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8019968: Reference CAS induces GC store barrier even on failure

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Reviewed-by: kvn, adinn, roland
This commit is contained in:
Aleksey Shipilev 2015-08-12 09:58:39 +03:00
parent 78fd2e42c6
commit 63a173e2c4
1 changed files with 16 additions and 1 deletions
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17
hotspot/src/share/vm/opto/library_call.cpp
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@ -2730,7 +2730,22 @@ bool LibraryCallKit::inline_unsafe_load_store(BasicType type, LoadStoreKind kind
load_store = _gvn.transform(new CompareAndSwapPNode(control(), mem, adr, newval, oldval));
}
}
post_barrier(control(), load_store, base, adr, alias_idx, newval, T_OBJECT, true);
if (kind == LS_cmpxchg) {
// Emit the post barrier only when the actual store happened.
// This makes sense to check only for compareAndSet that can fail to set the value.
// CAS success path is marked more likely since we anticipate this is a performance
// critical path, while CAS failure path can use the penalty for going through unlikely
// path as backoff. Which is still better than doing a store barrier there.
IdealKit ideal(this);
ideal.if_then(load_store, BoolTest::ne, ideal.ConI(0), PROB_STATIC_FREQUENT); {
sync_kit(ideal);
post_barrier(ideal.ctrl(), load_store, base, adr, alias_idx, newval, T_OBJECT, true);
ideal.sync_kit(this);
} ideal.end_if();
final_sync(ideal);
} else {
post_barrier(control(), load_store, base, adr, alias_idx, newval, T_OBJECT, true);
}
break;
default:
fatal(err_msg_res("unexpected type %d: %s", type, type2name(type)));