feat: migrate wasm_optimize to native loom toolchain v1.1.14 (#512)

MODULE.bazel

@@ -261,6 +261,18 @@ use_repo(meld, "meld_toolchain")
 
 register_toolchains("@meld_toolchain//:meld_toolchain")
 
+# Loom toolchain for WebAssembly component optimization (native binary, v1.x).
+# wasm_optimize consumes this (loom_toolchain_type); the old @loom_wasm 0.3.0
+# component path was removed (#512).
+loom = use_extension("//wasm:extensions.bzl", "loom")
+loom.register(
+    name = "loom",
+    version = "1.1.14",
+)
+use_repo(loom, "loom_toolchain")
+
+register_toolchains("@loom_toolchain//:loom_toolchain")
+
 # spar toolchain: AADL architecture model -> WIT generation
 spar = use_extension("//wasm:extensions.bzl", "spar")
 spar.register(
@@ -331,13 +343,9 @@ wasm_component_download(
     version = "0.7.0",
 )
 
-# LOOM WebAssembly optimizer (version in //checksums/tools/loom.json)
-wasm_component_download(
-    name = "loom_wasm",
-    filename = "loom.wasm",
-    tool_name = "loom",
-    version = "0.3.0",
-)
+# LOOM: consumed via the native loom toolchain (@loom_toolchain, above).
+# The old @loom_wasm 0.3.0 component download was removed — loom v1.x is
+# native-only and wasm_optimize now runs the native binary directly (#512).
 
 # WASM Tools Component toolchain for universal wasm-tools operations
 register_toolchains("//toolchains:wasm_tools_component_toolchain_local")

test/p3/BUILD.bazel

@@ -6,6 +6,7 @@ P2 tests verify no regression, P3 tests verify the new attribute is accepted.
 
 load("@bazel_skylib//rules:build_test.bzl", "build_test")
 load("@rules_wasm_component//rust:defs.bzl", "rust_wasm_component", "rust_wasm_component_bindgen")
+load("@rules_wasm_component//wasm:defs.bzl", "wasm_optimize")
 load("@rules_wasm_component//wit:defs.bzl", "wit_library")
 
 package(default_visibility = ["//visibility:public"])
@@ -38,6 +39,20 @@ build_test(
     targets = [":hello_p2"],
 )
 
+# ============================================================================
+# Native loom optimize (covers wasm_optimize on the native loom toolchain, #512)
+# ============================================================================
+
+wasm_optimize(
+    name = "hello_p2_optimized",
+    component = ":hello_p2",
+)
+
+build_test(
+    name = "loom_optimize_build_test",
+    targets = [":hello_p2_optimized"],
+)
+
 # ============================================================================
 # P3 build (experimental — async bindings via wit-bindgen crate runtime)
 # ============================================================================

toolchains/BUILD.bazel

@@ -90,6 +90,12 @@ toolchain_type(
     visibility = ["//visibility:public"],
 )
 
+# Toolchain type for Loom (WebAssembly component optimization)
+toolchain_type(
+    name = "loom_toolchain_type",
+    visibility = ["//visibility:public"],
+)
+
 # Toolchain type for spar (AADL architecture model -> WIT generation)
 toolchain_type(
     name = "spar_toolchain_type",
@@ -349,6 +355,14 @@ bzl_library(
     deps = [":tool_registry"],
 )
 
+# Bzl library for Loom toolchain implementation
+bzl_library(
+    name = "loom_toolchain",
+    srcs = ["loom_toolchain.bzl"],
+    visibility = ["//visibility:public"],
+    deps = [":tool_registry"],
+)
+
 # Export .bzl files for testing
 exports_files([
     "tool_registry.bzl",

