Sync Windows build flags between GYP and GN

build/config/compiler/BUILD.gn

Index: build/config/compiler/BUILD.gn
diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index 3930c79765d18a00abdad07a9808c5137ccc47a1..8e6295e5f4f8fc363493ad99e1788147d4489f43 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -1091,12 +1091,12 @@ config("no_size_t_to_int_warning") {
 #   configs += [ "//build/config/compiler/optimize_max" ]
 
 # Shared settings for both "optimize" and "optimize_max" configs.
+# IMPORTANT: On Windows "/O1" and "/O2" must go before the common flags.
 if (is_win) {
   common_optimize_on_cflags = [
-    "/O2",
-    "/Ob2",  # both explicit and auto inlining.
-    "/Oy-",  # disable omitting frame pointers, must be after /o2.
-    "/Os",  # favor size over speed.
+    "/Ob2",  # Both explicit and auto inlining.
+    "/Oy-",  # Disable omitting frame pointers, must be after /O2.
+    "/GF",  # Enable string pooling.

[scottmg, 2015/06/16 20:07:48]

looks like this is on by default for O1 and O2 too too so could probably drop
here, but also fine if you want to kepe it for consistency (I might keep /Os in
that case then too)

[brettw, 2015/06/16 21:02:28]

I'll remove it.

   ]
   if (!is_asan) {
     common_optimize_on_cflags += [
@@ -1162,15 +1162,16 @@ if (is_win) {
 
 # Default "optimization on" config. On Windows, this favors size over speed.
 config("optimize") {
-  cflags = common_optimize_on_cflags
-  ldflags = common_optimize_on_ldflags
   if (is_win) {
-    cflags += [ "/Os" ]  # favor size over speed.
+    # Favor size over speed, /O1 must be before the common flags. The GYP
+    # build also specifies /Os but this is implied by /O1.
+    cflags = [ "/O1" ] + common_optimize_on_cflags + [ "/Oi" ]
   } else if (is_android || is_ios) {
-    cflags += [ "-Os" ]  # Favor size over speed.
+    cflags += [ "-Os" ] + common_optimize_on_cflags  # Favor size over speed.
   } else {
-    cflags += [ "-O2" ]
+    cflags += [ "-O2" ] + common_optimize_on_cflags
   }
+  ldflags = common_optimize_on_ldflags
 }
 
 # Turn off optimizations.
@@ -1202,11 +1203,11 @@ config("no_optimize") {
 # optimization and link-time code generation which is very expensive and should
 # be used sparingly.
 config("optimize_max") {
-  cflags = common_optimize_on_cflags
   ldflags = common_optimize_on_ldflags
   if (is_win) {
-    cflags -= [ "/Os" ]
-    cflags += [ "/Ot" ]  # Favor speed over size.
+    # Favor speed over size, /O2 must be before the common flags. The GYP
+    # build also specifies /O2 and /Oi but these are implied by /O2.
+    cflags = [ "/O2" ] + common_optimize_on_cflags
     if (is_official_build && !is_clang) {
       # TODO(GYP): TODO(dpranke): Should these only be on in an official
       # build, or on all the time? For now we'll require official build so
@@ -1224,7 +1225,7 @@ config("optimize_max") {
       ldflags += [ "/LTCG" ]
     }
   } else {
-    cflags += [ "-O2" ]
+    cflags = [ "-O2" ] + common_optimize_on_cflags
   }
 }