build_tools/bazel/wasm/BUILD.bazel - 3p/openxla/iree - Git at Google

 # Copyright 2026 The IREE Authors
 #
 # Licensed under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

 # Wasm cross-compilation toolchains using wasi-sdk.
 #
 # Two toolchains are provided:
 #
 # 1. wasm32 (freestanding): for production runtime builds.
 #    --target=wasm32-unknown-unknown, uses IREE's minimal libc headers,
 #    no system libraries.  bazel build --config=wasm32 //some:target
 #
 # 2. wasm32_wasi (hosted): for building with full C/C++ stdlib.
 #    --target=wasm32-wasi, uses wasi-sdk's sysroot (musl + libc++).
 #    bazel build --config=wasm32_wasi //some:target
 #
 # Both toolchains are downloaded automatically from GitHub releases.
 # Normal host builds are completely unaffected.

 load("@rules_cc//cc/toolchains:args.bzl", "cc_args")
 load("@rules_cc//cc/toolchains:tool.bzl", "cc_tool")
 load("@rules_cc//cc/toolchains:tool_map.bzl", "cc_tool_map")
 load("@rules_cc//cc/toolchains:toolchain.bzl", "cc_toolchain")
 load("@wasi_sdk//:paths.bzl", "WASI_RESOURCE_DIR", "WASI_SYSROOT_PATH")
 load(":wasm_clang_linker.bzl", "wasm_clang_linker")

 package(default_visibility = ["//visibility:public"])

 #===------------------------------------------------------------------------===#
 # Platform definitions
 #===------------------------------------------------------------------------===#

 platform(
     name = "wasm32",
     constraint_values = [
         "@platforms//cpu:wasm32",
         "@platforms//os:none",
     ],
 )

 # WASI is a custom OS constraint — @platforms doesn't define it.
 constraint_value(
     name = "wasi",
     constraint_setting = "@platforms//os:os",
 )

 platform(
     name = "wasm32_wasi",
     constraint_values = [
         "@platforms//cpu:wasm32",
         ":wasi",
     ],
 )

 #===------------------------------------------------------------------------===#
 # Freestanding wasm32 toolchain (for production runtime builds)
 #===------------------------------------------------------------------------===#

 cc_tool(
     name = "clang_tool",
     src = "@wasi_sdk//:clang",
 )

 # Clang-based linker driver: invokes clang with --target=wasm32 and
 # -fuse-ld=lld, so Bazel's GCC driver conventions (-Wl,X, -shared,
 # @paramfile) pass through without translation. A wasm-ld symlink is
 # co-located with clang via -B for linker discovery.
 wasm_clang_linker(
     name = "wasm_link_driver",
     clang = "@wasi_sdk//:clang",
     extra_flags = [
         "--target=wasm32-unknown-unknown",
         "-nostdlib",
     ],
     lld = "@wasi_sdk//:lld",
 )

 cc_tool(
     name = "wasm_link_tool",
     src = ":wasm_link_driver",
 )

 cc_tool(
     name = "ar_tool",
     src = "@wasi_sdk//:llvm-ar",
 )

 cc_tool_map(
     name = "wasm32_tool_map",
     tools = {
         "@rules_cc//cc/toolchains/actions:assembly_actions": ":clang_tool",
         "@rules_cc//cc/toolchains/actions:c_compile": ":clang_tool",
         "@rules_cc//cc/toolchains/actions:cpp_compile_actions": ":clang_tool",
         "@rules_cc//cc/toolchains/actions:link_executable_actions": ":wasm_link_tool",
         "@rules_cc//cc/toolchains/actions:dynamic_library_link_actions": ":wasm_link_tool",
         "@rules_cc//cc/toolchains/actions:ar_actions": ":ar_tool",
     },
 )

 cc_args(
     name = "wasm32_compile_args",
     actions = [
         "@rules_cc//cc/toolchains/actions:c_compile",
         "@rules_cc//cc/toolchains/actions:cpp_compile_actions",
         "@rules_cc//cc/toolchains/actions:assembly_actions",
     ],
     args = [
         # Target triple.
         "--target=wasm32-unknown-unknown",

         # Freestanding: no system headers, no libc assumptions.
         # -nostdinc disables all default include paths. By default we provide
         # IREE's libc headers below; users embedding IREE into another wasm
         # environment can pass --define=iree_wasm_libc=custom and provide
         # their own declared headers and include paths.
         "-nostdinc",
         "-nostdlib",
         "-ffreestanding",
     ] + select({
         "//build_tools/bazel:iree_wasm_libc_custom": [],
         "//conditions:default": [
             # Wasm libc headers (freestanding + hosted shims).
             # Path is relative to the execroot, where source files live.
             "-isystem",
             "build_tools/wasm/libc/include",
         ],
     }) + [

