[llvm-commits] X*log2(Y*0.5)->X*log2(Y)-X (under fast math)

[Shuxin Yang]

hi, Pedro:

   Just curious, *NOT* review.
  o.   What's the advantage of this transformation if the costs (say, in 
term of latency) between
fadd/fsub and fmpy is negligible?

   o. As far as I can understand, this change only catch log2(0.5 x x) 
=> log2x - 1.
Is it able to figure out a FP value is negative-power-of-2 (to make this 
transformation more general)?

Thanks
Shuxin

On 11/30/12 9:39 AM, Pedro Artigas wrote:
> Hello All,
>
> This patch implements the above algebra transform under fast math flag.
>
> Thanks
>
> Pedro Artigas
>
>
>
> _______________________________________________
> llvm-commits mailing list
> llvm-commits at cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20121130/83061c4a/attachment.html>