Re: Ping: Re: [PATCH 1/2] gcc: Remove unneeded global flag.

[Andrew Burgess <andrew.burgess@embecosm.com>]

* Christophe Lyon <christophe.lyon@linaro.org> [2016-11-21 13:47:09 +0100]:

> On 20 November 2016 at 18:27, Mike Stump <mikestump@comcast.net> wrote:
> > On Nov 19, 2016, at 1:59 PM, Andrew Burgess <andrew.burgess@embecosm.com> wrote:
> >>> So, your new test fails on arm* targets:
> >>
> >> After a little digging I think the problem might be that
> >> -freorder-blocks-and-partition is not supported on arm.
> >>
> >> This should be detected as the new tests include:
> >>
> >>    /* { dg-require-effective-target freorder } */
> >>
> >> however this test passed on arm as -freorder-blocks-and-partition does
> >> not issue any warning unless -fprofile-use is also passed.
> >>
> >> The patch below extends check_effective_target_freorder to check using
> >> -fprofile-use.  With this change in place the tests are skipped on
> >> arm.
> >
> >> All feedback welcome,
> >
> > Seems reasonable, unless a -freorder-blocks-and-partition/-fprofile-use person thinks this is the wrong solution.
> >
> 
> Hi,
> 
> As promised, I tested this patch: it makes
> gcc.dg/tree-prof/section-attr-[123].c
> unsupported on arm*, and thus they are not failing anymore :-)
> 
> However, it also makes other tests unsupported, while they used to pass:
> 
>   gcc.dg/pr33648.c
>   gcc.dg/pr46685.c
>   gcc.dg/tree-prof/20041218-1.c
>   gcc.dg/tree-prof/bb-reorg.c
>   gcc.dg/tree-prof/cold_partition_label.c
>   gcc.dg/tree-prof/comp-goto-1.c
>   gcc.dg/tree-prof/pr34999.c
>   gcc.dg/tree-prof/pr45354.c
>   gcc.dg/tree-prof/pr50907.c
>   gcc.dg/tree-prof/pr52027.c
>   gcc.dg/tree-prof/va-arg-pack-1.c
> 
> and failures are now unsupported:
>   gcc.dg/tree-prof/cold_partition_label.c
>   gcc.dg/tree-prof/section-attr-1.c
>   gcc.dg/tree-prof/section-attr-2.c
>   gcc.dg/tree-prof/section-attr-3.c
> 
> So, maybe this patch is too strong?

In all of the cases that used to pass the tests are compile only tests
(except for cold_partition_label, which I discuss below).

On ARM passing -fprofile-use and -freorder-blocks-and-partition
results in a warning, and the -freorder-blocks-and-partition flag is
ignored.  However, disabling -freorder-blocks-and-partition doesn't
stop any of the tests compiling, hence the passes.

All the tests include:

  /* { dg-require-effective-target freorder } */

which I understand to mean, the tests requires the 'freorder' feature
to be supported (which corresponds to -freorder-blocks-and-partition).

For cold_partition_label and my new tests it's seems clear that the
lack of support for -freorder-blocks-and-partition on ARM is the cause
of the test failures.

So, is it reasonable to give up the other tests as "unsupported"?  I'd
be inclined to say yes, but I happy to rework the patch if anyone has
a suggestion for an alternative approach.

One possibility would be to split the 'freorder' feature into two, one
being 'Can -freorder-blocks-and-partition be used without causing an
error (so ARM would say yes to this)', and a new feature would be
'Does -freorder-blocks-and-partition actually _work_ on the target?'
we'd then use this in cold_partition_label and in my new tests.
Though this doesn't feel a great solution....

Thanks,
Andrew