[llvm] r221318 - Analysis: Make isSafeToSpeculativelyExecute fire less for divides

[Chandler Carruth]

On Sat, Nov 8, 2014 at 11:43 PM, David Majnemer <david.majnemer at gmail.com>
wrote:

>
> I'm pretty sure the LangRef has a bug here.  It cannot literally mean
> undefined behavior or the program hits UB once an add nsw that produces
> poison is used as the operand to another add.
>

Yes this is the known bug in the poison spec. None have wanted to fix it
because it seems likely better to remove the need for poison by specifying
(and implementing if necessary) the relevant optimization opportunities in
terms of undef, which is a much simpler construct.
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