Richard Biener <[email protected]> writes:
> On Tue, Oct 8, 2024 at 10:36 AM liuhongt <[email protected]> wrote:
>>
>> >So should we adjust very-cheap to allow niter peeling as proposed or
>> >should we switch the default at -O2 to cheap?
>> I prefer the former.
>>
>> Update in V2:
>> Adjust testcase after relax O2 vectorization.
>>
>> Ok for trunk?
>
> OK.
We'd also need to update the documentation:
... The @samp{very-cheap} model only
allows vectorization if the vector code would entirely replace the
scalar code that is being vectorized. For example, if each iteration
of a vectorized loop would only be able to handle exactly four iterations
of the scalar loop, the @samp{very-cheap} model would only allow
vectorization if the scalar iteration count is known to be a multiple
of four.
And since it's a change in documented behaviour, it should probably
be in the release notes too.
Thanks,
Richard
>
> Thanks,
> Richard.
>
>> gcc/ChangeLog:
>>
>> * tree-vect-loop.cc (vect_analyze_loop_costing): Enable
>> vectorization for LOOP_VINFO_PEELING_FOR_NITER in very cheap
>> cost model.
>> (vect_analyze_loop): Disable epilogue vectorization in very
>> cheap cost model.
>> ---
>> gcc/tree-vect-loop.cc | 6 +++---
>> 1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
>> index 242d5e2d916..06afd8cae79 100644
>> --- a/gcc/tree-vect-loop.cc
>> +++ b/gcc/tree-vect-loop.cc
>> @@ -2356,8 +2356,7 @@ vect_analyze_loop_costing (loop_vec_info loop_vinfo,
>> a copy of the scalar code (even if we might be able to vectorize it).
>> */
>> if (loop_cost_model (loop) == VECT_COST_MODEL_VERY_CHEAP
>> && (LOOP_VINFO_PEELING_FOR_ALIGNMENT (loop_vinfo)
>> - || LOOP_VINFO_PEELING_FOR_GAPS (loop_vinfo)
>> - || LOOP_VINFO_PEELING_FOR_NITER (loop_vinfo)))
>> + || LOOP_VINFO_PEELING_FOR_GAPS (loop_vinfo)))
>> {
>> if (dump_enabled_p ())
>> dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
>> @@ -3638,7 +3637,8 @@ vect_analyze_loop (class loop *loop, vec_info_shared
>> *shared)
>> /* No code motion support for multiple epilogues
>> so for now
>> not supported when multiple exits. */
>> && !LOOP_VINFO_EARLY_BREAKS (first_loop_vinfo)
>> - && !loop->simduid);
>> + && !loop->simduid
>> + && loop_cost_model (loop) >
>> VECT_COST_MODEL_VERY_CHEAP);
>> if (!vect_epilogues)
>> return first_loop_vinfo;
>>
>> --
>> 2.31.1
>>
