Merge "class_linker: Change allocation of MethodType dex_cache entries."
diff --git a/compiler/optimizing/code_generator_arm.cc b/compiler/optimizing/code_generator_arm.cc
index 9f92b20..959a0f1 100644
--- a/compiler/optimizing/code_generator_arm.cc
+++ b/compiler/optimizing/code_generator_arm.cc
@@ -601,11 +601,21 @@
DISALLOW_COPY_AND_ASSIGN(ArraySetSlowPathARM);
};
-// Slow path marking an object during a read barrier.
+// Slow path marking an object reference `ref` during a read
+// barrier. The field `obj.field` in the object `obj` holding this
+// reference does not get updated by this slow path after marking (see
+// ReadBarrierMarkAndUpdateFieldSlowPathARM below for that).
+//
+// This means that after the execution of this slow path, `ref` will
+// always be up-to-date, but `obj.field` may not; i.e., after the
+// flip, `ref` will be a to-space reference, but `obj.field` will
+// probably still be a from-space reference (unless it gets updated by
+// another thread, or if another thread installed another object
+// reference (different from `ref`) in `obj.field`).
class ReadBarrierMarkSlowPathARM : public SlowPathCodeARM {
public:
- ReadBarrierMarkSlowPathARM(HInstruction* instruction, Location obj)
- : SlowPathCodeARM(instruction), obj_(obj) {
+ ReadBarrierMarkSlowPathARM(HInstruction* instruction, Location ref)
+ : SlowPathCodeARM(instruction), ref_(ref) {
DCHECK(kEmitCompilerReadBarrier);
}
@@ -613,9 +623,9 @@
void EmitNativeCode(CodeGenerator* codegen) OVERRIDE {
LocationSummary* locations = instruction_->GetLocations();
- Register reg = obj_.AsRegister<Register>();
+ Register ref_reg = ref_.AsRegister<Register>();
DCHECK(locations->CanCall());
- DCHECK(!locations->GetLiveRegisters()->ContainsCoreRegister(reg));
+ DCHECK(!locations->GetLiveRegisters()->ContainsCoreRegister(ref_reg)) << ref_reg;
DCHECK(instruction_->IsInstanceFieldGet() ||
instruction_->IsStaticFieldGet() ||
instruction_->IsArrayGet() ||
@@ -634,40 +644,208 @@
// entrypoint. Also, there is no need to update the stack mask,
// as this runtime call will not trigger a garbage collection.
CodeGeneratorARM* arm_codegen = down_cast<CodeGeneratorARM*>(codegen);
- DCHECK_NE(reg, SP);
- DCHECK_NE(reg, LR);
- DCHECK_NE(reg, PC);
+ DCHECK_NE(ref_reg, SP);
+ DCHECK_NE(ref_reg, LR);
+ DCHECK_NE(ref_reg, PC);
// IP is used internally by the ReadBarrierMarkRegX entry point
// as a temporary, it cannot be the entry point's input/output.
- DCHECK_NE(reg, IP);
- DCHECK(0 <= reg && reg < kNumberOfCoreRegisters) << reg;
+ DCHECK_NE(ref_reg, IP);
+ DCHECK(0 <= ref_reg && ref_reg < kNumberOfCoreRegisters) << ref_reg;
// "Compact" slow path, saving two moves.
//
// Instead of using the standard runtime calling convention (input
// and output in R0):
//
- // R0 <- obj
+ // R0 <- ref
// R0 <- ReadBarrierMark(R0)
- // obj <- R0
+ // ref <- R0
//
- // we just use rX (the register holding `obj`) as input and output
+ // we just use rX (the register containing `ref`) as input and output
// of a dedicated entrypoint:
//
// rX <- ReadBarrierMarkRegX(rX)
//
int32_t entry_point_offset =
- CodeGenerator::GetReadBarrierMarkEntryPointsOffset<kArmPointerSize>(reg);
+ CodeGenerator::GetReadBarrierMarkEntryPointsOffset<kArmPointerSize>(ref_reg);
// This runtime call does not require a stack map.
arm_codegen->InvokeRuntimeWithoutRecordingPcInfo(entry_point_offset, instruction_, this);
__ b(GetExitLabel());
}
private:
- const Location obj_;
+ // The location (register) of the marked object reference.
+ const Location ref_;
DISALLOW_COPY_AND_ASSIGN(ReadBarrierMarkSlowPathARM);
};
+// Slow path marking an object reference `ref` during a read barrier,
+// and if needed, atomically updating the field `obj.field` in the
+// object `obj` holding this reference after marking (contrary to
+// ReadBarrierMarkSlowPathARM above, which never tries to update
+// `obj.field`).
+//
+// This means that after the execution of this slow path, both `ref`
+// and `obj.field` will be up-to-date; i.e., after the flip, both will
+// hold the same to-space reference (unless another thread installed
+// another object reference (different from `ref`) in `obj.field`).
+class ReadBarrierMarkAndUpdateFieldSlowPathARM : public SlowPathCodeARM {
+ public:
+ ReadBarrierMarkAndUpdateFieldSlowPathARM(HInstruction* instruction,
+ Location ref,
+ Register obj,
+ Location field_offset,
+ Register temp1,
+ Register temp2)
+ : SlowPathCodeARM(instruction),
+ ref_(ref),
+ obj_(obj),
+ field_offset_(field_offset),
+ temp1_(temp1),
+ temp2_(temp2) {
+ DCHECK(kEmitCompilerReadBarrier);
+ }
+
+ const char* GetDescription() const OVERRIDE { return "ReadBarrierMarkAndUpdateFieldSlowPathARM"; }
+
+ void EmitNativeCode(CodeGenerator* codegen) OVERRIDE {
+ LocationSummary* locations = instruction_->GetLocations();
+ Register ref_reg = ref_.AsRegister<Register>();
+ DCHECK(locations->CanCall());
+ DCHECK(!locations->GetLiveRegisters()->ContainsCoreRegister(ref_reg)) << ref_reg;
+ // This slow path is only used by the UnsafeCASObject intrinsic.
+ DCHECK((instruction_->IsInvokeVirtual() && instruction_->GetLocations()->Intrinsified()))
+ << "Unexpected instruction in read barrier marking and field updating slow path: "
+ << instruction_->DebugName();
+ DCHECK(instruction_->GetLocations()->Intrinsified());
+ DCHECK_EQ(instruction_->AsInvoke()->GetIntrinsic(), Intrinsics::kUnsafeCASObject);
+ DCHECK(field_offset_.IsRegisterPair()) << field_offset_;
+
+ __ Bind(GetEntryLabel());
+
+ // Save the old reference.
+ // Note that we cannot use IP to save the old reference, as IP is
+ // used internally by the ReadBarrierMarkRegX entry point, and we
+ // need the old reference after the call to that entry point.
+ DCHECK_NE(temp1_, IP);
+ __ Mov(temp1_, ref_reg);
+
+ // No need to save live registers; it's taken care of by the
+ // entrypoint. Also, there is no need to update the stack mask,
+ // as this runtime call will not trigger a garbage collection.
+ CodeGeneratorARM* arm_codegen = down_cast<CodeGeneratorARM*>(codegen);
+ DCHECK_NE(ref_reg, SP);
+ DCHECK_NE(ref_reg, LR);
+ DCHECK_NE(ref_reg, PC);
+ // IP is used internally by the ReadBarrierMarkRegX entry point
+ // as a temporary, it cannot be the entry point's input/output.
+ DCHECK_NE(ref_reg, IP);
+ DCHECK(0 <= ref_reg && ref_reg < kNumberOfCoreRegisters) << ref_reg;
+ // "Compact" slow path, saving two moves.
+ //
+ // Instead of using the standard runtime calling convention (input
+ // and output in R0):
+ //
+ // R0 <- ref
+ // R0 <- ReadBarrierMark(R0)
+ // ref <- R0
+ //
+ // we just use rX (the register containing `ref`) as input and output
+ // of a dedicated entrypoint:
+ //
+ // rX <- ReadBarrierMarkRegX(rX)
+ //
+ int32_t entry_point_offset =
+ CodeGenerator::GetReadBarrierMarkEntryPointsOffset<kArmPointerSize>(ref_reg);
+ // This runtime call does not require a stack map.
+ arm_codegen->InvokeRuntimeWithoutRecordingPcInfo(entry_point_offset, instruction_, this);
+
+ // If the new reference is different from the old reference,
+ // update the field in the holder (`*(obj_ + field_offset_)`).
+ //
+ // Note that this field could also hold a different object, if
+ // another thread had concurrently changed it. In that case, the
+ // LDREX/SUBS/ITNE sequence of instructions in the compare-and-set
+ // (CAS) operation below would abort the CAS, leaving the field
+ // as-is.
+ Label done;
+ __ cmp(temp1_, ShifterOperand(ref_reg));
+ __ b(&done, EQ);
+
+ // Update the the holder's field atomically. This may fail if
+ // mutator updates before us, but it's OK. This is achieved
+ // using a strong compare-and-set (CAS) operation with relaxed
+ // memory synchronization ordering, where the expected value is
+ // the old reference and the desired value is the new reference.
+
+ // Convenience aliases.
+ Register base = obj_;
+ // The UnsafeCASObject intrinsic uses a register pair as field
+ // offset ("long offset"), of which only the low part contains
+ // data.
+ Register offset = field_offset_.AsRegisterPairLow<Register>();
+ Register expected = temp1_;
+ Register value = ref_reg;
+ Register tmp_ptr = IP; // Pointer to actual memory.
+ Register tmp = temp2_; // Value in memory.
+
+ __ add(tmp_ptr, base, ShifterOperand(offset));
+
+ if (kPoisonHeapReferences) {
+ __ PoisonHeapReference(expected);
+ if (value == expected) {
+ // Do not poison `value`, as it is the same register as
+ // `expected`, which has just been poisoned.
+ } else {
+ __ PoisonHeapReference(value);
+ }
+ }
+
+ // do {
+ // tmp = [r_ptr] - expected;
+ // } while (tmp == 0 && failure([r_ptr] <- r_new_value));
+
+ Label loop_head;
+ __ Bind(&loop_head);
+
+ __ ldrex(tmp, tmp_ptr);
+
+ __ subs(tmp, tmp, ShifterOperand(expected));
+
+ __ it(EQ, ItState::kItT);
+ __ strex(tmp, value, tmp_ptr, EQ);
+ __ cmp(tmp, ShifterOperand(1), EQ);
+
+ __ b(&loop_head, EQ);
+
+ if (kPoisonHeapReferences) {
+ __ UnpoisonHeapReference(expected);
+ if (value == expected) {
+ // Do not unpoison `value`, as it is the same register as
+ // `expected`, which has just been unpoisoned.
+ } else {
+ __ UnpoisonHeapReference(value);
+ }
+ }
+
+ __ Bind(&done);
+ __ b(GetExitLabel());
+ }
+
+ private:
+ // The location (register) of the marked object reference.
+ const Location ref_;
+ // The register containing the object holding the marked object reference field.
+ const Register obj_;
+ // The location of the offset of the marked reference field within `obj_`.
+ Location field_offset_;
+
+ const Register temp1_;
+ const Register temp2_;
+
+ DISALLOW_COPY_AND_ASSIGN(ReadBarrierMarkAndUpdateFieldSlowPathARM);
+};
+
// Slow path generating a read barrier for a heap reference.
class ReadBarrierForHeapReferenceSlowPathARM : public SlowPathCodeARM {
public:
@@ -6644,7 +6822,9 @@
Location index,
ScaleFactor scale_factor,
Location temp,
- bool needs_null_check) {
+ bool needs_null_check,
+ bool always_update_field,
+ Register* temp2) {
DCHECK(kEmitCompilerReadBarrier);
DCHECK(kUseBakerReadBarrier);
@@ -6689,8 +6869,9 @@
// The actual reference load.
if (index.IsValid()) {
- // Load types involving an "index": ArrayGet and
- // UnsafeGetObject/UnsafeGetObjectVolatile intrinsics.
+ // Load types involving an "index": ArrayGet,
+ // UnsafeGetObject/UnsafeGetObjectVolatile and UnsafeCASObject
+ // intrinsics.
// /* HeapReference<Object> */ ref = *(obj + offset + (index << scale_factor))
if (index.IsConstant()) {
size_t computed_offset =
@@ -6698,9 +6879,9 @@
__ LoadFromOffset(kLoadWord, ref_reg, obj, computed_offset);
} else {
// Handle the special case of the
- // UnsafeGetObject/UnsafeGetObjectVolatile intrinsics, which use
- // a register pair as index ("long offset"), of which only the low
- // part contains data.
+ // UnsafeGetObject/UnsafeGetObjectVolatile and UnsafeCASObject
+ // intrinsics, which use a register pair as index ("long
+ // offset"), of which only the low part contains data.
Register index_reg = index.IsRegisterPair()
? index.AsRegisterPairLow<Register>()
: index.AsRegister<Register>();
@@ -6716,8 +6897,21 @@
__ MaybeUnpoisonHeapReference(ref_reg);
// Slow path marking the object `ref` when it is gray.
- SlowPathCodeARM* slow_path =
- new (GetGraph()->GetArena()) ReadBarrierMarkSlowPathARM(instruction, ref);
+ SlowPathCodeARM* slow_path;
+ if (always_update_field) {
+ DCHECK(temp2 != nullptr);
+ // ReadBarrierMarkAndUpdateFieldSlowPathARM only supports address
+ // of the form `obj + field_offset`, where `obj` is a register and
+ // `field_offset` is a register pair (of which only the lower half
+ // is used). Thus `offset` and `scale_factor` above are expected
+ // to be null in this code path.
+ DCHECK_EQ(offset, 0u);
+ DCHECK_EQ(scale_factor, ScaleFactor::TIMES_1);
+ slow_path = new (GetGraph()->GetArena()) ReadBarrierMarkAndUpdateFieldSlowPathARM(
+ instruction, ref, obj, /* field_offset */ index, temp_reg, *temp2);
+ } else {
+ slow_path = new (GetGraph()->GetArena()) ReadBarrierMarkSlowPathARM(instruction, ref);
+ }
AddSlowPath(slow_path);
// if (rb_state == ReadBarrier::gray_ptr_)
diff --git a/compiler/optimizing/code_generator_arm.h b/compiler/optimizing/code_generator_arm.h
index 4d59b47..c676d75 100644
--- a/compiler/optimizing/code_generator_arm.h
+++ b/compiler/optimizing/code_generator_arm.h
@@ -508,6 +508,18 @@
bool needs_null_check);
// Factored implementation used by GenerateFieldLoadWithBakerReadBarrier
// and GenerateArrayLoadWithBakerReadBarrier.
+
+ // Factored implementation, used by GenerateFieldLoadWithBakerReadBarrier,
+ // GenerateArrayLoadWithBakerReadBarrier and some intrinsics.
+ //
+ // Load the object reference located at the address
+ // `obj + offset + (index << scale_factor)`, held by object `obj`, into
+ // `ref`, and mark it if needed.
+ //
+ // If `always_update_field` is true, the value of the reference is
+ // atomically updated in the holder (`obj`). This operation
+ // requires an extra temporary register, which must be provided as a
+ // non-null pointer (`temp2`).
void GenerateReferenceLoadWithBakerReadBarrier(HInstruction* instruction,
Location ref,
Register obj,
@@ -515,7 +527,9 @@
Location index,
ScaleFactor scale_factor,
Location temp,
- bool needs_null_check);
+ bool needs_null_check,
+ bool always_update_field = false,
+ Register* temp2 = nullptr);
// Generate a read barrier for a heap reference within `instruction`
// using a slow path.
diff --git a/compiler/optimizing/code_generator_arm64.cc b/compiler/optimizing/code_generator_arm64.cc
index 9e59d8c..60d7faf 100644
--- a/compiler/optimizing/code_generator_arm64.cc
+++ b/compiler/optimizing/code_generator_arm64.cc
@@ -589,11 +589,21 @@
}
}
-// Slow path marking an object during a read barrier.
+// Slow path marking an object reference `ref` during a read
+// barrier. The field `obj.field` in the object `obj` holding this
+// reference does not get updated by this slow path after marking (see
+// ReadBarrierMarkAndUpdateFieldSlowPathARM64 below for that).
+//
+// This means that after the execution of this slow path, `ref` will
+// always be up-to-date, but `obj.field` may not; i.e., after the
+// flip, `ref` will be a to-space reference, but `obj.field` will
+// probably still be a from-space reference (unless it gets updated by
+// another thread, or if another thread installed another object
+// reference (different from `ref`) in `obj.field`).
class ReadBarrierMarkSlowPathARM64 : public SlowPathCodeARM64 {
public:
- ReadBarrierMarkSlowPathARM64(HInstruction* instruction, Location obj)
- : SlowPathCodeARM64(instruction), obj_(obj) {
+ ReadBarrierMarkSlowPathARM64(HInstruction* instruction, Location ref)
+ : SlowPathCodeARM64(instruction), ref_(ref) {
DCHECK(kEmitCompilerReadBarrier);
}
@@ -602,7 +612,8 @@
void EmitNativeCode(CodeGenerator* codegen) OVERRIDE {
LocationSummary* locations = instruction_->GetLocations();
DCHECK(locations->CanCall());
- DCHECK(!locations->GetLiveRegisters()->ContainsCoreRegister(obj_.reg()));
+ DCHECK(ref_.IsRegister()) << ref_;
+ DCHECK(!locations->GetLiveRegisters()->ContainsCoreRegister(ref_.reg())) << ref_.reg();
DCHECK(instruction_->IsInstanceFieldGet() ||
instruction_->IsStaticFieldGet() ||
instruction_->IsArrayGet() ||
@@ -621,40 +632,204 @@
// entrypoint. Also, there is no need to update the stack mask,
// as this runtime call will not trigger a garbage collection.
CodeGeneratorARM64* arm64_codegen = down_cast<CodeGeneratorARM64*>(codegen);
- DCHECK_NE(obj_.reg(), LR);
- DCHECK_NE(obj_.reg(), WSP);
- DCHECK_NE(obj_.reg(), WZR);
+ DCHECK_NE(ref_.reg(), LR);
+ DCHECK_NE(ref_.reg(), WSP);
+ DCHECK_NE(ref_.reg(), WZR);
// IP0 is used internally by the ReadBarrierMarkRegX entry point
// as a temporary, it cannot be the entry point's input/output.
- DCHECK_NE(obj_.reg(), IP0);
- DCHECK(0 <= obj_.reg() && obj_.reg() < kNumberOfWRegisters) << obj_.reg();
+ DCHECK_NE(ref_.reg(), IP0);
+ DCHECK(0 <= ref_.reg() && ref_.reg() < kNumberOfWRegisters) << ref_.reg();
// "Compact" slow path, saving two moves.
//
// Instead of using the standard runtime calling convention (input
// and output in W0):
//
- // W0 <- obj
+ // W0 <- ref
// W0 <- ReadBarrierMark(W0)
- // obj <- W0
+ // ref <- W0
//
- // we just use rX (the register holding `obj`) as input and output
+ // we just use rX (the register containing `ref`) as input and output
// of a dedicated entrypoint:
//
// rX <- ReadBarrierMarkRegX(rX)
//
int32_t entry_point_offset =
- CodeGenerator::GetReadBarrierMarkEntryPointsOffset<kArm64PointerSize>(obj_.reg());
+ CodeGenerator::GetReadBarrierMarkEntryPointsOffset<kArm64PointerSize>(ref_.reg());
// This runtime call does not require a stack map.
arm64_codegen->InvokeRuntimeWithoutRecordingPcInfo(entry_point_offset, instruction_, this);
__ B(GetExitLabel());
}
private:
- const Location obj_;
+ // The location (register) of the marked object reference.
+ const Location ref_;
DISALLOW_COPY_AND_ASSIGN(ReadBarrierMarkSlowPathARM64);
};
+// Slow path marking an object reference `ref` during a read barrier,
+// and if needed, atomically updating the field `obj.field` in the
+// object `obj` holding this reference after marking (contrary to
+// ReadBarrierMarkSlowPathARM64 above, which never tries to update
+// `obj.field`).
+//
+// This means that after the execution of this slow path, both `ref`
+// and `obj.field` will be up-to-date; i.e., after the flip, both will
+// hold the same to-space reference (unless another thread installed
+// another object reference (different from `ref`) in `obj.field`).
+class ReadBarrierMarkAndUpdateFieldSlowPathARM64 : public SlowPathCodeARM64 {
+ public:
+ ReadBarrierMarkAndUpdateFieldSlowPathARM64(HInstruction* instruction,
+ Location ref,
+ Register obj,
+ Location field_offset,
+ Register temp)
+ : SlowPathCodeARM64(instruction),
+ ref_(ref),
+ obj_(obj),
+ field_offset_(field_offset),
+ temp_(temp) {
+ DCHECK(kEmitCompilerReadBarrier);
+ }
+
+ const char* GetDescription() const OVERRIDE {
+ return "ReadBarrierMarkAndUpdateFieldSlowPathARM64";
+ }
+
+ void EmitNativeCode(CodeGenerator* codegen) OVERRIDE {
+ LocationSummary* locations = instruction_->GetLocations();
+ Register ref_reg = WRegisterFrom(ref_);
+ DCHECK(locations->CanCall());
+ DCHECK(ref_.IsRegister()) << ref_;
+ DCHECK(!locations->GetLiveRegisters()->ContainsCoreRegister(ref_.reg())) << ref_.reg();
+ // This slow path is only used by the UnsafeCASObject intrinsic.
+ DCHECK((instruction_->IsInvokeVirtual() && instruction_->GetLocations()->Intrinsified()))
+ << "Unexpected instruction in read barrier marking and field updating slow path: "
+ << instruction_->DebugName();
+ DCHECK(instruction_->GetLocations()->Intrinsified());
+ DCHECK_EQ(instruction_->AsInvoke()->GetIntrinsic(), Intrinsics::kUnsafeCASObject);
+ DCHECK(field_offset_.IsRegister()) << field_offset_;
+
+ __ Bind(GetEntryLabel());
+
+ // Save the old reference.
+ // Note that we cannot use IP to save the old reference, as IP is
+ // used internally by the ReadBarrierMarkRegX entry point, and we
+ // need the old reference after the call to that entry point.
+ DCHECK_NE(LocationFrom(temp_).reg(), IP0);
+ __ Mov(temp_.W(), ref_reg);
+
+ // No need to save live registers; it's taken care of by the
+ // entrypoint. Also, there is no need to update the stack mask,
+ // as this runtime call will not trigger a garbage collection.
+ CodeGeneratorARM64* arm64_codegen = down_cast<CodeGeneratorARM64*>(codegen);
+ DCHECK_NE(ref_.reg(), LR);
+ DCHECK_NE(ref_.reg(), WSP);
+ DCHECK_NE(ref_.reg(), WZR);
+ // IP0 is used internally by the ReadBarrierMarkRegX entry point
+ // as a temporary, it cannot be the entry point's input/output.
+ DCHECK_NE(ref_.reg(), IP0);
+ DCHECK(0 <= ref_.reg() && ref_.reg() < kNumberOfWRegisters) << ref_.reg();
+ // "Compact" slow path, saving two moves.
+ //
+ // Instead of using the standard runtime calling convention (input
+ // and output in W0):
+ //
+ // W0 <- ref
+ // W0 <- ReadBarrierMark(W0)
+ // ref <- W0
+ //
+ // we just use rX (the register containing `ref`) as input and output
+ // of a dedicated entrypoint:
+ //
+ // rX <- ReadBarrierMarkRegX(rX)
+ //
+ int32_t entry_point_offset =
+ CodeGenerator::GetReadBarrierMarkEntryPointsOffset<kArm64PointerSize>(ref_.reg());
+ // This runtime call does not require a stack map.
+ arm64_codegen->InvokeRuntimeWithoutRecordingPcInfo(entry_point_offset, instruction_, this);
+
+ // If the new reference is different from the old reference,
+ // update the field in the holder (`*(obj_ + field_offset_)`).
+ //
+ // Note that this field could also hold a different object, if
+ // another thread had concurrently changed it. In that case, the
+ // LDXR/CMP/BNE sequence of instructions in the compare-and-set
+ // (CAS) operation below would abort the CAS, leaving the field
+ // as-is.
+ vixl::aarch64::Label done;
+ __ Cmp(temp_.W(), ref_reg);
+ __ B(eq, &done);
+
+ // Update the the holder's field atomically. This may fail if
+ // mutator updates before us, but it's OK. This is achieved
+ // using a strong compare-and-set (CAS) operation with relaxed
+ // memory synchronization ordering, where the expected value is
+ // the old reference and the desired value is the new reference.
+
+ MacroAssembler* masm = arm64_codegen->GetVIXLAssembler();
+ UseScratchRegisterScope temps(masm);
+
+ // Convenience aliases.
+ Register base = obj_.W();
+ Register offset = XRegisterFrom(field_offset_);
+ Register expected = temp_.W();
+ Register value = ref_reg;
+ Register tmp_ptr = temps.AcquireX(); // Pointer to actual memory.
+ Register tmp_value = temps.AcquireW(); // Value in memory.
+
+ __ Add(tmp_ptr, base.X(), Operand(offset));
+
+ if (kPoisonHeapReferences) {
+ arm64_codegen->GetAssembler()->PoisonHeapReference(expected);
+ if (value.Is(expected)) {
+ // Do not poison `value`, as it is the same register as
+ // `expected`, which has just been poisoned.
+ } else {
+ arm64_codegen->GetAssembler()->PoisonHeapReference(value);
+ }
+ }
+
+ // do {
+ // tmp_value = [tmp_ptr] - expected;
+ // } while (tmp_value == 0 && failure([tmp_ptr] <- r_new_value));
+
+ vixl::aarch64::Label loop_head, exit_loop;
+ __ Bind(&loop_head);
+ __ Ldxr(tmp_value, MemOperand(tmp_ptr));
+ __ Cmp(tmp_value, expected);
+ __ B(&exit_loop, ne);
+ __ Stxr(tmp_value, value, MemOperand(tmp_ptr));
+ __ Cbnz(tmp_value, &loop_head);
+ __ Bind(&exit_loop);
+
+ if (kPoisonHeapReferences) {
+ arm64_codegen->GetAssembler()->UnpoisonHeapReference(expected);
+ if (value.Is(expected)) {
+ // Do not unpoison `value`, as it is the same register as
+ // `expected`, which has just been unpoisoned.
+ } else {
+ arm64_codegen->GetAssembler()->UnpoisonHeapReference(value);
+ }
+ }
+
+ __ Bind(&done);
+ __ B(GetExitLabel());
+ }
+
+ private:
+ // The location (register) of the marked object reference.
+ const Location ref_;
+ // The register containing the object holding the marked object reference field.
+ const Register obj_;
+ // The location of the offset of the marked reference field within `obj_`.
+ Location field_offset_;
+
+ const Register temp_;
+
+ DISALLOW_COPY_AND_ASSIGN(ReadBarrierMarkAndUpdateFieldSlowPathARM64);
+};
+
// Slow path generating a read barrier for a heap reference.
class ReadBarrierForHeapReferenceSlowPathARM64 : public SlowPathCodeARM64 {
public:
@@ -768,7 +943,7 @@
DCHECK((instruction_->AsInvoke()->GetIntrinsic() == Intrinsics::kUnsafeGetObject) ||
(instruction_->AsInvoke()->GetIntrinsic() == Intrinsics::kUnsafeGetObjectVolatile))
<< instruction_->AsInvoke()->GetIntrinsic();
- DCHECK_EQ(offset_, 0U);
+ DCHECK_EQ(offset_, 0u);
DCHECK(index_.IsRegister());
}
}
@@ -5174,7 +5349,7 @@
// /* HeapReference<Object> */ ref = *(obj + offset)
Location no_index = Location::NoLocation();
- size_t no_scale_factor = 0U;
+ size_t no_scale_factor = 0u;
GenerateReferenceLoadWithBakerReadBarrier(instruction,
ref,
obj,
@@ -5225,7 +5400,8 @@
size_t scale_factor,
Register temp,
bool needs_null_check,
- bool use_load_acquire) {
+ bool use_load_acquire,
+ bool always_update_field) {
DCHECK(kEmitCompilerReadBarrier);
DCHECK(kUseBakerReadBarrier);
// If we are emitting an array load, we should not be using a
@@ -5278,7 +5454,9 @@
// The actual reference load.
if (index.IsValid()) {
- // Load types involving an "index".
+ // Load types involving an "index": ArrayGet,
+ // UnsafeGetObject/UnsafeGetObjectVolatile and UnsafeCASObject
+ // intrinsics.
if (use_load_acquire) {
// UnsafeGetObjectVolatile intrinsic case.
// Register `index` is not an index in an object array, but an
@@ -5287,9 +5465,9 @@
DCHECK(instruction->GetLocations()->Intrinsified());
DCHECK(instruction->AsInvoke()->GetIntrinsic() == Intrinsics::kUnsafeGetObjectVolatile)
<< instruction->AsInvoke()->GetIntrinsic();
- DCHECK_EQ(offset, 0U);
- DCHECK_EQ(scale_factor, 0U);
- DCHECK_EQ(needs_null_check, 0U);
+ DCHECK_EQ(offset, 0u);
+ DCHECK_EQ(scale_factor, 0u);
+ DCHECK_EQ(needs_null_check, 0u);
// /* HeapReference<Object> */ ref = *(obj + index)
MemOperand field = HeapOperand(obj, XRegisterFrom(index));
LoadAcquire(instruction, ref_reg, field, /* needs_null_check */ false);
@@ -5300,10 +5478,10 @@
uint32_t computed_offset = offset + (Int64ConstantFrom(index) << scale_factor);
Load(type, ref_reg, HeapOperand(obj, computed_offset));
} else {
- Register temp2 = temps.AcquireW();
- __ Add(temp2, obj, offset);
- Load(type, ref_reg, HeapOperand(temp2, XRegisterFrom(index), LSL, scale_factor));
- temps.Release(temp2);
+ Register temp3 = temps.AcquireW();
+ __ Add(temp3, obj, offset);
+ Load(type, ref_reg, HeapOperand(temp3, XRegisterFrom(index), LSL, scale_factor));
+ temps.Release(temp3);
}
}
} else {
@@ -5320,8 +5498,19 @@
GetAssembler()->MaybeUnpoisonHeapReference(ref_reg);
// Slow path marking the object `ref` when it is gray.
- SlowPathCodeARM64* slow_path =
- new (GetGraph()->GetArena()) ReadBarrierMarkSlowPathARM64(instruction, ref);
+ SlowPathCodeARM64* slow_path;
+ if (always_update_field) {
+ // ReadBarrierMarkAndUpdateFieldSlowPathARM64 only supports
+ // address of the form `obj + field_offset`, where `obj` is a
+ // register and `field_offset` is a register. Thus `offset` and
+ // `scale_factor` above are expected to be null in this code path.
+ DCHECK_EQ(offset, 0u);
+ DCHECK_EQ(scale_factor, 0u); /* "times 1" */
+ slow_path = new (GetGraph()->GetArena()) ReadBarrierMarkAndUpdateFieldSlowPathARM64(
+ instruction, ref, obj, /* field_offset */ index, temp);
+ } else {
+ slow_path = new (GetGraph()->GetArena()) ReadBarrierMarkSlowPathARM64(instruction, ref);
+ }
AddSlowPath(slow_path);
// if (rb_state == ReadBarrier::gray_ptr_)
diff --git a/compiler/optimizing/code_generator_arm64.h b/compiler/optimizing/code_generator_arm64.h
index eb28ecb..3de4627 100644
--- a/compiler/optimizing/code_generator_arm64.h
+++ b/compiler/optimizing/code_generator_arm64.h
@@ -594,6 +594,13 @@
bool needs_null_check);
// Factored implementation used by GenerateFieldLoadWithBakerReadBarrier
// and GenerateArrayLoadWithBakerReadBarrier.
+ //
+ // Load the object reference located at the address
+ // `obj + offset + (index << scale_factor)`, held by object `obj`, into
+ // `ref`, and mark it if needed.
+ //
+ // If `always_update_field` is true, the value of the reference is
+ // atomically updated in the holder (`obj`).
void GenerateReferenceLoadWithBakerReadBarrier(HInstruction* instruction,
Location ref,
vixl::aarch64::Register obj,
@@ -602,7 +609,8 @@
size_t scale_factor,
vixl::aarch64::Register temp,
bool needs_null_check,
- bool use_load_acquire);
+ bool use_load_acquire,
+ bool always_update_field = false);
// Generate a read barrier for a heap reference within `instruction`
// using a slow path.
diff --git a/compiler/optimizing/code_generator_x86.cc b/compiler/optimizing/code_generator_x86.cc
index 02c1c3b..015333d 100644
--- a/compiler/optimizing/code_generator_x86.cc
+++ b/compiler/optimizing/code_generator_x86.cc
@@ -426,11 +426,25 @@
DISALLOW_COPY_AND_ASSIGN(ArraySetSlowPathX86);
};
-// Slow path marking an object during a read barrier.
+// Slow path marking an object reference `ref` during a read
+// barrier. The field `obj.field` in the object `obj` holding this
+// reference does not get updated by this slow path after marking (see
+// ReadBarrierMarkAndUpdateFieldSlowPathX86 below for that).
+//
+// This means that after the execution of this slow path, `ref` will
+// always be up-to-date, but `obj.field` may not; i.e., after the
+// flip, `ref` will be a to-space reference, but `obj.field` will
+// probably still be a from-space reference (unless it gets updated by
+// another thread, or if another thread installed another object
+// reference (different from `ref`) in `obj.field`).
class ReadBarrierMarkSlowPathX86 : public SlowPathCode {
public:
- ReadBarrierMarkSlowPathX86(HInstruction* instruction, Location obj, bool unpoison)
- : SlowPathCode(instruction), obj_(obj), unpoison_(unpoison) {
+ ReadBarrierMarkSlowPathX86(HInstruction* instruction,
+ Location ref,
+ bool unpoison_ref_before_marking)
+ : SlowPathCode(instruction),
+ ref_(ref),
+ unpoison_ref_before_marking_(unpoison_ref_before_marking) {
DCHECK(kEmitCompilerReadBarrier);
}
@@ -438,9 +452,9 @@
void EmitNativeCode(CodeGenerator* codegen) OVERRIDE {
LocationSummary* locations = instruction_->GetLocations();
- Register reg = obj_.AsRegister<Register>();
+ Register ref_reg = ref_.AsRegister<Register>();
DCHECK(locations->CanCall());
- DCHECK(!locations->GetLiveRegisters()->ContainsCoreRegister(reg));
+ DCHECK(!locations->GetLiveRegisters()->ContainsCoreRegister(ref_reg)) << ref_reg;
DCHECK(instruction_->IsInstanceFieldGet() ||
instruction_->IsStaticFieldGet() ||
instruction_->IsArrayGet() ||
@@ -455,44 +469,211 @@
<< instruction_->DebugName();
__ Bind(GetEntryLabel());
- if (unpoison_) {
+ if (unpoison_ref_before_marking_) {
// Object* ref = ref_addr->AsMirrorPtr()
- __ MaybeUnpoisonHeapReference(reg);
+ __ MaybeUnpoisonHeapReference(ref_reg);
}
// No need to save live registers; it's taken care of by the
// entrypoint. Also, there is no need to update the stack mask,
// as this runtime call will not trigger a garbage collection.