         # C/C++ settings.
         "-std=c17",
         "-fno-exceptions",
         "-fno-rtti",
         "-fvisibility=hidden",
         "-fno-short-wchar",

         # Wasm feature flags: these correspond to widely-supported proposals
         # that are baseline in all modern engines (Chrome 91+, Firefox 89+,
         # Safari 15+, Node 16+).
         "-mbulk-memory",
         "-msign-ext",
         "-mnontrapping-fptoint",

         # Freestanding wasm is currently single-mutator. Disable IREE threading
         # and synchronization primitives until the libc heap, errno, and worker
         # lifecycle have a real pthread/TLS contract.
         "-DIREE_SYNCHRONIZATION_DISABLE_UNSAFE=1",
         "-DIREE_THREADING_ENABLE=0",

         # Web platform define (injected by toolchain, not auto-detected).
         "-DIREE_PLATFORM_WEB=1",
     ],
     data = select({
         "//build_tools/bazel:iree_wasm_libc_custom": [],
         "//conditions:default": ["//build_tools/wasm/libc:headers"],
     }),
 )

 cc_args(
     name = "wasm32_link_args",
     actions = [
         "@rules_cc//cc/toolchains/actions:link_executable_actions",
         "@rules_cc//cc/toolchains/actions:dynamic_library_link_actions",
     ],
     args = [
         # Import-memory model: the embedder creates WebAssembly.Memory and
         # passes it to the module so it can control memory sizing.
         "-Wl,--import-memory",

         # No _start entry point — Wasm modules are libraries invoked
         # by the JS host, not standalone executables.
         "-Wl,--no-entry",

         # Export all non-hidden symbols so the JS host can call them.
         "-Wl,--export-dynamic",

         # Allow undefined symbols — they become Wasm imports that the JS host
         # must provide (csprng, topology, clock, etc.). --allow-undefined is
         # kept for compatibility; --import-undefined makes the import contract
         # explicit so bridge functions are preserved as imports at link time.
         "-Wl,--allow-undefined",
         "-Wl,--import-undefined",

         # Max memory: 4GB (the wasm32 address space limit).
         # Initial memory is determined by the module's data segments.
         "-Wl,--max-memory=4294967296",
     ],
 )

 cc_toolchain(
     name = "wasm32_cc_toolchain",
     args = [
         ":wasm32_compile_args",
         ":wasm32_link_args",
     ],
     compiler = "clang",
     enabled_features = [
         "@rules_cc//cc/toolchains/args:experimental_replace_legacy_action_config_features",
     ],
     known_features = [
         "@rules_cc//cc/toolchains/args:experimental_replace_legacy_action_config_features",
     ],
     # No standard includes — we provide everything via our libc shim.
     supports_header_parsing = False,
     supports_param_files = True,
     tool_map = ":wasm32_tool_map",
 )

 # Register for each host platform where wasi-sdk is available.
 [toolchain(
     name = "wasm32_toolchain_" + os + "_" + cpu,
     exec_compatible_with = [
         "@platforms//os:" + os,
         "@platforms//cpu:" + cpu,
     ],
     target_compatible_with = [
         "@platforms//cpu:wasm32",
         "@platforms//os:none",
     ],
     toolchain = ":wasm32_cc_toolchain",
     toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
 ) for os, cpu in [
     ("linux", "x86_64"),
     ("linux", "aarch64"),
     ("macos", "x86_64"),
     ("macos", "aarch64"),
 ]]

 #===------------------------------------------------------------------------===#
 # WASI-hosted wasm32 toolchain (for tests with gtest/gbenchmark)
 #===------------------------------------------------------------------------===#
 #
 # Uses the same clang binary as the freestanding toolchain, but with
 # --sysroot and -resource-dir pointing at the wasi-sdk's sysroot (musl +
 # libc++ + compiler-rt) using execroot-relative paths from paths.bzl.
 #
 # -no-canonical-prefixes prevents clang from resolving symlinks and
 # producing absolute paths, which would fail Bazel's header inclusion check.

