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  • Hash : 1a5c7a16
    Author : Tobin Ehlis
    Date : 2020-02-25T12:02:31

    Reland "Vulkan:Include precision qualifier in GLSL"
    
    Currently still ignoring precision qualifiers for Vulkan shaders by
    default, but have added feature "enablePrecisionQualifiers" that can be
    enabled in order to include precision qualifiers.
    
    With this initial implementation, it's possible to get precision
    qualifier mis-matches in the generated GLSL 4.50. According to the
    spec this is allowed. From GLSLangSpec 4.50 section 4.7 "Precision and
    Precision Qualifiers":
    
    For the purposes of determining if an output from one shader stage
    matches an input of the next stage, the precision qualifier need not
    match.
    
    However, when converted to SPIR-V and run through the shader validation
    any mismatches will cause shader validation errors. Initially just
    ignoring those errors with this commit.
    
    Bug: angleproject:3078
    Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2057749
    Reviewed-by: Jamie Madill <jmadill@chromium.org>
    Reviewed-by: Tobin Ehlis <tobine@google.com>
    Reviewed-by: Tim Van Patten <timvp@google.com>
    Commit-Queue: Tobin Ehlis <tobine@google.com>
    Change-Id: Ieecca604bb2c834c9b1c2bcab85279d1f8755dfa
    Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2086280
    

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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. It has a lot in common with other explicit APIs such as Microsoft’s D3D12 and Apple’s 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.

    Back-end Design

    The RendererVk class represents an EGLDisplay. RendererVk 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

    The back-end records commands into command buffers via the the following ContextVk APIs:

    • endRenderPassAndGetCommandBuffer: returns a secondary command buffer outside a RenderPass instance.
    • flushAndBeginRenderPass: returns a secondary command buffer inside a RenderPass instance.
    • flushAndGetPrimaryCommandBuffer: returns the primary command buffer. You should rarely need this API.

    Note: All of these commands may write out (aka flush) prior pending commands into a primary command buffer. When a RenderPass is open endRenderPassAndGetCommandBuffer will flush the pending RenderPass commands. flushAndBeginRenderPass will flush out pending commands outside a RenderPass to a primary buffer. On submit ANGLE submits the primary command buffer to a VkQueue.

    If you need to record inside a RenderPass, use flushAndBeginRenderPass. Otherwise, use endRenderPassAndGetCommandBuffer. You should rarely need to call flushAndGetPrimaryCommandBuffer. It’s there for commands like debug labels, barriers and queries that need to be recorded serially on the primary command buffer.

    The back-end usually records Image and Buffer barriers through additional ContextVk APIs:

    • onBufferRead and onBufferWrite accumulate VkBuffer barriers.
    • onImageRead and onImageWrite accumulate VkImage barriers.
    • onRenderPassImageWrite is a special API for write barriers inside a RenderPass instance.

    After the back-end records commands to the primary buffer we flush (e.g. on swap) or when we call ContextVk::finishToSerial.

    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.
        ANGLE_TRY(contextVk->onBufferWrite(VK_ACCESS_TRANSFER_WRITE_BIT, destBuffer));
        ANGLE_TRY(contextVk->onBufferRead(VK_ACCESS_TRANSFER_READ_BIT, srcBuffer));
    
        # Get a pointer to a secondary command buffer for command recording. May "flush" the RP.
        vk::CommandBuffer *commandBuffer;
        ANGLE_TRY(contextVk->endRenderPassAndGetCommandBuffer(&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: