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_arm64.cc b/compiler/optimizing/intrinsics_arm64.cc
index 6b34daa..9f6863c 100644
--- a/compiler/optimizing/intrinsics_arm64.cc
+++ b/compiler/optimizing/intrinsics_arm64.cc
@@ -1031,10 +1031,15 @@
} else {
__ Dmb(InnerShareable, BarrierWrites);
__ Bind(&loop_head);
- __ Ldxr(tmp_value, MemOperand(tmp_ptr));
- // TODO: Do we need a read barrier here when `type == Primitive::kPrimNot`?
+ // TODO: When `type == Primitive::kPrimNot`, 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 IntrinsicLocationsBuilderARM64::VisitUnsafeCASObject).
+ DCHECK(!(type == Primitive::kPrimNot && kEmitCompilerReadBarrier));
+ __ Ldxr(tmp_value, MemOperand(tmp_ptr));
__ Cmp(tmp_value, expected);
__ B(&exit_loop, ne);
__ Stxr(tmp_32, value, MemOperand(tmp_ptr));
@@ -1057,15 +1062,17 @@
CreateIntIntIntIntIntToInt(arena_, invoke);
}
void IntrinsicLocationsBuilderARM64::VisitUnsafeCASObject(HInvoke* invoke) {
- // The UnsafeCASObject intrinsic does not always work when heap
+ // 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 (see TODO in GenCAS below).
+ //
+ // Also, the UnsafeCASObject intrinsic does not always work when heap
// poisoning is enabled (it breaks run-test 004-UnsafeTest); turn it
- // off temporarily as a quick fix.
+ // off temporarily as a quick fix (b/26204023).
//
- // TODO(rpl): Fix it and turn it back on.
- //
- // TODO(rpl): Also, we should investigate whether we need a read
- // barrier in the generated code.
- if (kPoisonHeapReferences) {
+ // TODO(rpl): Fix these two issues and re-enable this intrinsic.
+ if (kEmitCompilerReadBarrier || kPoisonHeapReferences) {
return;
}