[Bug target/59874] Missing builtin (__builtin_clzs) when compiling with g++

[manuel.lauss at googlemail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59874

--- Comment #4 from Manuel Lauss <manuel.lauss at googlemail dot com> ---
(In reply to Uroš Bizjak from comment #3)
> (In reply to Manuel Lauss from comment #2)
> 
> > I've run into this issue with current gcc-6-branch while building for
> > example qt-5.7.  gcc-5-branch can build this source just fine:
> 
> __builtin_clzs and __builtin_ctzs are internal x86 builtins and were
> recently removed. You should use __lzcnt16 and __tzcnt_u16 intrinsics.

Done,

> 
> >     return v ? __builtin_ctzs(v) : 16U;
> >      return v ? __builtin_clzs(v) : 16U;
> 
> You don't need this, the instruction does exactly the above.

without it there are errors with missing constexprs.

Thanks, I've successfully built qt-5.7 with updated source.