Don't move normal loads across volatile/atomic loads.
Don't move normal loads across volatile/atomic loads.

It is technically allowed to move a normal load across a volatile load,
but probably not a good idea.

It is not allowed to move a load across an atomic load with
Ordering > Monotonic, and we model those with MOVolatile as well.

I recently removed the mayStore flag from atomic load instructions, so
they don't need a pseudo-opcode. This patch makes up for the difference.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@162857 91177308-0d34-0410-b5e6-96231b3b80d8

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