Using Indirect Command Buffers seems to break XCode's ability to debug Metal shaders. Attempting to debug a vertex shader either yields errors like Unable to connect to device (6) or Function argument 'vertexBuffer.0' does not have a valid vertex buffer binding at index '0'. I've tried the XCode versions 13.1 (13A1030d) and 13.2 beta 2 (13C5081f). Is this a known problem/limitation of XCode's Metal Shader debugger? Are there any workarounds for this? Are there better ways to "debug" Metal shaders in general? I thought my code was doing something bad/weird (I'm still new to Metal), but found even the Apple Developer sample code Encoding Indirect Command Buffers on the CPU, XCode cannot debug the shaders. I've reduced a reproduction to a simple, single file Swift MacOS application drawing a triangle (see Github Repo link below). Setting up Render Pipeline: let desc = MTLRenderPipelineDescriptor() desc.label = "RenderPipeline" desc.vertexFunction = vertexFn desc.fragmentFunction = fragFn desc.colorAttachments[0].pixelFormat = COLOR_PIXEL_FORMAT desc.supportIndirectCommandBuffers = true desc.inputPrimitiveTopology = .triangle let vertexDesc = MTLVertexDescriptor() vertexDesc.attributes[0].bufferIndex = 0 vertexDesc.attributes[0].offset = 0 vertexDesc.attributes[0].format = .float4 vertexDesc.layouts[0].stride = MemoryLayout<VertexPosition>.stride vertexDesc.layouts[0].stepRate = 1 vertexDesc.layouts[0].stepFunction = .perVertex desc.vertexDescriptor = vertexDesc Setting up Indirect Command Buffer: let desc = MTLIndirectCommandBufferDescriptor() desc.commandTypes = .draw desc.inheritBuffers = false desc.inheritPipelineState = false desc.maxVertexBufferBindCount = 1 desc.maxFragmentBufferBindCount = 0 let buf = device.makeIndirectCommandBuffer(descriptor: desc, maxCommandCount: 1, options: MTLResourceOptions.storageModeManaged)! buf.label = "IndirectCommandBuffer" let renderEncoder = buf.indirectRenderCommandAt(0) renderEncoder.setRenderPipelineState(pipelineState) renderEncoder.setVertexBuffer(vertexFnArgBuffer, offset: 0, at: 0) renderEncoder.drawPrimitives(.triangle, vertexStart: 0, vertexCount: 3, instanceCount: 1, baseInstance: 0) Issue command: let commandBuffer = commandQueue.makeCommandBuffer()! commandBuffer.label = "@CommandBuffer" let renderEncoder = commandBuffer.makeRenderCommandEncoder(descriptor: view.currentRenderPassDescriptor!)! renderEncoder.label = "@RenderCommandEncoder" renderEncoder.setViewport(drawableViewport) renderEncoder.use(vertexFnArgBuffer, usage: .read, stages: .vertex) renderEncoder.executeCommandsInBuffer(indirectCommandBuffer, range: 0..<1) renderEncoder.endEncoding() commandBuffer.present(view.currentDrawable!) commandBuffer.commit() The XCode project is pushed to this Github Repo peterwmwong/MetalGPUFrameCaptureDebugRepro and includes a GIF and MOV screen capture of the specific errors I encountered attempting to debug the simple shader. Any help would be appreciated! Thanks.

I'm trying to use an Argument Buffer with a Buffer pointer and noticed crashes XCode 13.2 (19585) while debugging (Frame Capture) on a MBP M1 Max (macOS 12.2.1): Crashed Thread: 24 Dispatch queue: gputools.GPUMTLVariablesViewContentProvider.0x2d0638a40 Exception Type: EXC_BAD_ACCESS (SIGSEGV) Exception Codes: KERN_INVALID_ADDRESS at 0x0000000000000a10 Exception Codes: 0x0000000000000001, 0x0000000000000a10 Exception Note: EXC_CORPSE_NOTIFY I've created a small reproduction project (with screen recordings): https://github.com/peterwmwong/ArgumentBufferXCodeCrashRepro It's essentially a stripped down version of Apple Developer sample code: https://developer.apple.com/documentation/metal/buffers/managing_groups_of_resources_with_argument_buffers?language=objc Basically, this is the setup of the Argument Buffer (SceneArgumentBuffer) and Buffer pointer (Rectangle *) it references: typedef struct Rectangle { vector_float4 color; vector_float2 size; } Rectangle; struct SceneArgumentBuffer { device Rectangle *rects [[ id(SceneArgumentBufferIDRectangles) ]]; }; vertex VertexOut vertexShader( uint instanceID [[ instance_id ]], uint vertexID [[ vertex_id ]], constant SceneArgumentBuffer &args [[ buffer(VertexBufferIndexArgumentBuffer) ]]) { const Rectangle rect = args.rects[instanceID]; // ... } uint16_t numRects = 2; _rectanglesBuffer = [_device newBufferWithLength:sizeof(Rectangle) * numRects options:MTLResourceStorageModeShared]; _rectanglesBuffer.label = @"Rects Buffer"; Rectangle * const rects = _rectanglesBuffer.contents; rects[0].color = simd_make_float4(0.0, 1.0, 0.0, 1.0); rects[0].size = simd_make_float2(0.75, 0.75); rects[1].color = simd_make_float4(0.0, 0.0, 1.0, 1.0); rects[1].size = simd_make_float2(0.5, 0.25); // Argument buffer creation and encoding id<MTLArgumentEncoder> argumentEncoder = [vertexFunction newArgumentEncoderWithBufferIndex:VertexBufferIndexArgumentBuffer]; _argumentBuffer = [_device newBufferWithLength:argumentEncoder.encodedLength options:0]; _argumentBuffer.label = @"Argument Buffer"; [argumentEncoder setArgumentBuffer:_argumentBuffer offset:0]; [argumentEncoder setBuffer:_rectanglesBuffer offset:0 atIndex:SceneArgumentBufferIDRectangles]; // Encoding into a Render Command id<MTLRenderCommandEncoder> renderEncoder = [commandBuffer renderCommandEncoderWithDescriptor:renderPassDescriptor]; [renderEncoder useResource:_rectanglesBuffer usage:MTLResourceUsageRead stages:MTLRenderStageVertex]; [renderEncoder setVertexBuffer:_argumentBuffer offset:0 atIndex:VertexBufferIndexArgumentBuffer]; My application "works". Runs as expected, access to argument buffer and referenced buffer yields correct information to draw the screen correctly... it's just stinks (maintenance/development nightmare) that debugging is hosed. I can't debug shaders or look at pipeline statistics. Is this suppose to work? Are there any weird XCode/Metal environment variables or settings that I should be using to get this to work? Any help/suggestions would be appreciated, thanks!

