[PATCH][X86] __builtin_ctz/clz sometimed defined for zero input

[Robinson, Paul]

> On Mon, Oct 27, 2014 at 11:05:43PM +0000, Robinson, Paul wrote:
> > New patch attached that defines new builtins and uses them in
> > lzcntintrin.h.
> 
> Wouldn't the point of the new builtins to *require* the 0 case to be
> defined?
> 
> Joerg

Yes, that is what they do. The second parameter to llvm.ct*z specifies
"the zero case is undef" so passing false means the zero case is defined.
--paulr