[llvm-dev] RFC: A change in InstCombine canonical form

[Ehsan Amiri via llvm-dev]

On Tue, Mar 22, 2016 at 6:42 PM, Philip Reames <listmail at philipreames.com>
wrote:

>
>
> On 03/22/2016 02:44 PM, Ehsan Amiri wrote:
>
> Thanks.
>
> *Phillip, *As Hal said I do not think (1) is a very large item. Please
> let me know if I am mistaken.
>
> I have no specific reason to believe it will be a large amount of work,
> but prior experience tells me changes to canonical form have a tendency of
> exposing unexpected issues.  To be clear, I am supportive of you
> implementing solution 1.
>


Thanks Phillip. Do you mean exposing bugs that were unknown before? or
something else?

If the problem is that some transformations will start to have problems
because they do not know how to deal with the new canonical form, that's
alarming. If the chances of exposing such problem is not too high, then we
can possibly go ahead with (1) and fallback to (2) if (1) starts to be
complicated. But if the risk is too high, then we may want to prefer (2) to
(1).

Any suggestions?
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20160322/ec709520/attachment.html>