 # Linker driver for WASI: same co-location trick as freestanding, but
 # targeting wasm32-wasi (with system libraries, no -nostdlib).
 wasm_clang_linker(
     name = "wasm_wasi_link_driver",
     clang = "@wasi_sdk//:clang",
     extra_flags = [
         "--target=wasm32-wasi",
         # Force __main_argc_argv as a strong undefined from the start.
         # wasi-libc's crt1-command.o calls __main_void, and libc.a provides
         # a weak __main_void that dispatches to __main_argc_argv (also weak).
         # But libc.a is linked implicitly by clang AFTER user archives, so
         # when the linker processes gtest_main.a (which defines
         # __main_argc_argv via int main(int, char**)), the symbol isn't
         # yet needed and the archive member isn't extracted. Making it
         # strong undefined up front forces extraction during the first pass.
         "-Wl,--undefined=__main_argc_argv",
     ],
     # Strip host-oriented flags that Bazel's built-in features inject into
     # params files: -pthread enables --shared-memory (requires atomics-
     # compiled sysroot libraries), -pie is meaningless for wasm.
     filter_flags = [
         "-pthread",
         "-pie",
         "-fsanitize=address",
     ],
     lld = "@wasi_sdk//:lld",
     # System libraries appended AFTER all Bazel-generated arguments ("$@").
     # Bazel places toolchain cc_args before user objects/archives, but the
     # linker's single-pass archive extraction requires system libraries to
     # come after user archives: libc's __main_void creates a weak ref to
     # __main_argc_argv, which gtest_main (a user archive) defines. If -lc++
     # comes before user archives, the linker never resolves this forward ref.
     suffix_flags = [
         "-lwasi-emulated-signal",
         "-lwasi-emulated-process-clocks",
         "-lc++",
         "-lc++abi",
     ],
 )

 cc_tool(
     name = "wasi_link_tool",
     src = ":wasm_wasi_link_driver",
 )

 cc_tool_map(
     name = "wasm32_wasi_tool_map",
     tools = {
         # Same clang as freestanding — sysroot is passed via cc_args.
         "@rules_cc//cc/toolchains/actions:assembly_actions": ":clang_tool",
         "@rules_cc//cc/toolchains/actions:c_compile": ":clang_tool",
         "@rules_cc//cc/toolchains/actions:cpp_compile_actions": ":clang_tool",
         "@rules_cc//cc/toolchains/actions:link_executable_actions": ":wasi_link_tool",
         "@rules_cc//cc/toolchains/actions:dynamic_library_link_actions": ":wasi_link_tool",
         "@rules_cc//cc/toolchains/actions:ar_actions": ":ar_tool",
     },
 )

 cc_args(
     name = "wasm32_wasi_compile_args",
     actions = [
         "@rules_cc//cc/toolchains/actions:c_compile",
         "@rules_cc//cc/toolchains/actions:cpp_compile_actions",
         "@rules_cc//cc/toolchains/actions:assembly_actions",
     ],
     args = [
         "--target=wasm32-wasi",

         # Sysroot: wasi-libc (musl) + libc++ headers.
         # Path is execroot-relative (from @wasi_sdk//:paths.bzl).
         "--sysroot=" + WASI_SYSROOT_PATH,

         # Resource directory: clang builtins (stddef.h, stdarg.h, etc.)
         # and compiler-rt. Overrides clang's default of resolving through
         # symlinks to find its resource dir (which produces absolute paths).
         "-resource-dir=" + WASI_RESOURCE_DIR,

         # Prevent clang from canonicalizing include paths to absolute.
         # Without this, clang resolves symlinks in --sysroot and
         # -resource-dir, producing absolute paths that fail Bazel's
         # header inclusion check.
         "-no-canonical-prefixes",

         # IREE code style: no exceptions, no RTTI.
         "-fno-exceptions",
         "-fno-rtti",
         "-fvisibility=hidden",
         "-fno-short-wchar",

         # Wasm feature flags (same as freestanding).
         "-mbulk-memory",
         "-msign-ext",
         "-mnontrapping-fptoint",

         # Web platform define.
         "-DIREE_PLATFORM_WEB=1",

         # WASI preview1 is single-threaded: no pthreads, no shared memory,
         # no atomics instructions. Disable synchronization primitives (turns
         # mutexes/notifications/futexes into no-ops) and threading support.
         "-DIREE_SYNCHRONIZATION_DISABLE_UNSAFE=1",
         "-DIREE_THREADING_ENABLE=0",

