Add an optimize_for_fuzzing GN flag to build with -O1

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 5fcc050b1741aacfeebd2a964c30ec32f1460e4b..04b768a670b75aae2af76297844bbe75dacd868e 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -1463,6 +1463,25 @@ config("optimize_speed") {
   }
 }
 
+config("optimize_fuzzing") {
+  if (is_nacl_irt) {
+    # The NaCl IRT is a special case and always wants its own config.
+    # Various components do:
+    #   if (!is_debug) {
+    #     configs -= [ "//build/config/compiler:default_optimization" ]
+    #     configs += [ "//build/config/compiler:optimize_max" ]
+    #   }
+    # So this config has to have the selection logic just like
+    # "default_optimization", below.
+    configs = [ "//build/config/nacl:irt_optimize" ]
+  } else {
+    # Only supported on non-Windows.
+    assert(!is_win)

[Dirk Pranke, 2016/10/03 20:37:13]

I would:

- get rid of lines 1467-1477 since they shouldn't ever execute (due to the
ordering on lines 1488-1495)

- make lines 1478-1481 unconditional,

- add an assert(!is_nacl_irt)

- add a second argument to the (!is_win) assert explaining that this isn't
supported on windows (and delete the comment, which would become redundant).

- and get rid of the (!is_win) test on line 1494, below.

[Oliver Chang, 2016/10/03 20:54:24]

Done.

+    cflags = [ "-O1" ] + common_optimize_on_cflags
+    ldflags = common_optimize_on_ldflags
+  }
+}
+
 # The default optimization applied to all targets. This will be equivalent to
 # either "optimize" or "no_optimize", depending on the build flags.
 config("default_optimization") {
@@ -1472,6 +1491,8 @@ config("default_optimization") {
     configs = [ "//build/config/nacl:irt_optimize" ]
   } else if (is_debug) {
     configs = [ ":no_optimize" ]
+  } else if (!is_win && optimize_for_fuzzing) {
+    configs = [ ":optimize_fuzzing" ]

[Dirk Pranke, 2016/10/03 20:37:13]

I would get rid of the (!is_win) check here, as per the comments above.

[Oliver Chang, 2016/10/03 20:54:25]

Done.

   } else {
     configs = [ ":optimize" ]
   }