[PATCH] D16672: SmallPtrSet: Avoid initializing Array in the small case.

[Matthias Braun via llvm-commits]

MatzeB created this revision.
MatzeB added reviewers: dblaikie, chandlerc, reames, bkramer, hfinkel.
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This patch avoids the initial memset at the cost of making iterators
slightly more complex. This should be beneficial as most SmallPtrSets
hold no or only a few elements, while iterating over them is less
common.

It's not a measurable change in compiletime but valgrind/callgrind shows saving of ~0.25% instructions in my tests.

Repository:
  rL LLVM

http://reviews.llvm.org/D16672

Files:
  include/llvm/ADT/SmallPtrSet.h

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