RFR (S) 8153792: EA: assert(ptn->as_LocalVar()->edge_count() > 0) failed: sanity when compiling compareAndExchange

[Aleksey Shipilev]

Hi,

Please review the bugfix for the EA assert failure when compiling new
compareAndExchange intrinsics:
  https://bugs.openjdk.java.net/browse/JDK-8153792

The bug is caused by the initial VarHandles change in the EA, and is
actually a simple overlook: Op_CompareAndExchange* were added at the
same switch case as Op_GetAndSet* (since they are similar), but the
condition within the case itself was not changed. So, EA misses an edge
from the load, and complains.

Easy fix:
  http://cr.openjdk.java.net/~shade/8153792/webrev.01/

Testing: local Linux x86/fastdebug and failing test; RBT (hs-comp-tier0)

Thanks,
-Aleksey

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