[LLVMdev] sqrt

[Chris Lattner]

On Jan 7, 2010, at 7:06 AM, Jon Harrop wrote:

>
> What is the state of sqrt in LLVM?
>
> It was an intrinsic but there are no OCaml bindings for it and, last  
> I looked,
> it generated inefficient code on Linux due to this bug:
>
>  http://www.llvm.org/PR3219
>
> Is the intrinsic deprecated? Am I losing a lot of performance by  
> calling sqrt
> from libm instead of using the intrinsic?

There is a fundamental difference between sqrt() and llvm.sqrt: the  
former is defined on negative values and sets errno (on linux).  The  
later is undefined.  Both work well for their stated purpose,  
llvm.sqrt should not be slower than sqrt even on linux.  Both  
llvm.sqrt and sqrt could be much better on linux, but noone seems  
compelled to do the work.

-Chris