Re: [PATCH] gcc-plugins: Disable GCC_PLUGIN_CYC_COMPLEXITY for s390

[Guenter Roeck]

On Tue, Feb 23, 2021 at 07:03:47PM +0100, Heiko Carstens wrote:
> On Tue, Feb 23, 2021 at 09:41:40AM -0800, Guenter Roeck wrote:
> > > I tried to explain why we don't want to set COMPILE_TEST for s390
> > > anymore. It overrides architecture dependencies in Kconfig, and lots
> > > of drivers do not set dependencies for HAS_IOMEM, HAS_DMA, and friends
> > > correctly.
> > > This generates constantly fallout which is irrelevant for s390 and
> > > also for other architectures. It generates just work with close to
> > > zero benefit. For drivers which matter for s390 we still see those
> > > errors.
> > > 
> > > > On the other side, if that flag would be set explicitly by
> > > > all{yes,mod}config, it would really beg for being misused. We
> > > > might then as well add a new flag that is explicitly associated
> > > > with all{yes,mod}config, but not with randconfig.
> > > 
> > > I think that makes most sense, probably also have a flag that is set
> > > for randconfig.
> > 
> > Not sure what value such an option would have, and how it would be used.
> > I would argue that randconfig should not set COMPILE_TEST to start with,
> > since its purpose should be to test random valid configurations and not
> > to compile test arbitrary (and in that case random) code. But that is
> > a different question, and just my personal opinion.
> > 
> > Overall, the question is what kind of additional option you would find
> > useful for s390. You make it clear that you don't want COMPILE_TEST.
> > At the same time, you still want all{mod,yes}config, but presumably
> > excluding options currently restricted by !COMPILE_TEST (such as
> > DEBUG_INFO, BPF_PRELOAD, UBSAN_TRAP, GCC_PLUGIN_CYC_COMPLEXITY,
> > and a few others). SUPPRESS_NOISY_TESTS would not cover that, but
> > neither would RANDCONFIG (or whatever it would be called).
> 
> Well, if we would have e.g. RANDCONFIG, then we could probably revert
> 334ef6ed06fa ("init/Kconfig: make COMPILE_TEST depend on !S390") and
> instead let COMPILE_TEST depend on !RANDCONFIG.
> I think this _could_ solve all common problems we currently see.
> 
> And it would also do what you suggested.

Sounds good.

Question is how one would set such a flag. The code in scripts/kconfig/conf.c
doesn't really set COMPILE_TEST in conjunction with randconfig; that is
just as random as all other configuration flags. Would something like
the patch below be acceptable ?

Thanks,
Guenter

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