This project demonstrates the metal-source: error: unsupported binary format error when trying to use metal-source on a harvested GPU archive.

Background

The WWDC 2022 session Target and optimize GPU binaries with Metal 3 suggests the metal-source tool can generate the JSON Pipeline Scripts.

Using the session's (5:55) command line directions:

> metal-source -flatbuffers=json harvested-binaryArchive.metallib -o /tmp/descriptors.mtlp-json

Reproduction Overview

Running this project...

1. Displays XCode environment and version information

   # Runs the following shell commands
   xcrun --show-sdk-path
   xcrun xcodebuild -version

2. Create a simple render pipeline

   let device = MTLCreateSystemDefaultDevice()!
   let commandQueue = device.makeCommandQueue()!
   let lib = try device.makeLibrary(
       source: """
       #include <metal_stdlib>
       using namespace metal;
   
       struct VertexOut {
           float4 position  [[position]];
           float point_size [[point_size]];
       };
   
   
       [[vertex]]
       VertexOut main_vertex() {
           return {
               .position = float4(0),
               .point_size = 128.0
           };
       }
   
       [[fragment]]
       half4 main_fragment() {
           return half4(1);
       }
       """,
       options: nil
   )
   let pipelineDesc = MTLRenderPipelineDescriptor()
   pipelineDesc.vertexFunction = lib.makeFunction(name: "main_vertex")
   pipelineDesc.fragmentFunction = lib.makeFunction(name: "main_fragment")
   pipelineDesc.colorAttachments[0]?.pixelFormat = .bgra8Unorm

3. 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))
   print("Created archive: \(archivePath)")

4. Verify/Display Information about GPU Archive

   # Runs the following shell command
   xcrun metal-readobj harvested-archive.metallib

5. Attempt to use metal-source to get pipeline descriptor

   # Runs the following shell command
   xcrun metal-source -flatbuffers=json harvested-archive.metallib -o descriptors.json

Example output showing error

Environment

• MacBook Pro 2021 M1 Max
• macOS Version 13.0 Beta 22A5266r
• Xcode Version 14.0 beta 14A5228

-----------
Environment
-----------


Command: xcrun --show-sdk-path
Result: /Applications/Xcode-beta.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk


Command: xcrun xcodebuild -version
Result: Xcode 14.0
Build version 14A5229c


------------------------
Creating Render Pipeline
------------------------

2022-06-23 11:43:39.920133-0500 x-metal-source-on-harvested-gpu-archive[8264:109027] Metal GPU Frame Capture Enabled
2022-06-23 11:43:39.920532-0500 x-metal-source-on-harvested-gpu-archive[8264:109027] Metal API Validation Enabled

----------------------
Harvesting GPU Archive
----------------------

Created archive: /var/folders/bd/9qd81pgj4xj01bg4sgp43dvr0000gn/T/harvested-archive.metallib

--------------------------------------------
Verify/Display Information about GPU Archive
--------------------------------------------


Command: xcrun metal-readobj /var/folders/bd/9qd81pgj4xj01bg4sgp43dvr0000gn/T/harvested-archive.metallib
Result: 2022-06-23 11:43:39.980679-0500 xcrun[8269:109521] Failed to open macho file at /Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/metal-readobj for reading: Too many levels of symbolic links

File: /var/folders/bd/9qd81pgj4xj01bg4sgp43dvr0000gn/T/harvested-archive.metallib
Format: MetalLib
Arch: air64
AddressSize: 64bit

File: /var/folders/bd/9qd81pgj4xj01bg4sgp43dvr0000gn/T/harvested-archive.metallib
Format: Mach-O 64-bit Apple GPU
Arch: agx2
AddressSize: 64bit


---------------------------------------------
Using metal-source to get pipeline descriptor
---------------------------------------------


Command: xcrun metal-source -flatbuffers=json /var/folders/bd/9qd81pgj4xj01bg4sgp43dvr0000gn/T/harvested-archive.metallib -o /var/folders/bd/9qd81pgj4xj01bg4sgp43dvr0000gn/T/descriptors.json
Result: metal-source: error: unsupported binary format

Program ended with exit code: 0