On Oct 15, 2015, at 6:18 AM, Richard Sandiford <richard.sandif...@arm.com>
wrote:
> Stripping unnecessary sign ops at the gimple level means that we're
> no longer able to optimise:
>
> if (cos(y<10 ? -fabs(x) : tan(x<20 ? -x : -fabs(y)))
> != cos(y<10 ? x : tan(x<20 ? x : y)))
> link_error ();
>
> because we're currently not able to fold away the equality in:
>
> int
> f1 (double x, double y)
> {
> double z1 = __builtin_cos(y<10 ? x : __builtin_tan(x<20 ? x : y));
> double z2 = __builtin_cos(y<10 ? x : __builtin_tan(x<20 ? x : y));
> return z1 == z2;
> }
>
> The missed fold is being tracked as PR 67975. This patch splits the
> test out into a separate file so that we can XFAIL it until the PR
> is fixed.
So, with my peanut gallery hat on, I’m not a fan of this sort of thing. If
others want to do this though, I’d let that be their call.
As a counter example, I’d be fine with #if 0ing the tests that don’t work, and
putting in the PR the reserve of that patch to remove the added #if 0 when that
PR is fixed. The test case remains complete, and once the PR is fixed, the
test suite will be as it was. Having tests that we know fail doesn’t enhance
the quality of the compiler any. It is a nice tracking mechanism, if no PR
exists, but, when a PR exists, we don’t need the test case to track the issue,
as the PR will. In general, adding #if 0 to tests is undesirable, but, when
one cannot toggle subtests easily or mark subtest failures easily, I prefer it
over splitting.
