Add memory barriers (Issue 3338450)

Add missing barriers required for volatile access on Arm.  Also,
flipped long volatile field accesses to the slow path.  The
previous codegen was not only missing barriers, but was not
using 64-bit atomics.

Change-Id: I4aa2be2bf81971e5ae664c762ceaf2ea58ce231b
3 files changed
tree: 974ca2e66c6df38c149693fb0d700f7365d4f29a
  2. build/
  3. oat_process/
  4. oat_runtime/
  5. src/
  6. test/
  7. tools/