Re: [AArch64] Enable generation of FRINTNZ instructions

["Andre Vieira (lists)" <andre.simoesdiasvieira@arm.com>]

On 07/11/2022 11:05, Richard Biener wrote:
> On Fri, 4 Nov 2022, Andre Vieira (lists) wrote:
>
>> Sorry for the delay, just been reminded I still had this patch outstanding
>> from last stage 1. Hopefully since it has been mostly reviewed it could go in
>> for this stage 1?
>>
>> I addressed the comments and gave the slp-part of vectorizable_call some TLC
>> to make it work.
>>
>> I also changed vect_get_slp_defs as I noticed that the call from
>> vectorizable_call was creating an auto_vec with 'nargs' that might be less
>> than the number of children in the slp_node
> how so?  Please fix that in the caller.  It looks like it probably
> shoud use vect_nargs instead?
Well that was my first intuition, but when I looked at it further the 
variant it's calling:
void vect_get_slp_defs (vec_info *, slp_tree slp_node, vec<vec<tree> > 
*vec_oprnds, unsigned n)

Is actually creating a vector of vectors of slp defs. So for each child 
of slp_node it calls:
void vect_get_slp_defs (slp_tree slp_node, vec<tree> *vec_defs)

Which returns a vector of vectorized defs. So vect_nargs would be the 
right size for the inner vec<tree> of vec_defs, but the outer should 
have the same number of elements as the original slp_node has children.

However, at the call site (vectorizable_call), the operand we pass to 
vect_get_slp_defs 'vec_defs', is initialized before the code-path is 
specialized for slp_node. I'll go see if I can change the call site to 
not have to do that, given the continue at the end of the if (slp_node) 
BB I don't think it needs to use vec_defs after it, but it may require 
some massaging to be able to define it separately for each code-path.

>
>> , so that quick_push might not be
>> safe as is, so I added the reserve (n) to ensure it's safe to push. I didn't
>> actually come across any failure because of it though. Happy to split this
>> into a separate patch if needed.
>>
>> Bootstrapped and regression tested on aarch64-none-linux-gnu and
>> x86_64-pc-linux-gnu.
>>
>> OK for trunk?
> I'll leave final approval to Richard but
>
> -     This only needs 1 bit, but occupies the full 16 to ensure a nice
> +     This only needs 1 bit, but occupies the full 15 to ensure a nice
>        layout.  */
>     unsigned int vectorizable : 16;
>
> you don't actually change the width of the bitfield.  I would find
> it more natural to have
>
>    signed int type0 : 7;
>    signed int type0_vtrans : 1;
>    signed int type1 : 7;
>    signed int type1_vtrans : 1;
>
> with typeN_vtrans specifying how the types transform when vectorized.
> I would imagine another variant we could need is narrow/widen
> according to either result or other argument type?  That said,
> just your flag would then be
>
>    signed int type0 : 7;
>    signed int pad   : 1;
>    signed int type1 : 7;
>    signed int type1_vect_as_scalar : 1;
>
> ?
That's a cool idea! I'll leave it as a single bit for now like that, if 
we want to re-use it for multiple transformations we will obviously need 
to rename & give it more bits.
>
>> gcc/ChangeLog:
>>
>>          * config/aarch64/aarch64.md (ftrunc<mode><frintnz_mode>2): New
>> pattern.
>>          * config/aarch64/iterators.md (FRINTNZ): New iterator.
>>          (frintnz_mode): New int attribute.
>>          (VSFDF): Make iterator conditional.
>>          * internal-fn.def (FTRUNC_INT): New IFN.
>>          * internal-fn.cc (ftrunc_int_direct): New define.
>>          (expand_ftrunc_int_optab_fn): New custom expander.
>>          (direct_ftrunc_int_optab_supported_p): New supported_p.
>>          * internal-fn.h (direct_internal_fn_info): Add new member
>>          type1_is_scalar_p.
>>          * match.pd: Add to the existing TRUNC pattern match.
>>          * optabs.def (ftrunc_int): New entry.
>>          * stor-layout.h (element_precision): Moved from here...
>>          * tree.h (element_precision): ... to here.
>>          (element_type): New declaration.
>>          * tree.cc (element_type): New function.
>>          (element_precision): Changed to use element_type.
>>          * tree-vect-stmts.cc (vectorizable_internal_function): Add
>> support for
>>          IFNs with different input types.
>>          (vect_get_scalar_oprnds): New function.
>>          (vectorizable_call): Teach to handle IFN_FTRUNC_INT.
>>          * tree-vect-slp.cc (check_scalar_arg_ok): New function.
>>          (vect_slp_analyze_node_operations): Use check_scalar_arg_ok.
>>          (vect_get_slp_defs): Ensure vec_oprnds has enough slots to push.
>>          * doc/md.texi: New entry for ftrunc pattern name.
>>          * doc/sourcebuild.texi (aarch64_frintzx_ok): New target.
>>
>> gcc/testsuite/ChangeLog:
>>
>>          * gcc.target/aarch64/merge_trunc1.c: Adapted to skip if frintnz
>> instructions available.
>>          * lib/target-supports.exp: Added aarch64_frintnzx_ok target and
>> aarch64_frintz options.
>>          * gcc.target/aarch64/frintnz.c: New test.
>>          * gcc.target/aarch64/frintnz_vec.c: New test.
>>          * gcc.target/aarch64/frintnz_slp.c: New test.
>>