[LLVMdev] speed and code size issues

Nuno Lopes nunoplopes at sapo.pt
Sun Jul 19 07:09:58 PDT 2009

Hi John,

Thanks for the answers. I'm looking forward for the paper ;)


----- Original Message -----
> Hi Nuno,
> The "right answer" for each function for a given input is determined by
> voting; any compiler whose output diagrees with the majority is considered
> to be wrong.  So far, there is always a majority that agree on the answer.
> Rather than testing, I'd like to use an equivalence checker for object
> code.  We're working on borrowing one, but don't have anything yet.
> Equivalence checkers for object code are still very much at the research
> stage, it seems.  Luckily, for this particular purpose the checker does
> not need to scale to large inputs.
> Generating the tests is really easy: DFS with bounded depth over a grammar
> for a C subset.  Then it takes a bit of effort to prune stupid programs,
> such as those that attempt to shift by <0 or >=bitwidth.
>> In summary, do you have any paper coming along? :)
> We intend to write one but I'm waiting to see what aspects of this turn
> out to be interesting or useful!  Really this is just an offshoot from our
> random testing work where DFS provides an alternative way to drive the
> program generator.
> John Regehr 

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