<Vulkan> Use rendered vkImage as Texture - vulkan

Question

I want to use a vkImage rendered at a previous render pass as Texture to do the composite operation in a fragment shader. From here I learned vkCmdPipelineBarrier is used to wait for GPU finish a rendering operation and I write this code. It works well on Snapdragon devices. But not on Mali-G52. The Write-after-write error is partly happed. Is this code not enough? Any suggestions?
vkCmdEndRenderPass(cb);
vkCmdBeginRenderPass(cb, &renderPassBeginInfo, VK_SUBPASS_CONTENTS_INLINE);
VkViewport viewport = vks::initializers::viewport((float)offscreenPass.width, (float)offscreenPass.height, 0.0f, 1.0f);
vkCmdSetViewport(cb, 0, 1, &viewport);
VkRect2D scissor = vks::initializers::rect2D(offscreenPass.width, offscreenPass.height, 0, 0);
vkCmdSetScissor(cb, 0, 1, &scissor);
// https://github.com/KhronosGroup/Vulkan-Samples/blob/master/samples/performance/pipeline_barriers/pipeline_barriers.cpp
VkImageMemoryBarrier imageMemoryBarrier = vks::initializers::imageMemoryBarrier();
imageMemoryBarrier.oldLayout = VK_IMAGE_LAYOUT_UNDEFINED;
imageMemoryBarrier.newLayout = VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL;
imageMemoryBarrier.srcAccessMask = 0;
imageMemoryBarrier.dstAccessMask = 0;
imageMemoryBarrier.image = offscreenPass.color[drawframe].image;
imageMemoryBarrier.subresourceRange.aspectMask = VK_IMAGE_ASPECT_COLOR_BIT;
imageMemoryBarrier.subresourceRange.baseMipLevel = 0;
imageMemoryBarrier.subresourceRange.levelCount = 1;
imageMemoryBarrier.subresourceRange.baseArrayLayer = 0;
imageMemoryBarrier.subresourceRange.layerCount = 1;
vkCmdPipelineBarrier(
cb,
VK_PIPELINE_STAGE_BOTTOM_OF_PIPE_BIT,
VK_PIPELINE_STAGE_TOP_OF_PIPE_BIT,
0, 0, nullptr, 0, nullptr, 1, &imageMemoryBarrier);
imageMemoryBarrier.oldLayout = VK_IMAGE_LAYOUT_UNDEFINED;
imageMemoryBarrier.newLayout = VK_IMAGE_LAYOUT_DEPTH_STENCIL_READ_ONLY_OPTIMAL;
imageMemoryBarrier.image = offscreenPass.depth.image;
imageMemoryBarrier.srcAccessMask = 0;
imageMemoryBarrier.dstAccessMask = 0;
vkCmdPipelineBarrier(
cb,
VK_PIPELINE_STAGE_BOTTOM_OF_PIPE_BIT,
VK_PIPELINE_STAGE_TOP_OF_PIPE_BIT,
0, 0, nullptr, 0, nullptr, 1, &imageMemoryBarrier);
I have tried every pattern written here.

Answer 1

If you want to synchronize render passes then your pipeline barrier must be outside of the render pass in the command stream. I.e. it must be after the vkCmdEndRenderPass() of the first pass, and before the vkCmdBeginRenderPass() of the second pass. Pipeline barriers issued inside a render pass, as you are currently doing, are used for synchronization only within the current subpass.
Also, try to avoid:
srcStage=VK_PIPELINE_STAGE_BOTTOM_OF_PIPE_BIT
dstStage=VK_PIPELINE_STAGE_TOP_OF_PIPE_BIT
... for pipeline barriers when you only consume the output of the first pass as a fragment shader input in the second. This is overly conservative and needlessly serializes execution of the geometry processing too. In this case, you should use:
srcStage=VK_PIPELINE_STAGE_BOTTOM_OF_PIPE_BIT
dstStage=VK_PIPELINE_STAGE_FRAGMENT_BIT
... which allows the non-dependent vertex shading and binning for the second pass to run in parallel to the first pass.

Answer 2

Self solved.
The difference in the precision of sampler2D between Adreno and Mali causes this issue. I can read correct data using "precision highp sampler2D".