with a declarator.
    //
    _emitType(type, &arrayDeclarator);

    emitSemantics(param, false);

    emitLayoutSemantics(param, "register");

    m_writer->emit(";\n\n");
}

bool GLSLSourceEmitter::tryEmitGlobalParamImpl(IRGlobalParam* varDecl, IRType* varType)
{
    // There are a number of types that are (or can be)
        // "first-class" in D3D HLSL, but are second-class in GLSL in
        // that they require explicit global declarations for each value/object,
        // and don't support declaration as ordinary variables.
        //
        // This includes constant buffers (`uniform` blocks) and well as
        // structured and byte-address buffers (both mapping to `buffer` blocks).
        //
        // We intercept these types, and arrays thereof, to produce the required
        // global declarations. This assumes that earlier "legalization" passes
        // already performed the work of pulling fields with these types out of
        // aggregates.
        //
        // Note: this also assumes that these types are not used as function
        // parameters/results, local variables, etc. Additional legalization
        // steps are required to guarantee these conditions.
        //
    if (auto paramBlockType = as<IRUniformParameterGroupType>(unwrapArray(varType)))
    {
        _emitGLSLParameterGroup(varDecl, paramBlockType);
        return true;
    }
    if (auto structuredBufferType = as<IRHLSLStructuredBufferTypeBase>(unwrapArray(varType)))
    {
        _emitGLSLStructuredBuffer(varDecl, structuredBufferType);
        return true;
    }
    if (auto byteAddressBufferType = as<IRByteAddressBufferTypeBase>(unwrapArray(varType)))
    {
        _emitGLSLByteAddressBuffer(varDecl, byteAddressBufferType);
        return true;
    }
    else if (const auto glslSSBOType = as<IRGLSLShaderStorageBufferType>(unwrapArray(varType)))
    {
        _emitGLSLSSBO(varDecl, glslSSBOType);
        return true;
    }

    // We want to skip the declaration of any system-value variables
    // when outputting GLSL (well, except in the case where they
    // actually *require* redeclaration...).
    //
    // Note: these won't be variables the user declare explicitly
    // in their code, but rather variables that we generated as
    // part of legalizing the varying input/output signature of
    // an entry point for GL/Vulkan.
    //
    // TODO: This could be handled more robustly by attaching an
    // appropriate decoration to these variables to indicate their
    // purpose.
    //
    if (auto linkageDecoration = varDecl->findDecoration<IRLinkageDecoration>())
    {
        auto name = linkageDecoration->getMangledName();
        if (name.startsWith("gl_"))
        {
            _maybeEmitGLSLBuiltin(varDecl, name);
            return true;
        }
    }

    // When emitting unbounded-size resource arrays with GLSL we need
    // to use the `GL_EXT_nonuniform_qualifier` extension to ensure
    // that they are not treated as "implicitly-sized arrays" which
    // are arrays that have a fixed size that just isn't specified
    // at the declaration site (instead being inferred from use sites).
    //
    // While the extension primarily introduces the `nonuniformEXT`
    // qualifier that we use to implement `NonUniformResourceIndex`,
    // it also changes the GLSL language semantics around (resource) array
    // declarations that don't specify a size.
    //
    if (as<IRUnsizedArrayType>(varType))
    {
        if (isResourceType(unwrapArray(varType)))
        {
            _requireGLSLExtension(UnownedStringSlice::fromLiteral("GL_EXT_nonuniform_qualifier"));
        }
    }

    // A varying fragment input parameter with the `pervertex` modifier
    // needs to be emitted as an array.
    //
    if( auto interpolationModeDecor = varDecl->findDecoration<IRInterpolationModeDecoration>() )
    {
        if( interpolationModeDecor->getMode() == IRInterpolationMode::PerVertex )
        {
            if( m_entryPointStage == Stage::Fragment )
            {
                _emitGLSLPerVertexVaryingFragmentInput(varDecl, varType);
                return true;
            }
        }
    }

    // Do the default thing
    return false;
}

void GLSLSourceEmitter::emitImageFormatModifierImpl(IRInst* varDecl, IRType* varType)
{
    // As a special case, if we are emitting a GLSL declaration
    // for an HLSL `RWTexture*` then we need to emit a `format` layout qualifier.

    if(auto resourceType = as<IRTextureType>(unwrapArray(varType)))
    {
        switch (resourceType->getAccess())
        {
            case SLANG_RESOURCE_ACCESS_READ_WRITE:
            case SLANG_RESOURCE_ACCESS_RASTER_ORDERED:
            {
                _emitGLSLImageFormatModifier(varDecl, resourceType);
            }
            break;

            default:
                break;
        }
    }
}

void GLSLSourceEmitter::emitLayoutQualifiersImpl(IRVarLayout* layout)
{
    // Layout-related modifiers need to come before the declaration,
    // so deal with them here.
    _emitGLSLLayoutQualifiers(layout, nullptr);

    // try to emit an appropriate leading qualifier
    for (auto rr : layout->getOffsetAttrs())
    {
        switch (rr->getResourceKind())
        {
            // These can occur for vk-shift-* scenarios, and are in effect equivalent to DescriptorTableSlot
            case LayoutResourceKind::ShaderResource:
            case LayoutResourceKind::ConstantBuffer:
            case LayoutResourceKind::SamplerState:
            case LayoutResourceKind::UnorderedAccess:

            // 
            case LayoutResourceKind::Uniform:

            //
            case LayoutResourceKind::DescriptorTableSlot:
                m_writer->emit("uniform ");
                break;

            case LayoutResourceKind::VaryingInput:
            {
                m_writer->emit("in ");
            }
            break;

            case LayoutResourceKind::VaryingOutput:
            {
                m_writer->emit("out ");
            }
            break;

            case LayoutResourceKind::RayPayload:
            {
                m_writer->emit("rayPayloadInEXT ");
            }
            break;

            case LayoutResourceKind::CallablePayload:
            {
                m_writer->emit("callableDataInEXT ");
            }
            break;

            case LayoutResourceKind::HitAttributes:
            {
                m_writer->emit("hitAttributeEXT ");
            }
            break;

            default:
                continue;
        }

        break;
    }
}

static const char* _getGLSLVectorCompareFunctionName(IROp op)
{
    // Glsl vector comparisons use functions...
    // https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/equal.xhtml

    switch (op)
    {
        case kIROp_Eql:     return "equal";
        case kIROp_Neq:     return "notEqual";
        case kIROp_Greater: return "greaterThan";
        case kIROp_Less:    return "lessThan";
        case kIROp_Geq:     return "greaterThanEqual";
        case kIROp_Leq:     return "lessThanEqual";
        default:    return nullptr;
    }
}

void GLSLSourceEmitter::_maybeEmitGLSLCast(IRType* castType, IRInst* inst)
{
    // Wrap in cast if a cast type is specified
    if (castType)
    {
        emitType(castType);
        m_writer->emit("(");