CodeGeneratorX86* x86_codegen = down_cast<CodeGeneratorX86*>(codegen);
- DCHECK_NE(reg, ESP);
- DCHECK(0 <= reg && reg < kNumberOfCpuRegisters) << reg;
+ DCHECK_NE(ref_reg, ESP);
+ DCHECK(0 <= ref_reg && ref_reg < kNumberOfCpuRegisters) << ref_reg;
// "Compact" slow path, saving two moves.
//
// Instead of using the standard runtime calling convention (input
// and output in EAX):
//
- // EAX <- obj
+ // EAX <- ref
// EAX <- ReadBarrierMark(EAX)
- // obj <- EAX
+ // ref <- EAX
//
- // we just use rX (the register holding `obj`) as input and output
+ // we just use rX (the register containing `ref`) as input and output
// of a dedicated entrypoint:
//
// rX <- ReadBarrierMarkRegX(rX)
//
int32_t entry_point_offset =
- CodeGenerator::GetReadBarrierMarkEntryPointsOffset<kX86PointerSize>(reg);
+ CodeGenerator::GetReadBarrierMarkEntryPointsOffset<kX86PointerSize>(ref_reg);
// This runtime call does not require a stack map.
x86_codegen->InvokeRuntimeWithoutRecordingPcInfo(entry_point_offset, instruction_, this);
__ jmp(GetExitLabel());
}
private:
- const Location obj_;
- const bool unpoison_;
+ // The location (register) of the marked object reference.
+ const Location ref_;
+ // Should the reference in `ref_` be unpoisoned prior to marking it?
+ const bool unpoison_ref_before_marking_;
DISALLOW_COPY_AND_ASSIGN(ReadBarrierMarkSlowPathX86);
};
+// Slow path marking an object reference `ref` during a read barrier,
+// and if needed, atomically updating the field `obj.field` in the
+// object `obj` holding this reference after marking (contrary to
+// ReadBarrierMarkSlowPathX86 above, which never tries to update
+// `obj.field`).
+//
+// This means that after the execution of this slow path, both `ref`
+// and `obj.field` will be up-to-date; i.e., after the flip, both will
+// hold the same to-space reference (unless another thread installed
+// another object reference (different from `ref`) in `obj.field`).
+class ReadBarrierMarkAndUpdateFieldSlowPathX86 : public SlowPathCode {
+ public:
+ ReadBarrierMarkAndUpdateFieldSlowPathX86(HInstruction* instruction,
+ Location ref,
+ Register obj,
+ const Address& field_addr,
+ bool unpoison_ref_before_marking,
+ Register temp)
+ : SlowPathCode(instruction),
+ ref_(ref),
+ obj_(obj),
+ field_addr_(field_addr),
+ unpoison_ref_before_marking_(unpoison_ref_before_marking),
+ temp_(temp) {
+ DCHECK(kEmitCompilerReadBarrier);
+ }
+
+ const char* GetDescription() const OVERRIDE { return "ReadBarrierMarkAndUpdateFieldSlowPathX86"; }
+
+ void EmitNativeCode(CodeGenerator* codegen) OVERRIDE {
+ LocationSummary* locations = instruction_->GetLocations();
+ Register ref_reg = ref_.AsRegister<Register>();
+ DCHECK(locations->CanCall());
+ DCHECK(!locations->GetLiveRegisters()->ContainsCoreRegister(ref_reg)) << ref_reg;
+ // This slow path is only used by the UnsafeCASObject intrinsic.
+ DCHECK((instruction_->IsInvokeVirtual() && instruction_->GetLocations()->Intrinsified()))
+ << "Unexpected instruction in read barrier marking and field updating slow path: "
+ << instruction_->DebugName();
+ DCHECK(instruction_->GetLocations()->Intrinsified());
+ DCHECK_EQ(instruction_->AsInvoke()->GetIntrinsic(), Intrinsics::kUnsafeCASObject);
+
+ __ Bind(GetEntryLabel());
+ if (unpoison_ref_before_marking_) {
+ // Object* ref = ref_addr->AsMirrorPtr()
+ __ MaybeUnpoisonHeapReference(ref_reg);
+ }
+
+ // Save the old (unpoisoned) reference.
+ __ movl(temp_, ref_reg);
+
+ // No need to save live registers; it's taken care of by the
+ // entrypoint. Also, there is no need to update the stack mask,
+ // as this runtime call will not trigger a garbage collection.
+ CodeGeneratorX86* x86_codegen = down_cast<CodeGeneratorX86*>(codegen);
+ DCHECK_NE(ref_reg, ESP);
+ DCHECK(0 <= ref_reg && ref_reg < kNumberOfCpuRegisters) << ref_reg;
+ // "Compact" slow path, saving two moves.
+ //
+ // Instead of using the standard runtime calling convention (input
+ // and output in EAX):
+ //
+ // EAX <- ref
+ // EAX <- ReadBarrierMark(EAX)
+ // ref <- EAX
+ //
+ // we just use rX (the register containing `ref`) as input and output
+ // of a dedicated entrypoint:
+ //
+ // rX <- ReadBarrierMarkRegX(rX)
+ //
+ int32_t entry_point_offset =
+ CodeGenerator::GetReadBarrierMarkEntryPointsOffset<kX86PointerSize>(ref_reg);
+ // This runtime call does not require a stack map.
+ x86_codegen->InvokeRuntimeWithoutRecordingPcInfo(entry_point_offset, instruction_, this);
+
+ // If the new reference is different from the old reference,
+ // update the field in the holder (`*field_addr`).
+ //
+ // Note that this field could also hold a different object, if
+ // another thread had concurrently changed it. In that case, the
+ // LOCK CMPXCHGL instruction in the compare-and-set (CAS)
+ // operation below would abort the CAS, leaving the field as-is.
+ NearLabel done;
+ __ cmpl(temp_, ref_reg);
+ __ j(kEqual, &done);
+
+ // Update the the holder's field atomically. This may fail if
+ // mutator updates before us, but it's OK. This is achieved
+ // using a strong compare-and-set (CAS) operation with relaxed
+ // memory synchronization ordering, where the expected value is
+ // the old reference and the desired value is the new reference.
+ // This operation is implemented with a 32-bit LOCK CMPXLCHG
+ // instruction, which requires the expected value (the old
+ // reference) to be in EAX. Save EAX beforehand, and move the
+ // expected value (stored in `temp_`) into EAX.
+ __ pushl(EAX);
+ __ movl(EAX, temp_);
+
+ // Convenience aliases.
+ Register base = obj_;
+ Register expected = EAX;
+ Register value = ref_reg;
+
+ bool base_equals_value = (base == value);
+ if (kPoisonHeapReferences) {
+ if (base_equals_value) {
+ // If `base` and `value` are the same register location, move
+ // `value` to a temporary register. This way, poisoning
+ // `value` won't invalidate `base`.
+ value = temp_;
+ __ movl(value, base);
+ }
+
+ // Check that the register allocator did not assign the location
+ // of `expected` (EAX) to `value` nor to `base`, so that heap
+ // poisoning (when enabled) works as intended below.
+ // - If `value` were equal to `expected`, both references would
+ // be poisoned twice, meaning they would not be poisoned at
+ // all, as heap poisoning uses address negation.
+ // - If `base` were equal to `expected`, poisoning `expected`
+ // would invalidate `base`.
+ DCHECK_NE(value, expected);
+ DCHECK_NE(base, expected);
+
+ __ PoisonHeapReference(expected);
+ __ PoisonHeapReference(value);
+ }
+
+ __ LockCmpxchgl(field_addr_, value);
+
+ // 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 unpoison it.
+ } else {
+ __ UnpoisonHeapReference(value);
+ }
+ // No need to unpoison `expected` (EAX), as it is be overwritten below.
+ }
+
+ // Restore EAX.
+ __ popl(EAX);
+
+ __ Bind(&done);
+ __ jmp(GetExitLabel());
+ }
+
+ private:
+ // The location (register) of the marked object reference.
+ const Location ref_;
+ // The register containing the object holding the marked object reference field.
+ const Register obj_;
+ // The address of the marked reference field. The base of this address must be `obj_`.
+ const Address field_addr_;
+
+ // Should the reference in `ref_` be unpoisoned prior to marking it?
