Make /fastlink builds as optimized as non-/fastlink builds

build/config/win/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/clang/clang.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/config/win/visual_studio_version.gni")
 import("//build/toolchain/toolchain.gni")
 
@@ skipping 74 matching lines @@
     # Clang runtime libraries, such as the sanitizer runtimes, live here.
     lib_dirs = [ "$clang_base_path/lib/clang/$clang_version/lib/windows" ]
   }
 
   # Ensures that the PDB file contains FIXUP information (growing the PDB file
   # by about 5%) but does not otherwise alter the output binary. This
   # information is used by the Syzygy optimization tool when decomposing the
   # release image. It is enabled for syzyasan builds and opportunistically for
   # other builds where it is not prohibited (not supported when incrementally
   # linking, using /debug:fastlink, or building with clang).
-  if (is_syzyasan ||
-      (!is_debug && !is_component_build && !is_win_fastlink && !is_clang)) {
-    ldflags = [ "/PROFILE" ]
+  if (is_syzyasan || (!is_debug && !is_component_build && !is_clang)) {
+    if (is_win_fastlink) {

[scottmg, 2016/11/10 21:56:27]

I think this changes the behaviour for is_syzyasan with is_win_fastlink.

I don't think we need to support that combinations, but maybe it would be
clearer to just move the is_syzyasan to a separate if that always sets /PROFILE
and assert(!is_fastlink), and make a second that sets the linker opt flags that
doesn't consider is_syzyasan at all.

[brucedawson, 2016/11/10 22:04:06]

Good catch. Logic is hard. Agreed that it probably doesn't matter but we should
maintain existing logic.

[brucedawson, 2016/11/14 21:34:55]

Done.

+      # /PROFILE implies the following linker flags. Therefore if we are
+      # skipping /PROFILE because it is incompatible with /DEBUG:FASTLINK
+      # we should explicitly add these flags in order to avoid unintended
+      # consequences such as larger binaries.
+      ldflags = [
+        "/OPT:REF",
+        "/OPT:ICF",
+        "/INCREMENTAL:NO",
+        "/FIXED:NO",
+      ]
+    } else {
+      ldflags = [ "/PROFILE" ]
+    }
   }
 
   # arflags apply only to static_libraries. The normal linker configs are only
   # set for executable and shared library targets so arflags must be set
   # elsewhere. Since this is relatively contained, we just apply them in this
   # more general config and they will only have an effect on static libraries.
   arflags = [
     # "No public symbols found; archive member will be inaccessible." This
     # means that one or more object files in the library can never be
     # pulled in to targets that link to this library. It's just a warning that
@@ skipping 298 matching lines @@
 
 # Internal stuff --------------------------------------------------------------
 
 # Config used by the MIDL template to disable warnings.
 config("midl_warnings") {
   if (is_clang) {
     # MIDL generates code like "#endif !_MIDL_USE_GUIDDEF_".
     cflags = [ "-Wno-extra-tokens" ]
   }
 }