Re: [PATCH 1/2] vec: Add array_slice constructors from non-const and gc vectors

[Richard Biener <rguenther@suse.de>]

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On Fri, 26 Aug 2022, Martin Jambor wrote:

> Hi,
> 
> On Fri, Aug 26 2022, Richard Biener wrote:
> >> Am 26.08.2022 um 18:39 schrieb Martin Jambor <mjambor@suse.cz>:
> >>
> >> Hi,
> >>
> >> This patch adds constructors of array_slice that are required to
> >> create them from non-const (heap or auto) vectors or from GC vectors.
> >>
> >> The use of non-const array_slices is somewhat limited, as creating one
> >> from const vec<some_type> still leads to array_slice<const some_type>,
> >> so I eventually also only resorted to having read-only array_slices.
> >> But I do need the constructor from the gc vector.
> >>
> >> Bootstrapped and tested along code that actually uses it on
> >> x86_64-linux.  OK for trunk?
> >>
> >> Thanks,
> >>
> >> Martin
> >>
> >>
> >> gcc/ChangeLog:
> >>
> >> 2022-08-08  Martin Jambor  <mjambor@suse.cz>
> >>
> >>    * vec.h (array_slice): Add constructors for non-const reference to
> >>    heap vector and pointers to heap vectors.
> >> ---
> >> gcc/vec.h | 12 ++++++++++++
> >> 1 file changed, 12 insertions(+)
> >>
> >> diff --git a/gcc/vec.h b/gcc/vec.h
> >> index eed075addc9..b0477e1044c 100644
> >> --- a/gcc/vec.h
> >> +++ b/gcc/vec.h
> >> @@ -2264,6 +2264,18 @@ public:
> >>   array_slice (const vec<OtherT> &v)
> >>     : m_base (v.address ()), m_size (v.length ()) {}
> >>
> >> +  template<typename OtherT>
> >> +  array_slice (vec<OtherT> &v)
> >> +    : m_base (v.address ()), m_size (v.length ()) {}
> >> +
> >> +  template<typename OtherT>
> >> +  array_slice (const vec<OtherT, va_gc> *v)
> >> +    : m_base (v ? v->address () : nullptr), m_size (v ? v->length () : 0) {}
> >> +
> >> +  template<typename OtherT>
> >> +  array_slice (vec<OtherT, va_gc> *v)
> >> +    : m_base (v ? v->address () : nullptr), m_size (v ? v->length () : 0) {}
> >> +
> >
> > I don?t quite understand why the generic ctor doesn?t cover the GC case.  It looks more like reference vs pointer?
> >
> 
> If you think that this should work:
> 
>   vec<tree, va_gc> *heh = cfun->local_decls;
>   array_slice<tree> arr_slice (*heh);
> 
> then it does not:
> 
>   /home/mjambor/gcc/mine/src/gcc/ipa-cp.cc:6693:36: error: no matching function for call to ?array_slice<tree_node*>::array_slice(vec<tree_node*, va_gc>&)?
>    6693 |   array_slice<tree> arr_slice (*heh);
>         |                                    ^
>   In file included from /home/mjambor/gcc/mine/src/gcc/hash-table.h:248,
>                    from /home/mjambor/gcc/mine/src/gcc/coretypes.h:486,
>                    from /home/mjambor/gcc/mine/src/gcc/ipa-cp.cc:105:
>   /home/mjambor/gcc/mine/src/gcc/vec.h:2264:3: note: candidate: ?template<class OtherT> array_slice<T>::array_slice(const vec<OtherT>&) [with T = tree_node*]?
>    2264 |   array_slice (const vec<OtherT> &v)
>         |   ^~~~~~~~~~~
>   /home/mjambor/gcc/mine/src/gcc/vec.h:2264:3: note:   template argument deduction/substitution failed:
>   /home/mjambor/gcc/mine/src/gcc/ipa-cp.cc:6693:36: note:   mismatched types ?va_heap? and ?va_gc?
>    6693 |   array_slice<tree> arr_slice (*heh);
>         |                                    ^
> 
>   [... I trimmed notes about all other candidates...]
> 
> Or did you mean something else?

Hmm, so what if you change

  template<typename OtherT>
  array_slice (const vec<OtherT> &v)
    : m_base (v.address ()), m_size (v.length ()) {}

to

  template<typename OtherT, typename l, typename a>
  array_slice (const vec<OtherT, l, a> &v)
    : m_base (v.address ()), m_size (v.length ()) {}

instead?  Thus allow any allocation / placement template arg?

Richard.

> Thanks,
> 
> Martin
> 

-- 
Richard Biener <rguenther@suse.de>
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