[llvm] r176214 - The FastISEL should be fast. But when we record statistics we use atomic operations to increment the counters.

[Eric Christopher]

On Wed, Feb 27, 2013 at 2:30 PM, Nadav Rotem <nrotem at apple.com> wrote:

> Hi Eric,
>
>
>> This patch disables the counters on non-debug builds. This reduces the
>> runtime of SelectionDAGISel::SelectCodeCommon by ~5%.
>>
>
>
> Most of the statistics numbers are under #ifndef NDEBUG.
>

Throughout all of llvm? If so, cool. Was just wondering if we should solve
this elsewhere rather than in each pass.


> Hey, good idea. Wonder if we should do this in general and make statistics
> gathering dependent upon NDEBUG?
>
>
>> -      unsigned NumFastIselRemaining = std::distance(Begin, End);
>> +      unsigned NumFastIselRemaining = 0;
>> +      NumFastIselRemaining = std::distance(Begin, End);
>>
>
> Eh?
>
>
>
> I wanted to silence a warning because this variable is unused in Release.
>  Do you prefer that I silence it in another way ?
>
>
 It's used just a few lines below:

      unsigned NumFastIselRemaining = 0;
      NumFastIselRemaining = std::distance(Begin, End);
      // Do FastISel on as many instructions as possible.

      for (; BI != Begin; --BI) {
        const Instruction *Inst = llvm::prior(BI);

        // If we no longer require this instruction, skip it.

        if (isFoldedOrDeadInstruction(Inst, FuncInfo)) {
          --NumFastIselRemaining;
          continue;
        }


none of which is conditional on NDEBUG afaict? I could be missing something
though.

I do see RemainingNow, NumFastIselSuccess, and NumDAGIselRetries as unused.

The normal way is to cast to void if it's actually not being used for some
reason.

-eric
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