+ const bool unpoison_ref_before_marking_;
+
+ const Register temp_;
+
+ DISALLOW_COPY_AND_ASSIGN(ReadBarrierMarkAndUpdateFieldSlowPathX86);
+};
+
// Slow path generating a read barrier for a heap reference.
class ReadBarrierForHeapReferenceSlowPathX86 : public SlowPathCode {
public:
@@ -6831,7 +7012,7 @@
// Slow path marking the GC root `root`.
SlowPathCode* slow_path = new (GetGraph()->GetArena()) ReadBarrierMarkSlowPathX86(
- instruction, root, /* unpoison */ false);
+ instruction, root, /* unpoison_ref_before_marking */ false);
codegen_->AddSlowPath(slow_path);
__ fs()->cmpl(Address::Absolute(Thread::IsGcMarkingOffset<kX86PointerSize>().Int32Value()),
@@ -6896,7 +7077,9 @@
Location ref,
Register obj,
const Address& src,
- bool needs_null_check) {
+ bool needs_null_check,
+ bool always_update_field,
+ Register* temp) {
DCHECK(kEmitCompilerReadBarrier);
DCHECK(kUseBakerReadBarrier);
@@ -6953,8 +7136,15 @@
// Note: Reference unpoisoning modifies the flags, so we need to delay it after the branch.
// Slow path marking the object `ref` when it is gray.
- SlowPathCode* slow_path = new (GetGraph()->GetArena()) ReadBarrierMarkSlowPathX86(
- instruction, ref, /* unpoison */ true);
+ SlowPathCode* slow_path;
+ if (always_update_field) {
+ DCHECK(temp != nullptr);
+ slow_path = new (GetGraph()->GetArena()) ReadBarrierMarkAndUpdateFieldSlowPathX86(
+ instruction, ref, obj, src, /* unpoison_ref_before_marking */ true, *temp);
+ } else {
+ slow_path = new (GetGraph()->GetArena()) ReadBarrierMarkSlowPathX86(
+ instruction, ref, /* unpoison_ref_before_marking */ true);
+ }
AddSlowPath(slow_path);
// We have done the "if" of the gray bit check above, now branch based on the flags.
diff --git a/compiler/optimizing/code_generator_x86.h b/compiler/optimizing/code_generator_x86.h
index e7d9a43..167017e 100644
--- a/compiler/optimizing/code_generator_x86.h
+++ b/compiler/optimizing/code_generator_x86.h
@@ -499,13 +499,24 @@
uint32_t data_offset,
Location index,
bool needs_null_check);
- // Factored implementation used by GenerateFieldLoadWithBakerReadBarrier
- // and GenerateArrayLoadWithBakerReadBarrier.
+ // Factored implementation, used by GenerateFieldLoadWithBakerReadBarrier,
+ // GenerateArrayLoadWithBakerReadBarrier and some intrinsics.
+ //
+ // Load the object reference located at address `src`, held by
+ // object `obj`, into `ref`, and mark it if needed. The base of
+ // address `src` must be `obj`.
+ //
+ // If `always_update_field` is true, the value of the reference is
+ // atomically updated in the holder (`obj`). This operation
+ // requires a temporary register, which must be provided as a
+ // non-null pointer (`temp`).
void GenerateReferenceLoadWithBakerReadBarrier(HInstruction* instruction,
Location ref,
Register obj,
const Address& src,
- bool needs_null_check);
+ bool needs_null_check,
+ bool always_update_field = false,
+ Register* temp = nullptr);
// Generate a read barrier for a heap reference within `instruction`
// using a slow path.
diff --git a/compiler/optimizing/code_generator_x86_64.cc b/compiler/optimizing/code_generator_x86_64.cc
index 4b64c1b..2232504 100644
--- a/compiler/optimizing/code_generator_x86_64.cc
+++ b/compiler/optimizing/code_generator_x86_64.cc
@@ -445,11 +445,25 @@
DISALLOW_COPY_AND_ASSIGN(ArraySetSlowPathX86_64);
};
-// Slow path marking an object during a read barrier.
+// Slow path marking an object reference `ref` during a read
+// barrier. The field `obj.field` in the object `obj` holding this
+// reference does not get updated by this slow path after marking (see
+// ReadBarrierMarkAndUpdateFieldSlowPathX86_64 below for that).
+//
+// This means that after the execution of this slow path, `ref` will
+// always be up-to-date, but `obj.field` may not; i.e., after the
+// flip, `ref` will be a to-space reference, but `obj.field` will
+// probably still be a from-space reference (unless it gets updated by
+// another thread, or if another thread installed another object
+// reference (different from `ref`) in `obj.field`).
class ReadBarrierMarkSlowPathX86_64 : public SlowPathCode {
public:
- ReadBarrierMarkSlowPathX86_64(HInstruction* instruction, Location obj, bool unpoison)
- : SlowPathCode(instruction), obj_(obj), unpoison_(unpoison) {
+ ReadBarrierMarkSlowPathX86_64(HInstruction* instruction,
+ Location ref,
+ bool unpoison_ref_before_marking)
+ : SlowPathCode(instruction),
+ ref_(ref),
+ unpoison_ref_before_marking_(unpoison_ref_before_marking) {
DCHECK(kEmitCompilerReadBarrier);
}
@@ -457,10 +471,10 @@
void EmitNativeCode(CodeGenerator* codegen) OVERRIDE {
LocationSummary* locations = instruction_->GetLocations();
- CpuRegister cpu_reg = obj_.AsRegister<CpuRegister>();
- Register reg = cpu_reg.AsRegister();
+ CpuRegister ref_cpu_reg = ref_.AsRegister<CpuRegister>();
+ Register ref_reg = ref_cpu_reg.AsRegister();
DCHECK(locations->CanCall());
- DCHECK(!locations->GetLiveRegisters()->ContainsCoreRegister(reg));
+ DCHECK(!locations->GetLiveRegisters()->ContainsCoreRegister(ref_reg)) << ref_reg;
DCHECK(instruction_->IsInstanceFieldGet() ||
instruction_->IsStaticFieldGet() ||
instruction_->IsArrayGet() ||
@@ -475,44 +489,218 @@
<< instruction_->DebugName();
__ Bind(GetEntryLabel());
- if (unpoison_) {
+ if (unpoison_ref_before_marking_) {
// Object* ref = ref_addr->AsMirrorPtr()
- __ MaybeUnpoisonHeapReference(cpu_reg);
+ __ MaybeUnpoisonHeapReference(ref_cpu_reg);
}
// No need to save live registers; it's taken care of by the
// entrypoint. Also, there is no need to update the stack mask,
// as this runtime call will not trigger a garbage collection.
CodeGeneratorX86_64* x86_64_codegen = down_cast<CodeGeneratorX86_64*>(codegen);
- DCHECK_NE(reg, RSP);
- DCHECK(0 <= reg && reg < kNumberOfCpuRegisters) << reg;
+ DCHECK_NE(ref_reg, RSP);
+ DCHECK(0 <= ref_reg && ref_reg < kNumberOfCpuRegisters) << ref_reg;
// "Compact" slow path, saving two moves.
//
// Instead of using the standard runtime calling convention (input
// and output in R0):
//
- // RDI <- obj
+ // RDI <- ref
// RAX <- ReadBarrierMark(RDI)
- // obj <- RAX
+ // ref <- RAX
//
- // we just use rX (the register holding `obj`) as input and output
+ // we just use rX (the register containing `ref`) as input and output
// of a dedicated entrypoint:
//
// rX <- ReadBarrierMarkRegX(rX)
//
int32_t entry_point_offset =
- CodeGenerator::GetReadBarrierMarkEntryPointsOffset<kX86_64PointerSize>(reg);
+ CodeGenerator::GetReadBarrierMarkEntryPointsOffset<kX86_64PointerSize>(ref_reg);
// This runtime call does not require a stack map.
x86_64_codegen->InvokeRuntimeWithoutRecordingPcInfo(entry_point_offset, instruction_, this);
__ jmp(GetExitLabel());
}
private:
- const Location obj_;
- const bool unpoison_;
+ // The location (register) of the marked object reference.
+ const Location ref_;
+ // Should the reference in `ref_` be unpoisoned prior to marking it?
+ const bool unpoison_ref_before_marking_;
DISALLOW_COPY_AND_ASSIGN(ReadBarrierMarkSlowPathX86_64);
};
+// Slow path marking an object reference `ref` during a read barrier,
+// and if needed, atomically updating the field `obj.field` in the
+// object `obj` holding this reference after marking (contrary to
+// ReadBarrierMarkSlowPathX86_64 above, which never tries to update
+// `obj.field`).
+//
+// This means that after the execution of this slow path, both `ref`
+// and `obj.field` will be up-to-date; i.e., after the flip, both will
+// hold the same to-space reference (unless another thread installed
+// another object reference (different from `ref`) in `obj.field`).