        // Emit the operand
        emitOperand(inst, getInfo(EmitOp::General));

        m_writer->emit(")");
    }
    else
    {
        // Emit the operand
        emitOperand(inst, getInfo(EmitOp::General));
    }
}

void GLSLSourceEmitter::_emitLegalizedBoolVectorBinOp(IRInst* inst, IRVectorType* type, const EmitOpInfo& op, const EmitOpInfo& inOuterPrec)
{
    auto elementCount = type->getElementCount();

    EmitOpInfo outerPrec = inOuterPrec;
    auto prec = getInfo(EmitOp::Postfix);
    bool needClose = maybeEmitParens(outerPrec, prec);

    emitType(type);
    m_writer->emit("(uvec");
    emitSimpleValue(elementCount);
    m_writer->emit("(");
    emitOperand(inst->getOperand(0), getInfo(EmitOp::General));
    m_writer->emit(")");
    m_writer->emit(op.op);
    m_writer->emit("uvec");
    emitSimpleValue(elementCount);
    m_writer->emit("(");
    emitOperand(inst->getOperand(1), getInfo(EmitOp::General));
    m_writer->emit("))");

    maybeCloseParens(needClose);
}

bool GLSLSourceEmitter::_tryEmitLogicalBinOp(IRInst* inst, const EmitOpInfo& bitOp, const EmitOpInfo& inOuterPrec)
{
    // Logical operation on scalar `bool` values are directly
    // supported by GLSL. They have short-circuiting behavior,
    // but we need not worry about that because our logic
    // for folding sub-expressions into their use sites will
    // never fold a sub-expression that would have side effects.
    //
    // Thus we fall back to the default handling for scalar
    // cases (which should only arise for `bool` operands).
    //
    IRType* type = inst->getDataType();
    auto vectorType = as<IRVectorType>(type);
    if(!vectorType)
        return false;

    // For vector cases, we need to convert the operands to
    // a type that supports vector operations, and then use
    // bit operations there.
    //
    _emitLegalizedBoolVectorBinOp(inst, vectorType, bitOp, inOuterPrec);
    return true;
}

bool GLSLSourceEmitter::_tryEmitBitBinOp(IRInst* inst, const EmitOpInfo& bitOp, const EmitOpInfo& boolOp, const EmitOpInfo& inOuterPrec)
{
    // The bitwise binary operations are supported in GLSL,
    // but do not support `bool` or vector-of-`bool` operands.
    //
    // We start by checking if we have a `bool`-based case,
    // and fall back to the default emit logic if not.
    //
    IRType* type = inst->getDataType();
    IRType* elementType = type;
    auto vectorType = as<IRVectorType>(type);
    if(vectorType)
        elementType = vectorType->getElementType();
    if(!as<IRBoolType>(elementType))
        return false;

    // If we have a vector case, then it will be handled
    // by casting the `bool` vectors to vectors of
    // integers and doing the bitwise op there, where
    // it should yield an equivalent result.
    //
    if(vectorType)
    {
        _emitLegalizedBoolVectorBinOp(inst, vectorType, bitOp, inOuterPrec);
    }
    else
    {
        // In the scalar case, we will translate
        // bitwise operations on `bool` values to
        // the equivalent logical operation, knowing
        // that our appraoch to folding of sub-expressions
        // into use sites will avoid any potential issues
        // around short-circuiting behavior.
        //
        auto prec = boolOp;
        EmitOpInfo outerPrec = inOuterPrec;
        bool needClose = maybeEmitParens(outerPrec, prec);

        emitOperand(inst->getOperand(0), leftSide(outerPrec, prec));
        m_writer->emit(prec.op);
        emitOperand(inst->getOperand(1), rightSide(outerPrec, prec));

        maybeCloseParens(needClose);
    }
    return true;

}

void GLSLSourceEmitter::emitBufferPointerTypeDefinition(IRInst* ptrType)
{
    _requireGLSLExtension(UnownedStringSlice("GL_EXT_buffer_reference"));

    auto constPtrType = as<IRHLSLConstBufferPointerType>(ptrType);
    auto ptrTypeName = getName(ptrType);
    auto alignment = getIntVal(constPtrType->getBaseAlignment());
    m_writer->emit("layout(buffer_reference, std430, buffer_reference_align = ");
    m_writer->emitInt64(alignment);
    m_writer->emit(") readonly buffer ");
    m_writer->emit(ptrTypeName);
    m_writer->emit("\n");
    m_writer->emit("{\n");
    m_writer->indent();
    emitType((IRType*)constPtrType->getValueType(), "_data");
    m_writer->emit(";\n");
    m_writer->dedent();
    m_writer->emit("};\n");
}

// Is this type only used by SSBO declarations, if so then we don't need to
// emit it and it'll be emitted inline there.
static bool isSSBOInternalStructType(IRInst* inst)
{
    if(!as<IRStructType>(inst))
        return false;

    bool onlySSBOUses = true;
    for(auto use = inst->firstUse; use; use = use->nextUse)
    {
        if(!as<IRGLSLShaderStorageBufferType>(use->user))
        {
            onlySSBOUses = false;
            break;
        }
    }
    return onlySSBOUses;
}

void GLSLSourceEmitter::emitGlobalInstImpl(IRInst* inst)
{
    switch (inst->getOp())
    {
    case kIROp_HLSLConstBufferPointerType:
        emitBufferPointerTypeDefinition(inst);
        break;
    // No need to use structs which are just taking part in a SSBO declaration
    case kIROp_StructType:
        if(isSSBOInternalStructType(inst))
            break;
        [[fallthrough]];
    default:
        Super::emitGlobalInstImpl(inst);
        break;
    }
}

bool GLSLSourceEmitter::tryEmitInstExprImpl(IRInst* inst, const EmitOpInfo& inOuterPrec)
{
    switch (inst->getOp())
    {
        case kIROp_MakeVectorFromScalar:
        case kIROp_MatrixReshape:
        {
            // Simple constructor call
            EmitOpInfo outerPrec = inOuterPrec;
            bool needClose = false;

            auto prec = getInfo(EmitOp::Postfix);
            needClose = maybeEmitParens(outerPrec, prec);

            emitType(inst->getDataType());
            m_writer->emit("(");
            emitOperand(inst->getOperand(0), getInfo(EmitOp::General));
            m_writer->emit(")");

            maybeCloseParens(needClose);
            // Handled
            return true;
        }
        case kIROp_Mul:
        {
            // Component-wise multiplication needs to be special cased,
            // because GLSL uses infix `*` to express inner product
            // when working with matrices.

