[LLVMdev] Floats as Doubles in Vectors

Renato Golin
Mon, 28 Jan 2013 10:13:38 -0000

On 28 January 2013 03:16, Nadav Rotem <nrotem at apple.com> wrote:

> I think that the best approach would be to improve the cost model because
> on blue gene <8 x float> ops would be more expensive than <4 x
float>.
>

+1. Clean and simple.

The few cycles you lose by getting the cost of all options (and realizing
one is 10 and the other is 100) could be negligible close to the complexity
of having a scheme where you can invalidate/or not, your computation at any
time, plus the decision of where to put all the shades of grey into these
two categories. If the cost model is accurate, the compiler will probably
find better solutions that we could possibly dream of. ;)

Plus, as Nadav said, there could be some extreme cases where it ends up
profitable.

cheers,
--renato
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