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

[Martin Jambor <mjambor@suse.cz>]

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?

Thanks,

Martin