Re: Google Summer of Code 2018: Call for mentors and ideas

[Joseph Myers <joseph@codesourcery.com>]

On Wed, 17 Jan 2018, Martin Jambor wrote:

> 3?) Joseph Myers brought up idea to do "built-in functions for TS 18661
>     floating-point functions - which has the feature that there are a
>     lot of similar built-in functions for C99/C11 functions to serve as
>     a guide for how to implement things)" ...Joseph, would you be
>     willing to mentor it?

Yes, provided at least one other mentor is available as well as I may not 
be around all the time during the GSoC period, including one of the 
evaluation periods.

(The outline I put on the wiki page is:

  GCC supports built-in functions for math.h and complex.h functions in 
  the C99/C11 standards (both folding calls for constant arguments, and 
  expanding inline when the processor supports appropriate functionality). 
  More such functions have been added in ISO/IEC TS 18661, supporting 
  features of IEEE 754-2008. It would be useful to have built-in functions 
  for those, both folding for constant arguments, and expanding inline 
  where appropriate (e.g. for roundeven and the functions rounding result 
  to narrower type, on some processors; roundeven can be inlined on x86 
  for SSE4.1 and later, and the narrowing functions on IA64 and POWER8, 
  for example). Existing built-in functions would provide a guide for how 
  to do this.

This project has the feature that there are lots of smaller subprojects 
each of which would be a useful enhancement to GCC, so a student could 
start off with e.g. roundeven built-in functions, closely following how 
existing code handles round / floor / ceil / trunc, before going on to 
more complicated functions such as the narrowing ones or the fromfp 
functions - with scope for functions from TS 18661-3 and TS 18661-4 if 
they run out of useful functions from TS 18661-1.  If a student were 
interested I could provide more detailed lists of possible subprojects.)

-- 
Joseph S. Myers
joseph@codesourcery.com