LLVM codgen improvement, count bits intrinsics

[Johan Engelen]

On Saturday, 27 April 2019 at 20:25:01 UTC, NaN wrote:
> Where do you sugest to LLVM people that codegem could be 
> improved?

On their mailinglist or in their bug tracker.

> The bit scan forward and reverse both test for zero and do 
> jumps (when you want zero defined), when they could be doing 
> conditional moves because both instructions st the zero flag if 
> the input is zero.

Two remarks:
1. Conditional move is not necessarily faster than branching
2. On recent CPUs `tzcnt` is the better instruction that has 
defined output for input 0

-Johan