         # WASI emulation layers.
         # Signal: gtest includes <csignal> for its test runner.
         "-D_WASI_EMULATED_SIGNAL",
         # Process clocks: Google Benchmark uses getrusage(RUSAGE_SELF)
         # for CPU timing. WASI emulates this using wall clock time, which
         # is equivalent for single-threaded wasm (wall time ≈ CPU time).
         "-D_WASI_EMULATED_PROCESS_CLOCKS",
         # Google Benchmark compatibility: benchmark doesn't detect WASI as a
         # platform and #errors on missing cycle counter and thread CPU time.
         # Thread CPU time: wasi-libc defines CLOCK_THREAD_CPUTIME_ID as
         # integer 3 in <time.h> but clockid_t is an opaque pointer type
         # (const struct __clockid*) and no extern symbol exists for it.
         # Aliasing to CLOCK_MONOTONIC gives wall-clock time, identical to
         # CPU time in single-threaded wasm.
         "-DCLOCK_THREAD_CPUTIME_ID=CLOCK_MONOTONIC",
         # Cycle counter: benchmark's cycleclock.h has no __wasm__ branch.
         # NaCl's path uses clock_gettime(CLOCK_MONOTONIC) which is exactly
         # what we want, and NaCl is a dead platform (no collision risk).
         # The only other effect is HOST_NAME_MAX=64 in sysinfo.cc.
         "-DBENCHMARK_OS_NACL",

         # WASI lacks dup/dup2/mkstemp/fork — disable gtest features that
         # require them. gtest's auto-detection correctly skips death tests
         # (no GTEST_OS_* matches WASI) and POSIX regex (unknown platform
         # defaults to 0). But stream redirection auto-detects to 1 for any
         # platform not in the explicit exclusion list, so we override it.
         "-DGTEST_HAS_STREAM_REDIRECTION=0",
     ],
     data = [
         "@wasi_sdk//:clang_resources",
         "@wasi_sdk//:sysroot",
     ],
 )

 cc_args(
     name = "wasm32_wasi_cxx_args",
     actions = [
         "@rules_cc//cc/toolchains/actions:cpp_compile_actions",
     ],
     args = [
         # IREE requires C++17 (matching host builds).
         "-std=c++17",

         # Explicit C++ standard library include paths.
         #
         # Clang's addLibCxxIncludePaths auto-detection probes the filesystem
         # relative to its InstalledDir (resolved from the binary's symlink
         # chain). In Bazel's processwrapper-sandbox the symlink layout differs
         # from the real execroot, so the probing fails and clang silently
         # skips the C++ include directories. Providing the paths explicitly
         # via -isystem makes the build sandbox-independent.
         #
         # Target-specific headers first (wasm32-wasi overrides), then generic.
         "-isystem",
         WASI_SYSROOT_PATH + "/include/wasm32-wasi/c++/v1",
         "-isystem",
         WASI_SYSROOT_PATH + "/include/c++/v1",
     ],
 )

 cc_args(
     name = "wasm32_wasi_link_args",
     actions = [
         "@rules_cc//cc/toolchains/actions:link_executable_actions",
         "@rules_cc//cc/toolchains/actions:dynamic_library_link_actions",
     ],
     args = [
         # Target triple and sysroot for finding crt1.o, libc.a, libc++.a.
         "--target=wasm32-wasi",
         "--sysroot=" + WASI_SYSROOT_PATH,
         "-resource-dir=" + WASI_RESOURCE_DIR,
         "-no-canonical-prefixes",

         # System libraries (-lc++, -lc++abi, -lwasi-emulated-signal) are in
         # the linker wrapper's suffix_flags, not here. Bazel places cc_args
         # before user objects/archives, but the linker's single-pass archive
         # extraction requires system libraries after user archives.
     ],
     data = [
         "@wasi_sdk//:clang_resources",
         "@wasi_sdk//:sysroot",
     ],
 )

 cc_toolchain(
     name = "wasm32_wasi_cc_toolchain",
     args = [
         ":wasm32_wasi_compile_args",
         ":wasm32_wasi_cxx_args",
         ":wasm32_wasi_link_args",
     ],
     compiler = "clang",
     enabled_features = [
         "@rules_cc//cc/toolchains/args:experimental_replace_legacy_action_config_features",
     ],
     known_features = [
         "@rules_cc//cc/toolchains/args:experimental_replace_legacy_action_config_features",
     ],
     supports_header_parsing = False,
     supports_param_files = True,
     tool_map = ":wasm32_wasi_tool_map",
 )

 [toolchain(
     name = "wasm32_wasi_toolchain_" + os + "_" + cpu,
     exec_compatible_with = [
         "@platforms//os:" + os,
         "@platforms//cpu:" + cpu,
     ],
     target_compatible_with = [
         "@platforms//cpu:wasm32",
         ":wasi",
     ],
     toolchain = ":wasm32_wasi_cc_toolchain",
     toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
 ) for os, cpu in [
     ("linux", "x86_64"),
     ("linux", "aarch64"),
     ("macos", "x86_64"),
     ("macos", "aarch64"),
 ]]
	# Copyright 2026 The IREE Authors
	#
	# Licensed under the Apache License v2.0 with LLVM Exceptions.
	# See https://llvm.org/LICENSE.txt for license information.
	# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

