[PATCH] Replace custom getNumPreds/etc with PredIteratorCache that does the same thing

[Quentin Colombet]

Thanks for checking.

I was wondering since the PredIteratorCache seems a bit more complicated.

Q.
> On Apr 30, 2015, at 12:38 PM, Daniel Berlin <dberlin at dberlin.org> wrote:
> 
> FWIW, while I did not speed test *this* change, In timings elsewhere,
> i've found that PredIteratorCache is often slower than the pred
> iterator for counting preds
> (because it copies the pred list), and only faster in really
> degenerate cases for walking preds.
> 
> So i'm not going to submit this.
> 
> 
> On Thu, Apr 30, 2015 at 12:01 PM, Quentin Colombet <qcolombet at apple.com> wrote:
>> Hi Daniel,
>> 
>> Don’t know either if that makes sense, but LGTM ;).
>> 
>> Cheers,
>> -Quentin
>> 
>> 
>> ================
>> Comment at: lib/Transforms/Utils/PromoteMemoryToRegister.cpp:269
>> @@ -267,3 +268,3 @@
>> 
>> -  /// Lazily compute the number of predecessors a block has.
>> -  DenseMap<const BasicBlock *, unsigned> BBNumPreds;
>> +  /// Cache of predecessor info
>> +  PredIteratorCache PredCache;
>> ----------------
>> Period at the end of the comment ;).
>> 
>> http://reviews.llvm.org/D9167
>> 
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