This patch moves the class for scheduling adjacent instructions,
MacroFusion, to the target.
In AArch64, it also expands the fusion to all instructions pairs in a
scheduling block, beyond just among the predecessors of the branch at the
end.
Differential revision: https://reviews.llvm.org/D28489
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@293737 91177308-0d34-0410-b5e6-96231b3b80d8
