From: Richard Sandiford <richard.sandiford@linaro.org>
To: Richard Guenther <richard.guenther@gmail.com>
Cc: gcc-patches@gcc.gnu.org, patches@linaro.org
Subject: Re: [5/9] Main target-independent support for direct interleaving
Date: Mon, 18 Apr 2011 12:58:00 -0000 [thread overview]
Message-ID: <g47harah0u.fsf@linaro.org> (raw)
In-Reply-To: <BANLkTinE+1mu3NVAEzYDMZ3-uFu-Fv+G4g@mail.gmail.com> (Richard Guenther's message of "Mon, 18 Apr 2011 14:08:50 +0200")
Richard Guenther <richard.guenther@gmail.com> writes:
> On Mon, Apr 18, 2011 at 1:24 PM, Richard Sandiford
> <richard.sandiford@linaro.org> wrote:
>> Richard Guenther <richard.guenther@gmail.com> writes:
>>> On Tue, Apr 12, 2011 at 3:59 PM, Richard Sandiford
>>> <richard.sandiford@linaro.org> wrote:
>>>> Index: gcc/doc/md.texi
>>>> ===================================================================
>>>> --- gcc/doc/md.texi 2011-04-12 12:16:46.000000000 +0100
>>>> +++ gcc/doc/md.texi 2011-04-12 14:48:28.000000000 +0100
>>>> @@ -3846,6 +3846,48 @@ into consecutive memory locations. Oper
>>>> consecutive memory locations, operand 1 is the first register, and
>>>> operand 2 is a constant: the number of consecutive registers.
>>>>
>>>> +@cindex @code{vec_load_lanes@var{m}@var{n}} instruction pattern
>>>> +@item @samp{vec_load_lanes@var{m}@var{n}}
>>>> +Perform an interleaved load of several vectors from memory operand 1
>>>> +into register operand 0. Both operands have mode @var{m}. The register
>>>> +operand is viewed as holding consecutive vectors of mode @var{n},
>>>> +while the memory operand is a flat array that contains the same number
>>>> +of elements. The operation is equivalent to:
>>>> +
>>>> +@smallexample
>>>> +int c = GET_MODE_SIZE (@var{m}) / GET_MODE_SIZE (@var{n});
>>>> +for (j = 0; j < GET_MODE_NUNITS (@var{n}); j++)
>>>> + for (i = 0; i < c; i++)
>>>> + operand0[i][j] = operand1[j * c + i];
>>>> +@end smallexample
>>>> +
>>>> +For example, @samp{vec_load_lanestiv4hi} loads 8 16-bit values
>>>> +from memory into a register of mode @samp{TI}@. The register
>>>> +contains two consecutive vectors of mode @samp{V4HI}@.
>>>
>>> So vec_load_lanestiv2qi would load ... ? c == 8 here. Intuitively
>>> such operation would have adjacent blocks of siv2qi memory. But
>>> maybe you want to constrain the mode size to GET_MODE_SIZE (@var{n})
>>> * GET_MODE_NUNITS (@var{n})? In which case the mode m is
>>> redundant? You could specify that we load NUNITS adjacent vectors into
>>> an integer mode of appropriate size.
>>
>> Like you say, vec_load_lanestiv2qi would load 16 QImode elements into
>> 8 consecutive V2QI registers. The first element from register vector I
>> would come from operand1[I] and the second element would come from
>> operand1[I + 8]. That's meant to be a valid combination.
>
> Ok, but the C loop from the example doesn't seem to match. Or I couldn't
> wrap my head around it despite looking for 5 minutes and already having
> coffee ;) I would have expected the vectors being in memory as
>
> v0[0], v1[0], v0[1], v1[1], v2[0], v3[1]. v2[1], v3[1], ...
>
> not
>
> v0[0], v1[0], v2[0], ...
>
> as I would have thought the former is more useful (simple unrolling for
> stride 2).
The second one's right. All lane 0 elements, followed by all lane 1
elements, etc. I think that's what the C loop says.
> We'd need a separate set of optabs for such an interleaving
> scheme? In which case we might want to come up with a more
> specific name than load_lane?
Yeah, if someone has a single instruction that does your first example,
then it would need a new optab. The individual vector pairs could be
represented using the current optab though, if each pair needs a
separate instruction. E.g. with your v2qi example, vec_load_lanessiv2qi
would load:
v0[0], v1[0], v0[1], v1[1]
and you could repeat for the others. So load_lanes (as defined here)
could be treated as a primitive, and your first example could be something
like "repeat_load_lanes".
If you don't like the name "load_lanes" though, I'm happy to use
something else.
Richard
next prev parent reply other threads:[~2011-04-18 12:20 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-12 13:21 [0/9] Direct support for loads and stores of interleaved vectors Richard Sandiford
2011-04-12 13:25 ` [1/9] Generalise vect_create_data_ref_ptr Richard Sandiford
2011-04-12 13:30 ` Richard Guenther
2011-04-12 13:28 ` [2/9] Reindent parts of vectorizable_load and vectorizable_store Richard Sandiford
2011-04-12 13:33 ` Richard Guenther
2011-04-12 14:39 ` Richard Sandiford
2011-04-12 13:40 ` [3/9] STMT_VINFO_RELATED_STMT handling in vectorizable_store Richard Sandiford
2011-04-17 10:25 ` Ira Rosen
2011-04-12 13:44 ` [4/9] Move power-of-two checks for interleaving Richard Sandiford
2011-04-12 13:57 ` Richard Guenther
2011-04-12 13:59 ` [5/9] Main target-independent support for direct interleaving Richard Sandiford
2011-04-17 14:26 ` Ira Rosen
2011-04-18 11:54 ` Richard Guenther
2011-04-18 11:57 ` Richard Sandiford
2011-04-18 12:54 ` Richard Guenther
2011-04-18 12:58 ` Richard Sandiford [this message]
2011-04-18 13:22 ` Richard Guenther
2011-04-12 14:01 ` [6/9] NEON vec_load_lanes and vec_store_lanes patterns Richard Sandiford
2011-04-15 13:20 ` Richard Earnshaw
2011-04-12 14:14 ` [7/9] Testsuite: remove vect_{extract_even_odd,strided}_wide Richard Sandiford
2011-04-15 12:43 ` Richard Guenther
2011-04-12 14:19 ` [8/9] Testsuite: split tests for strided accesses Richard Sandiford
2011-04-15 12:44 ` Richard Guenther
2011-04-12 14:29 ` [9/9] Testsuite: Replace vect_strided with vect_stridedN Richard Sandiford
2011-04-15 12:44 ` Richard Guenther
2011-04-12 14:34 ` [10/9] Add tests for stride-3 accesses Richard Sandiford
2011-04-15 12:45 ` Richard Guenther
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