            // Are we targetting GLSL, and are both operands matrices?
            if (as<IRMatrixType>(inst->getOperand(0)->getDataType())
                && as<IRMatrixType>(inst->getOperand(1)->getDataType()))
            {
                m_writer->emit("matrixCompMult(");
                emitOperand(inst->getOperand(0), getInfo(EmitOp::General));
                m_writer->emit(", ");
                emitOperand(inst->getOperand(1), getInfo(EmitOp::General));
                m_writer->emit(")");
                return true;
            }
            break;
        }
        case kIROp_Select:
        {
            if (inst->getOperand(0)->getDataType()->getOp() != kIROp_BoolType)
            {
                // For GLSL, emit a call to `mix` if condition is a vector
                m_writer->emit("mix(");
                emitOperand(inst->getOperand(2), leftSide(getInfo(EmitOp::General), getInfo(EmitOp::General)));
                m_writer->emit(", ");
                emitOperand(inst->getOperand(1), leftSide(getInfo(EmitOp::General), getInfo(EmitOp::General)));
                m_writer->emit(", ");
                emitOperand(inst->getOperand(0), leftSide(getInfo(EmitOp::General), getInfo(EmitOp::General)));
                m_writer->emit(")");
                return true;
            }
            break;
        }
        case kIROp_BitCast:
        {
            auto toType = extractBaseType(inst->getDataType());
            auto fromType = extractBaseType(inst->getOperand(0)->getDataType());
            switch (toType)
            {
                default:
                    diagnoseUnhandledInst(inst);
                    break;

                case BaseType::UInt:
                    if (fromType == BaseType::Float)
                    {
                        m_writer->emit("floatBitsToUint");
                    }
                    else
                    {
                        emitType(inst->getDataType());
                    }
                    break;

                case BaseType::Int:
                    if (fromType == BaseType::Float)
                    {
                        m_writer->emit("floatBitsToInt");
                    }
                    else
                    {
                        emitType(inst->getDataType());
                    }
                    break;
                case BaseType::UInt16:
                    if (fromType == BaseType::Half)
                    {
                        m_writer->emit("uint16_t(packHalf2x16(vec2(");
                        emitOperand(inst->getOperand(0), getInfo(EmitOp::General));
                        m_writer->emit(", 0.0)))");
                        return true;
                    }
                    else
                    {
                        emitType(inst->getDataType());
                    }
                    break;
                case BaseType::Int16:
                    if (fromType == BaseType::Half)
                    {
                        m_writer->emit("int16_t(packHalf2x16(vec2(");
                        emitOperand(inst->getOperand(0), getInfo(EmitOp::General));
                        m_writer->emit(", 0.0)))");
                        return true;
                    }
                    else
                    {
                        emitType(inst->getDataType());
                    }
                    break;
                case BaseType::Half:
                    switch (fromType)
                    {
                    case BaseType::Int16:
                    case BaseType::UInt16:
                    case BaseType::Int:
                    case BaseType::UInt:
                        m_writer->emit("float16_t(unpackHalf2x16(uint(");
                        emitOperand(inst->getOperand(0), getInfo(EmitOp::General));
                        m_writer->emit(")).x)");
                        return true;
                    default:
                        emitType(inst->getDataType());
                        break;
                    }
                    break;
                case BaseType::Float:
                    switch (fromType)
                    {
                    case BaseType::Int:
                        m_writer->emit("intBitsToFloat");
                        break;
                    case BaseType::UInt:
                        m_writer->emit("uintBitsToFloat");
                        break;
                    default:
                        emitType(inst->getDataType());
                        break;
                    }
                    break;
                case BaseType::Bool:
                    m_writer->emit("bool");
                    break;
            }

            m_writer->emit("(");
            emitOperand(inst->getOperand(0), getInfo(EmitOp::General));
            m_writer->emit(")");

            return true;
        }
        case kIROp_And:
            return _tryEmitLogicalBinOp(inst, getInfo(EmitOp::BitAnd), inOuterPrec);
        case kIROp_Or:
            return _tryEmitLogicalBinOp(inst, getInfo(EmitOp::BitOr), inOuterPrec);
        case kIROp_Not:
        {
            IRInst* operand = inst->getOperand(0);
            if (const auto vectorType = as<IRVectorType>(operand->getDataType()))
            {
                EmitOpInfo outerPrec = inOuterPrec;
                bool needClose = false;

                // Handle as a function call
                auto prec = getInfo(EmitOp::Postfix);
                needClose = maybeEmitParens(outerPrec, prec);

                m_writer->emit("not(");
                emitOperand(operand, getInfo(EmitOp::General));
                m_writer->emit(")");

                maybeCloseParens(needClose);
                return true;
            }
            return false;
        }

        // When emitting a bitwise operation in GLSL, we need to special-case the handling
        // of `bool` and vectors of `bool` so that they produce valid results by operating
        // on the single-bit truth value.
        //
        // In the case of a vector we will convert to `uint` vectors and perform the
        // bitwise op on them before converting back to `bool` vectors.
        //
        // In the scalar case we will apply the corresponding logical operation to
        // the `bool` operands.
        //
        case kIROp_BitAnd:
            return _tryEmitBitBinOp(inst, getInfo(EmitOp::BitAnd), getInfo(EmitOp::And), inOuterPrec);
        case kIROp_BitOr:
            return _tryEmitBitBinOp(inst, getInfo(EmitOp::BitOr), getInfo(EmitOp::Or), inOuterPrec);
        case kIROp_BitXor:
            // Note: on scalar `bool` operands, a bitwise XOR (`^`) is equivalent to a not-equal (`!=`) comparison.
            return _tryEmitBitBinOp(inst, getInfo(EmitOp::BitXor), getInfo(EmitOp::Neq), inOuterPrec);

