src/dawn/native/webgpu/BindGroupLayoutWGPU.cpp

// Copyright 2025 The Dawn & Tint Authors
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#include "dawn/native/webgpu/BindGroupLayoutWGPU.h"

#include <vector>

#include "absl/container/inlined_vector.h"
#include "dawn/common/MatchVariant.h"
#include "dawn/common/StringViewUtils.h"
#include "dawn/native/webgpu/CaptureContext.h"
#include "dawn/native/webgpu/ComputePipelineWGPU.h"
#include "dawn/native/webgpu/DeviceWGPU.h"
#include "dawn/native/webgpu/Forward.h"
#include "dawn/native/webgpu/RenderPipelineWGPU.h"

namespace dawn::native::webgpu {

namespace {
WGPUExternalTextureBindingLayout ToWGPU(const ExternalTextureBindingLayout* entry) {
    return {
        .chain =
            {
                .next = nullptr,
                .sType = WGPUSType_ExternalTextureBindingLayout,
            },
    };
}
}  // namespace

// static
ResultOrError<Ref<BindGroupLayout>> BindGroupLayout::Create(
    Device* device,
    const UnpackedPtr<BindGroupLayoutDescriptor>& descriptor) {
    return AcquireRef(new BindGroupLayout(device, descriptor));
}

BindGroupLayout::BindGroupLayout(Device* device,
                                 const UnpackedPtr<BindGroupLayoutDescriptor>& descriptor)
    : BindGroupLayoutInternalBase(device, descriptor),
      RecordableObject(schema::ObjectType::BindGroupLayout),
      ObjectWGPU(device->wgpu.bindGroupLayoutRelease),
      mBindGroupAllocator(MakeFrontendBindGroupAllocator<BindGroup>(4096)) {
    // Rebuild the descriptor and resolve internal bindings to regular ones.
    absl::InlinedVector<WGPUBindGroupLayoutEntry, 8> entries(descriptor->entryCount);

    // Pre-calculate the number of external textures to prevent InlinedVector reallocation.
    size_t externalTextureCount = GetExternalTextureCount();
    // Use an inline size of 1 since external textures are rare, and reserve the required capacity
    // immediately.
    absl::InlinedVector<WGPUExternalTextureBindingLayout, 1> externalTextureEntries;
    externalTextureEntries.reserve(externalTextureCount);

    for (size_t i = 0; i < entries.size(); i++) {
        UnpackedPtr<BindGroupLayoutEntry> entry = Unpack(&descriptor->entries[i]);
        entries[i] = *ToAPI(*entry);

        switch (entry->buffer.type) {
            case kInternalStorageBufferBinding:
                entries[i].buffer.type = WGPUBufferBindingType_Storage;
                break;
            case kInternalReadOnlyStorageBufferBinding:
                entries[i].buffer.type = WGPUBufferBindingType_ReadOnlyStorage;
                break;
            default:
                break;
        }

        if (auto* externalTextureLayout = entry.Get<ExternalTextureBindingLayout>()) {
            externalTextureEntries.push_back(ToWGPU(externalTextureLayout));
            entries[i].nextInChain = &externalTextureEntries.back().chain;
        }
    }

    WGPUBindGroupLayoutDescriptor desc = {};
    desc.nextInChain = nullptr;
    desc.label = ToOutputStringView(descriptor->label);
    desc.entryCount = descriptor->entryCount;
    desc.entries = entries.data();

    mInnerHandle = device->wgpu.deviceCreateBindGroupLayout(device->GetInnerHandle(), &desc);
    DAWN_ASSERT(mInnerHandle);
}

Ref<BindGroup> BindGroupLayout::AllocateBindGroup(
    const UnpackedPtr<BindGroupDescriptor>& descriptor) {
    Device* device = ToBackend(GetDevice());
    return AcquireRef(mBindGroupAllocator->Allocate(device, descriptor));
}

void BindGroupLayout::DeallocateBindGroup(BindGroup* bindGroup) {
    mBindGroupAllocator->Deallocate(bindGroup);
}

void BindGroupLayout::ReduceMemoryUsage() {
    mBindGroupAllocator->DeleteEmptySlabs();
}

MaybeError BindGroupLayout::AddReferenced(CaptureContext& captureContext) {
    // BindGroupLayouts don't reference anything.
    return {};
}

void BindGroupLayout::SetLabelImpl() {
    ToBackend(GetDevice())->CaptureSetLabel(this, GetLabel());
}

MaybeError BindGroupLayout::CaptureCreationParameters(CaptureContext& captureContext) {
    const auto& bindingMap = GetBindingMap();

    schema::BindGroupLayout data{{
        .numEntries = uint32_t(bindingMap.size()),
    }};
    Serialize(captureContext, data);

    for (const auto& [bindingNumber, apiBindingIndex] : bindingMap) {
        const auto& bindingInfo = GetAPIBindingInfo(apiBindingIndex);

        schema::BindGroupLayoutBinding binding{{
            .binding = uint32_t(bindingNumber),
            .visibility = bindingInfo.visibility,
            .bindingArraySize = uint32_t(bindingInfo.arraySize),
        }};

        DAWN_TRY(MatchVariant(
            bindingInfo.bindingLayout,
            [&](const BufferBindingInfo& info) -> MaybeError {
                schema::BindGroupLayoutEntryTypeBufferBinding entry{{
                    .binding = binding,
                    .data{{
                        .type = info.type,
                        .minBindingSize = info.minBindingSize,
                        .hasDynamicOffset = info.hasDynamicOffset,
                    }},
                }};
                Serialize(captureContext, entry);
                return {};
            },
            [&](const SamplerBindingInfo& info) -> MaybeError {
                schema::BindGroupLayoutEntryTypeSamplerBinding entry{{
                    .binding = binding,
                    .data{{
                        .type = info.type,
                    }},
                }};
                Serialize(captureContext, entry);
                return {};
            },
            [&](const StorageTextureBindingInfo& info) -> MaybeError {
                schema::BindGroupLayoutEntryTypeStorageTextureBinding entry{{
                    .binding = binding,
                    .data{{
                        .format = info.format,
                        .viewDimension = info.viewDimension,
                        .access = info.access,
                    }},
                }};
                Serialize(captureContext, entry);
                return {};
            },
            [&](const TextureBindingInfo& info) -> MaybeError {
                schema::BindGroupLayoutEntryTypeTextureBinding entry{{
                    .binding = binding,
                    .data{{
                        .sampleType = info.sampleType,
                        .viewDimension = info.viewDimension,
                        .multisampled = info.multisampled,
                    }},
                }};
                Serialize(captureContext, entry);
                return {};
            },
            [&](const auto& info) -> MaybeError {
                return DAWN_INTERNAL_ERROR("Unsupported bind layout entry type");
            }));
    }

    return {};
}

}  // namespace dawn::native::webgpu