[llvm-dev] getScalarizationOverhead()

[Jonas Paulsson via llvm-dev]

On 2017-01-20 14:31, Hal Finkel wrote:
>
> On 01/20/2017 06:11 AM, Jonas Paulsson via llvm-dev wrote:
>> Hi,
>>
>> I wonder why getScalarizationOverhead() does not take into account 
>> the number of operands of the instruction? This should influence the 
>> number of extracts needed, so instead of
>>
>> Scalarization cost = NumEls * (insert + extract)
>>
>> it would be better to do
>>
>> Scalarization cost = NumEls * (insert + (extract * numOperands))
>
> I suspect this is an oversight (although we need to be a bit careful 
> here because if two operands are the same, which is not uncommon, we 
> don't want to double the cost).
>
>  -Hal

Do you in those cases of an identical operand want to count just a cost 
of "1" for a register move, instead of the "extraction cost"?

/Jonas