        // Comparisons
        case kIROp_Eql:
        case kIROp_Neq:
        case kIROp_Greater:
        case kIROp_Less:
        case kIROp_Geq:
        case kIROp_Leq:
        {
            // If the comparison is between vectors use GLSL vector comparisons
            IRInst* left = inst->getOperand(0);
            IRInst* right = inst->getOperand(1);

            auto leftVectorType = as<IRVectorType>(left->getDataType());
            auto rightVectorType = as<IRVectorType>(right->getDataType());

            // If either side is a vector handle as a vector
            if (leftVectorType || rightVectorType)
            {
                const char* funcName = _getGLSLVectorCompareFunctionName(inst->getOp());
                SLANG_ASSERT(funcName);

                // Determine the vector type
                const auto vecType = leftVectorType ? leftVectorType : rightVectorType;

                // Handle as a function call
                auto prec = getInfo(EmitOp::Postfix);

                EmitOpInfo outerPrec = inOuterPrec;
                bool needClose = maybeEmitParens(outerPrec, prec);

                m_writer->emit(funcName);
                m_writer->emit("(");
                _maybeEmitGLSLCast((leftVectorType ? nullptr : vecType), left);
                m_writer->emit(",");
                _maybeEmitGLSLCast((rightVectorType ? nullptr : vecType), right);
                m_writer->emit(")");

                maybeCloseParens(needClose);

                return true;
            }

            // Use the default
            break;
        }
        case kIROp_FRem:
        {
            IRInst* left = inst->getOperand(0);
            IRInst* right = inst->getOperand(1);

            // Handle as a function call
            auto prec = getInfo(EmitOp::Postfix);

            EmitOpInfo outerPrec = inOuterPrec;
            bool needClose = maybeEmitParens(outerPrec, prec);

            // TODO: the GLSL `mod` function amounts to a floating-point
            // modulus rather than a floating-point remainder. We need
            // to fix this to emit the right SPIR-V opcode, but there is
            // no built-in GLSL function that maps to the opcode we want.
            //
            m_writer->emit("mod(");
            emitOperand(left, getInfo(EmitOp::General));
            m_writer->emit(",");
            emitOperand(right, getInfo(EmitOp::General));
            m_writer->emit(")");

            maybeCloseParens(needClose);

            return true;
        }
        // TODO: We should also special-case `kIROp_IRem` here,
        // so that we emit a remainder instead of a modulus. As for
        // `FRem` there is no direct GLSL translation, so we will
        // leave things with the default behavior for now.

        case kIROp_StringLit:
        {
            const auto handler = StringEscapeUtil::getHandler(StringEscapeUtil::Style::Slang);

            StringBuilder buf;
            const UnownedStringSlice slice = as<IRStringLit>(inst)->getStringSlice();
            StringEscapeUtil::appendQuoted(handler, slice, buf);

            m_writer->emit(buf);

            return true;
        }
        case kIROp_GetVulkanRayTracingPayloadLocation:
        {
            auto payloadVar = inst->getOperand(0);
            IRInst* location = getVulkanPayloadLocation(payloadVar);
            if (!location)
            {
                SLANG_DIAGNOSE_UNEXPECTED(getSink(), inst, "no payload location assigned.");
                m_writer->emit("0");
            }
            m_writer->emit(getIntVal(location));
            return true;
        }
        case kIROp_ImageLoad:
        {
            auto imageOp = as<IRImageLoad>(inst);
            m_writer->emit("imageLoad(");
            emitOperand(imageOp->getImage(), getInfo(EmitOp::General));
            m_writer->emit(",");
            emitOperand(imageOp->getCoord(), getInfo(EmitOp::General));
            if (imageOp->hasAuxCoord1())
            {
                m_writer->emit(",");
                emitOperand(imageOp->getAuxCoord1(), getInfo(EmitOp::General));
            }
            m_writer->emit(")");
            return true;
        }
        case kIROp_ImageStore:
        {
            auto imageOp = as<IRImageStore>(inst);
            m_writer->emit("imageStore(");
            emitOperand(imageOp->getImage(), getInfo(EmitOp::General));
            m_writer->emit(",");
            emitOperand(imageOp->getCoord(), getInfo(EmitOp::General));
            if (imageOp->hasAuxCoord1())
            {
                m_writer->emit(",");
                emitOperand(imageOp->getAuxCoord1(), getInfo(EmitOp::General));
            }
            m_writer->emit(",");
            emitOperand(imageOp->getValue(), getInfo(EmitOp::General));
            m_writer->emit(")");
            return true;
        }
        case kIROp_StructuredBufferLoad:
        case kIROp_StructuredBufferLoadStatus:
        case kIROp_RWStructuredBufferLoad:
        case kIROp_RWStructuredBufferLoadStatus:
        case kIROp_RWStructuredBufferGetElementPtr:
        {
            auto outerPrec = inOuterPrec;
            auto prec = getInfo(EmitOp::Postfix);
            bool needClose = maybeEmitParens(outerPrec, prec);

            emitOperand(inst->getOperand(0), leftSide(outerPrec, prec));
            m_writer->emit("._data[");
            // glsl only support int/uint as array index
            m_writer->emit("uint(");
            emitOperand(inst->getOperand(1), getInfo(EmitOp::General));
            m_writer->emit(")");
            m_writer->emit("]");

            maybeCloseParens(needClose);
            return true;
        }
        case kIROp_RWStructuredBufferStore:
        {
            auto outerPrec = inOuterPrec;

            auto assignPrec = getInfo(EmitOp::Assign);
            bool assignNeedsClose = maybeEmitParens(outerPrec, assignPrec);

            {
                auto subscriptPrec = getInfo(EmitOp::Postfix);
                bool subscriptNeedsClose = maybeEmitParens(assignPrec, subscriptPrec);

                emitOperand(inst->getOperand(0), leftSide(assignPrec, subscriptPrec));
                m_writer->emit("._data[");
                emitOperand(inst->getOperand(1), getInfo(EmitOp::General));
                m_writer->emit("]");

                maybeCloseParens(subscriptNeedsClose);
            }

            m_writer->emit(" = ");
            emitOperand(inst->getOperand(2), rightSide(outerPrec, assignPrec));
            maybeCloseParens(assignNeedsClose);
            return true;
        }
        case kIROp_NonUniformResourceIndex:
        {
            // Need to emit as a Function call for HLSL
            m_writer->emit("nonuniformEXT");
            m_writer->emit("(");
            emitOperand(inst->getOperand(0), getInfo(EmitOp::General));
            m_writer->emit(")");

