runtimes/cpu: sandbox CPU PJRT plugin, simplifying as there are no additional NEEDED dependencies.

runtimes/cpu/BUILD.bazel

@@ -1,3 +1,4 @@
+load("@aspect_bazel_lib//lib:copy_to_directory.bzl", "copy_to_directory")
 load("@rules_zig//zig:defs.bzl", "zig_library")
 
 config_setting(
@@ -20,14 +21,21 @@ cc_library(
     name = "empty",
 )
 
-cc_library(
-    name = "libpjrt_cpu",
-    defines = ["ZML_RUNTIME_CPU"],
-    deps = select({
+copy_to_directory(
+    name = "sandbox",
+    out = "sandbox/lib",
+    srcs = select({
         ":darwin_arm64": ["@libpjrt_cpu_darwin_arm64//:libpjrt_cpu"],
         ":darwin_amd64": ["@libpjrt_cpu_darwin_amd64//:libpjrt_cpu"],
         "@platforms//os:linux": ["@libpjrt_cpu_linux_amd64//:libpjrt_cpu"],
     }),
+    include_external_repositories = ["**"],
+)
+
+cc_library(
+    name = "libpjrt_cpu",
+    defines = ["ZML_RUNTIME_CPU"],
+    data = [":sandbox"],
 )
 
 zig_library(
@@ -41,6 +49,8 @@ zig_library(
         "//runtimes:cpu.enabled": [
             ":libpjrt_cpu",
             "//async",
+            "//stdx",
+            "@rules_zig//zig/runfiles",
         ],
         "//conditions:default": [":empty"],
     }),

runtimes/cpu/cpu.bzl

@@ -6,18 +6,16 @@ package(default_visibility = ["//visibility:public"])
 """
 
 _BUILD_LINUX = "\n".join([
-    packages.load_("@zml//bazel:cc_import.bzl", "cc_import"),
-    packages.cc_import(
+    packages.filegroup(
         name = "libpjrt_cpu",
-        shared_library = "libpjrt_cpu.so",
-        soname = "libpjrt_cpu.so",
+        srcs = ["libpjrt_cpu.so"],
         visibility = ["@zml//runtimes/cpu:__subpackages__"],
     ),
 ])
 
-_BUILD_DARWIN = packages.cc_import(
+_BUILD_DARWIN = packages.filegroup(
     name = "libpjrt_cpu",
-    shared_library = "libpjrt_cpu.dylib",
+    srcs = ["libpjrt_cpu.dylib"],
     visibility = ["@zml//runtimes/cpu:__subpackages__"],
 )
 

runtimes/cpu/cpu.zig

@@ -3,6 +3,12 @@ const builtin = @import("builtin");
 const asynk = @import("async");
 const c = @import("c");
 const pjrt = @import("pjrt");
+const bazel_builtin = @import("bazel_builtin");
+const std = @import("std");
+const stdx = @import("stdx");
+const runfiles = @import("runfiles");
+
+const log = std.log.scoped(.@"zml/runtime/cpu");
 
 pub fn isEnabled() bool {
     return @hasDecl(c, "ZML_RUNTIME_CPU");
@@ -13,10 +19,31 @@ pub fn load() !*const pjrt.Api {
         return error.Unavailable;
     }
 
+    var arena = std.heap.ArenaAllocator.init(std.heap.c_allocator);
+    defer arena.deinit();
+
+    var r_ = try runfiles.Runfiles.create(.{ .allocator = arena.allocator() }) orelse {
+        stdx.debug.panic("Unable to find runfiles", .{});
+    };
+
+    const source_repo = bazel_builtin.current_repository;
+    const r = r_.withSourceRepo(source_repo);
+
+    var path_buf: [std.fs.max_path_bytes]u8 = undefined;
+    const sandbox_path = try r.rlocation("zml/runtimes/cpu/sandbox/lib", &path_buf) orelse {
+        log.err("Failed to find sandbox path for CPU runtime", .{});
+        return error.FileNotFound;
+    };
+
+    return blk: {
         const ext = switch (builtin.os.tag) {
             .windows => ".dll",
             .macos, .ios, .watchos => ".dylib",
             else => ".so",
         };
-    return try asynk.callBlocking(pjrt.Api.loadFrom, .{"libpjrt_cpu" ++ ext});
+
+        var lib_path_buf: [std.fs.max_path_bytes]u8 = undefined;
+        const path = try stdx.fs.path.bufJoinZ(&lib_path_buf, &.{ sandbox_path, "libpjrt_cpu" ++ ext });
+        break :blk asynk.callBlocking(pjrt.Api.loadFrom, .{path});
+    };
 }