[llvm-dev] [poison] is select-of-select to logic+select allowed?

[John Regehr via llvm-dev]

OK then: let's add a -conservative-select option, initially off by default.

We still have to pick a semantics. Nuno's table is by far the best way 
to visualize the tradeoffs that I've seen.

John


On 05/23/2017 11:37 AM, Sanjoy Das via llvm-dev wrote:
> Hi,
> 
> On Tue, May 23, 2017 at 9:27 AM, John Regehr <regehr at cs.utah.edu> wrote:
>> Would it make sense to first commit to a semantics for select, document
>> this, and attempt to comment out all now-invalid optimizations?  We don't
>> want to remove them entirely since, as Nuno points out, we can bring some of
>> them back later using appropriate freezes.
> 
> This sounds like a good plan.  I'd only suggest that instead of
> commenting out the optimizations altogether we put it under an off by
> default flag, if practical.  This would make it easier to run A/B
> tests.
> 
> -- Sanjoy
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