            // Forcibly enabling the GL extension when using 'implict-sized' arrays
            // with the qualifier. May be this is not advisable.
            _requireGLSLExtension(UnownedStringSlice::fromLiteral("GL_EXT_nonuniform_qualifier"));

            // Handled
            return true;
        }
        case kIROp_BeginFragmentShaderInterlock:
        {
            _requireGLSLVersion(420);
            _requireGLSLExtension(UnownedStringSlice::fromLiteral("GL_ARB_fragment_shader_interlock"));
            m_writer->emit("beginInvocationInterlockARB()");
            return true;
        }
        case kIROp_EndFragmentShaderInterlock:
        {
            _requireGLSLVersion(420);
            _requireGLSLExtension(UnownedStringSlice::fromLiteral("GL_ARB_fragment_shader_interlock"));
            m_writer->emit("endInvocationInterlockARB()");
            return true;
        }
        default: break;
    }

    // Not handled
    return false;
}

bool GLSLSourceEmitter::tryEmitInstStmtImpl(IRInst* inst)
{
    switch (inst->getOp())
    {
    case kIROp_AtomicCounterIncrement:
        {
            auto oldValName = getName(inst);
            m_writer->emit("int ");
            m_writer->emit(oldValName);
            m_writer->emit(" = ");
            m_writer->emit("atomicAdd(");
            emitOperand(inst->getOperand(0), getInfo(EmitOp::General));
            m_writer->emit(", 1);\n");
            return true;
        }
    case kIROp_AtomicCounterDecrement:
        {
            auto oldValName = getName(inst);
            m_writer->emit("int ");
            m_writer->emit(oldValName);
            m_writer->emit(" = ");
            m_writer->emit("atomicAdd(");
            emitOperand(inst->getOperand(0), getInfo(EmitOp::General));
            m_writer->emit(", -1);\n");
            return true;
        }
    case kIROp_StructuredBufferGetDimensions:
        {
            emitInstResultDecl(inst);
            m_writer->emit("uvec2(");
            emitOperand(inst->getOperand(0), getInfo(EmitOp::General));
            m_writer->emit("._data.length(), ");
            auto elementType = as<IRHLSLStructuredBufferTypeBase>(inst->getOperand(0)->getDataType())->getElementType();
            IRIntegerValue stride = 0;
            if (auto sizeDecor = elementType->findDecoration<IRSizeAndAlignmentDecoration>())
            {
                stride = align(sizeDecor->getSize(), (int)sizeDecor->getAlignment());
            }
            m_writer->emit(stride);
            m_writer->emit(");\n");
            return true;
        }
    default:
        return false;
    }
}

void GLSLSourceEmitter::handleRequiredCapabilitiesImpl(IRInst* inst)
{
    // Does this function declare any requirements on GLSL version or
    // extensions, which should affect our output?

    for (auto decoration : inst->getDecorations())
    {
        switch (decoration->getOp())
        {
            default:
                break;

            case kIROp_RequireGLSLExtensionDecoration:
            {
                _requireGLSLExtension(((IRRequireGLSLExtensionDecoration*)decoration)->getExtensionName());
                break;
            }
            case kIROp_RequireGLSLVersionDecoration:
            {
                _requireGLSLVersion(int(((IRRequireGLSLVersionDecoration*)decoration)->getLanguageVersion()));
                break;
            }
            case kIROp_RequireSPIRVVersionDecoration:
            {
                auto intValue = static_cast<IRRequireSPIRVVersionDecoration*>(decoration)->getSPIRVVersion();
                SemanticVersion version;
                version.setFromInteger(SemanticVersion::IntegerType(intValue));
                _requireSPIRVVersion(version);
                break;
            }

        }
    }

    // The function may have various requirment declaring functions its body. We also need to look for them.
    auto func = as<IRFunc>(inst);
    if (!func)
        return;
    auto block = func->getFirstBlock();
    if (!block)
        return;
    for (auto childInst : block->getChildren())
    {
        if (auto requireGLSLExt = as<IRRequireGLSLExtension>(childInst))
        {
            _requireGLSLExtension(requireGLSLExt->getExtensionName());
        }
        else if (const auto requireComputeDerivative = as<IRRequireComputeDerivative>(childInst))
        {
            // only allowed 1 of derivative_group_quadsNV or derivative_group_linearNV
            if (m_entryPointStage != Stage::Compute
                || m_requiredAfter.requireComputeDerivatives.getLength() > 0)
                return;

            _requireGLSLExtension(UnownedStringSlice("GL_NV_compute_shader_derivatives"));

            // This will only run once per program.
            HashSet<IRFunc*>* entryPointsUsingInst = getReferencingEntryPoints(m_referencingEntryPoints, func);

            for (auto entryPoint : *entryPointsUsingInst)
            {
                bool isQuad = !entryPoint->findDecoration<IRDerivativeGroupLinearDecoration>();
                auto numThreadsDecor = entryPoint->findDecoration<IRNumThreadsDecoration>();
                if (isQuad)
                {
                    verifyComputeDerivativeGroupModifiers(getSink(), inst->sourceLoc, true, false, numThreadsDecor);
                    m_requiredAfter.requireComputeDerivatives = "layout(derivative_group_quadsNV) in;";
                }
                else
                {
                    verifyComputeDerivativeGroupModifiers(getSink(), inst->sourceLoc, false, true, numThreadsDecor);
                    m_requiredAfter.requireComputeDerivatives = "layout(derivative_group_linearNV) in;";
                }
            }
        }
    }
}

static Index _getGLSLVersion(ProfileVersion profile)
{
    switch (profile)
    {
#define CASE(TAG, VALUE) case ProfileVersion::TAG: return VALUE;
        CASE(GLSL_150, 150);
        CASE(GLSL_330, 330);
        CASE(GLSL_400, 400);
        CASE(GLSL_410, 410);
        CASE(GLSL_420, 420);
        CASE(GLSL_430, 430);
        CASE(GLSL_440, 440);
        CASE(GLSL_450, 450);
        CASE(GLSL_460, 460);
#undef CASE

    default:
        break;
    }
    return -1;
}

void GLSLSourceEmitter::emitFrontMatterImpl(TargetRequest* targetReq)
{
    auto effectiveProfile = m_effectiveProfile;
    if (effectiveProfile.getFamily() == ProfileFamily::GLSL)
    {
        _requireGLSLVersion(effectiveProfile.getVersion());
    }

