Add BUILD.gn for third_party/yasm.

third_party/yasm/yasm_assemble.gni

Index: third_party/yasm/yasm_assemble.gni
diff --git a/third_party/yasm/yasm_assemble.gni b/third_party/yasm/yasm_assemble.gni
new file mode 100644
index 0000000000000000000000000000000000000000..dd7fca2a804a4168e9abe15787396e93c607d37e
--- /dev/null
+++ b/third_party/yasm/yasm_assemble.gni
@@ -0,0 +1,107 @@
+# Copyright 2014 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# This provides the yasm_assemble() template which uses YASM to assemble
+# assembly files.
+#
+# Files to be assembled with YASM should have an extension of .asm.
+#
+# There are three variables with this template:
+# yasm_flags : Pass additional flags into YASM.
+# yasm_output_path : Output directory for the compiled object files.
+# yasm_includes : Includes used by .asm code.  Changes to which should force
+#                 recompilation.
+#
+# Sample usage:
+# yasm_assemble("my_yasm_target") {
+#   sources = [ "ultra_optimized_awesome.asm" ]
+#   yasm_flags = [ "-I", "assembly_include", ],
+#   yasm_output_path = "$target_gen_dir/project"
+#   yasm_includes = [ "ultra_optimized_awesome.inc" ]
+# }
+
+import("//build/gn_helper_scripts.gni")
+
+if (is_mac || is_ios) {
+  if (cpu_arch == "x86") {
+    _yasm_flags = [
+      "-fmacho32",
+      "-m", "x86",
+    ]
+  } else if (cpu_arch == "x64") {
+    _yasm_flags = [
+      "-fmacho64",
+      "-m", "amd64",
+    ]
+  }
+} else if (is_posix) {
+  if (cpu_arch == "x86") {
+    _yasm_flags = [
+      "-felf32",
+      "-m", "x86",
+    ]
+  } else if (cpu_arch == "x64") {
+    _yasm_flags = [
+      "-DPIC",
+      "-felf64",
+      "-m", "amd64",
+    ]
+  }
+} else if (is_win) {
+  if (cpu_arch == "x86") {
+    _yasm_flags = [
+      "-DPREFIX",
+      "-fwin32",
+      "-m", "x86",
+    ]
+  } else if (cpu_arch == "x64") {
+    _yasm_flags = [
+      "-fwin64",
+      "-m", "amd64",
+    ]
+  }
+}
+
+if (is_win) {
+  asm_obj_extension = "obj"
+} else {
+  asm_obj_extension = "o"
+}
+
+template("yasm_assemble") {
+  # TODO(ajwong): Support use_system_yasm.
+
+  assert(defined(invoker.yasm_output_path))
+  yasm_output_path = invoker.yasm_output_path
+
+  source_set(target_name) {
+    sources = process_file_template(
+      invoker.sources,
+      "$yasm_output_path/{{source_name_part}}.o")
+    deps = [ ":${target_name}_yasm" ]
+  }
+
+  run_executable_foreach("${target_name}_yasm") {
+    sources = invoker.sources
+    binary_name = "yasm"
+    outputs = [ "$yasm_output_path/{{source_name_part}}.$asm_obj_extension" ]
+    args = _yasm_flags
+    if (defined(invoker.yasm_flags)) {
+      args += invoker.yasm_flags
+    }
+    args += [
+      "-o", rebase_path(outputs[0], root_build_dir),
+      "{{source}}"
+    ]
+
+    if (defined(invoker.yasm_includes)) {
+      source_prereqs = rebase_path(invoker.yasm_includes, root_build_dir)
+    }
+
+    # Only depend on YASM on x86 systems. Force compilation of .asm files for
+    # ARM to fail.
+    assert(cpu_arch == "x86" || cpu_arch == "x64")
+    deps = [ "//third_party/yasm($host_toolchain)" ]
+  }
+}