Is there a limit to the number MTLIO load texture commands that can safely be executed in a single command buffer? When I tried loading each face (6) of a cube texture using a single command buffer, some of the faces will have bad data. Basically... let cmdBuf = ioCommandQueue.makeCommandBuffer() for slice in 0...5 { cmdBuf.load(cubeTexture, slice: slice, level: 0, size: size, sourceBytesPerRow:bytesPerRow, sourceBytesPerImage: bytesPerImage, destinationOrigin: destOrigin, sourceHandle: fileHandles[slice], sourceHandleOffset: 0) } cmdBuf.commit() cmdBuf.waitUntilCompleted() /* This passes, even though my texture is messed up...? */ assert(cmdBuf.status == .complete) // Also, no errors or warnings when XCode Diagnostics / Metal Validation is turned on. If I use multiple command buffers (one load texture command each), everything is fine... for slice in 0...5 { // IMPORTANT: Moved inside the LOOP let cmdBuf = ioCommandQueue.makeCommandBuffer() cmdBuf.load(cubeTexture, slice: slice, level: 0, size: size, sourceBytesPerRow:bytesPerRow, sourceBytesPerImage: bytesPerImage, destinationOrigin: destOrigin, sourceHandle: fileHandles[slice], sourceHandleOffset: 0) // IMPORTANT: Moved inside the LOOP cmdBuf.commit() cmdBuf.waitUntilCompleted() assert(cmdBuf.status == .complete) } I'm assuming this a bug (opened FB10582329)... Or at the very least, some documentation or Metal Validation log would be helpful to understanding what's going wrong/workaround. I've uploaded reduced reproduction (Single Swift file, command line application, XCode project) to this GitHub Repository: https://github.com/peterwmwong/x-mtlio-load-multiple-textures Thanks.

I tried with the latest Xcode 14 RC, but still am unable to extract a pipeline script from a harvested binary archive, as per WWDC 2022 session video. Here's what I've tried (Runnable XCode project on Github): // Create a simple render pipeline let device = MTLCreateSystemDefaultDevice()! let lib = device.makeDefaultLibrary()! let pipelineDesc = MTLRenderPipelineDescriptor() pipelineDesc.vertexFunction = lib.makeFunction(name: "main_vertex") pipelineDesc.fragmentFunction = lib.makeFunction(name: "main_fragment") pipelineDesc.colorAttachments[0]?.pixelFormat = .bgra8Unorm // Harvest GPU Archive let archivePath = NSTemporaryDirectory().appending("harvested-archive.metallib") let archiveDesc = MTLBinaryArchiveDescriptor() let archive = try device.makeBinaryArchive(descriptor: archiveDesc) try archive.addRenderPipelineFunctions(descriptor: pipelineDesc) try archive.serialize(to: NSURL.fileURL(withPath: archivePath)) // In a terminal... > xcrun metal-source -flatbuffers=json harvested-archive.metallib -o descriptors.mtlp-json Unfortunately, metal-source produces a directory of metallibs and no pipeline JSON script in sight. Did I miss something? Has the process changed since the WWDC 2022? Thanks.

With the Xcode 15 RC, the documentation for Metal Pipelines Script (man metal-pipelines-script) doesn't mention anything about defining a Mesh Render Pipeline (MTLMeshRenderPipelineDescriptor). Is there way to do offline compilation OR harvest binary archives for mesh shaders?