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  • Hash : 6bd7a518
    Author : Yuxin Hu
    Date : 2025-03-19T13:35:48

    Vulkan: Allow pipelineStatisticsQuery substitute PGO
    
    Some devices are missing VK_EXT_primitives_generated_query
    extension and primitivesGeneratedQuery (PGO) feature, which are
    required for GLES3.2 extensions geometryShaderEXT and
    tessellationShaderEXT. On such devices, when app requests to create
    a GLES 3.2 context, the eglCreateContext call will fail due to not
    able to support GLES 3.2.
    
    We add a new feature flag
    allowPipelineStaticsForPrimitivesGeneratedQuery,
    and enable it on devices where we can fallback to using
    pipelineStatisticsQuery (PSQ) as an approximation for
    VK_EXT_primitives_generated_query, to broaden support for GLES 3.2
    contexts. This is an opt-in feature for vendors that can functionally
    substitute PGQ with PSQ.
    Expose geometryShaderEXT and tessellationShaderEXT
    extensions if allowPipelineStaticsForPrimitivesGeneratedQuery feature
    is enabled.
    
    Bug: b/333987915
    Change-Id: I9f0affbc3cc383ed6c50bcfc5d4d6f7f8a708aaa
    Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/6362627
    Reviewed-by: Charlie Lao <cclao@google.com>
    Reviewed-by: mohan maiya <m.maiya@samsung.com>
    Commit-Queue: Yuxin Hu <yuxinhu@google.com>
    

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    Description

    A conformant OpenGL ES implementation for Windows, Mac, Linux, iOS and Android.

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  • README.md

  • ANGLE: Vulkan Back-end

    ANGLE’s Vulkan back-end implementation lives in this folder.

    Vulkan is an explicit graphics API. 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.

    Back-end Design

    The vk::Renderer class represents an EGLDisplay. vk::Renderer owns shared global resources like the VkDevice, VkQueue, the Vulkan format tables and internal Vulkan shaders. The ContextVk 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

    A render pass has three states: unstarted, started and active (we call it active in short), started but inactive (we call it inactive in short). 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.
    • onRenderPassFinished: Puts render pass into inactive state where you can not record more commands into secondary command buffer, except in some special cases where ANGLE does some optimization internally.
    • flushCommandsAndEndRenderPassWithoutSubmit: Marks the end of render pass. It flushes secondary command buffer into vulkan’s primary command buffer, puts secondary command buffer back to unstarted state and then goes into recycler for reuse.

    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 vk::Renderer::finishQueueSerial, ANGLE submits the primary command buffer to a VkQueue.

    See the code 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(dstBuffer);
        access.onBufferTransferRead(srcBuffer);
    
        // Get a pointer to a secondary command buffer for command recording.
        vk::OutsideRenderPassCommandBuffer *commandBuffer;
        ANGLE_TRY(contextVk->getOutsideRenderPassCommandBuffer(access, &commandBuffer));
    
        // Record the copy command into the secondary buffer. We're done!
        commandBuffer->copyBuffer(srcBuffer->getBuffer(), dstBuffer->getBuffer(), copyCount, copies);

    Additional Reading

    More implementation details can be found in the doc directory: