build: Enable function sections and data sections during LTO.

build/config/compiler/BUILD.gn

 # Copyright (c) 2013 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.
 
 import("//build/config/android/config.gni")
 import("//build/config/chrome_build.gni")
 import("//build/config/chromecast_build.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/nacl/config.gni")
 import("//build/toolchain/cc_wrapper.gni")
@@ skipping 494 matching lines @@
       } else if (is_mac) {
         ldflags += [ "-Wl,-mllvm,-O1" ]
       }
     }
 
     # Work-around for http://openradar.appspot.com/20356002
     if (is_mac) {
       ldflags += [ "-Wl,-all_load" ]
     }
 
-    # Allows the linker to apply ICF to the LTO object file. Also, when
-    # targeting ARM, without this flag, LTO produces a .text section that is
-    # larger than the maximum call displacement, preventing the linker from
-    # relocating calls (http://llvm.org/PR22999).
+    # Allows the linker to apply --gc-sections and ICF to the LTO object file.
+    # Also, when targeting ARM, without this flag, LTO produces a .text section
+    # that is larger than the maximum call displacement, preventing the linker
+    # from relocating calls (http://llvm.org/PR22999).
     if (is_linux) {
-      ldflags += [ "-Wl,-plugin-opt,-function-sections" ]
+      if (use_lld) {
+        ldflags += [
+          "-Wl,-mllvm,-function-sections",
+          "-Wl,-mllvm,-data-sections",
+        ]
+      } else {
+        ldflags += [
+          "-Wl,-plugin-opt,-function-sections",
+          "-Wl,-plugin-opt,-data-sections",
+        ]
+      }
     }
   }
 
   # Pass the same C/C++ flags to the objective C/C++ compiler.
   cflags_objc += cflags_c
   cflags_objcc += cflags_cc
 
   # Assign any flags set for the C compiler to asmflags so that they are sent
   # to the assembler. The Windows assembler takes different types of flags
   # so only do so for posix platforms.
@@ skipping 1200 matching lines @@
 
 if (is_ios || is_mac) {
   # On Mac and iOS, this enables support for ARC (automatic ref-counting).
   # See http://clang.llvm.org/docs/AutomaticReferenceCounting.html.
   config("enable_arc") {
     common_flags = [ "-fobjc-arc" ]
     cflags_objc = common_flags
     cflags_objcc = common_flags
   }
 }