[cfe-commits] [Patch] -Wduplicate-enum which fixes PR6343

[Richard Trieu]

On Thu, Jul 19, 2012 at 8:25 PM, Richard Trieu <rtrieu at google.com> wrote:

> On Wed, Jul 18, 2012 at 9:14 PM, Ted Kremenek <kremenek at apple.com> wrote:
>
>> On Jul 18, 2012, at 6:34 PM, Richard Trieu <rtrieu at google.com> wrote:
>>
>> A set could work for detecting the values, but both EnumConstantDecls are
>> needed for the diagnostic, not just the values.  Possibly a map from
>> APSInt->EnumConstantDecl* would work.  But either way, I would be dealing
>> with getting APSInts to play nice with each other.
>>
>>
>> That seems reasonable to me.  The primary performance issue I see is the
>> quadratic algorithmic complexity.  If the APSInt comparisons are an issue,
>> we can see if we can find ways to optimize that further.
>>
>
> I created two more variations on and measured some timings.  Both used a
> map, one with a custom compare function and one that extended the APSInt
> value before insertion.  The APSInt extension had the better time, so I'll
> be giving the number for that one.
>
> At 10,000 elements, there was a 6-10% slow down.  This amounts to .01-.03
> seconds difference on .13-.27 second runtime.
>
> At 100,000 elements, 8-12% slow down.  .2-.3 seconds on 1.34 to 2.66
> second run time.
>
> At 1,000,000 elements, 7-14% slow down.  Around 2 second difference for
> runs of 13.6 to 26.7 seconds.
>
> A new patch has been attached which has the APSInt bit extension before
> adding to the map.
>

Added some logic to avoid warning on:
enum { A1, A2 = A1 };

Changed the wording to remove "previous" since the element could have been
declared afterwards.
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