[PATCH] Fix aliasing issue caused by MemCpyOptimizer (PR18304)

[Nick Lewycky]

David Wiberg wrote:
> Hello,
>
> The attached patch fixes an aliasing issue caused by MemCpyOptimizer
> by performing the following changes:
> - Added requirement that the callee does not capture the src pointer for
>    the transformation to apply.
> - Updated test cases by adding nocapture attributes where applicable
>
> See http://lists.cs.uiuc.edu/pipermail/llvmdev/2014-June/073819.html
> for some more information. My main concern is performance regressions
> but I haven't been able to get any benchmark results.

You updated the tests, but please include a "negative test" for 
something that gets miscompiled without your code change.

Nick