GN: Fix skia build on mac, use -msse4.1 everywhere

GN: Fix skia build on mac, use -msse4.1 everywhere

Two issues with GN:
*) We need to set SK_BUILD_FOR_MAC on mac
*) On mac, the sse4 opts are built with -msse4.1 (which is what
GCC_ENABLE_SSE41_EXTENSIONS=YES expands to) not -msse4

and for consistency use -msse4.1 on linux as well.

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=281969

[Nico, 2014-07-08 17:20:53]

https://codereview.chromium.org/377833002/diff/1/skia/BUILD.gn
File skia/BUILD.gn (right):

https://codereview.chromium.org/377833002/diff/1/skia/BUILD.gn#newcode569
skia/BUILD.gn:569: cflags += [ "-msse4.1" ]
Is this actually needed? This currently uses msse4.1 in gyp probably because
there's GCC_ENABLE_SSE41_EXTENSIONS but no GCC_ENABLE_SSE4_EXTENSIONS in Xcode
(maybe there's no chip that supports sse4 but no sse4.1 in apple computers?) In
gyp, it makes sense to keep this separate, but in gn it might not.

[jamesr, 2014-07-08 19:07:34]

If you mean should we pass '-msse4' instead of '-msse4.1' on mac, the answer is
passing -msse4 produces this error:

'+sse4' is not a recognized feature for this target (ignoring feature)

although I feel like I've been seeing that on linux so perhaps the right answer
is to pass -msse4.1 everywhere.  There's no such thing as SSE4 that isn't
SSE4.1, afaik, The possible levels of CPU support according to wikipedia are:

SSE4.1 (47 instructions, Intel Core+, AMD K10+)
SSE 4.2 (7 more instructions, Intel Nehalem Core i7+, AMD Bulldozer+
SSE 4a (intel barcelona+)

[Nico, 2014-07-08 19:10:28]

If -msse4.1 works on linux, then using that everywhere would be cool too. I'd
like to use the same on both platforms, if possible.

(If -msse4 doesn't work on linux, maybe you can change the gyp file too.)

[jamesr, 2014-07-09 01:34:38]

-msse4.1 appears to work (the trybots compile and there aren't any unexpected
warnings).  How about now?

It appears I still have to use the xcode_settings stuff on mac - it appears
manipulations to the cflags gyp variable doesn't work.

[Nico, 2014-07-09 01:36:29]

On 2014/07/09 01:34:38, jamesr wrote:
> -msse4.1 appears to work (the trybots compile and there aren't any unexpected
> warnings).  How about now?

lgtm

> It appears I still have to use the xcode_settings stuff on mac - it appears
> manipulations to the cflags gyp variable doesn't work.

Correct, cflags is only used on linux (and cros and android) in gyp. On Mac,
it's xcode_settings, on Win it's msvs_settings.

[Nico, 2014-07-09 01:36:50]

(fix cl description though)

[jamesr, 2014-07-09 01:38:54]

The CQ bit was checked by jamesr@chromium.org

[commit-bot: I haz the power, 2014-07-09 01:41:22]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/jamesr@chromium.org/377833002/40001

[commit-bot: I haz the power, 2014-07-09 06:02:14]

Change committed as 281969