Re: [PATCH] vect: Check that vector factor is a compile-time constant

[Michael Collison <collison@rivosinc.com>]

Richard how would I check for a full masked main vector loop?

On 2/22/23 03:20, Richard Biener wrote:
> On Wed, Feb 22, 2023 at 12:03 AM Michael Collison <collison@rivosinc.com> wrote:
>> While working on autovectorizing for the RISCV port I encountered an
>> issue where vect_do_peeling assumes that the vectorization factor is a
>> compile-time constant. The vectorization is not a compile-time constant
>> on RISCV.
>>
>> Tested on RISCV and x86_64-linux-gnu. Okay?
> I wonder how you arrive at prologue peeling with a non-constant VF?
> In any case it would probably be better to use constant_lower_bound (vf)
> here?  Also it looks wrong to apply this limit in case we are using
> a fully masked main vector loop.  But as said, the specific case of
> non-constant VF and prologue peeling probably wasn't supposed to happen,
> instead the prologue usually is applied via an offset to a fully masked loop?
>
> Richard?
>
> Thanks,
> Richard.
>
>> Michael
>>
>> gcc/
>>
>>       * tree-vect-loop-manip.cc (vect_do_peeling): Verify
>>       that vectorization factor is a compile-time constant.
>>
>> ---
>>    gcc/tree-vect-loop-manip.cc | 2 +-
>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/gcc/tree-vect-loop-manip.cc b/gcc/tree-vect-loop-manip.cc
>> index 6aa3d2ed0bf..1ad1961c788 100644
>> --- a/gcc/tree-vect-loop-manip.cc
>> +++ b/gcc/tree-vect-loop-manip.cc
>> @@ -2930,7 +2930,7 @@ vect_do_peeling (loop_vec_info loop_vinfo, tree
>> niters, tree nitersm1,
>>          niters = vect_build_loop_niters (loop_vinfo, &new_var_p);
>>          /* It's guaranteed that vector loop bound before vectorization is at
>>         least VF, so set range information for newly generated var. */
>> -      if (new_var_p)
>> +      if (new_var_p && vf.is_constant ())
>>        {
>>          value_range vr (type,
>>                  wi::to_wide (build_int_cst (type, vf)),
>> --
>> 2.34.1
>>