Layout transition between multiple subpasses in Vulkan

Question

I am trying to do two simple subpasses, where the second one has a dependency on the first one.

//subpass 1
VkAttachmentReference colorReferences = { 0, VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL };

VkSubpassDescription subpass1 = {};
subpass1.pipelineBindPoint = VK_PIPELINE_BIND_POINT_GRAPHICS;
subpass1.pColorAttachments = &colorReferences;
subpass1.colorAttachmentCount = 1;

//subpass 2
VkAttachmentReference inputRefernce = { 0, VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL };

VkSubpassDescription subpass2 = {};
subpass2.pipelineBindPoint = VK_PIPELINE_BIND_POINT_GRAPHICS;
subpass2.inputAttachmentCount = 1;
subpass2.pInputAttachments = &inputRefernce;

//Render pass
VkAttachmentDescription attachmentDescs = {};
attachmentDescs.samples = VK_SAMPLE_COUNT_1_BIT;
attachmentDescs.loadOp = VK_ATTACHMENT_LOAD_OP_CLEAR;
attachmentDescs.storeOp = VK_ATTACHMENT_STORE_OP_STORE;
attachmentDescs.stencilLoadOp = VK_ATTACHMENT_LOAD_OP_DONT_CARE;
attachmentDescs.stencilStoreOp = VK_ATTACHMENT_STORE_OP_DONT_CARE;
attachmentDescs.format = VK_FORMAT_R16G16B16A16_SFLOAT;
attachmentDescs.initialLayout = VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL;
attachmentDescs.finalLayout = VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL;

VkSubpassDependency dependency = {};

dependency.srcSubpass = 0;
dependency.dstSubpass = 1;  
dependency.srcStageMask = VK_PIPELINE_STAGE_ALL_GRAPHICS_BIT;
dependency.dstStageMask = VK_PIPELINE_STAGE_ALL_GRAPHICS_BIT;
dependency.srcAccessMask = VK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT;
dependency.dstAccessMask = VK_ACCESS_SHADER_READ_BIT;

VkSubpassDescription subpasses[2] = { subpass1, subpass2 };
VkRenderPassCreateInfo renderPassInfo = {};
renderPassInfo.sType = VK_STRUCTURE_TYPE_RENDER_PASS_CREATE_INFO;
renderPassInfo.pAttachments = &attachmentDescs;
renderPassInfo.attachmentCount = 1;
renderPassInfo.subpassCount = 2;
renderPassInfo.pSubpasses = subpasses;
renderPassInfo.dependencyCount = 1;
renderPassInfo.pDependencies = &dependency;

vkUtils::checkResult(vkCreateRenderPass(_context->device, &renderPassInfo, nullptr, &_renderPass));

I have a dependency between the first and the second subpass. The specification says:

If an attachment specifies the VK_ATTACHMENT_LOAD_OP_CLEAR load operation, then it will logically be cleared at the start of the first subpass where it is used.

It will only be cleared at the start of the first subpass the attachment is used. And because there is a dependency between them, it should not be cleared in the second subpass.

The first use of an attachment must not specify a layout equal to VK_IMAGE_LAYOUT_DEPTH_STENCIL_READ_ONLY_OPTIMAL or VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL if the attachment specifies that the > loadOp is VK_ATTACHMENT_LOAD_OP_CLEAR. [...]

I get this error from the validation layer:

Cannot clear attachment 0 with invalid first layout VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL.

But the VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL layout is in the second subpass, not the first one?

Could you post code that can compile? Because you declared a variable subpass1, then talk about an undeclared variable subpass. — Nicol Bolas
– Nicol Bolas, Commented Jul 18, 2016 at 20:25
That was not the only place. Please copy it directly from your source code. — Nicol Bolas
– Nicol Bolas, Commented Jul 18, 2016 at 20:44
done:) but so much for a text, maybe I can shorter it done if a solution is found — hidayat
– hidayat, Commented Jul 18, 2016 at 20:49
with VkAttachmentDescription attachmentDescs[5]; you assume your _attachments.size() == 5 — krOoze
– krOoze, Commented Jul 18, 2016 at 21:41
@NicolBolas I have made the code smaller with only one attachment so it is easier to find the problem. — hidayat
– hidayat, Commented Jul 19, 2016 at 4:58

krOoze · Accepted Answer · 2016-07-18 23:34:46Z

3

It seems to be a bug in the layers, which simply do not check which usage is first (It was probably introduced in 1.0.17 SDK - 1.0.13 should not report this...): https://github.com/KhronosGroup/Vulkan-LoaderAndValidationLayers/blob/sdk-1.0.17/layers/core_validation.cpp#L8557

spec quote:

The first use of an attachment must not specify a layout equal to VK_IMAGE_LAYOUT_DEPTH_STENCIL_READ_ONLY_OPTIMAL or VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL if the attachment specifies that the loadOp is VK_ATTACHMENT_LOAD_OP_CLEAR. [...]

edited Jul 18, 2016 at 23:34

answered Jul 18, 2016 at 21:12

krOoze

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4 Comments

hidayat Over a year ago

It says: the first use use ...., its in the second subpass that I am using VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL, in the first subpass the layout is VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL

krOoze Over a year ago

Yeah, the layer does not seem to discriminate the first use (it iterates over all subpasses). I wonder why the 0 attachment didn't get reported though. Does your app work despite the reported errors?

hidayat Over a year ago

I have not finish the last part of the application, but I will soon, and maybe its a validation bug:)

krOoze Over a year ago

I have already reported it and it's being fixed as we speak: github.com/KhronosGroup/Vulkan-LoaderAndValidationLayers/pull/…

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