[PATCH] D26817: [APFloat] Implement PPCDoubleDouble add and subtract.

[Tim Shen via llvm-commits]

timshen added a comment.

In https://reviews.llvm.org/D26817#600068, @hfinkel wrote:

> In https://reviews.llvm.org/D26817#600060, @timshen wrote:
>
> > In https://reviews.llvm.org/D26817#600032, @hfinkel wrote:
> >
> > > Can you please comment on how similar/different this algorithm is from the one in compiler-rt/lib/builtins/ppc/gcc_qadd.c (and other nearby files)?
> >
> >
> > I didn't look at compiler-rt/lib/builtins/ppc/gcc_qadd.c. These algorithms take time to reason about, so currently the only thing I know is that they are different :P. I chose libgcc's version, because it has a paper to refer to.
>
>
> Okay, can you explain your comment about overflow/underflow. Can't you do it the same way that the libgcc implementations do?


You are right. libgcc just let the underlying double arithmetic modify the fenv exception flags, so we should do the same thing.


https://reviews.llvm.org/D26817