llvm dev - Apr 2012 - [LLVMdev] SIV tests in LoopDependence Analysis, Sanjoy's patch

I wrote:
>> private:
>>  Value *source, *destination;
>>  Kind kind;
>>  SmallVector<const Level *, 4>  levels;
> I'd malloc an ordinary vector of the appropriate length,
> since we know the length at allocation time.
and Duncan Sands replied:
> if the number of levels is usually small it is usually better to use a
> SmallVector (like in the code above) and do:
>  levels.reserve(known_size);
> That way you avoid a malloc if known_size <= 4.
Surely faster, but what about the space impact, especially if the size
is 0 or 1?
Do we care?  I have several ideas to save space, but there's almost always
a time cost. I worry, being afraid we'll need to represent many, many
dependences.

Thanks,
Preston