On 11/14/22 07:35, Jakub Jelinek wrote:
On Mon, Nov 14, 2022 at 07:30:18AM -0700, Jeff Law via Gcc-patches wrote:
To Jakub's concern. I thought sqrt was treated like +-/* WRT accuracy
requirements by IEEE. ie, for any input there is a well defined answer for
a confirming IEEE implementation. In fact, getting to that .5ulp bound is
a significant amount of the cost for a NR or Goldschmidt (or hybrid)
implementation if you've got a reasonable (say 12 or 14 bit) estimator and
high performance fmacs.
That might be the case (except for the known libquadmath sqrtq case
PR105101 which fortunately is not a builtin).
But we'll need to ulps infrastructure for other functions anyway and
it would be nice to write a short testcase first that will test
sqrt{,f,l,f32,f64,f128} and can be easily adjusted to test other functions.
I'll try to cook something up tomorrow.
Agreed we'll need it elsewhere, so no objection to building it out if
it's not going to delay things for sqrt.
Jeff
