Disable the UnsafeCASObject intrinsic with read barriers.
The current implementations of the UnsafeCASObject
intrinsics are missing a read barrier. Temporarily disable
them when read barriers are enabled.
Also re-enable the jsr166.LinkedTransferQueueTest tests that
were failing on the concurrent collector configuration, as
the UnsafeCASObject JNI implementation now correctly
implements the read barrier which was missing.
Bug: 25883050
Bug: 26205973
Change-Id: Iaf5d515532949662d0ac6702c9452a00aa0a23e6
diff --git a/compiler/optimizing/intrinsics_x86.cc b/compiler/optimizing/intrinsics_x86.cc
index fd454d8..0d9adbf 100644
--- a/compiler/optimizing/intrinsics_x86.cc
+++ b/compiler/optimizing/intrinsics_x86.cc
@@ -2085,6 +2085,17 @@
}
void IntrinsicLocationsBuilderX86::VisitUnsafeCASObject(HInvoke* invoke) {
+ // The UnsafeCASObject intrinsic is missing a read barrier, and
+ // therefore sometimes does not work as expected (b/25883050).
+ // Turn it off temporarily as a quick fix, until the read barrier is
+ // implemented.
+ //
+ // TODO(rpl): Implement a read barrier in GenCAS below and re-enable
+ // this intrinsic.
+ if (kEmitCompilerReadBarrier) {
+ return;
+ }
+
CreateIntIntIntIntIntToInt(arena_, Primitive::kPrimNot, invoke);
}
@@ -2136,6 +2147,13 @@
__ PoisonHeapReference(value);
}
+ // TODO: Add a read barrier for the reference stored in the object
+ // before attempting the CAS, similar to the one in the
+ // art::Unsafe_compareAndSwapObject JNI implementation.
+ //
+ // Note that this code is not (yet) used when read barriers are
+ // enabled (see IntrinsicLocationsBuilderX86::VisitUnsafeCASObject).
+ DCHECK(!kEmitCompilerReadBarrier);
__ LockCmpxchgl(Address(base, offset, TIMES_1, 0), value);
// LOCK CMPXCHG has full barrier semantics, and we don't need
@@ -2145,11 +2163,8 @@
__ setb(kZero, out.AsRegister<Register>());
__ movzxb(out.AsRegister<Register>(), out.AsRegister<ByteRegister>());
- // In the case of the `UnsafeCASObject` intrinsic, accessing an
- // object in the heap with LOCK CMPXCHG does not require a read
- // barrier, as we do not keep a reference to this heap location.
- // However, if heap poisoning is enabled, we need to unpoison the
- // values that were poisoned earlier.
+ // If heap poisoning is enabled, we need to unpoison the values
+ // that were poisoned earlier.
if (kPoisonHeapReferences) {
if (base_equals_value) {
// `value` has been moved to a temporary register, no need to