[OpenMP] Change in initial size of DSAStackTy::StackTy

[esakella]

Summary

Hello,

I have made a small change in the initial size of the StackTy SmallVector of class DSAStackTy.

I reduced the initial size of this SmallVector from 64 elements to 4 elements, in order to improve the memory consumption during the creation of the Sema, whose constructor calls the Sema::InitDataSharingAttributesStack() function, which in turn creates a DSAStackTy.

After profiling Clang (I just gave it a simple source file to compile) before and after this change, the difference in memory consumption is up to almost 400 KB.

Would that change be acceptable?

Thank you,
Sakellari Elisavet

[ABataev]

LG. Will you commit it yourself or you want me to do this?

[karies]

Committed as r259637

lib/Sema/SemaOpenMP.cpp

           CancelRegion(false), AssociatedLoops(1), InnerTeamsRegionLoc() {}
   };
 
-  typedef SmallVector<SharingMapTy, 64> StackTy;
+  typedef SmallVector<SharingMapTy, 4> StackTy;
 
   /// \brief Stack of used declaration and their data-sharing attributes.
   StackTy Stack;