[PATCH] D14690: Don't force std::set for SmallSet

[Duncan P. N. Exon Smith via llvm-commits]

> On 2015-Nov-15, at 17:43, Rafael Ávila de Espíndola via llvm-commits <llvm-commits at lists.llvm.org> wrote:
> 
> rafael created this revision.
> rafael added a reviewer: chandlerc.
> rafael added a subscriber: llvm-commits.
> rafael set the repository for this revision to rL LLVM.
> Herald added a reviewer: tstellarAMD.
> Herald added a subscriber: arsenm.
> 
> It is a bit surprising that MapVector uses a DenseMap but SetVector uses a std::set.
> 
> 
> Repository:
>  rL LLVM
> 
> http://reviews.llvm.org/D14690
> 
> Files:
>  include/llvm/ADT/SmallSet.h
>  lib/Analysis/AliasAnalysisEvaluator.cpp
>  lib/CodeGen/AggressiveAntiDepBreaker.h
>  lib/CodeGen/SelectionDAG/SelectionDAG.cpp
>  lib/ExecutionEngine/Orc/OrcMCJITReplacement.h
>  lib/Target/AMDGPU/R600ControlFlowFinalizer.cpp
>  lib/Target/X86/X86FrameLowering.cpp
>  lib/Transforms/IPO/MergeFunctions.cpp
>  utils/TableGen/AsmMatcherEmitter.cpp
>  utils/TableGen/FixedLenDecoderEmitter.cpp
> 
> <D14690.40241.patch>_______________________________________________
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Seems reasonable to me.

> Index: include/llvm/ADT/SmallSet.h
> ===================================================================
> --- include/llvm/ADT/SmallSet.h
> +++ include/llvm/ADT/SmallSet.h
> @@ -15,26 +15,26 @@
>  #define LLVM_ADT_SMALLSET_H
>  
>  #include "llvm/ADT/None.h"
> +#include "llvm/ADT/DenseSet.h"
>  #include "llvm/ADT/SmallPtrSet.h"
>  #include "llvm/ADT/SmallVector.h"
> -#include <set>
>  
>  namespace llvm {
>  
> -/// SmallSet - This maintains a set of unique values, optimizing for the case
> -/// when the set is small (less than N).  In this case, the set can be
> -/// maintained with no mallocs.  If the set gets large, we expand to using an
> -/// std::set to maintain reasonable lookup times.
> +/// This maintains a set of unique values, optimizing for the case when the set
> +/// is small (less than N).  In this case, the set can be maintained with no
> +/// mallocs.  If the set gets large, we expand to using another implementation
> +/// to maintain reasonable lookup times.
>  ///
>  /// Note that this set does not provide a way to iterate over members in the
>  /// set.
> -template <typename T, unsigned N,  typename C = std::less<T> >
> +template <typename T, unsigned N, typename BigSet = DenseSet<T>>
>  class SmallSet {
>    /// Use a SmallVector to hold the elements here (even though it will never
>    /// reach its 'large' stage) to avoid calling the default ctors of elements
>    /// we will never use.
>    SmallVector<T, N> Vector;
> -  std::set<T, C> Set;
> +  BigSet Set;

Does `sizeof(SmallSet<T, 1>)` change with this?

>    typedef typename SmallVector<T, N>::const_iterator VIterator;
>    typedef typename SmallVector<T, N>::iterator mutable_iterator;
>  
>