	# Wasm cross-compilation toolchains using wasi-sdk.
	#
	# Two toolchains are provided:
	#
	# 1. wasm32 (freestanding): for production runtime builds.
	# --target=wasm32-unknown-unknown, uses IREE's minimal libc headers,
	# no system libraries. bazel build --config=wasm32 //some:target
	#
	# 2. wasm32_wasi (hosted): for building with full C/C++ stdlib.
	# --target=wasm32-wasi, uses wasi-sdk's sysroot (musl + libc++).
	# bazel build --config=wasm32_wasi //some:target
	#
	# Both toolchains are downloaded automatically from GitHub releases.
	# Normal host builds are completely unaffected.

	load("@rules_cc//cc/toolchains:args.bzl", "cc_args")
	load("@rules_cc//cc/toolchains:tool.bzl", "cc_tool")
	load("@rules_cc//cc/toolchains:tool_map.bzl", "cc_tool_map")
	load("@rules_cc//cc/toolchains:toolchain.bzl", "cc_toolchain")
	load("@wasi_sdk//:paths.bzl", "WASI_RESOURCE_DIR", "WASI_SYSROOT_PATH")
	load(":wasm_clang_linker.bzl", "wasm_clang_linker")

	package(default_visibility = ["//visibility:public"])

	#===------------------------------------------------------------------------===#
	# Platform definitions
	#===------------------------------------------------------------------------===#

	platform(
	name = "wasm32",
	constraint_values = [
	"@platforms//cpu:wasm32",
	"@platforms//os:none",
	],
	)

	# WASI is a custom OS constraint — @platforms doesn't define it.
	constraint_value(
	name = "wasi",
	constraint_setting = "@platforms//os:os",
	)

	platform(
	name = "wasm32_wasi",
	constraint_values = [
	"@platforms//cpu:wasm32",
	":wasi",
	],
	)

	#===------------------------------------------------------------------------===#
	# Freestanding wasm32 toolchain (for production runtime builds)
	#===------------------------------------------------------------------------===#

	cc_tool(
	name = "clang_tool",
	src = "@wasi_sdk//:clang",
	)

	# Clang-based linker driver: invokes clang with --target=wasm32 and
	# -fuse-ld=lld, so Bazel's GCC driver conventions (-Wl,X, -shared,
	# @paramfile) pass through without translation. A wasm-ld symlink is
	# co-located with clang via -B for linker discovery.
	wasm_clang_linker(
	name = "wasm_link_driver",
	clang = "@wasi_sdk//:clang",
	extra_flags = [
	"--target=wasm32-unknown-unknown",
	"-nostdlib",
	],
	lld = "@wasi_sdk//:lld",
	)

	cc_tool(
	name = "wasm_link_tool",
	src = ":wasm_link_driver",
	)

	cc_tool(
	name = "ar_tool",
	src = "@wasi_sdk//:llvm-ar",
	)

	cc_tool_map(
	name = "wasm32_tool_map",
	tools = {
	"@rules_cc//cc/toolchains/actions:assembly_actions": ":clang_tool",
	"@rules_cc//cc/toolchains/actions:c_compile": ":clang_tool",
	"@rules_cc//cc/toolchains/actions:cpp_compile_actions": ":clang_tool",
	"@rules_cc//cc/toolchains/actions:link_executable_actions": ":wasm_link_tool",
	"@rules_cc//cc/toolchains/actions:dynamic_library_link_actions": ":wasm_link_tool",
	"@rules_cc//cc/toolchains/actions:ar_actions": ":ar_tool",
	},
	)

	cc_args(
	name = "wasm32_compile_args",
	actions = [
	"@rules_cc//cc/toolchains/actions:c_compile",
	"@rules_cc//cc/toolchains/actions:cpp_compile_actions",
	"@rules_cc//cc/toolchains/actions:assembly_actions",
	],
	args = [
	# Target triple.
	"--target=wasm32-unknown-unknown",

	# Freestanding: no system headers, no libc assumptions.
	# -nostdinc disables all default include paths. By default we provide
	# IREE's libc headers below; users embedding IREE into another wasm
	# environment can pass --define=iree_wasm_libc=custom and provide
	# their own declared headers and include paths.
	"-nostdinc",
	"-nostdlib",
	"-ffreestanding",
	] + select({
	"//build_tools/bazel:iree_wasm_libc_custom": [],
	"//conditions:default": [
	# Wasm libc headers (freestanding + hosted shims).
	# Path is relative to the execroot, where source files live.
	"-isystem",
	"build_tools/wasm/libc/include",
	],
	}) + [

