[PATCH] [AArch64]Redundant store instructions should be removed as dead code

[James Molloy]

Hi,

As David has now finished his internship at ARM, I took the liberty of committing this after updating it for review feedback.

  * Vertical space maximised as requested.
  * reachesChainWithoutSideEffects() is not required, as it is guaranteed that the two chains are both stores with no intervening chains.

Committed in r218569.

Cheers,

James

http://reviews.llvm.org/D5455