[LLVMdev] Proposal: Move host CPU auto-detection out of the TargetMachine

[Richard Sandiford]

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