Pass correct flags for use_lto==1 with Clang.

build/common.gypi

 # Copyright (c) 2012 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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 2965 matching lines @@
       }],
       ['enable_ipc_fuzzer==1', {
         'defines': ['ENABLE_IPC_FUZZER=1'],
       }],
       ['video_hole==1', {
         'defines': ['VIDEO_HOLE=1'],
       }],
       ['v8_use_external_startup_data==1', {
        'defines': ['V8_USE_EXTERNAL_STARTUP_DATA'],
       }],
+      ['use_lto==1 and (target_arch=="ia32" or target_arch=="x64")', {
+        # Required for third_party/zlib/crc_folding.c and various other code
+        # that uses SSE.
+        'ldflags+': ['-Wl,-plugin-opt,mcpu=corei7-avx'],

[Nico, 2015/01/29 18:48:01]

nit: i think you don't need the +, gyp merges lists by default

Isn't avx fairly new? I think we require cpus with SSE2, but not avx.

[pcc, 2015/01/29 19:11:13]

Done.
I'm not sure if there is a way to avoid this at the moment, as I've found that
LLVM LTO currently compiles all functions in the program for the same
sub-target. As I recall, LLVM has a concept of function-specific codegen
attributes to support this exact scenario, but for some reason it doesn't help
here. Eventually once this is fixed we should be able to remove this flag.

+      }],
     ],  # conditions for 'target_defaults'
     'target_conditions': [
       ['<(use_libpci)==1', {
         'defines': ['USE_LIBPCI=1'],
       }],
       ['<(use_openssl)==1', {
         'defines': ['USE_OPENSSL=1'],
       }],
       ['<(use_openssl_certs)==1', {
         'defines': ['USE_OPENSSL_CERTS=1'],
@@ skipping 2778 matching lines @@
        ['CC.host_wrapper', '<(gomadir)/gomacc'],
        ['CXX.host_wrapper', '<(gomadir)/gomacc'],
       ],
     }],
     ['use_lto==1', {
       'target_defaults': {
         'target_conditions': [
           ['_toolset=="target"', {
             'cflags': [
               '-flto',
+            ],
+          }],
+        ],
+      },
+    }],
+    ['use_lto==1 and clang==0', {
+      'target_defaults': {
+        'target_conditions': [
+          ['_toolset=="target"', {
+            'cflags': [
               '-ffat-lto-objects',
             ],
           }],
         ],
       },
     }],
-    ['use_lto==1 or use_lto_o2==1', {
+    ['(use_lto==1 or use_lto_o2==1) and clang==0', {
       'target_defaults': {
         'target_conditions': [
           ['_toolset=="target"', {
             'ldflags': [
               '-flto=32',
             ],
           }],
         ],
       },
     }],
+    ['(use_lto==1 or use_lto_o2==1) and clang==1', {
+      'target_defaults': {
+        'target_conditions': [
+          ['_toolset=="target"', {
+            'ldflags': [
+              '-flto',

[Nico, 2015/01/29 18:48:01]

i'd be nice if gcc's and clang's flag here were compatible :-/

+            ],
+          }],
+        ],
+      },
+    }],
   ],
   'xcode_settings': {
     # DON'T ADD ANYTHING NEW TO THIS BLOCK UNLESS YOU REALLY REALLY NEED IT!
     # This block adds *project-wide* configuration settings to each project
     # file.  It's almost always wrong to put things here.  Specify your
     # custom xcode_settings in target_defaults to add them to targets instead.
 
     'conditions': [
       # In an Xcode Project Info window, the "Base SDK for All Configurations"
       # setting sets the SDK on a project-wide basis. In order to get the
@@ skipping 50 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }