[Draft] iOS support

CMakePresets.json

@@ -45,7 +45,8 @@
         "CMAKE_TOOLCHAIN_FILE": "${sourceDir}/third-party/ios-cmake/ios.toolchain.cmake",
         "EXECUTORCH_BUILD_PRESET_FILE": "${sourceDir}/tools/cmake/preset/macos.cmake",
         "PLATFORM": "MAC_ARM64",
-        "DEPLOYMENT_TARGET": "12.0",
+        "DEPLOYMENT_TARGET": "14.0",
+        "CMAKE_OSX_DEPLOYMENT_TARGET": "14.0",
         "CMAKE_MACOSX_BUNDLE": "OFF"
       },
       "condition": {

Package.swift

@@ -52,6 +52,13 @@ let products = deliverables([
       "sqlite3",
     ],
   ],
+  "backend_mlx": [
+    "frameworks": [
+      "Metal",
+      "MetalPerformanceShaders",
+    ],
+    "forceLoad": true,
+  ],
   "backend_mps": [
     "frameworks": [
       "Metal",
@@ -113,15 +120,20 @@ for (key, value) in products {
     name: key,
     path: "cmake-out/\(key).xcframework"
   ))
+  let forceLoad = value["forceLoad"] as? Bool ?? false
+  var linkerSettings: [LinkerSetting] =
+      (value["frameworks"] as? [String] ?? []).map { .linkedFramework($0) } +
+      (value["libraries"] as? [String] ?? []).map { .linkedLibrary($0) }
+  if forceLoad {
+    linkerSettings.append(.unsafeFlags(["-all_load"]))
+  }
   let target: Target = .target(
     name: "\(key)\(dependencies_suffix)",
     dependencies: ([key] + (value["targets"] as? [String] ?? []).map {
       key.hasSuffix(debug_suffix) ? $0 + debug_suffix : $0
     }).map { .target(name: $0) },
     path: ".Package.swift/\(key)",
-    linkerSettings:
-      (value["frameworks"] as? [String] ?? []).map { .linkedFramework($0) } +
-      (value["libraries"] as? [String] ?? []).map { .linkedLibrary($0) }
+    linkerSettings: linkerSettings
   )
   packageTargets.append(target)
 }

backends/mlx/CMakeLists.txt

@@ -1,3 +1,3 @@
 #
 # Copyright (c) Meta Platforms, Inc. and affiliates.
 # All rights reserved.
@@ -212,10 +212,24 @@
     CACHE BOOL "Use JIT compiled Metal kernels"
 )
 
+# For iOS builds, embed the metallib in the library so apps don't need to
+# bundle it separately. This avoids the runtime "metallib not found" issue
+# with static xcframeworks.
+if(CMAKE_SYSTEM_NAME MATCHES "iOS")
+  set(MLX_EMBED_METALLIB
+      ON
+      CACHE BOOL "Embed metallib in static library for iOS" FORCE
+  )
+  message(STATUS "iOS build: embedding metallib in static library")
+endif()
+
 # Auto-apply patches to MLX submodule. Each patch is applied idempotently: `git
 # apply --check` tests whether the patch is still applicable (i.e. not yet
 # applied), and only then applies it.
-set(_mlx_patches "${CMAKE_CURRENT_SOURCE_DIR}/patches/mlx_json.patch")
+# Note: mlx_ios_metal.patch includes the json changes from mlx_json.patch
+set(_mlx_patches
+    "${CMAKE_CURRENT_SOURCE_DIR}/patches/mlx_ios_metal.patch"
+)
 foreach(_patch IN LISTS _mlx_patches)
   if(EXISTS "${_patch}" AND EXISTS "${MLX_SOURCE_DIR}")
     get_filename_component(_patch_name "${_patch}" NAME)