src/dawn/native/IndirectDrawMetadata.h

// Copyright 2021 The Dawn & Tint Authors
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#ifndef SRC_DAWN_NATIVE_INDIRECTDRAWMETADATA_H_
#define SRC_DAWN_NATIVE_INDIRECTDRAWMETADATA_H_

#include <cstdint>
#include <map>
#include <utility>
#include <vector>

#include "absl/container/flat_hash_set.h"
#include "dawn/common/NonCopyable.h"
#include "dawn/common/Ref.h"
#include "dawn/native/Buffer.h"
#include "dawn/native/CommandBufferStateTracker.h"
#include "dawn/native/Commands.h"
#include "partition_alloc/pointers/raw_ptr.h"

namespace dawn::native {

class RenderBundleBase;
struct CombinedLimits;

// In the unlikely scenario that indirect offsets used over a single buffer span more than
// this length of the buffer, we split the validation work into multiple batches.
uint64_t ComputeMaxIndirectValidationBatchOffsetRange(const CombinedLimits& limits);

// Metadata corresponding to the validation requirements of a single render pass. This metadata
// is accumulated while its corresponding render pass is encoded, and is later used to encode
// validation commands to be inserted into the command buffer just before the render pass's own
// commands.
class IndirectDrawMetadata : public NonCopyable {
  public:
    enum class DrawType : uint8_t {
        NonIndexed,
        Indexed,
    };

    struct IndirectDraw {
        uint64_t inputBufferOffset;
        uint64_t numIndexBufferElements;
        uint64_t indexBufferOffsetInElements;
        // When validation is enabled, the original indirect buffer is validated and copied to a new
        // indirect buffer containing only valid commands. The pointer to the command allocated in
        // the command allocator is used to swap the indirect buffer for the validated one before
        // the backend processes the command. Valid until the backend has processed the
        // commands.
        raw_ptr<DrawIndirectCmd> cmd;
    };

    struct IndirectValidationBatch {
        uint64_t minOffset;
        uint64_t maxOffset;
        std::vector<IndirectDraw> draws;
    };

    struct IndirectMultiDraw {
        DrawType type;

        Ref<BufferBase> indexBuffer = nullptr;
        uint64_t indexBufferSize = 0;
        uint64_t indexBufferOffsetInBytes = 0;
        wgpu::IndexFormat indexFormat = wgpu::IndexFormat::Undefined;
        wgpu::PrimitiveTopology topology = wgpu::PrimitiveTopology::Undefined;
        bool duplicateBaseVertexInstance;

        // When validation is enabled, the original indirect buffer is validated and copied to a new
        // indirect buffer containing only valid commands. The pointer to the command allocated in
        // the command allocator is used to swap the indirect buffer for the validated one before
        // the backend processes the command. Valid until the backend has processed the
        // commands.
        raw_ptr<MultiDrawIndirectCmd> cmd;
    };

    // Tracks information about every draw call in this render pass which uses the same indirect
    // buffer and the same-sized index buffer. Calls are grouped by indirect offset ranges so
    // that validation work can be chunked efficiently if necessary.
    class IndexedIndirectBufferValidationInfo {
      public:
        explicit IndexedIndirectBufferValidationInfo(BufferBase* indirectBuffer);

        // Logs a new drawIndexedIndirect call for the render pass. `cmd` is updated with an
        // assigned (and deferred) buffer ref and relative offset before returning.
        void AddIndirectDraw(uint32_t maxDrawCallsPerIndirectValidationBatch,
                             uint64_t maxBatchOffsetRange,
                             IndirectDraw draw);

        // Adds draw calls from an already-computed batch, e.g. from a previously encoded
        // RenderBundle. The added batch is merged into an existing batch if possible, otherwise
        // it's added to mBatch.
        void AddBatch(uint32_t maxDrawCallsPerIndirectValidationBatch,
                      uint64_t maxBatchOffsetRange,
                      const IndirectValidationBatch& batch);

        const std::vector<IndirectValidationBatch>& GetBatches() const;

        BufferBase* GetIndirectBuffer() const;

      private:
        friend class IndirectDrawMetadata;
        Ref<BufferBase> mIndirectBuffer;

        // A list of information about validation batches that will need to be executed for the
        // corresponding indirect buffer prior to a single render pass. These are kept sorted by
        // minOffset and may overlap iff the number of offsets in one batch would otherwise
        // exceed some large upper bound (roughly ~33M draw calls).
        //
        // Since the most common expected cases will overwhelmingly require only a single
        // validation pass per render pass, this is optimized for efficient updates to a single
        // batch rather than for efficient manipulation of a large number of batches.
        std::vector<IndirectValidationBatch> mBatches;
    };

    struct IndexedIndirectConfig {
        uintptr_t inputIndirectBufferPtr;
        bool duplicateBaseVertexInstance;
        DrawType drawType;

        bool operator<(const IndexedIndirectConfig& other) const;
        bool operator==(const IndexedIndirectConfig& other) const;
    };

    using IndexedIndirectBufferValidationInfoMap =
        std::map<IndexedIndirectConfig, IndexedIndirectBufferValidationInfo>;

    explicit IndirectDrawMetadata(const CombinedLimits& limits);
    ~IndirectDrawMetadata();

    IndirectDrawMetadata(IndirectDrawMetadata&&);
    IndirectDrawMetadata& operator=(IndirectDrawMetadata&&);

    IndexedIndirectBufferValidationInfoMap* GetIndexedIndirectBufferValidationInfo();

    void AddBundle(RenderBundleBase* bundle);
    void AddIndexedIndirectDraw(wgpu::IndexFormat indexFormat,
                                uint64_t indexBufferSize,
                                uint64_t indexBufferOffset,
                                BufferBase* indirectBuffer,
                                uint64_t indirectOffset,
                                bool duplicateBaseVertexInstance,
                                DrawIndexedIndirectCmd* cmd);

    void AddIndirectDraw(BufferBase* indirectBuffer,
                         uint64_t indirectOffset,
                         bool duplicateBaseVertexInstance,
                         DrawIndirectCmd* cmd);

    void AddMultiDrawIndirect(wgpu::PrimitiveTopology topology,
                              bool duplicateBaseVertexInstance,
                              MultiDrawIndirectCmd* cmd);

    void AddMultiDrawIndexedIndirect(BufferBase* indexBuffer,
                                     wgpu::IndexFormat indexFormat,
                                     uint64_t indexBufferSize,
                                     uint64_t indexBufferOffset,
                                     wgpu::PrimitiveTopology topology,
                                     bool duplicateBaseVertexInstance,
                                     MultiDrawIndexedIndirectCmd* cmd);

    void ClearIndexedIndirectBufferValidationInfo();

    const std::vector<IndirectMultiDraw>& GetIndirectMultiDraws() const;

  private:
    IndexedIndirectBufferValidationInfoMap mIndexedIndirectBufferValidationInfo;
    absl::flat_hash_set<RenderBundleBase*> mAddedBundles;

    std::vector<IndirectMultiDraw> mMultiDraws;

    uint64_t mMaxBatchOffsetRange;
    uint32_t mMaxDrawCallsPerBatch;
};

}  // namespace dawn::native

#endif  // SRC_DAWN_NATIVE_INDIRECTDRAWMETADATA_H_