Re: [PATCH 1/5] Fix asymmetric comparison functions

[Jakub Jelinek <jakub@redhat.com>]

On Thu, Dec 17, 2015 at 02:47:29PM +0300, Yury Gribov wrote:
> On 12/17/2015 02:41 PM, Richard Biener wrote:
> >On Thu, 17 Dec 2015, Yury Gribov wrote:
> >
> >>Some obvious symmetry fixes.
> >>
> >>Cc-ing
> >>* Andrey (Belevantsev) for bb_top_order_comparator
> >>* Andrew (MacLeod) for compare_case_labels
> >>* Andrew (Pinski) for resort_field_decl_cmp
> >>* Diego for pair_cmp
> >>* Geoff for resort_method_name_cmp
> >>* Jakub for compare_case_labels
> >>* Jason for method_name_cmp
> >>* Richard for insert_phi_nodes_compare_var_infos, compare_case_labels
> >>* Steven for cmp_v_in_regset_pool
> >
> >So for compare_case_labels we only ever have one label with
> >!CASE_LOW - which means you only run into the case that needs
> >!CASE_LOW && !CASE_LOW if comparing an element with itself, correct?
> >
> >In this case (missing "same element" handling rather than symmetry
> >fixing) I'd prefer a
> >
> >  if (case1 == case2)
> >    return 0;
> >
> >So just to confirm - do the patches also contain same element
> >compare fixings?
> 
> Yes, that's a fix for same element.  How about adding if + gcc_assert that
> both cases can't be NULL otherwise?

Some of the qsort comparison functions are hot paths, we don't really want
to slow them down.  So, if anything, gcc_checking_assert rather than
gcc_assert.
But, which qsort is so lame that it calls comparison on the same element?

	Jakub