Make GN builds produce an ICD JSON in the build dir

src/Vulkan/BUILD.gn

@@ -14,6 +14,7 @@
 
 import("//build_overrides/build.gni")
 import("../swiftshader.gni")
+import("vulkan.gni")
 
 # Need a separate config to ensure the warnings are added to the end.
 config("swiftshader_libvulkan_private_config") {
@@ -96,13 +97,9 @@ swiftshader_source_set("swiftshader_libvulkan_headers") {
       "VkSemaphoreExternalLinux.hpp",
     ]
   } else if (is_fuchsia) {
-    sources += [
-      "VkSemaphoreExternalFuchsia.hpp",
-    ]
+    sources += [ "VkSemaphoreExternalFuchsia.hpp" ]
   } else {
-    sources += [
-      "VkSemaphoreExternalNone.hpp",
-    ]
+    sources += [ "VkSemaphoreExternalNone.hpp" ]
   }
 }
 
@@ -168,8 +165,8 @@ swiftshader_shared_library("swiftshader_libvulkan") {
   }
 
   deps = [
-    "../../third_party/marl:Marl",
     "${swiftshader_spirv_tools_dir}:SPIRV-Tools",
+    "../../third_party/marl:Marl",
     "../Device",
     "../Pipeline",
     "../Reactor:swiftshader_llvm_reactor",
@@ -188,3 +185,39 @@ swiftshader_shared_library("swiftshader_libvulkan") {
     ":swiftshader_libvulkan_headers",
   ]
 }
+
+# Generates an ICD JSON file that can be used by all targets in this GN build
+# (ANGLE, Dawn, Chromium).
+action("icd_file") {
+  output_icd_file = "${root_build_dir}/${swiftshader_icd_file_name}"
+  input_file = swiftshader_icd_file_name
+
+  if (is_win) {
+    library_path = ".\\vk_swiftshader.dll"
+  } else if (is_mac) {
+    library_path = "./libvk_swiftshader.dylib"
+  } else {
+    library_path = "./libvk_swiftshader.so"
+  }
+
+  script = "write_icd_json.py"
+  args = [
+    "--input",
+    rebase_path(input_file, root_build_dir),
+    "--output",
+    rebase_path(output_icd_file, root_build_dir),
+    "--library_path",
+    library_path,
+  ]
+
+  inputs = [
+    input_file,
+  ]
+  outputs = [
+    output_icd_file,
+  ]
+
+  deps = [
+    ":swiftshader_libvulkan",
+  ]
+}

src/Vulkan/vulkan.gni

+# Copyright 2019 The SwiftShader Authors. 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
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# File containing GN "constants" for Swiftshader Vulkan so that GN-based
+# projects depending on Swiftshader don't need to hardcode them.
+
+# The name of the Swiftshader Vulkan ICD file in the $root_build_dir that's
+# produced by ${swiftshader_dir}/src/Vulkan:icd_file
+swiftshader_icd_file_name = "vk_swiftshader_icd.json"

src/Vulkan/write_icd_json.py

+# Copyright 2019 The SwiftShader Authors. 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
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import argparse, json, sys
+
+def run():
+    parser = argparse.ArgumentParser(
+        description = "Generates the correct ICD JSON file for swiftshader in GN builds"
+    )
+    parser.add_argument('--input', type=str, help='The template ICD JSON')
+    parser.add_argument('--output', type=str, help='The output ICD JSON in the GN build dir')
+    parser.add_argument('--library_path', type=str, help='The file containing a list of directories to check for stale files')
+    args = parser.parse_args()
+
+    with open(args.input) as infile:
+        with open(args.output, 'wb') as outfile:
+            data = json.load(infile)
+            data['ICD']['library_path'] = args.library_path
+            json.dump(data, outfile)
+
+    return 0
+
+if __name__ == "__main__":
+    sys.exit(run())