Re: [PATCH i386 AVX512] [75/n] Update vec_init.

[Jakub Jelinek <jakub at redhat dot com>]

On Fri, Oct 17, 2014 at 04:28:12PM +0400, Kirill Yukhin wrote:
> > I wonder whether for these modes it can ever be beneficial to build them
> > through interleaves/concatenations etc., if it wouldn't be better to build
> > them by storing all values into memory and just reading it back.
> I've tried this example:
> #include <immintrin.h>
> 
> unsigned char a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14,
>   a15, a16, a17, a18, a19, a20, a21, a22, a23, a24, a25, a26, a27, a28, a29,
>   a30, a31, a32, a33, a34, a35, a36, a37, a38, a39, a40, a41, a42, a43, a44,
>   a45, a46, a47, a48, a49, a50, a51, a52, a53, a54, a55, a56, a57, a58, a59,
>   a60, a61, a62, a63;
> 
> __m512i foo ()
> {
>   return __extension__ (__m512i)(__v64qi){
>     a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14,
>       a15, a16, a17, a18, a19, a20, a21, a22, a23, a24, a25, a26, a27, a28, a29,
>       a30, a31, a32, a33, a34, a35, a36, a37, a38, a39, a40, a41, a42, a43, a44,
>       a45, a46, a47, a48, a49, a50, a51, a52, a53, a54, a55, a56, a57, a58, a59,
>       a60, a61, a62, a63 };
> }
> 
> w/ and w/o -mavx512bw (and always -mavx512f).
> 
> When, this code works, we've got 127 lines of assembly to do this init.
> W/o AVX-512BW we've got > 300 lines of code (mostly on GPRs, using sal, and etc.)
> 
> Then I've looked into actual assembly w/ -mavx512bw and it turns out that no
> AVX-512BW insn were generated, only AVX-512F (and below). Fixed iterator.

Ok, if it is shorter than copying all those into memory and reading from
memory, so be it.

> > > -(define_mode_iterator VI48F_512 [V16SI V16SF V8DI V8DF])
> > > +(define_mode_iterator VI48F_I12_AVX512BW
> > > +  [V16SI V16SF V8DI V8DF
> > > +  (V32HI "TARGET_AVX512BW") (V64QI "TARGET_AVX512BW")])
> > 
> > What does the I12 stand for?  Wasn't it meant to be VI48F_512_AVX512BW
> > or I512?
> Actually, I am not awere of any name convention for iterators.
> As far as I understand, name [more or less] for vector mode
> should reflect:
>   - Type family of the unit: float or int
>   - Size of the unit: 1, 2, 4 etc. bytes
>   - If possible, target predicates to enable certain modes in
>     given iterator.
> 
> The name is:
>   - Vector (V)
>   - I48F - contains both ints and floats of size 4 and 8
>   - I12 - contains ints of size 1 and 2
>   - AVX512BW - affected by the target (according to previous note - to be removed)
> 
> Maybe it'll be better to name it: VF48_I1248?

I'll leave that to Uros, the patch is ok by me.

	Jakub