Add support for sub-architecture when building for iOS

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index 43f73de1845bbf7255a8ae320a09b397e14bb083..e859749716089e2129bea36d4cd461b263ab4367 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -136,8 +136,9 @@
         'host_arch%': '<(host_arch)',
 
         # Default architecture we're building for is the architecture we're
-        # building on.
+        # building on, and possibly sub-architecture (for iOS builds).
         'target_arch%': '<(host_arch)',
+        'target_subarch%': '',
 
         # This is set when building the Android WebView inside the Android
         # build system, using the 'android' gyp backend. The WebView code is
@@ -220,6 +221,18 @@
           }, {
             'gomadir': '<!(/bin/echo -n ${HOME}/goma)',
           }],
+
+          # Set the default "target_subarch" on iOS. Valid values are "arm32",
+          # "arm64" and "both" (meaning a fat binary).
+          #
+          # TODO(sdefresne): change the default from "arm32" to "both" for
+          # "target_subarch" once http://crbug.com/339477 is fixed.
+          #
+          # TODO(sdefresne): set the "target_arch" to "arm" once compilation
+          # of skia has been fixed for simulator. http://crbug.com/342377
+          ['OS=="ios"', {
+            'target_subarch%': 'arm32',
+          }],
         ],
       },
 
@@ -227,6 +240,7 @@
       'chromeos%': '<(chromeos)',
       'host_arch%': '<(host_arch)',
       'target_arch%': '<(target_arch)',
+      'target_subarch%': '<(target_subarch)',
       'toolkit_views%': '<(toolkit_views)',
       'toolkit_uses_gtk%': '<(toolkit_uses_gtk)',
       'desktop_linux%': '<(desktop_linux)',
@@ -866,6 +880,7 @@
     'branding%': '<(branding)',
     'buildtype%': '<(buildtype)',
     'target_arch%': '<(target_arch)',
+    'target_subarch%': '<(target_subarch)',
     'host_arch%': '<(host_arch)',
     'toolkit_views%': '<(toolkit_views)',
     'ui_compositor_image_transport%': '<(ui_compositor_image_transport)',
@@ -1082,6 +1097,13 @@
     'clang%': '<(clang)',
     'make_clang_dir%': 'third_party/llvm-build/Release+Asserts',
 
+    # Control which version of clang to use when 'clang' is set to 1 when
+    # building for iOS (Apple has not yet open-sourced support for "arm64"
+    # so when building for that 'target_arch' we have to use clang shipped
+    # with Xcode that does not supports some flags).
+    # TODO(sdefresne): remove this once http://crbug.com/341453 is fixed.
+    'clang_xcode%': 0,
+
     # These two variables can be set in GYP_DEFINES while running
     # |gclient runhooks| to let clang run a plugin in every compilation.
     # Only has an effect if 'clang=1' is in GYP_DEFINES as well.
@@ -1726,7 +1748,13 @@
           ['"<(GENERATOR)"=="ninja"', {
             'clang%': 1,
             'host_os%': "mac",
-          }]
+          }],
+          # Apple has not upstreamed the support for "arm64" yet, so when
+          # building for "arm64" or "both", we need to use the clang that
+          # is provided with Xcode.
+          ['target_subarch!="arm32"', {
+            'clang_xcode%': 1,
+          }],
         ],
       }],
       ['enable_extensions==1', {
@@ -4029,9 +4057,6 @@
             # Note that the prebuilt Clang binaries should not be used for iOS
             # development except for ASan builds.
             ['clang==1', {
-              'CC': '$(SOURCE_ROOT)/<(clang_dir)/clang',
-              'LDPLUSPLUS': '$(SOURCE_ROOT)/<(clang_dir)/clang++',
-
               # gnu++11 instead of c++11 is needed because some code uses
               # typeof() (a GNU extension).
               # TODO(thakis): Eventually switch this to c++11 instead of
@@ -4066,24 +4091,37 @@
 
