Add gn option 'is_lto' to enable Link Time Optimization builds.

Add gn option 'is_lto' to enable Link Time Optimization builds.

We'll launch LTO builds on Linux first, and then add CFI
(control flow integrity) on top of that.

BUG=589915
Committed: https://crrev.com/2de2f30ff962315aef7d81159918548db9a00566
Cr-Commit-Position: refs/heads/master@{#377695}

[krasin1, 2016-02-25 20:17:57]

krasin@chromium.org changed reviewers:
+ dpranke@google.com, krasin@chromium.org, pcc@google.com

[krasin1, 2016-02-25 20:17:57]

Peter, Dirk,

this is a tiny CL that introduces is_lto option to GN config. We need it to
launch LTO prior to CFI, so that we have 2 smaller launches instead of one big.

Please, take a look.

[Dirk Pranke, 2016-02-25 20:31:46]

dpranke@chromium.org changed reviewers:
+ dpranke@chromium.org

[Dirk Pranke, 2016-02-25 20:31:46]

lgtm

[krasin1, 2016-02-25 21:33:37]

A late discovery, but I feel necessary to ask for opinions: in GYP we have
"use_lto", in GN I am about to add "is_lto".

Should I go this way, or keep "use_lto" in both cases to avoid confusion?

[Dirk Pranke, 2016-02-25 21:42:19]

On 2016/02/25 21:33:37, krasin1 wrote:
> A late discovery, but I feel necessary to ask for opinions: in GYP we have
> "use_lto", in GN I am about to add "is_lto".
> 
> Should I go this way, or keep "use_lto" in both cases to avoid confusion?

I might go with 'use_lto' since it's more of a feature flag, but you can see the

argument for either way and we're not entirely consistent. 

It doesn't matter too much.

[krasin1, 2016-02-25 21:42:30]

On 2016/02/25 21:33:37, krasin1 wrote:
> A late discovery, but I feel necessary to ask for opinions: in GYP we have
> "use_lto", in GN I am about to add "is_lto".
> 
> Should I go this way, or keep "use_lto" in both cases to avoid confusion?

To defend is_lto: I don't see a meaningful difference lto and cfi in this case.
We have is_cfi in GN, thus we should probably have is_lto.

[krasin1, 2016-02-25 21:43:17]

On 2016/02/25 21:42:19, Dirk Pranke wrote:
> On 2016/02/25 21:33:37, krasin1 wrote:
> > A late discovery, but I feel necessary to ask for opinions: in GYP we have
> > "use_lto", in GN I am about to add "is_lto".
> > 
> > Should I go this way, or keep "use_lto" in both cases to avoid confusion?
> 
> I might go with 'use_lto' since it's more of a feature flag, but you can see
the
> 
> argument for either way and we're not entirely consistent. 
> 
> It doesn't matter too much.

okay, then I will submit it as is.

[krasin1, 2016-02-25 21:43:20]

The CQ bit was checked by krasin@chromium.org

[commit-bot: I haz the power, 2016-02-25 21:51:52]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1734043003/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1734043003/20001

[commit-bot: I haz the power, 2016-02-25 22:56:33]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-02-25 22:58:48]

Description was changed from

==========
Add gn option 'is_lto' to enable Link Time Optimization builds.

We'll launch LTO builds on Linux first, and then add CFI
(control flow integrity) on top of that.

BUG=589915
==========

to

==========
Add gn option 'is_lto' to enable Link Time Optimization builds.

We'll launch LTO builds on Linux first, and then add CFI
(control flow integrity) on top of that.

BUG=589915

Committed: https://crrev.com/2de2f30ff962315aef7d81159918548db9a00566
Cr-Commit-Position: refs/heads/master@{#377695}
==========

[commit-bot: I haz the power, 2016-02-25 22:58:48]

Patchset 2 (id:??) landed as
https://crrev.com/2de2f30ff962315aef7d81159918548db9a00566
Cr-Commit-Position: refs/heads/master@{#377695}

[brettw, 2016-03-24 20:27:45]

brettw@chromium.org changed reviewers:
+ brettw@chromium.org

[brettw, 2016-03-24 20:27:46]

https://codereview.chromium.org/1734043003/diff/20001/build/config/sanitizers...
File build/config/sanitizers/sanitizers.gni (right):

https://codereview.chromium.org/1734043003/diff/20001/build/config/sanitizers...
build/config/sanitizers/sanitizers.gni:73: is_lto = is_cfi
This shouldn't be in this file because it has nothing to do with sanitizers.