Fix a comment typo and add comments.

const unsigned TinyTripCountThreshold = 16;

/// When performing a runtime memory check, do not check more than this

/// numner of pointers. Notice that the check is quadratic!

/// number of pointers. Notice that the check is quadratic!

const unsigned RuntimeMemoryCheckThreshold = 2;

namespace {

    /// Widen each instruction in the old loop to a new one in the new loop.

    /// Use the Legality module to find the induction and reduction variables.

    vectorizeLoop(Legal);

    // register the new loop.

    // Register the new loop and update the analysis passes.

    updateAnalysis();

 }

  void createEmptyLoop(LoopVectorizationLegality *Legal);

  /// Copy and widen the instructions from the old loop.

  void vectorizeLoop(LoopVectorizationLegality *Legal);

  /// Insert the new loop to the loop hierarchy and pass manager.

  /// Insert the new loop to the loop hierarchy and pass manager

  /// and update the analysis passes.

  void updateAnalysis();

  /// This instruction is un-vectorizable. Implement it as a sequence

  bool isReductionInstr(Instruction *I, ReductionKind Kind);

  /// Returns True, if 'Phi' is an induction variable.

  bool isInductionVariable(PHINode *Phi);

  /// Return true if we

  /// Return true if can compute the address bounds of Ptr within the loop.

  bool hasComputableBounds(Value *Ptr);

  /// The loop that we evaluate.