swift234

Add APIs to update preserved analysis information for dominance and loop info

Use it in loop rotation.

The pattern to update analysis information is:

  // The AnalysisInfo was preserved for this function.
  if (Changed) {
    // Preserve the analyis for this function by decoupling it from the analysis
    // cache.
    auto PreservedAnalysis = Analysis.preserveAnalysis(Function);

    // Invalidate analysis for this function.
    PM.invalidateAnalysis(Function, InvalidationKind::CFG);

    // Update the preserved analysis for this function.
    Analysis.updateAnalysis(F, std::move(PreservedAnalysis));
  }

Swift SVN r19918