llvm dev - Apr 2014 - [LLVMdev] Proposal: Move host CPU auto-detection out of the TargetMachine

Eric Christopher <echristo at gmail.com> writes:
> I'm not a huge fan of this because then you get to decide on a default
> for all the ports, but I can understand if people want to move this
> way to reduce uncertainty.
FWIW, since it's one of the three targets Jim mentioned, -march=z10 is
the obvious default for SystemZ.

On the other hand, I think it's good to run the tests on both z10 and z196,
since there were significant additions to the architecture in z196.
Until now we've been getting that by implicitly using -mcpu=z10 for
cross testing on the usual x86_64 buildbots and implicitly using
-mcpu=native (-mcpu=z196) on the z buildbot.

We could do it instead by having two llcs and FileChecks per
CodeGen/SystemZ test, which would give better cross-toolchain
coverage, but would almost double the test time.  Would that
still be OK?

Thanks,
Richard

On Apr 10, 2014, at 1:48 AM, Richard Sandiford <rsandifo at
linux.vnet.ibm.com> wrote:
> Eric Christopher <echristo at gmail.com> writes:
>> I'm not a huge fan of this because then you get to decide on a
default
>> for all the ports, but I can understand if people want to move this
>> way to reduce uncertainty.
> 
> FWIW, since it's one of the three targets Jim mentioned, -march=z10 is
> the obvious default for SystemZ.
Makes sense.
> 
> On the other hand, I think it's good to run the tests on both z10 and
z196,
> since there were significant additions to the architecture in z196.
> Until now we've been getting that by implicitly using -mcpu=z10 for
> cross testing on the usual x86_64 buildbots and implicitly using
> -mcpu=native (-mcpu=z196) on the z buildbot.
> 
> We could do it instead by having two llcs and FileChecks per
> CodeGen/SystemZ test, which would give better cross-toolchain
> coverage, but would almost double the test time.  Would that
> still be OK?
If you really want to run both variations of the tests, yes, absolutely, and
that’s the right way to do it. Having the tests run differently in a
cross-compile vs. a host-compile situation is exactly the sort of thing I’m
hoping to move away from.

-Jim

Jim Grosbach <grosbach at apple.com> writes:
>> On the other hand, I think it's good to run the tests on both z10
and z196,
>> since there were significant additions to the architecture in z196.
>> Until now we've been getting that by implicitly using -mcpu=z10 for
>> cross testing on the usual x86_64 buildbots and implicitly using
>> -mcpu=native (-mcpu=z196) on the z buildbot.
>> 
>> We could do it instead by having two llcs and FileChecks per
>> CodeGen/SystemZ test, which would give better cross-toolchain
>> coverage, but would almost double the test time.  Would that
>> still be OK?
>
> If you really want to run both variations of the tests, yes, absolutely,
> and that’s the right way to do it. Having the tests run differently in a
> cross-compile vs. a host-compile situation is exactly the sort of thing
> I’m hoping to move away from.
OK, in that case I'll do the SystemZ side if the x86 change goes in.

Thanks,
Richard