	# C/C++ settings.
	"-std=c17",
	"-fno-exceptions",
	"-fno-rtti",
	"-fvisibility=hidden",
	"-fno-short-wchar",

	# Wasm feature flags: these correspond to widely-supported proposals
	# that are baseline in all modern engines (Chrome 91+, Firefox 89+,
	# Safari 15+, Node 16+).
	"-mbulk-memory",
	"-msign-ext",
	"-mnontrapping-fptoint",

	# Freestanding wasm is currently single-mutator. Disable IREE threading
	# and synchronization primitives until the libc heap, errno, and worker
	# lifecycle have a real pthread/TLS contract.
	"-DIREE_SYNCHRONIZATION_DISABLE_UNSAFE=1",
	"-DIREE_THREADING_ENABLE=0",

	# Web platform define (injected by toolchain, not auto-detected).
	"-DIREE_PLATFORM_WEB=1",
	],
	data = select({
	"//build_tools/bazel:iree_wasm_libc_custom": [],
	"//conditions:default": ["//build_tools/wasm/libc:headers"],
	}),
	)

	cc_args(
	name = "wasm32_link_args",
	actions = [
	"@rules_cc//cc/toolchains/actions:link_executable_actions",
	"@rules_cc//cc/toolchains/actions:dynamic_library_link_actions",
	],
	args = [
	# Import-memory model: the embedder creates WebAssembly.Memory and
	# passes it to the module so it can control memory sizing.
	"-Wl,--import-memory",

	# No _start entry point — Wasm modules are libraries invoked
	# by the JS host, not standalone executables.
	"-Wl,--no-entry",

	# Export all non-hidden symbols so the JS host can call them.
	"-Wl,--export-dynamic",

	# Allow undefined symbols — they become Wasm imports that the JS host
	# must provide (csprng, topology, clock, etc.). --allow-undefined is
	# kept for compatibility; --import-undefined makes the import contract
	# explicit so bridge functions are preserved as imports at link time.
	"-Wl,--allow-undefined",
	"-Wl,--import-undefined",

	# Max memory: 4GB (the wasm32 address space limit).
	# Initial memory is determined by the module's data segments.
	"-Wl,--max-memory=4294967296",
	],
	)

	cc_toolchain(
	name = "wasm32_cc_toolchain",
	args = [
	":wasm32_compile_args",
	":wasm32_link_args",
	],
	compiler = "clang",
	enabled_features = [
	"@rules_cc//cc/toolchains/args:experimental_replace_legacy_action_config_features",
	],
	known_features = [
	"@rules_cc//cc/toolchains/args:experimental_replace_legacy_action_config_features",
	],
	# No standard includes — we provide everything via our libc shim.
	supports_header_parsing = False,
	supports_param_files = True,
	tool_map = ":wasm32_tool_map",
	)

	# Register for each host platform where wasi-sdk is available.
	[toolchain(
	name = "wasm32_toolchain_" + os + "_" + cpu,
	exec_compatible_with = [
	"@platforms//os:" + os,
	"@platforms//cpu:" + cpu,
	],
	target_compatible_with = [
	"@platforms//cpu:wasm32",
	"@platforms//os:none",
	],
	toolchain = ":wasm32_cc_toolchain",
	toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
	) for os, cpu in [
	("linux", "x86_64"),
	("linux", "aarch64"),
	("macos", "x86_64"),
	("macos", "aarch64"),
	]]

	#===------------------------------------------------------------------------===#
	# WASI-hosted wasm32 toolchain (for tests with gtest/gbenchmark)
	#===------------------------------------------------------------------------===#
	#
	# Uses the same clang binary as the freestanding toolchain, but with
	# --sysroot and -resource-dir pointing at the wasi-sdk's sysroot (musl +
	# libc++ + compiler-rt) using execroot-relative paths from paths.bzl.
	#
	# -no-canonical-prefixes prevents clang from resolving symlinks and
	# producing absolute paths, which would fail Bazel's header inclusion check.

