"Andre Vieira (lists)" <andre.simoesdiasvie...@arm.com> writes:
> On 17/12/2021 12:44, Richard Sandiford wrote:
>>
>>> @@ -3252,16 +3257,31 @@ vectorizable_call (vec_info *vinfo,
>>> rhs_type = unsigned_type_node;
>>> }
>>>
>>> - int mask_opno = -1;
>>> + /* The argument that is not of the same type as the others. */
>>> + int diff_opno = -1;
>>> + bool masked = false;
>>> if (internal_fn_p (cfn))
>>> - mask_opno = internal_fn_mask_index (as_internal_fn (cfn));
>>> + {
>>> + if (cfn == CFN_FTRUNC_INT)
>>> + /* For FTRUNC this represents the argument that carries the type of the
>>> + intermediate signed integer. */
>>> + diff_opno = 1;
>>> + else
>>> + {
>>> + /* For masked operations this represents the argument that carries the
>>> + mask. */
>>> + diff_opno = internal_fn_mask_index (as_internal_fn (cfn));
>>> + masked = diff_opno >= 0;
>>> + }
>>> + }
>> I think it would be cleaner not to process argument 1 at all for
>> CFN_FTRUNC_INT. There's no particular need to vectorise it.
>
> I agree with this, will change the loop to continue for argument 1 when
> dealing with non-masked CFN's.
>
>>> }
>>> […]
>>> diff --git a/gcc/tree.c b/gcc/tree.c
>>> index
>>> 845228a055b2cfac0c9ca8c0cda1b9df4b0095c6..f1e9a1eb48769cb11aa69730e2480ed5522f78c1
>>> 100644
>>> --- a/gcc/tree.c
>>> +++ b/gcc/tree.c
>>> @@ -6645,11 +6645,11 @@ valid_constant_size_p (const_tree size,
>>> cst_size_error *perr /* = NULL */)
>>> return true;
>>> }
>>>
>>> -/* Return the precision of the type, or for a complex or vector type the
>>> - precision of the type of its elements. */
>>> +/* Return the type, or for a complex or vector type the type of its
>>> + elements. */
>>>
>>> -unsigned int
>>> -element_precision (const_tree type)
>>> +tree
>>> +element_type (const_tree type)
>>> {
>>> if (!TYPE_P (type))
>>> type = TREE_TYPE (type);
>>> @@ -6657,7 +6657,16 @@ element_precision (const_tree type)
>>> if (code == COMPLEX_TYPE || code == VECTOR_TYPE)
>>> type = TREE_TYPE (type);
>>>
>>> - return TYPE_PRECISION (type);
>>> + return (tree) type;
>> I think we should stick a const_cast in element_precision and make
>> element_type take a plain “type”. As it stands element_type is an
>> implicit const_cast for many cases.
>>
>> Thanks,
> Was just curious about something here, I thought the purpose of having
> element_precision (before) and element_type (now) take a const_tree as
> an argument was to make it clear we aren't changing the input type. I
> understand that as it stands element_type could be an implicit
> const_cast (which I should be using rather than the '(tree)' cast), but
> that's only if 'type' is a type that isn't complex/vector, either way,
> we are conforming to the promise that we aren't changing the incoming
> type, what the caller then does with the result is up to them no?
>
> I don't mind making the changes, just trying to understand the reasoning
> behind it.
The problem with the above is that functions like the following become
well-typed:
void
foo (const_tree t)
{
TYPE_MODE (element_type (t)) = VOIDmode;
}
even though element_type (t) could well be t.
One of the points of const_tree (and const pointer targets in general)
is to use the type system to enforce the promise that the value isn't
changed.
I guess the above is similar to the traditional problem with functions
like index and strstr, which take a const char * but return a char *.
So for example:
void
foo (const char *x)
{
index (x, '.') = 0;
}
is well-typed. But the equivalent C++ code (using iterators) would be
rejected. If C allowed overloading them the correct prototypes would be:
const char *index (const char *, int);
char *index (char *, int);
And I think the same applies here. Either we should provide two functions:
const_tree element_type (const_tree);
tree element_type (tree);
or just the latter.
Thanks,
Richard