                 # Warns when a const char[] is converted to bool.
                 '-Wstring-conversion',
+              ],
 
-                # Clang considers the `register` keyword as deprecated, but e.g.
-                # code generated by flex (used in angle) contains that keyword.
-                # http://crbug.com/255186
-                '-Wno-deprecated-register',
+              'conditions': [
+                ['clang_xcode==0', {
+                  'CC': '$(SOURCE_ROOT)/<(clang_dir)/clang',
+                  'LDPLUSPLUS': '$(SOURCE_ROOT)/<(clang_dir)/clang++',
+
+                  'WARNING_CFLAGS': [
+                    # Clang considers the `register` keyword as deprecated, but
+                    # e.g. code generated by flex (used in angle) contains that
+                    # keyword. http://crbug.com/255186
+                    #
+                    # Note: clang as shipped with Xcode is older and does not
+                    # treat the `register` as deprecated and does not define
+                    # this flag, so don't enable it if "clang_xcode" is "1".
+                    '-Wno-deprecated-register',
+                  ],
+                }],
               ],
             }],
-            ['clang==1 and clang_use_chrome_plugins==1', {
+            ['clang==1 and clang_xcode==0 and clang_use_chrome_plugins==1', {
               'OTHER_CFLAGS': [
                 '<@(clang_chrome_plugins_flags)',
               ],
             }],
-            ['clang==1 and clang_load!=""', {
+            ['clang==1 and clang_xcode==0 and clang_load!=""', {
               'OTHER_CFLAGS': [
                 '-Xclang', '-load', '-Xclang', '<(clang_load)',
               ],
             }],
-            ['clang==1 and clang_add_plugin!=""', {
+            ['clang==1 and clang_xcode==0 and clang_add_plugin!=""', {
               'OTHER_CFLAGS': [
                 '-Xclang', '-add-plugin', '-Xclang', '<(clang_add_plugin)',
               ],
@@ -4364,14 +4402,32 @@
             # Match OS X clang C++11 warning settings.
             '-Wno-c++11-narrowing',
           ],
+
+          # Limit the valid architectures depending on "target_subarch".
+          # This need to include the "arm" architectures but also the "x86"
+          # ones (they are used when building for the simulator).
+          'conditions': [
+            ['target_subarch=="arm32"', {
+              'VALID_ARCHS': ['armv7', 'i386'],
+            }],
+            ['target_subarch=="arm64"', {
+              'VALID_ARCHS': ['arm64', 'x86_64'],
+            }],
+            ['target_subarch=="both"', {
+              'VALID_ARCHS': ['arm64', 'armv7', 'x86_64', 'i386'],
+            }],
+          ],
         },
         'target_conditions': [
           ['_toolset=="host"', {
             'xcode_settings': {
               'SDKROOT': 'macosx<(mac_sdk)',  # -isysroot
               'MACOSX_DEPLOYMENT_TARGET': '<(mac_deployment_target)',
+              'VALID_ARCHS': [
+                'x86_64',
+              ],
               'ARCHS': [
-                'x86_64'
+                'x86_64',
               ],
             },
           }],
@@ -4381,6 +4437,7 @@
               # since we can't negate the iphone deployment target above, we
               # instead set it here for target only.
               'IPHONEOS_DEPLOYMENT_TARGET': '<(ios_deployment_target)',
+              'ARCHS': ['$(ARCHS_STANDARD_INCLUDING_64_BIT)'],
             },
           }],
           ['_type=="executable"', {
@@ -4777,7 +4834,8 @@
         ],
       },
     }],
-    ['clang==1 and OS!="win"', {
+    ['clang==1 and ((OS!="mac" and OS!="ios") or clang_xcode==0) '
+        'and OS!="win"', {
       'make_global_settings': [
         ['CC', '<(make_clang_dir)/bin/clang'],
         ['CXX', '<(make_clang_dir)/bin/clang++'],
@@ -4813,7 +4871,8 @@
     # TODO(yyanagisawa): supports GENERATOR==make
     #  make generator doesn't support CC_wrapper without CC
     #  in make_global_settings yet.
-    ['use_goma==1 and ("<(GENERATOR)"=="ninja" or clang==1)', {
+    ['use_goma==1 and ((OS!="mac" and OS!="ios") or clang_xcode==0) and '
+        '("<(GENERATOR)"=="ninja" or clang==1)', {
       'make_global_settings': [
        ['CC_wrapper', '<(gomadir)/gomacc'],
        ['CXX_wrapper', '<(gomadir)/gomacc'],
@@ -4861,7 +4920,6 @@
       ['OS=="ios"', {
         # Target both iPhone and iPad.
         'TARGETED_DEVICE_FAMILY': '1,2',
-        'VALID_ARCHS': 'armv7 i386',
       }, {  # OS!="ios"
         'conditions': [
           ['target_arch=="x64"', {