gn: Make target_cpu=x86 v8_target_arch=arm builds generate build files.

gn: Make target_cpu=x86 v8_target_arch=arm builds generate build files.

First, it's v8_target_arch, not v8_target_cpu
https://codereview.chromium.org/2006173002 got this wrong.

With this changed, things don't gn (//build/config/arm.gni only
sets arm_version if target_cpu is set to something arm-y for example).
Also fix up things enough so that `gn gen` succeeds with the gn args
that would be set on the target-x86-but-set-v8-target-arch-to-arm bot.

BUG=619503, 605732

[Nico, 2016-06-13 11:42:16]

Description was changed from

==========
gn: It's v8_target_arch, not v8_target_cpu

https://codereview.chromium.org/2006173002 got this wrong.

With this changed, things don't gn either (//build/config/arm.gni only
sets arm_version if target_cpu is set to something arm-y for example),
but with this they'll at least fail loudly instead of just printing a warning
that nobody noticed for close to two weeks.

BUG=619503
==========

to

==========
gn: It's v8_target_arch, not v8_target_cpu

https://codereview.chromium.org/2006173002 got this wrong.

With this changed, things don't gn either (//build/config/arm.gni only
sets arm_version if target_cpu is set to something arm-y for example),
but with this they'll at least fail loudly instead of just printing a warning
that nobody noticed for close to two weeks.

BUG=619503,605732
==========

[Nico, 2016-06-13 11:42:26]

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

[Nico, 2016-06-13 12:47:22]

Description was changed from

==========
gn: It's v8_target_arch, not v8_target_cpu

https://codereview.chromium.org/2006173002 got this wrong.

With this changed, things don't gn either (//build/config/arm.gni only
sets arm_version if target_cpu is set to something arm-y for example),
but with this they'll at least fail loudly instead of just printing a warning
that nobody noticed for close to two weeks.

BUG=619503,605732
==========

to

==========
gn: It's v8_target_arch, not v8_target_cpu

https://codereview.chromium.org/2006173002 got this wrong.

With this changed, things don't gn (//build/config/arm.gni only
sets arm_version if target_cpu is set to something arm-y for example).
Also fix up things enough so that `gn gen` succeeds with the gn args
that would be set on the target-x86-but-set-v8-target-arch-to-arm bot.

BUG=619503,605732
==========

[Nico, 2016-06-13 12:47:59]

thakis@chromium.org changed reviewers:
+ jochen@chromium.org

[Nico, 2016-06-13 12:47:59]

+jochen since I touched //build/config/arm.gni to pacify v8's BUILD.gn

[Nico, 2016-06-13 12:51:51]

Description was changed from

==========
gn: It's v8_target_arch, not v8_target_cpu

https://codereview.chromium.org/2006173002 got this wrong.

With this changed, things don't gn (//build/config/arm.gni only
sets arm_version if target_cpu is set to something arm-y for example).
Also fix up things enough so that `gn gen` succeeds with the gn args
that would be set on the target-x86-but-set-v8-target-arch-to-arm bot.

BUG=619503,605732
==========

to

==========
gn: Make target_cpu=x86 v8_target_arch=arm builds generate build files.

First, iIt's v8_target_arch, not v8_target_cpu
https://codereview.chromium.org/2006173002 got this wrong.

With this changed, things don't gn (//build/config/arm.gni only
sets arm_version if target_cpu is set to something arm-y for example).
Also fix up things enough so that `gn gen` succeeds with the gn args
that would be set on the target-x86-but-set-v8-target-arch-to-arm bot.

BUG=619503,605732
==========

[Nico, 2016-06-13 13:11:56]

Description was changed from

==========
gn: Make target_cpu=x86 v8_target_arch=arm builds generate build files.

First, iIt's v8_target_arch, not v8_target_cpu
https://codereview.chromium.org/2006173002 got this wrong.

With this changed, things don't gn (//build/config/arm.gni only
sets arm_version if target_cpu is set to something arm-y for example).
Also fix up things enough so that `gn gen` succeeds with the gn args
that would be set on the target-x86-but-set-v8-target-arch-to-arm bot.

BUG=619503,605732
==========

to

==========
gn: Make target_cpu=x86 v8_target_arch=arm builds generate build files.

First, it's v8_target_arch, not v8_target_cpu
https://codereview.chromium.org/2006173002 got this wrong.

With this changed, things don't gn (//build/config/arm.gni only
sets arm_version if target_cpu is set to something arm-y for example).
Also fix up things enough so that `gn gen` succeeds with the gn args
that would be set on the target-x86-but-set-v8-target-arch-to-arm bot.

BUG=619503,605732
==========

[jochen (gone - plz use gerrit), 2016-06-13 15:18:40]

https://codereview.chromium.org/2066483002/diff/20001/build/config/arm.gni
File build/config/arm.gni (right):

https://codereview.chromium.org/2066483002/diff/20001/build/config/arm.gni#ne...
build/config/arm.gni:108: }
why not just replace the if (current_cpu == "arm" || target_cpu == "arm") with
something like if (target_cpu_bitness==32)?

then you'd also get v8_target_arch=arm64 target_arch=x64 for free

[Nico, 2016-06-13 15:23:53]

https://codereview.chromium.org/2066483002/diff/20001/build/config/arm.gni
File build/config/arm.gni (right):

https://codereview.chromium.org/2066483002/diff/20001/build/config/arm.gni#ne...
build/config/arm.gni:108: }
On 2016/06/13 15:18:40, jochen (slow) wrote:
> why not just replace the if (current_cpu == "arm" || target_cpu == "arm") with
> something like if (target_cpu_bitness==32)?
> 
> then you'd also get v8_target_arch=arm64 target_arch=x64 for free

I'm guessing that the arm check is there so that the arm_* vars are only set in
arm builds. We need them to be set slightly more often (for this hybrid build
here), but not much more often. The advantage of doing it like I did is that it
makes it clear that the hybrid build always has x86 for the v8 embedder, and
that arm_version etc can't be overridden in that mode. (No bot currently needs
to be able to do that.)

I couldn't find any bots that build with current_cpu=x64 and
v8_target_arch=arm64 – is that a supported config?

[Dirk Pranke, 2016-06-13 16:14:22]

lgtm. 

I'd prefer it if the variable was called 'v8_target_cpu' for consistency w/ the
other _cpu variables, but obviously it isn't right now, so we should make things
work first and rename later if we agree it's the right thing to do.

[Nico, 2016-06-13 16:36:58]

I talked to Jochen a bit. He says v8_target_arch is also used to test v8 on a
bunch of configs (v8/chromium_config.py; (arm,mips,ppc,s390) x (32,64)). He
rightfully points out that this approach doesn't scale nicely to all these archs
and suggests moving the v8_target_arch concept into build/.

build is already somewhat chromium-specific, so that's probably less weird than
it sounds at first…dpranke, do you have an opinion on that?

[Dirk Pranke, 2016-06-14 20:02:27]

I definitely want //build to be useful for whatever v8 needs for standalone
builds and the other architectures,
but I'm not yet sure what the right way to do that is, and I'm not sure that
moving v8_target_arch into //build
is the right way to do that.

I'll try to come up w/ a proposal this afternoon and send it out. I'll also see
if I can find some time early
morning my time tomorrow (wed before 10am) that we can meet to talk about it.

[Dirk Pranke, 2016-08-31 23:35:40]

I believe this got resolved in other CLs, so, closing.