Hash :
9e7f08fc
Author :
Date :
2020-11-06T16:55:51
Vulkan: Fix incorrect reordering of barriers
Take the following situation, a simple copy from image to buffer:
ANGLE_TRY(contextVk->onBufferTransferWrite(buffer));
ANGLE_TRY(contextVk->onImageTransferRead(aspectFlags, image));
CommandBuffer &commandBuffer = contextVk->getOutsideRenderPassCommandBuffer();
commandBuffer.copyImageToBuffer(imageHandle, layout, bufferHandle, 1, regions);
Both `onBufferTransferWrite` and `onImageTransferRead` may flush either
the outsideRP or insideRP command buffers. If buffer is not previously
used, but image is used:
- onBufferTransferWrite: buffer usage is recorded in outsideRP1
- onImageTransferREad: outsiderRP1 is flushed, outsideRP2 is started
- copyImageToBuffer: recorded on outsideRP2, but buffer usage not
recorded there
- A following command that uses the buffer and requires barrier doesn't
close outsideRP2 as it believes it was not used there
Bug: angleproject:5319
Change-Id: Ib8994083fbc21969a538cda3784adee57b089415
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2523388
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Tim Van Patten <timvp@google.com>
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:
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.
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 for more details.
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);
More implementation details can be found in the doc directory: