src/emdawnwebgpu/BUILD.gn

# Copyright 2024 The Dawn & Tint Authors
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
# 1. Redistributions of source code must retain the above copyright notice, this
#    list of conditions and the following disclaimer.
#
# 2. Redistributions in binary form must reproduce the above copyright notice,
#    this list of conditions and the following disclaimer in the documentation
#    and/or other materials provided with the distribution.
#
# 3. Neither the name of the copyright holder nor the names of its
#    contributors may be used to endorse or promote products derived from
#    this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

import("../../scripts/dawn_overrides_with_defaults.gni")

import("${dawn_root}/generator/dawn_generator.gni")

dawn_json_generator("emdawnwebgpu_headers_gen") {
  target = "emdawnwebgpu_headers"
  outputs = [
    "src/emdawnwebgpu/include/dawn/webgpu_cpp_print.h",
    "src/emdawnwebgpu/include/webgpu/webgpu.h",
    "src/emdawnwebgpu/include/webgpu/webgpu_cpp.h",
    "src/emdawnwebgpu/include/webgpu/webgpu_cpp_chained_struct.h",
  ]
}

dawn_json_generator("emdawnwebgpu_js_gen") {
  target = "emdawnwebgpu_js"
  outputs = [
    "src/emdawnwebgpu/struct_info_webgpu.json",
    "src/emdawnwebgpu/library_webgpu_enum_tables.js",
    "src/emdawnwebgpu/library_webgpu_generated_sig_info.js",
  ]
}

# When Emscripten is available, we can use one of its helper scripts to generate
# the struct info needed for our bindings fork (third_party/emdawnwebgpu).
# Those helpers, and their tree of generated dependencies, are:
#
# - library_webgpu_generated_struct_info.js
#   is constructed by concatenating:
#     - Some glue "snippets" from txt files
#     - webgpu_generated_struct_info{32,64}.json
#       which are generated using an Emscripten tool "gen_struct_info.py", from:
#         - webgpu.h (generated from dawn.json)
#         - struct_info_webgpu.json (generated from dawn.json)
#
# The bindings also require the following helpers (generated above):
#
# - library_webgpu_enum_tables.js
# - library_webgpu_generated_sig_info.js
#   which we generate directly instead of using "gen_sig_info.py"

if (dawn_emscripten_dir != "") {
  template("webgpu_gen_struct_info") {
    action(target_name) {
      forward_variables_from(invoker, "*")

      deps = [
        ":emdawnwebgpu_headers_gen",  # for webgpu.h
        ":emdawnwebgpu_js_gen",  # for struct_info_webgpu.json
      ]

      script = dawn_emscripten_dir + "/tools/maint/gen_struct_info.py"
      args = [
        "-q",  # quiet
        rebase_path(sources[0], root_build_dir),  # input file
        "-o=" + rebase_path(outputs[0], root_build_dir),  # output file

        # Include dir where webgpu/webgpu.h can be found
        "-I=" + rebase_path(target_gen_dir, root_build_dir) + "/include",
      ]
      if (wasm64) {
        args += [ "--wasm64" ]
      }
    }
  }

  webgpu_gen_struct_info("webgpu_generated_struct_info32") {
    sources = [ "${target_gen_dir}/struct_info_webgpu.json" ]
    outputs = [ "${target_gen_dir}/webgpu_generated_struct_info32.json" ]
    wasm64 = false
  }

  webgpu_gen_struct_info("webgpu_generated_struct_info64") {
    sources = [ "${target_gen_dir}/struct_info_webgpu.json" ]
    outputs = [ "${target_gen_dir}/webgpu_generated_struct_info64.json" ]
    wasm64 = true
  }

  action("library_webgpu_generated_struct_info") {
    deps = [
      ":webgpu_generated_struct_info32",
      ":webgpu_generated_struct_info64",
    ]

    source_files = [
      # The order of these files is important.
      "snippets/library_webgpu_struct_info_part1.txt",
      "${target_gen_dir}/webgpu_generated_struct_info32.json",
      "snippets/library_webgpu_struct_info_part2.txt",
      "${target_gen_dir}/webgpu_generated_struct_info64.json",
      "snippets/library_webgpu_struct_info_part3.txt",
    ]

    sources = source_files
    outputs = [ "${target_gen_dir}/library_webgpu_generated_struct_info.js" ]

    script = "concat.py"
    args = []
    foreach(source, [ outputs[0] ] + sources) {
      args += [ rebase_path(source, root_build_dir) ]
    }
  }

  # NOTE: Do not use this directly, because it will not add dependencies on the
  # the included files. Use :emdawnwebgpu instead.
  config("emdawnwebgpu_config") {
    include_dirs = [
      # Include directory where webgpu/webgpu{,_cpp}.h can be found.
      # This needs to take precedent over Emscripten's built-in include
      # directory which also has these files (at an older revision).
      "${target_gen_dir}/include",
    ]
    ldflags = [
      # These will be processed in order; library_webgpu.js must come after
      # the generated files, because it depends on them.
      # (It will assert this, and also that -sUSE_WEBGPU is not enabled.)
      "--js-library=" +
          rebase_path("${target_gen_dir}/library_webgpu_enum_tables.js"),
      "--js-library=" + rebase_path(
              "${target_gen_dir}/library_webgpu_generated_struct_info.js"),
      "--js-library=" +
          rebase_path("${target_gen_dir}/library_webgpu_generated_sig_info.js"),
      "--js-library=" +
          rebase_path("../../third_party/emdawnwebgpu/library_webgpu.js"),

      # Emscripten only enables webgpu-externs.js with -sUSE_WEBGPU=1, so add them explicitly.
      "--closure-args=--externs=${dawn_emscripten_dir}/src/closure-externs/webgpu-externs.js",
    ]
  }

  # Dawn's WebGPU bindings for Emscripten. These don't actually use Dawn at all,
  # but generating them in Dawn lets us keep them in sync more easily.
  # When included in Emscripten they attempt to delete Emscripten's built-in
  # implementation and replace it with ours.
  #
  # This can be built as a standalone target to generate all the files needed
  # to feed into a separate project that is built using Emscripten.
  # Reference emdawnwebgpu_config for how to actually do that.
  #
  # EXPERIMENTALLY, this should also be usable as a dependency of a gn-native
  # Wasm build target, as an alternative to -sUSE_WEBGPU=1 which uses
  # Emscripten's built-in WebGPU bindings. This has not been well-tested.
  source_set("emdawnwebgpu") {
    public_configs = [ ":emdawnwebgpu_config" ]
    deps = [
      ":emdawnwebgpu_headers_gen",
      ":emdawnwebgpu_js_gen",
      ":library_webgpu_generated_struct_info",
    ]
    sources = get_target_outputs(":emdawnwebgpu_headers_gen") +
              [ "../../third_party/emdawnwebgpu/webgpu.cpp" ]
    inputs = [
      # TODO(crbug.com/371024051): Changing these files doesn't seem to trigger a relink. Why?
      "../../third_party/emdawnwebgpu/library_webgpu.js",
    ]
  }
}