[llvm-commits] [llvm-gcc-4.2] r82640 - /llvm-gcc-4.2/trunk/gcc/llvm-convert.cpp

[Dale Johannesen]

While this is certainly necessary given the current IR definition, I'm  
not too happy about it, as we will lose something because the  
optimizers must consider that sqrt might set errno.  What I'd like to  
do is redefine llvm.sqrt in the IR to mean "same behavior as sqrt  
except that it doesn't set errno", and likewise for llvm.pow, etc.  It  
looks like that was the original intent, actually, but that's not what  
it says.  Any objections?

On Sep 23, 2009, at 11:50 AMPDT, Dale Johannesen wrote:

> Author: johannes
> Date: Wed Sep 23 13:50:32 2009
> New Revision: 82640
>
> URL: http://llvm.org/viewvc/llvm-project?rev=82640&view=rev
> Log:
> The result of sqrt(negative) is implementation-defined, but follows
> IEEE754 in most current implementations. llvm.sqrt, which has  
> undefined
> behavior for such inputs, is an inappropriate substitute which can  
> change
> the result.