[llvm] r205409 - Remove duplicated DMB instructions

[Yi Kong]

Renato Golin <renato.golin at ...> writes:
> 
> Author: rengolin
> Date: Wed Apr  2 04:03:43 2014
> New Revision: 205409
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=205409&view=rev
> Log:
> Remove duplicated DMB instructions
> 
> ARM specific optimiztion, finding places in ARM machine code where 2 dmbs
> follow one another, and eliminating one of them.
> 
> Patch by Reinoud Elhorst.

I suppose this optimization also applies to DSBs? Also consecutive ISBs 
should be able to be merged as well?

-Yi