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Loop Predication is an optimization in C2. The general idea is to insert a predicate on the entry path to a loop,
and raise a uncommon trap if the check of the condition fails. The condition checks are promoted from inside the
loop body, and thus the checks inside the loop could be eliminated. Currently, loop predication optimization has
been applied to remove array range check and loop invariant checks (such as null checks and array checks).

  Array Range Check Elimination

    Use loop predicate to remove array range checks in a loop.

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   init, limit, offset and array a are loop invariants, and stride and scale are compile time constants.

  Loop Invariant Check Elimination

  Similar to array range check elimination, but the loop invariant check elimination is much simple. The check inside the

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Existing optimizations that perform elimination of checks inside the loops are iteration range splitting based.  The loop is peeled

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The major disadvantage of iteration range splitting based check elimination is the dramatic increase in code size due to the copies

of the loop. In addition, the checks in the pre- and post-loops are not eliminated, and thus the performance gain is limited if when the iteration

space is small.

Compared with the iteration range splitting based check elimination, loop predication has the following advantages:

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4. (for future work) Loop predication provides a unified interface that can be implemented (extended) to replace the existing iteration range

    splitting based check eliminations (loop peeling, partial peeling, range check elimination)

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