On Sonntag, 20. Mai 2018 15:07:59 CEST Richard Biener wrote: > On May 20, 2018 11:01:54 AM GMT+02:00, Allan Sandfeld Jensen <li...@carewolf.com> wrote: > >A little over a year back we had a regression in a point release of gcc > > > >because the builtin __builtin_clzs got removed from i386, in part > >because it > >is was wrongly named for a target specific builtin, but we were using > >it in Qt > >since it existed in multiple compilers. I got the patch removing it > >partially > >reverted and the problem solved, but in the meantime I had worked on a > >patch > >to make it a generic builtin instead. I have rebased it and added it > >below, > >should I clean it up futher, finish the other builtins add tests and > >propose > >it, or is this not something we want? > > Can't users simply do clz((unsigned short) s) - 16? GCC should be able to > handle this for instruction selection With The addition of some folding > patterns using the corresponding internal function. > Of course, but we already have the builtin for i386, and a version of the builtin for all integer types except short for all platforms. Note the patch also generally adds short versions for all the general integer builtins, not just clzs and they are not all that trivial to synthesize (without knowing the trick, which gcc does).
'Allan
