[LLVMdev] inconsistent wording in the LangRef regarding "shl nsw"

[Sanjoy Das]

> I wrote those optimizations with an understanding that (1) was the one true
> way.  Would you be apposed to switching to (2)? I have examples where
> implementing (1) creates real regressions where (2) does not.

I don't have fundamental reasons to favor (1) over (2).  I assumed
finding and fixing all the places within LLVM that implement and
assume (1) will be difficult and bug-prone, and therefore sticking
with (1) is the more pragmatic option.  I do think (2) is easier to
reason in, so if you think switching LLVM to consistently use (2) is
doable then I too will prefer (2).

In any case we should let this thread linger for a while before
changing anything, in case there are others with differing opinions.

-- Sanjoy