	# Linker driver for WASI: same co-location trick as freestanding, but
	# targeting wasm32-wasi (with system libraries, no -nostdlib).
	wasm_clang_linker(
	name = "wasm_wasi_link_driver",
	clang = "@wasi_sdk//:clang",
	extra_flags = [
	"--target=wasm32-wasi",
	# Force __main_argc_argv as a strong undefined from the start.
	# wasi-libc's crt1-command.o calls __main_void, and libc.a provides
	# a weak __main_void that dispatches to __main_argc_argv (also weak).
	# But libc.a is linked implicitly by clang AFTER user archives, so
	# when the linker processes gtest_main.a (which defines
	# __main_argc_argv via int main(int, char**)), the symbol isn't
	# yet needed and the archive member isn't extracted. Making it
	# strong undefined up front forces extraction during the first pass.
	"-Wl,--undefined=__main_argc_argv",
	],
	# Strip host-oriented flags that Bazel's built-in features inject into
	# params files: -pthread enables --shared-memory (requires atomics-
	# compiled sysroot libraries), -pie is meaningless for wasm.
	filter_flags = [
	"-pthread",
	"-pie",
	"-fsanitize=address",
	],
	lld = "@wasi_sdk//:lld",
	# System libraries appended AFTER all Bazel-generated arguments ("$@").
	# Bazel places toolchain cc_args before user objects/archives, but the
	# linker's single-pass archive extraction requires system libraries to
	# come after user archives: libc's __main_void creates a weak ref to
	# __main_argc_argv, which gtest_main (a user archive) defines. If -lc++
	# comes before user archives, the linker never resolves this forward ref.
	suffix_flags = [
	"-lwasi-emulated-signal",
	"-lwasi-emulated-process-clocks",
	"-lc++",
	"-lc++abi",
	],
	)

	cc_tool(
	name = "wasi_link_tool",
	src = ":wasm_wasi_link_driver",
	)

	cc_tool_map(
	name = "wasm32_wasi_tool_map",
	tools = {
	# Same clang as freestanding — sysroot is passed via cc_args.
	"@rules_cc//cc/toolchains/actions:assembly_actions": ":clang_tool",
	"@rules_cc//cc/toolchains/actions:c_compile": ":clang_tool",
	"@rules_cc//cc/toolchains/actions:cpp_compile_actions": ":clang_tool",
	"@rules_cc//cc/toolchains/actions:link_executable_actions": ":wasi_link_tool",
	"@rules_cc//cc/toolchains/actions:dynamic_library_link_actions": ":wasi_link_tool",
	"@rules_cc//cc/toolchains/actions:ar_actions": ":ar_tool",
	},
	)

	cc_args(
	name = "wasm32_wasi_compile_args",
	actions = [
	"@rules_cc//cc/toolchains/actions:c_compile",
	"@rules_cc//cc/toolchains/actions:cpp_compile_actions",
	"@rules_cc//cc/toolchains/actions:assembly_actions",
	],
	args = [
	"--target=wasm32-wasi",

	# Sysroot: wasi-libc (musl) + libc++ headers.
	# Path is execroot-relative (from @wasi_sdk//:paths.bzl).
	"--sysroot=" + WASI_SYSROOT_PATH,

	# Resource directory: clang builtins (stddef.h, stdarg.h, etc.)
	# and compiler-rt. Overrides clang's default of resolving through
	# symlinks to find its resource dir (which produces absolute paths).
	"-resource-dir=" + WASI_RESOURCE_DIR,

	# Prevent clang from canonicalizing include paths to absolute.
	# Without this, clang resolves symlinks in --sysroot and
	# -resource-dir, producing absolute paths that fail Bazel's
	# header inclusion check.
	"-no-canonical-prefixes",

	# IREE code style: no exceptions, no RTTI.
	"-fno-exceptions",
	"-fno-rtti",
	"-fvisibility=hidden",
	"-fno-short-wchar",

	# Wasm feature flags (same as freestanding).
	"-mbulk-memory",
	"-msign-ext",
	"-mnontrapping-fptoint",

	# Web platform define.
	"-DIREE_PLATFORM_WEB=1",

	# WASI preview1 is single-threaded: no pthreads, no shared memory,
	# no atomics instructions. Disable synchronization primitives (turns
	# mutexes/notifications/futexes into no-ops) and threading support.
	"-DIREE_SYNCHRONIZATION_DISABLE_UNSAFE=1",
	"-DIREE_THREADING_ENABLE=0",