toolchains/loom_toolchain.bzl

@@ -0,0 +1,128 @@
+# Copyright 2026 Ralf Anton Beier. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+
+"""Loom toolchain: native binary for WebAssembly component optimization.
+
+loom optimizes a WebAssembly component (constant folding, CSE, inlining, DCE,
+fused-component passes, optional Z3 verification). As of v1.x loom is
+distributed as native per-OS binaries (the v0.x `loom.wasm` component was
+dropped), so wasm_optimize runs the native binary directly instead of running
+loom.wasm under wasmtime. Mirrors toolchains/meld_toolchain.bzl, but loom ships
+tarballs (extracted) rather than a bare binary.
+"""
+
+load("//checksums:registry.bzl", "validate_tool_exists")
+load("//toolchains:tool_registry.bzl", "tool_registry")
+
+# Platforms where loom native binaries are downloaded + extracted here. loom
+# also ships a Windows binary (loom.exe), but that path is not wired yet
+# (binary-name differs); Windows gets the stub for now (see #512 follow-up).
+_SUPPORTED_PLATFORMS = [
+    "darwin_amd64",
+    "darwin_arm64",
+    "linux_amd64",
+]
+
+def _loom_toolchain_impl(ctx):
+    """Implementation of loom_toolchain rule."""
+    return [platform_common.ToolchainInfo(
+        loom = ctx.file.loom,
+    )]
+
+loom_toolchain = rule(
+    implementation = _loom_toolchain_impl,
+    attrs = {
+        "loom": attr.label(
+            allow_single_file = True,
+            executable = True,
+            cfg = "exec",
+            doc = "loom binary for component optimization",
+        ),
+    },
+    doc = "Declares a Loom toolchain for WebAssembly component optimization",
+)
+
+_STUB_BUILD = '''"""Loom toolchain stub: unsupported platform.
+
+loom has no wired native binary for this host, so we register a toolchain that
+is marked incompatible with any target. Toolchain resolution for wasm_optimize
+targets fails cleanly here; builds that never touch wasm_optimize are unaffected.
+"""
+
+load("@rules_wasm_component//toolchains:loom_toolchain.bzl", "loom_toolchain")
+
+package(default_visibility = ["//visibility:public"])
+
+exports_files(["loom_stub"])
+
+loom_toolchain(
+    name = "loom_toolchain_impl",
+    loom = "loom_stub",
+)
+
+toolchain(
+    name = "loom_toolchain",
+    target_compatible_with = ["@platforms//:incompatible"],
+    toolchain = ":loom_toolchain_impl",
+    toolchain_type = "@rules_wasm_component//toolchains:loom_toolchain_type",
+)
+'''
+
+def _loom_repository_impl(repository_ctx):
+    """Download + extract the loom native binary and create a toolchain repo."""
+    platform = tool_registry.detect_platform(repository_ctx)
+    version = repository_ctx.attr.version
+
+    if platform not in _SUPPORTED_PLATFORMS or not validate_tool_exists(repository_ctx, "loom", version, platform):
+        print("Loom: no wired native binary for platform {} (version {}); emitting stub".format(platform, version))
+        repository_ctx.file("loom_stub", content = "", executable = True)
+        repository_ctx.file("BUILD.bazel", _STUB_BUILD)
+        return
+
+    print("Setting up loom {} for platform {}".format(version, platform))
+
+    # loom ships a tarball containing ./loom; tool_registry extracts it (the
+    # 1.1.14 registry entries have no `binary: true`) and returns the binary
+    # path. strip_prefix is "" (flat archive) — see _calculate_strip_prefix.
+    tool_registry.download(
+        repository_ctx,
+        "loom",
+        version,
+        platform,
+    )
+
+    repository_ctx.file("BUILD.bazel", '''"""Loom toolchain repository"""
+
+load("@rules_wasm_component//toolchains:loom_toolchain.bzl", "loom_toolchain")
+
+package(default_visibility = ["//visibility:public"])
+
+loom_toolchain(
+    name = "loom_toolchain_impl",
+    loom = ":loom",
+)
+
+toolchain(
+    name = "loom_toolchain",
+    exec_compatible_with = [],
+    target_compatible_with = [],
+    toolchain = ":loom_toolchain_impl",
+    toolchain_type = "@rules_wasm_component//toolchains:loom_toolchain_type",
+)
+''')
+
+loom_repository = repository_rule(
+    implementation = _loom_repository_impl,
+    attrs = {
+        "version": attr.string(
+            default = "1.1.14",
+            doc = "Loom version to download",
+        ),
+    },
+    doc = "Downloads loom and creates a toolchain repository",
+)

toolchains/tool_registry.bzl

@@ -143,6 +143,11 @@ _URL_PATTERNS = {
         "filename": "{suffix}",  # e.g., "meld-aarch64-apple-darwin"
         "is_binary": True,
     },
+    "loom": {
+        # loom v1.x releases are tarballs (extracted; url_suffix IS the filename)
+        "base": "https://github.com/{repo}/releases/download/v{version}",
+        "filename": "{suffix}",  # e.g., "loom-v1.1.14-aarch64-apple-darwin.tar.gz"
+    },
     "spar": {
         # spar releases are tar.gz/zip archives: spar-v{version}-{triple}.{ext}
         "base": "https://github.com/{repo}/releases/download/v{version}",