    // HACK: We aren't picking GLSL versions carefully right now,
    // and so we might end up only requiring the initial 1.10 version,
    // even though even basic functionality needs a higher version.
    //
    // For now, we'll work around this by just setting the minimum required
    // version to a high one:
    //
    // TODO: Either correctly compute a minimum required version, or require
    // the user to specify a version as part of the target.
    m_glslExtensionTracker->requireVersion(ProfileVersion::GLSL_450);

    Index glslVersion = _getGLSLVersion(m_glslExtensionTracker->getRequiredProfileVersion());
    if (glslVersion < 0)
    {
        // No information is available for us to guess a profile,
        // so it seems like we need to pick one out of thin air.
        //
        // Ideally we should infer a minimum required version based
        // on the constructs we have seen used in the user's code
        //
        // For now we just fall back to a reasonably recent version.

        glslVersion = 420;
    }

    m_writer->emit("#version ");
    m_writer->emit(glslVersion);
    m_writer->emit("\n");

    // Output the extensions
    if (m_glslExtensionTracker)
    {
        trackGLSLTargetCaps(m_glslExtensionTracker, targetReq->getTargetCaps());

        StringBuilder builder;
        m_glslExtensionTracker->appendExtensionRequireLines(builder);
        m_writer->emit(builder.getUnownedSlice());
    }

    // Reminder: the meaning of row/column major layout
    // in our semantics is the *opposite* of what GLSL
    // calls them, because what they call "columns"
    // are what we call "rows."
    //
    switch (getTargetProgram()->getOptionSet().getMatrixLayoutMode())
    {
    case kMatrixLayoutMode_RowMajor:
    default:
        m_writer->emit("layout(column_major) uniform;\n");
        m_writer->emit("layout(column_major) buffer;\n");
        break;

    case kMatrixLayoutMode_ColumnMajor:
        m_writer->emit("layout(row_major) uniform;\n");
        m_writer->emit("layout(row_major) buffer;\n");
        break;
    }
}

void GLSLSourceEmitter::emitVectorTypeNameImpl(IRType* elementType, IRIntegerValue elementCount)
{
    if (elementCount > 1)
    {
        _emitGLSLTypePrefix(elementType);
        m_writer->emit("vec");
        m_writer->emit(elementCount);
    }
    else
    {
        emitSimpleType(elementType);
    }
}

void GLSLSourceEmitter::emitTypeImpl(IRType* type, const StringSliceLoc* nameAndLoc)
{
    if (auto refType = as<IRRefType>(type))
    {
        _requireGLSLExtension(UnownedStringSlice("GL_EXT_spirv_intrinsics"));
        m_writer->emit("spirv_by_reference ");
        type = refType->getValueType();
    }
    return Super::emitTypeImpl(type, nameAndLoc);
}

void GLSLSourceEmitter::emitParamTypeImpl(IRType* type, String const& name)
{
    if (auto refType = as<IRRefType>(type))
    {
        type = refType->getValueType();

        if (as<IRRayQueryType>(type) || as<IRHitObjectType>(type))
        {
            // GLSL will automatically pass these by reference, so we don't need to do anything.
        }
        else
        {
            _requireGLSLExtension(UnownedStringSlice("GL_EXT_spirv_intrinsics"));
            m_writer->emit("spirv_by_reference ");
        }
    }
    else if (auto spirvLiteralType = as<IRSPIRVLiteralType>(type))
    {
        _requireGLSLExtension(UnownedStringSlice("GL_EXT_spirv_intrinsics"));
        m_writer->emit("spirv_literal ");
        type = spirvLiteralType->getValueType();
    }

    Super::emitParamTypeImpl(type, name);
}

void GLSLSourceEmitter::emitFuncDecorationImpl(IRDecoration* decoration)
{
    if (decoration->getOp() == kIROp_SPIRVOpDecoration)
    {
        m_glslExtensionTracker->requireExtension(UnownedStringSlice::fromLiteral("GL_EXT_spirv_intrinsics"));

        m_writer->emit("spirv_instruction(id = ");
        emitSimpleValue(decoration->getOperand(0));

        if (decoration->getOperandCount() >= 2)
        {
            if (auto stringLit = as<IRStringLit>(decoration->getOperand(1)))
            {
                m_writer->emit(toSlice(", set = "));

                auto handler = StringEscapeUtil::getHandler(StringEscapeUtil::Style::Cpp);

                StringBuilder buf;
                StringEscapeUtil::appendQuoted(handler, stringLit->getStringSlice(), buf);
            
                m_writer->emitRawTextSpan(buf.begin(), buf.end());
            }
        }

        m_writer->emit(")\n");
    }
    else
    {
        Super::emitFuncDecorationImpl(decoration);
    }
}

void GLSLSourceEmitter::emitSimpleTypeImpl(IRType* type)
{
    switch (type->getOp())
    {
        case kIROp_Int64Type:
        {
            _requireBaseType(BaseType::Int64);
            m_writer->emit(getDefaultBuiltinTypeName(type->getOp()));
            return;
        }
        case kIROp_UInt64Type:
        {
            _requireBaseType(BaseType::UInt64);
            m_writer->emit(getDefaultBuiltinTypeName(type->getOp()));
            return;
        }
        case kIROp_IntPtrType:
        {
#if SLANG_PTR_IS_64
            _requireBaseType(BaseType::Int64);
            m_writer->emit("int64_t");
#else
            m_writer->emit("int");
#endif
            return;
        }
        case kIROp_UIntPtrType:
        {
#if SLANG_PTR_IS_64
            _requireBaseType(BaseType::UInt64);
            m_writer->emit("uint64_t");
#else
            m_writer->emit("uint");
#endif
            return;
        }
        case kIROp_VoidType:
        case kIROp_BoolType:
        case kIROp_Int8Type:
        case kIROp_Int16Type:
        case kIROp_IntType:
        case kIROp_UInt8Type:
        case kIROp_UInt16Type:
        case kIROp_UIntType:
        case kIROp_FloatType:
        case kIROp_DoubleType:
        {
            _requireBaseType(cast<IRBasicType>(type)->getBaseType());
            m_writer->emit(getDefaultBuiltinTypeName(type->getOp()));
            return;
        }
        case kIROp_HalfType:
        {
            _requireBaseType(BaseType::Half);
            m_writer->emit("float16_t");
            return;
        }
        case kIROp_StructType:
        case kIROp_HLSLConstBufferPointerType:
            m_writer->emit(getName(type));
            return;

        case kIROp_VectorType:
        {
            auto vecType = (IRVectorType*)type;
            emitVectorTypeNameImpl(vecType->getElementType(), getIntVal(vecType->getElementCount()));
            return;
        }
        case kIROp_MatrixType:
        {
            auto matType = (IRMatrixType*)type;