	# WASI emulation layers.
	# Signal: gtest includes <csignal> for its test runner.
	"-D_WASI_EMULATED_SIGNAL",
	# Process clocks: Google Benchmark uses getrusage(RUSAGE_SELF)
	# for CPU timing. WASI emulates this using wall clock time, which
	# is equivalent for single-threaded wasm (wall time ≈ CPU time).
	"-D_WASI_EMULATED_PROCESS_CLOCKS",
	# Google Benchmark compatibility: benchmark doesn't detect WASI as a
	# platform and #errors on missing cycle counter and thread CPU time.
	# Thread CPU time: wasi-libc defines CLOCK_THREAD_CPUTIME_ID as
	# integer 3 in <time.h> but clockid_t is an opaque pointer type
	# (const struct __clockid*) and no extern symbol exists for it.
	# Aliasing to CLOCK_MONOTONIC gives wall-clock time, identical to
	# CPU time in single-threaded wasm.
	"-DCLOCK_THREAD_CPUTIME_ID=CLOCK_MONOTONIC",
	# Cycle counter: benchmark's cycleclock.h has no __wasm__ branch.
	# NaCl's path uses clock_gettime(CLOCK_MONOTONIC) which is exactly
	# what we want, and NaCl is a dead platform (no collision risk).
	# The only other effect is HOST_NAME_MAX=64 in sysinfo.cc.
	"-DBENCHMARK_OS_NACL",

	# WASI lacks dup/dup2/mkstemp/fork — disable gtest features that
	# require them. gtest's auto-detection correctly skips death tests
	# (no GTEST_OS_* matches WASI) and POSIX regex (unknown platform
	# defaults to 0). But stream redirection auto-detects to 1 for any
	# platform not in the explicit exclusion list, so we override it.
	"-DGTEST_HAS_STREAM_REDIRECTION=0",
	],
	data = [
	"@wasi_sdk//:clang_resources",
	"@wasi_sdk//:sysroot",
	],
	)

	cc_args(
	name = "wasm32_wasi_cxx_args",
	actions = [
	"@rules_cc//cc/toolchains/actions:cpp_compile_actions",
	],
	args = [
	# IREE requires C++17 (matching host builds).
	"-std=c++17",

	# Explicit C++ standard library include paths.
	#
	# Clang's addLibCxxIncludePaths auto-detection probes the filesystem
	# relative to its InstalledDir (resolved from the binary's symlink
	# chain). In Bazel's processwrapper-sandbox the symlink layout differs
	# from the real execroot, so the probing fails and clang silently
	# skips the C++ include directories. Providing the paths explicitly
	# via -isystem makes the build sandbox-independent.
	#
	# Target-specific headers first (wasm32-wasi overrides), then generic.
	"-isystem",
	WASI_SYSROOT_PATH + "/include/wasm32-wasi/c++/v1",
	"-isystem",
	WASI_SYSROOT_PATH + "/include/c++/v1",
	],
	)

	cc_args(
	name = "wasm32_wasi_link_args",
	actions = [
	"@rules_cc//cc/toolchains/actions:link_executable_actions",
	"@rules_cc//cc/toolchains/actions:dynamic_library_link_actions",
	],
	args = [
	# Target triple and sysroot for finding crt1.o, libc.a, libc++.a.
	"--target=wasm32-wasi",
	"--sysroot=" + WASI_SYSROOT_PATH,
	"-resource-dir=" + WASI_RESOURCE_DIR,
	"-no-canonical-prefixes",

	# System libraries (-lc++, -lc++abi, -lwasi-emulated-signal) are in
	# the linker wrapper's suffix_flags, not here. Bazel places cc_args
	# before user objects/archives, but the linker's single-pass archive
	# extraction requires system libraries after user archives.
	],
	data = [
	"@wasi_sdk//:clang_resources",
	"@wasi_sdk//:sysroot",
	],
	)

	cc_toolchain(
	name = "wasm32_wasi_cc_toolchain",
	args = [
	":wasm32_wasi_compile_args",
	":wasm32_wasi_cxx_args",
	":wasm32_wasi_link_args",
	],
	compiler = "clang",
	enabled_features = [
	"@rules_cc//cc/toolchains/args:experimental_replace_legacy_action_config_features",
	],
	known_features = [
	"@rules_cc//cc/toolchains/args:experimental_replace_legacy_action_config_features",
	],
	supports_header_parsing = False,
	supports_param_files = True,
	tool_map = ":wasm32_wasi_tool_map",
	)

	[toolchain(
	name = "wasm32_wasi_toolchain_" + os + "_" + cpu,
	exec_compatible_with = [
	"@platforms//os:" + os,
	"@platforms//cpu:" + cpu,
	],
	target_compatible_with = [
	"@platforms//cpu:wasm32",
	":wasi",
	],
	toolchain = ":wasm32_wasi_cc_toolchain",
	toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
	) for os, cpu in [
	("linux", "x86_64"),
	("linux", "aarch64"),
	("macos", "x86_64"),
	("macos", "aarch64"),
	]]