Re: PATCH: optimized libm single precision routines: erfcf, erff,expf for x86_64.

[Ulrich Drepper <drepper at gmail dot com>]

On Tue, Feb 21, 2012 at 15:32, Dmitrieva Liubov
<liubov.dmitrieva@gmail.com> wrote:
> The updated attached version is significantly hand-tuned assembler code.
> We are looking forward to accepting and releasing this change.

At least the changes made to the attached version should be made.
They are small but save another cycle or two.

I don't see why the computation of j has to be that complicated.  6
bits are taken from the mantissa.  These are then interpreted as a
signed value.  Why?  I know it works but is there really a reason?

If the bits are considered are unsigned that computation for the
access of the array DP_T as well as the computation of  n*k are
simpler (only AND, no shifting and subtracting).  The algo has to be
adapted but this should be possible.  I think nobody really paid
attention to that since the DP_T table was too large (it had 65
entries!).