            _emitGLSLTypePrefix(matType->getElementType());
            m_writer->emit("mat");
            emitVal(matType->getRowCount(), getInfo(EmitOp::General));
            // TODO(tfoley): only emit the next bit
            // for non-square matrix
            m_writer->emit("x");
            emitVal(matType->getColumnCount(), getInfo(EmitOp::General));
            return;
        }
        case kIROp_SamplerStateType:
        case kIROp_SamplerComparisonStateType:
        {
            auto samplerStateType = cast<IRSamplerStateTypeBase>(type);
            switch (samplerStateType->getOp())
            {
                case kIROp_SamplerStateType:			m_writer->emit("sampler");		break;
                case kIROp_SamplerComparisonStateType:	m_writer->emit("samplerShadow");	break;
                default:
                    SLANG_DIAGNOSE_UNEXPECTED(getSink(), SourceLoc(), "unhandled sampler state flavor");
                    break;
            }
            return;
        }
        case kIROp_NativeStringType:
        case kIROp_StringType:
        {
            m_writer->emit("int");
            return;
        }
        case kIROp_RayQueryType:
        {
            m_writer->emit("rayQueryEXT");
            return;
        }
        case kIROp_HitObjectType:
        {
            m_writer->emit("hitObjectNV");
            return;
        }
        case kIROp_TextureFootprintType:
        {
            m_glslExtensionTracker->requireExtension(UnownedStringSlice("GL_NV_shader_texture_footprint"));
            m_glslExtensionTracker->requireVersion(ProfileVersion::GLSL_450);

            m_writer->emit("gl_TextureFootprint");
            auto intLit = as<IRIntLit>(type->getOperand(0));
            if (intLit)
                m_writer->emit(intLit->getValue());
            m_writer->emit("DNV");
            return;
        }
        default: break;
    }

    // TODO: Ideally the following should be data-driven,
    // based on meta-data attached to the definitions of
    // each of these IR opcodes.
    if (auto texType = as<IRTextureType>(type))
    {
        if (texType->isCombined())
        {
            _emitGLSLTextureOrTextureSamplerType(texType, "sampler");
            return;
        }
        switch (texType->getAccess())
        {
            case SLANG_RESOURCE_ACCESS_READ_WRITE:
            case SLANG_RESOURCE_ACCESS_RASTER_ORDERED:
                _emitGLSLTextureOrTextureSamplerType(texType, "image");
                break;

            default:
                _emitGLSLTextureOrTextureSamplerType(texType, "texture");
                break;
        }
        return;
    }
    else if (auto imageType = as<IRGLSLImageType>(type))
    {
        _emitGLSLTextureOrTextureSamplerType(imageType, "image");
        return;
    }
    else if (auto subpassType = as<IRSubpassInputType>(type))
    {
        _emitGLSLSubpassInputType(subpassType);
        return;
    }
    else if (const auto structuredBufferType = as<IRHLSLStructuredBufferTypeBase>(type))
    {
        // TODO: We desugar global variables with structured-buffer type into GLSL
        // `buffer` declarations, but we don't currently handle structured-buffer types
        // in other contexts (e.g., as function parameters). The simplest thing to do
        // would be to emit a `StructuredBuffer<Foo>` as `Foo[]` and `RWStructuredBuffer<Foo>`
        // as `in out Foo[]`, but that is starting to get into the realm of transformations
        // that should really be handled during legalization, rather than during emission.
        //
        SLANG_DIAGNOSE_UNEXPECTED(getSink(), SourceLoc(), "structured buffer type used unexpectedly");
        return;
    }
    else if (auto untypedBufferType = as<IRUntypedBufferResourceType>(type))
    {
        switch (untypedBufferType->getOp())
        {
            case kIROp_RaytracingAccelerationStructureType:
            {
                if (!isRaytracingStage(m_entryPointStage))
                    _requireRayQuery();
                else
                    _requireRayTracing();
                m_writer->emit("accelerationStructureEXT");
                break;
            }
            default:
                SLANG_DIAGNOSE_UNEXPECTED(getSink(), SourceLoc(), "unhandled buffer type");
                break;
        }

        return;
    }

    auto decorated = getResolvedInstForDecorations(type);
    UnownedStringSlice intrinsicDef;
    IRInst* intrinsicInst;
    if (findTargetIntrinsicDefinition(decorated, intrinsicDef, intrinsicInst))
    {
        m_writer->emit(intrinsicDef);
        return;
    }

    SLANG_DIAGNOSE_UNEXPECTED(getSink(), SourceLoc(), "unhandled type");
}

void GLSLSourceEmitter::emitRateQualifiersAndAddressSpaceImpl(IRRate* rate, AddressSpace addressSpace)
{
    if(addressSpace == (AddressSpace)SpvStorageClassTaskPayloadWorkgroupEXT)
    {
        m_writer->emit("taskPayloadSharedEXT ");
    }
    else if (as<IRConstExprRate>(rate))
    {
        m_writer->emit("const ");

