[Bug tree-optimization/86609] Reassociate (int) round sequences

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86609

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2018-07-23
     Ever confirmed|0                           |1

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Well, it's general expression combining, you want

(for round (ROUNDF ROUND ROUNDL)
     iround (IROUNDF LROUND LLROUNDL)
 (simplify
  (fix_trunc (round @0))
  (iround @0)))

specifically without restricting to single-use (round @0).  Not sure
if that's a good idea in general.  Note the above needs more thought
about which {I,L,LL}ROUND* to use.

And no, reassoc wouldn't be the pass to deal with this.