+class ReadBarrierMarkAndUpdateFieldSlowPathX86_64 : public SlowPathCode {
+ public:
+ ReadBarrierMarkAndUpdateFieldSlowPathX86_64(HInstruction* instruction,
+ Location ref,
+ CpuRegister obj,
+ const Address& field_addr,
+ bool unpoison_ref_before_marking,
+ CpuRegister temp1,
+ CpuRegister temp2)
+ : SlowPathCode(instruction),
+ ref_(ref),
+ obj_(obj),
+ field_addr_(field_addr),
+ unpoison_ref_before_marking_(unpoison_ref_before_marking),
+ temp1_(temp1),
+ temp2_(temp2) {
+ DCHECK(kEmitCompilerReadBarrier);
+ }
+
+ const char* GetDescription() const OVERRIDE {
+ return "ReadBarrierMarkAndUpdateFieldSlowPathX86_64";
+ }
+
+ void EmitNativeCode(CodeGenerator* codegen) OVERRIDE {
+ LocationSummary* locations = instruction_->GetLocations();
+ CpuRegister ref_cpu_reg = ref_.AsRegister<CpuRegister>();
+ Register ref_reg = ref_cpu_reg.AsRegister();
+ DCHECK(locations->CanCall());
+ DCHECK(!locations->GetLiveRegisters()->ContainsCoreRegister(ref_reg)) << ref_reg;
+ // This slow path is only used by the UnsafeCASObject intrinsic.
+ DCHECK((instruction_->IsInvokeVirtual() && instruction_->GetLocations()->Intrinsified()))
+ << "Unexpected instruction in read barrier marking and field updating slow path: "
+ << instruction_->DebugName();
+ DCHECK(instruction_->GetLocations()->Intrinsified());
+ DCHECK_EQ(instruction_->AsInvoke()->GetIntrinsic(), Intrinsics::kUnsafeCASObject);
+
+ __ Bind(GetEntryLabel());
+ if (unpoison_ref_before_marking_) {
+ // Object* ref = ref_addr->AsMirrorPtr()
+ __ MaybeUnpoisonHeapReference(ref_cpu_reg);
+ }
+
+ // Save the old (unpoisoned) reference.
+ __ movl(temp1_, ref_cpu_reg);
+
+ // No need to save live registers; it's taken care of by the
+ // entrypoint. Also, there is no need to update the stack mask,
+ // as this runtime call will not trigger a garbage collection.
+ CodeGeneratorX86_64* x86_64_codegen = down_cast<CodeGeneratorX86_64*>(codegen);
+ DCHECK_NE(ref_reg, RSP);
+ DCHECK(0 <= ref_reg && ref_reg < kNumberOfCpuRegisters) << ref_reg;
+ // "Compact" slow path, saving two moves.
+ //
+ // Instead of using the standard runtime calling convention (input
+ // and output in R0):
+ //
+ // RDI <- ref
+ // RAX <- ReadBarrierMark(RDI)
+ // ref <- RAX
+ //
+ // we just use rX (the register containing `ref`) as input and output
+ // of a dedicated entrypoint:
+ //
+ // rX <- ReadBarrierMarkRegX(rX)
+ //
+ int32_t entry_point_offset =
+ CodeGenerator::GetReadBarrierMarkEntryPointsOffset<kX86_64PointerSize>(ref_reg);
+ // This runtime call does not require a stack map.
+ x86_64_codegen->InvokeRuntimeWithoutRecordingPcInfo(entry_point_offset, instruction_, this);
+
+ // If the new reference is different from the old reference,
+ // update the field in the holder (`*field_addr`).
+ //
+ // Note that this field could also hold a different object, if
+ // another thread had concurrently changed it. In that case, the
+ // LOCK CMPXCHGL instruction in the compare-and-set (CAS)
+ // operation below would abort the CAS, leaving the field as-is.
+ NearLabel done;
+ __ cmpl(temp1_, ref_cpu_reg);
+ __ j(kEqual, &done);
+
+ // Update the the holder's field atomically. This may fail if
+ // mutator updates before us, but it's OK. This is achived
+ // using a strong compare-and-set (CAS) operation with relaxed
+ // memory synchronization ordering, where the expected value is
+ // the old reference and the desired value is the new reference.
+ // This operation is implemented with a 32-bit LOCK CMPXLCHG
+ // instruction, which requires the expected value (the old
+ // reference) to be in EAX. Save RAX beforehand, and move the
+ // expected value (stored in `temp1_`) into EAX.
+ __ movq(temp2_, CpuRegister(RAX));
+ __ movl(CpuRegister(RAX), temp1_);
+
+ // Convenience aliases.
+ CpuRegister base = obj_;
+ CpuRegister expected = CpuRegister(RAX);
+ CpuRegister value = ref_cpu_reg;
+
+ bool base_equals_value = (base.AsRegister() == value.AsRegister());
+ Register value_reg = ref_reg;
+ if (kPoisonHeapReferences) {
+ if (base_equals_value) {
+ // If `base` and `value` are the same register location, move
+ // `value_reg` to a temporary register. This way, poisoning
+ // `value_reg` won't invalidate `base`.
+ value_reg = temp1_.AsRegister();
+ __ movl(CpuRegister(value_reg), base);
+ }
+
+ // Check that the register allocator did not assign the location
+ // of `expected` (RAX) to `value` nor to `base`, so that heap
+ // poisoning (when enabled) works as intended below.
+ // - If `value` were equal to `expected`, both references would
+ // be poisoned twice, meaning they would not be poisoned at
+ // all, as heap poisoning uses address negation.
+ // - If `base` were equal to `expected`, poisoning `expected`
+ // would invalidate `base`.
+ DCHECK_NE(value_reg, expected.AsRegister());
+ DCHECK_NE(base.AsRegister(), expected.AsRegister());
+
+ __ PoisonHeapReference(expected);
+ __ PoisonHeapReference(CpuRegister(value_reg));
+ }
+
+ __ LockCmpxchgl(field_addr_, CpuRegister(value_reg));
+
+ // If heap poisoning is enabled, we need to unpoison the values
+ // that were poisoned earlier.
+ if (kPoisonHeapReferences) {
+ if (base_equals_value) {
+ // `value_reg` has been moved to a temporary register, no need
+ // to unpoison it.
+ } else {
+ __ UnpoisonHeapReference(CpuRegister(value_reg));
+ }
+ // No need to unpoison `expected` (RAX), as it is be overwritten below.
+ }
+
+ // Restore RAX.
+ __ movq(CpuRegister(RAX), temp2_);
+
+ __ Bind(&done);
+ __ jmp(GetExitLabel());
+ }
+
+ private:
+ // The location (register) of the marked object reference.
+ const Location ref_;
+ // The register containing the object holding the marked object reference field.
+ const CpuRegister obj_;
+ // The address of the marked reference field. The base of this address must be `obj_`.
+ const Address field_addr_;
+
+ // Should the reference in `ref_` be unpoisoned prior to marking it?
+ const bool unpoison_ref_before_marking_;
+
+ const CpuRegister temp1_;
+ const CpuRegister temp2_;
+
+ DISALLOW_COPY_AND_ASSIGN(ReadBarrierMarkAndUpdateFieldSlowPathX86_64);
+};
+
// Slow path generating a read barrier for a heap reference.
class ReadBarrierForHeapReferenceSlowPathX86_64 : public SlowPathCode {
public:
@@ -4122,7 +4310,7 @@
// /* HeapReference<Object> */ out = *(base + offset)
if (kEmitCompilerReadBarrier && kUseBakerReadBarrier) {
// Note that a potential implicit null check is handled in this
- // CodeGeneratorX86::GenerateFieldLoadWithBakerReadBarrier call.
+ // CodeGeneratorX86_64::GenerateFieldLoadWithBakerReadBarrier call.
codegen_->GenerateFieldLoadWithBakerReadBarrier(
instruction, out, base, offset, /* needs_null_check */ true);
if (is_volatile) {
@@ -4569,7 +4757,7 @@
// *(obj + data_offset + index * sizeof(HeapReference<Object>))
if (kEmitCompilerReadBarrier && kUseBakerReadBarrier) {
// Note that a potential implicit null check is handled in this
- // CodeGeneratorX86::GenerateArrayLoadWithBakerReadBarrier call.
+ // CodeGeneratorX86_64::GenerateArrayLoadWithBakerReadBarrier call.
codegen_->GenerateArrayLoadWithBakerReadBarrier(
instruction, out_loc, obj, data_offset, index, /* needs_null_check */ true);
} else {
@@ -6264,7 +6452,7 @@
// Slow path marking the GC root `root`.
SlowPathCode* slow_path = new (GetGraph()->GetArena()) ReadBarrierMarkSlowPathX86_64(
- instruction, root, /* unpoison */ false);
+ instruction, root, /* unpoison_ref_before_marking */ false);
codegen_->AddSlowPath(slow_path);
__ gs()->cmpl(Address::Absolute(Thread::IsGcMarkingOffset<kX86_64PointerSize>().Int32Value(),
@@ -6330,7 +6518,10 @@
Location ref,
CpuRegister obj,
const Address& src,
- bool needs_null_check) {
+ bool needs_null_check,
+ bool always_update_field,
+ CpuRegister* temp1,
+ CpuRegister* temp2) {
DCHECK(kEmitCompilerReadBarrier);
DCHECK(kUseBakerReadBarrier);
@@ -6387,8 +6578,16 @@
// Note: Reference unpoisoning modifies the flags, so we need to delay it after the branch.
