[libvpx] Disable LTO for one target.

Disable LTO for one target.

This is to disable LTO on one target with which GCC fails to link.

BUG=408997
r291730

[Nico, 2014-08-25 16:31:02]

Is this intentionally only in libvpx?

There should be a tracking bug for lto, so that all changes done for it can link
to it (add a BUG= line to this CL after filing the bug) and discussion about
fallout can happen there.

[Nico, 2014-08-25 16:31:27]

(also, consider wrapping cl descriptions at about 78 colums, since `git log`
doesn't do any wrapping)

[Fabrice (no longer in Chrome), 2014-08-26 12:36:54]

On 2014/08/25 16:31:27, Nico (hiding) wrote:
> (also, consider wrapping cl descriptions at about 78 colums, since `git log`
> doesn't do any wrapping)

Silly git log.
Linking with this module (and others in other repositories) fails with
lto1: fatal error: target specific builtin not available
Until the bug is fixed, we are disabling lto on these modules.

[Fabrice (no longer in Chrome), 2014-08-29 13:58:04]

Friendly ping.

[Nico, 2014-08-29 14:00:35]

Sorry, this fell out of my inbox :-(

Thanks for filing a bug, maybe you can tweak the CL description to make clear
that this CL doesn't add LTO support, it instead disables LTO for a target where
it doesn't work, to prepare for turning it on globally. One comment below:

https://codereview.chromium.org/471653004/diff/40001/libvpx_srcs_arm_neon_cpu...
File libvpx_srcs_arm_neon_cpu_detect_intrinsics.gypi (right):

https://codereview.chromium.org/471653004/diff/40001/libvpx_srcs_arm_neon_cpu...
libvpx_srcs_arm_neon_cpu_detect_intrinsics.gypi:1: # This file is generated. Do
not edit.
I think you might have to edit the generate_gypi.sh script instead for this file

[Fabrice (no longer in Chrome), 2014-08-29 14:27:04]

Argl, I missed the auto-generated message. There we go.

https://codereview.chromium.org/471653004/diff/40001/libvpx_srcs_arm_neon_cpu...
File libvpx_srcs_arm_neon_cpu_detect_intrinsics.gypi (right):

https://codereview.chromium.org/471653004/diff/40001/libvpx_srcs_arm_neon_cpu...
libvpx_srcs_arm_neon_cpu_detect_intrinsics.gypi:1: # This file is generated. Do
not edit.
On 2014/08/29 14:00:35, Nico (hiding) wrote:
> I think you might have to edit the generate_gypi.sh script instead for this
file

Done.

[Nico, 2014-08-29 14:30:41]

lgtm

https://codereview.chromium.org/471653004/diff/60001/generate_gypi.sh
File generate_gypi.sh (right):

https://codereview.chromium.org/471653004/diff/60001/generate_gypi.sh#newcode84
generate_gypi.sh:84: echo "        # Disable LTO in neon targets due to compiler
bug" >> $2
Should this link to some tracking bug so that it's easy to find out when this
can be removed again? (maybe just the tracking bug you have?)

https://codereview.chromium.org/471653004/diff/60001/libvpx.gyp
File libvpx.gyp (right):

https://codereview.chromium.org/471653004/diff/60001/libvpx.gyp#newcode8
libvpx.gyp:8: # Link-Time Optimizations
"Disable LTO for neon targets, crbug.com/XXX"

The bug should also contain a copy of the stderr that's produced when this isn't
disabled, if someone gets that message in another target and googles for it
(they should be able to find your bug)

[Nico, 2014-08-29 14:31:35]

Oh, and one more: The deps are all still in svn, I'm not sure if the cq will do
the right thing here. The change needs to be made here
http://src.chromium.org/viewvc/chrome/trunk/deps/third_party/libvpx/ and then
it'll be mirrored ino the libvpx.git repo automatically.

[Fabrice (no longer in Chrome), 2014-08-29 14:45:00]

And there we go.
I am not sure how to land this though. I'm going to try CQ. If it does not work,
I'm not a committer, so I'm not sure I can land this.

https://codereview.chromium.org/471653004/diff/60001/generate_gypi.sh
File generate_gypi.sh (right):

https://codereview.chromium.org/471653004/diff/60001/generate_gypi.sh#newcode84
generate_gypi.sh:84: echo "        # Disable LTO in neon targets due to compiler
bug" >> $2
On 2014/08/29 14:30:41, Nico (hiding) wrote:
> Should this link to some tracking bug so that it's easy to find out when this
> can be removed again? (maybe just the tracking bug you have?)

Done.

https://codereview.chromium.org/471653004/diff/60001/libvpx.gyp
File libvpx.gyp (right):

https://codereview.chromium.org/471653004/diff/60001/libvpx.gyp#newcode8
libvpx.gyp:8: # Link-Time Optimizations
On 2014/08/29 14:30:41, Nico (hiding) wrote:
> "Disable LTO for neon targets, crbug.com/XXX"
> 
> The bug should also contain a copy of the stderr that's produced when this
isn't
> disabled, if someone gets that message in another target and googles for it
> (they should be able to find your bug)

Done.

[Fabrice (no longer in Chrome), 2014-08-29 14:45:09]

The CQ bit was checked by fdegans@chromium.org

[commit-bot: I haz the power, 2014-08-29 14:46:27]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-08-29 14:46:28]

Commit queue rejected this change because it did not recognize the base URL.
Please commit your change manually.

[Nico, 2014-08-29 15:23:14]

Transmitting file data ...
Committed revision 291730.

[Nico, 2014-08-29 15:24:09]

You now have to wait until
https://chromium.googlesource.com/chromium/deps/libvpx/ has that commit, and the
update DEPS to pull the new version.