kc3-lang/angle/src/libANGLE/renderer/vulkan/README.md

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• Hash : f691b3b5
  Author :
  Date : 2020-12-02T13:11:54
  

  Vulkan: Support PrimitivesGenerated query
  
  This query uses the Vulkan transform feedback extension.  In GL,
  GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN and GL_PRIMITIVES_GENERATED
  queries can be independently begun/ended.  However, Vulkan requires that
  queries from pools of the same type can only be active one at a time.
  This forbids the two GL queries from being handled by two VK queries
  when they are simultaneously begun.
  
  This change makes these queries share their QueryHelper objects.  The
  Vulkan transform feedback queries unconditionally retrieve both results
  anyway, so this is just a matter of making sure the two GL queries are
  merged as one when they are simultaneously used.
  
  The change fixes a number of issues as collateral:
  
  - TransformFeedbackPrimitivesWritten queries when !emulated were not
    released
  - Stashed queries were never released
  - If no render pass is open when a query ends, then getResult(no_wait)
    ended up waiting
  
  Bug: angleproject:5404
  Change-Id: I8ce13ea76ffd31b3152ded7c713c6466d0315504
  Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2573580
  Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
  Reviewed-by: Charlie Lao <cclao@google.com>
  Reviewed-by: Jamie Madill <jmadill@chromium.org>
  

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    // Ensure that ANGLE sets proper read and write barriers for the Buffers.
    vk::CommandBufferAccess access;
    access.onBufferTransferWrite(destBuffer);
    access.onBufferTransferRead(srcBuffer);

    // Get a pointer to a secondary command buffer for command recording.
    vk::CommandBuffer *commandBuffer;
    ANGLE_TRY(contextVk->getOutsideRenderPassCommandBuffer(access, &commandBuffer));

    // Record the copy command into the secondary buffer. We're done!
    commandBuffer->copyBuffer(srcBuffer->getBuffer(), destBuffer->getBuffer(), copyCount, copies);

Source

• src/libANGLE/renderer/vulkan/README.md

• # ANGLE: Vulkan Back-end
  
  ANGLE's Vulkan back-end implementation lives in this folder.
  
  [Vulkan](https://www.khronos.org/vulkan/) is an explicit graphics API. It has a lot in common with
  other explicit APIs such as Microsoft's [D3D12][D3D12 Guide] and Apple's
  [Metal](https://developer.apple.com/metal/). Compared to APIs like OpenGL or D3D11 explicit APIs can
  offer a number of significant benefits:
  
   * Lower API call CPU overhead.
   * A smaller API surface with more direct hardware control.
   * Better support for multi-core programming.
   * Vulkan in particular has open-source tooling and tests.
  
  [D3D12 Guide]: https://docs.microsoft.com/en-us/windows/desktop/direct3d12/directx-12-programming-guide
  
  ## Back-end Design
  
  The [`RendererVk`](RendererVk.cpp) class represents an `EGLDisplay`. `RendererVk` owns shared global
  resources like the [VkDevice][VkDevice], [VkQueue][VkQueue], the [Vulkan format tables](vk_format_utils.h)
  and [internal Vulkan shaders](shaders). The [ContextVk](ContextVk.cpp) class implements the back-end
  of a front-end OpenGL Context. ContextVk processes state changes and handles action commands like
  `glDrawArrays` and `glDrawElements`.
  
  ## Command recording
  
  The back-end records commands into command buffers via the following `ContextVk` APIs:
  
   * `beginNewRenderPass`: Writes out (aka flushes) prior pending commands into a primary command
     buffer, then starts a new render pass. Returns a secondary command buffer *inside* a render pass
     instance.
   * `getOutsideRenderPassCommandBuffer`: May flush prior command buffers and close the render pass if
     necessary, in addition to issuing the appropriate barriers. Returns a secondary command buffer
     *outside* a render pass instance.
   * `getStartedRenderPassCommands`: Returns a reference to the currently open render pass' commands
     buffer.
  
  The back-end (mostly) records Image and Buffer barriers through additional `CommandBufferAccess`
  APIs, the result of which is passed to `getOutsideRenderPassCommandBuffer`.  Note that the
  barriers are not actually recorded until `getOutsideRenderPassCommandBuffer` is called:
  
   * `onBufferTransferRead` and `onBufferComputeShaderRead` accumulate `VkBuffer` read barriers.
   * `onBufferTransferWrite` and `onBufferComputeShaderWrite` accumulate `VkBuffer` write barriers.
   * `onBuffferSelfCopy` is a special case for `VkBuffer` self copies. It behaves the same as write.
   * `onImageTransferRead` and `onImageComputerShadeRead` accumulate `VkImage` read barriers.
   * `onImageTransferWrite` and `onImageComputerShadeWrite` accumulate `VkImage` write barriers.
   * `onImageRenderPassRead` and `onImageRenderPassWrite` accumulate `VkImage` barriers inside a
     started RenderPass.
  
  After the back-end records commands to the primary buffer and we flush (e.g. on swap) or when we call
  `ContextVk::finishToSerial`, ANGLE submits the primary command buffer to a `VkQueue`.
  
  See the [code][CommandAPIs] for more details.
  
  ### Simple command recording example
  
  In this example we'll be recording a buffer copy command:
  
  ```
      // Ensure that ANGLE sets proper read and write barriers for the Buffers.
      vk::CommandBufferAccess access;
      access.onBufferTransferWrite(destBuffer);
      access.onBufferTransferRead(srcBuffer);
  
      // Get a pointer to a secondary command buffer for command recording.
      vk::CommandBuffer *commandBuffer;
      ANGLE_TRY(contextVk->getOutsideRenderPassCommandBuffer(access, &commandBuffer));
  
      // Record the copy command into the secondary buffer. We're done!
      commandBuffer->copyBuffer(srcBuffer->getBuffer(), destBuffer->getBuffer(), copyCount, copies);
  ```
  
  ## Additional Reading
  
  More implementation details can be found in the `doc` directory:
  
  - [Fast OpenGL State Transitions](doc/FastOpenGLStateTransitions.md)
  - [Shader Module Compilation](doc/ShaderModuleCompilation.md)
  - [OpenGL Line Segment Rasterization](doc/OpenGLLineSegmentRasterization.md)
  - [Format Tables and Emulation](doc/FormatTablesAndEmulation.md)
  - [Deferred Clears](doc/DeferredClears.md)
  - [Queries](doc/Queries.md)
  
  [VkDevice]: https://www.khronos.org/registry/vulkan/specs/1.1-extensions/man/html/VkDevice.html
  [VkQueue]: https://www.khronos.org/registry/vulkan/specs/1.1-extensions/man/html/VkQueue.html
  [CommandAPIs]: https://chromium.googlesource.com/angle/angle/+/df31624eaf3df986a0bdf3f58a87b79b0cc8db5c/src/libANGLE/renderer/vulkan/ContextVk.h#620
  
  

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