    }
    else if (as<IRGroupSharedRate>(rate))
    {
        m_writer->emit("shared ");
    }
}

bool GLSLSourceEmitter::_maybeEmitInterpolationModifierText(IRInterpolationMode mode, Stage stage, bool isInput)
{
    switch (mode)
    {
        case IRInterpolationMode::NoInterpolation:      
            m_writer->emit("flat "); return true;
        case IRInterpolationMode::NoPerspective:        
            m_writer->emit("noperspective "); return true;
        case IRInterpolationMode::Linear:               
            m_writer->emit("smooth "); return true;
        case IRInterpolationMode::Sample:              
            m_writer->emit("sample "); return true;
        case IRInterpolationMode::Centroid:             
            m_writer->emit("centroid "); return true;
        case IRInterpolationMode::PerVertex:
            if( stage == Stage::Fragment && isInput)
            {
                _requireFragmentShaderBarycentric();
                m_writer->emit("pervertexEXT ");
            }
            else 
            {
                m_writer->emit("flat ");
            }
            return true;
        default:
            return false;
    }
}

void GLSLSourceEmitter::emitInterpolationModifiersImpl(IRInst* varInst, IRType* valueType, IRVarLayout* layout)
{
    bool anyModifiers = false;

    Stage stage = Stage::Unknown;
    bool isInput = false;

    if (layout)
    {
        stage = layout->getStage();
        isInput = layout->findOffsetAttr(LayoutResourceKind::VaryingInput) != nullptr;
    }

    for (auto dd : varInst->getDecorations())
    {
        if (dd->getOp() != kIROp_InterpolationModeDecoration)
            continue;

        auto decoration = (IRInterpolationModeDecoration*)dd;

        anyModifiers |= _maybeEmitInterpolationModifierText(decoration->getMode(), stage, isInput);

        switch( decoration->getMode() )
        {
        default:
            break;

        case IRInterpolationMode::PerVertex:
            if( stage == Stage::Fragment )
            {
                if( isInput )
                {
                    _requireFragmentShaderBarycentric();
                }
            }
            break;
        }
    }

    // If the user didn't explicitly qualify a varying
    // with integer type, then we need to explicitly
    // add the `flat` modifier for GLSL.
    if (!anyModifiers)
    {
        // Only emit a default `flat` for fragment
        // stage varying inputs.
        //
        // TODO: double-check that this works for
        // signature matching even if the producing
        // stage didn't use `flat`.
        //
        // If this ends up being a problem we can instead
        // output everything with `flat` except for
        // fragment *outputs* (and maybe vertex inputs).
        //
        if (layout 
            && layout->getStage() == Stage::Fragment
            && layout->usesResourceKind(LayoutResourceKind::VaryingInput))
        {
            _maybeEmitGLSLFlatModifier(valueType);
        }
    }
}

void GLSLSourceEmitter::emitPackOffsetModifier(IRInst* varInst, IRType* valueType, IRPackOffsetDecoration* decoration)
{
    SLANG_UNUSED(varInst);
    SLANG_UNUSED(valueType);

    _requireGLSLExtension(UnownedStringSlice::fromLiteral("GL_ARB_enhanced_layouts"));
    m_writer->emit("layout(offset = ");
    m_writer->emit(decoration->getRegisterOffset()->getValue() * 16 + decoration->getComponentOffset()->getValue() * 4);
    m_writer->emit(")\n");
}

void GLSLSourceEmitter::emitMeshShaderModifiersImpl(IRInst* varInst)
{
    if(varInst->findDecoration<IRGLSLPrimitivesRateDecoration>())
    {
        m_writer->emit("perprimitiveEXT");
        m_writer->emit(" ");
    }
}

void GLSLSourceEmitter::emitVarDecorationsImpl(IRInst* varDecl)
{
    // Deal with Vulkan raytracing layout stuff *before* we
    // do the check for whether `layout` is null, because
    // the payload won't automatically get a layout applied
    // (it isn't part of the user-visible interface...)
    //

    for (auto decoration : varDecl->getDecorations())
    {
        UnownedStringSlice prefix;
        UnownedStringSlice postfix = toSlice("EXT");
        if (as<IRVulkanHitAttributesDecoration>(decoration))
        {
            prefix = toSlice("hitAttribute");
        }
        else if (as<IRPerVertexDecoration>(decoration))
        {
            _requireGLSLExtension(toSlice("GL_EXT_fragment_shader_barycentric"));
            prefix = toSlice("pervertex");
        }
        else
        {
            IRIntegerValue locationValue = -1;
            switch (decoration->getOp())
            {
            case kIROp_VulkanCallablePayloadDecoration:
                prefix = toSlice("callableData");
                locationValue = getIntVal(decoration->getOperand(0));
                break;
            case kIROp_VulkanCallablePayloadInDecoration:
                prefix = toSlice("callableDataIn");
                locationValue = getIntVal(decoration->getOperand(0));
                break;
            case kIROp_VulkanRayPayloadDecoration:
                prefix = toSlice("rayPayload");
                locationValue = getIntVal(decoration->getOperand(0));
                break;
            case kIROp_VulkanRayPayloadInDecoration:
                prefix = toSlice("rayPayloadIn");
                locationValue = getIntVal(decoration->getOperand(0));
                break;
            case kIROp_VulkanHitObjectAttributesDecoration:
                prefix = toSlice("hitObjectAttribute");
                postfix = toSlice("NV");
                locationValue = getIntVal(decoration->getOperand(0));
                break;
            default:
                continue;
            }
            m_writer->emit(toSlice("layout(location = "));
            m_writer->emit(locationValue);
            m_writer->emit(toSlice(")\n"));
        }

        SLANG_ASSERT(prefix.getLength());
        m_writer->emit(prefix);
        m_writer->emit(postfix);
        m_writer->emit(toSlice("\n"));

        // If we emit a location we are done.
        break;
    }

}

void GLSLSourceEmitter::emitMatrixLayoutModifiersImpl(IRVarLayout* layout)
{
    // When a variable has a matrix type, we want to emit an explicit
    // layout qualifier based on what the layout has been computed to be.
    //

    auto typeLayout = layout->getTypeLayout()->unwrapArray();

    if (auto matrixTypeLayout = as<IRMatrixTypeLayout>(typeLayout))
    {
        // Reminder: the meaning of row/column major layout
        // in our semantics is the *opposite* of what GLSL
        // calls them, because what they call "columns"
        // are what we call "rows."
        //
        switch (matrixTypeLayout->getMode())
        {
            case kMatrixLayoutMode_ColumnMajor:
                m_writer->emit("layout(row_major)\n");
                break;

            case kMatrixLayoutMode_RowMajor:
                m_writer->emit("layout(column_major)\n");
                break;
        }
    }
}


} // namespace Slang