[llvm-commits] [llvm] r42397 - /llvm/trunk/lib/Analysis/IPA/Andersens.cpp

[Chris Lattner]

On Sep 27, 2007, at 8:42 AM, Daniel Berlin wrote:

>      // Node class - This class is used to represent a node in the  
> constraint
> @@ -1735,6 +1750,7 @@
>  /// replaced by their the pointer equivalence class representative.
>  void Andersens::RewriteConstraints() {
>    std::vector<Constraint> NewConstraints;
> +  std::set<Constraint> Seen;
>
>    PEClass2Node.clear();
>    PENLEClass2Node.clear();
> @@ -1768,12 +1784,14 @@
>      // it.
>      if (C.Src == C.Dest && C.Type == Constraint::Copy)
>        continue;
> -
> +
>      C.Src = FindEquivalentNode(RHSNode, RHSLabel);
>      C.Dest = FindEquivalentNode(FindNode(LHSNode), LHSLabel);
> -    if (C.Src == C.Dest && C.Type == Constraint::Copy)
> +    if (C.Src == C.Dest && C.Type == Constraint::Copy
> +        || Seen.count(C) != 0)
>        continue;
>
> +    Seen.insert(C);
>      NewConstraints.push_back(C);
>    }
>    Constraints.swap(NewConstraints);

std::set is inefficient for several reasons, particularly because  
every insertion does a malloc.  If this is performance critical code  
you might want to try out SmallSet (assuming the set is small) or  
some sort of hash table like DenseMap.

-Chris