// Slow path marking the object `ref` when it is gray.
- SlowPathCode* slow_path = new (GetGraph()->GetArena()) ReadBarrierMarkSlowPathX86_64(
- instruction, ref, /* unpoison */ true);
+ SlowPathCode* slow_path;
+ if (always_update_field) {
+ DCHECK(temp1 != nullptr);
+ DCHECK(temp2 != nullptr);
+ slow_path = new (GetGraph()->GetArena()) ReadBarrierMarkAndUpdateFieldSlowPathX86_64(
+ instruction, ref, obj, src, /* unpoison_ref_before_marking */ true, *temp1, *temp2);
+ } else {
+ slow_path = new (GetGraph()->GetArena()) ReadBarrierMarkSlowPathX86_64(
+ instruction, ref, /* unpoison_ref_before_marking */ true);
+ }
AddSlowPath(slow_path);
// We have done the "if" of the gray bit check above, now branch based on the flags.
diff --git a/compiler/optimizing/code_generator_x86_64.h b/compiler/optimizing/code_generator_x86_64.h
index 57ef83f..70e22f9 100644
--- a/compiler/optimizing/code_generator_x86_64.h
+++ b/compiler/optimizing/code_generator_x86_64.h
@@ -434,13 +434,25 @@
uint32_t data_offset,
Location index,
bool needs_null_check);
- // Factored implementation used by GenerateFieldLoadWithBakerReadBarrier
- // and GenerateArrayLoadWithBakerReadBarrier.
+ // Factored implementation, used by GenerateFieldLoadWithBakerReadBarrier,
+ // GenerateArrayLoadWithBakerReadBarrier and some intrinsics.
+ //
+ // Load the object reference located at address `src`, held by
+ // object `obj`, into `ref`, and mark it if needed. The base of
+ // address `src` must be `obj`.
+ //
+ // If `always_update_field` is true, the value of the reference is
+ // atomically updated in the holder (`obj`). This operation
+ // requires two temporary registers, which must be provided as
+ // non-null pointers (`temp1` and `temp2`).
void GenerateReferenceLoadWithBakerReadBarrier(HInstruction* instruction,
Location ref,
CpuRegister obj,
const Address& src,
- bool needs_null_check);
+ bool needs_null_check,
+ bool always_update_field = false,
+ CpuRegister* temp1 = nullptr,
+ CpuRegister* temp2 = nullptr);
// Generate a read barrier for a heap reference within `instruction`
// using a slow path.
diff --git a/compiler/optimizing/intrinsics_arm.cc b/compiler/optimizing/intrinsics_arm.cc
index 96a6ecb..8790c1e 100644
--- a/compiler/optimizing/intrinsics_arm.cc
+++ b/compiler/optimizing/intrinsics_arm.cc
@@ -652,9 +652,9 @@
(invoke->GetIntrinsic() == Intrinsics::kUnsafeGetObject ||
invoke->GetIntrinsic() == Intrinsics::kUnsafeGetObjectVolatile);
LocationSummary* locations = new (arena) LocationSummary(invoke,
- can_call ?
- LocationSummary::kCallOnSlowPath :
- LocationSummary::kNoCall,
+ (can_call
+ ? LocationSummary::kCallOnSlowPath
+ : LocationSummary::kNoCall),
kIntrinsified);
if (can_call && kUseBakerReadBarrier) {
locations->SetCustomSlowPathCallerSaves(RegisterSet::Empty()); // No caller-save registers.
@@ -663,7 +663,7 @@
locations->SetInAt(1, Location::RequiresRegister());
locations->SetInAt(2, Location::RequiresRegister());
locations->SetOut(Location::RequiresRegister(),
- can_call ? Location::kOutputOverlap : Location::kNoOutputOverlap);
+ (can_call ? Location::kOutputOverlap : Location::kNoOutputOverlap));
if (type == Primitive::kPrimNot && kEmitCompilerReadBarrier && kUseBakerReadBarrier) {
// We need a temporary register for the read barrier marking slow
// path in InstructionCodeGeneratorARM::GenerateReferenceLoadWithBakerReadBarrier.
@@ -891,8 +891,13 @@
static void CreateIntIntIntIntIntToIntPlusTemps(ArenaAllocator* arena,
HInvoke* invoke,
Primitive::Type type) {
+ bool can_call = kEmitCompilerReadBarrier &&
+ kUseBakerReadBarrier &&
+ (invoke->GetIntrinsic() == Intrinsics::kUnsafeCASObject);
LocationSummary* locations = new (arena) LocationSummary(invoke,
- LocationSummary::kNoCall,
+ (can_call
+ ? LocationSummary::kCallOnSlowPath
+ : LocationSummary::kNoCall),
kIntrinsified);
locations->SetInAt(0, Location::NoLocation()); // Unused receiver.
locations->SetInAt(1, Location::RequiresRegister());
@@ -901,36 +906,65 @@
locations->SetInAt(4, Location::RequiresRegister());
// If heap poisoning is enabled, we don't want the unpoisoning
- // operations to potentially clobber the output.
- Location::OutputOverlap overlaps = (kPoisonHeapReferences && type == Primitive::kPrimNot)
+ // operations to potentially clobber the output. Likewise when
+ // emitting a (Baker) read barrier, which may call.
+ Location::OutputOverlap overlaps =
+ ((kPoisonHeapReferences && type == Primitive::kPrimNot) || can_call)
? Location::kOutputOverlap
: Location::kNoOutputOverlap;
locations->SetOut(Location::RequiresRegister(), overlaps);
+ // Temporary registers used in CAS. In the object case
+ // (UnsafeCASObject intrinsic), these are also used for
+ // card-marking, and possibly for (Baker) read barrier.
locations->AddTemp(Location::RequiresRegister()); // Pointer.
locations->AddTemp(Location::RequiresRegister()); // Temp 1.
}
-static void GenCas(LocationSummary* locations, Primitive::Type type, CodeGeneratorARM* codegen) {
+static void GenCas(HInvoke* invoke, Primitive::Type type, CodeGeneratorARM* codegen) {
DCHECK_NE(type, Primitive::kPrimLong);
ArmAssembler* assembler = codegen->GetAssembler();
+ LocationSummary* locations = invoke->GetLocations();
- Register out = locations->Out().AsRegister<Register>(); // Boolean result.
+ Location out_loc = locations->Out();
+ Register out = out_loc.AsRegister<Register>(); // Boolean result.
- Register base = locations->InAt(1).AsRegister<Register>(); // Object pointer.
- Register offset = locations->InAt(2).AsRegisterPairLow<Register>(); // Offset (discard high 4B).
- Register expected_lo = locations->InAt(3).AsRegister<Register>(); // Expected.
- Register value_lo = locations->InAt(4).AsRegister<Register>(); // Value.
+ Register base = locations->InAt(1).AsRegister<Register>(); // Object pointer.
+ Location offset_loc = locations->InAt(2);
+ Register offset = offset_loc.AsRegisterPairLow<Register>(); // Offset (discard high 4B).
+ Register expected = locations->InAt(3).AsRegister<Register>(); // Expected.
+ Register value = locations->InAt(4).AsRegister<Register>(); // Value.
- Register tmp_ptr = locations->GetTemp(0).AsRegister<Register>(); // Pointer to actual memory.
- Register tmp_lo = locations->GetTemp(1).AsRegister<Register>(); // Value in memory.
+ Location tmp_ptr_loc = locations->GetTemp(0);
+ Register tmp_ptr = tmp_ptr_loc.AsRegister<Register>(); // Pointer to actual memory.
+ Register tmp = locations->GetTemp(1).AsRegister<Register>(); // Value in memory.
if (type == Primitive::kPrimNot) {
+ // The only read barrier implementation supporting the
+ // UnsafeCASObject intrinsic is the Baker-style read barriers.
+ DCHECK(!kEmitCompilerReadBarrier || kUseBakerReadBarrier);
+
// Mark card for object assuming new value is stored. Worst case we will mark an unchanged
// object and scan the receiver at the next GC for nothing.
bool value_can_be_null = true; // TODO: Worth finding out this information?
- codegen->MarkGCCard(tmp_ptr, tmp_lo, base, value_lo, value_can_be_null);
+ codegen->MarkGCCard(tmp_ptr, tmp, base, value, value_can_be_null);
+
+ if (kEmitCompilerReadBarrier && kUseBakerReadBarrier) {
+ // Need to make sure the reference stored in the field is a to-space
+ // one before attempting the CAS or the CAS could fail incorrectly.
+ codegen->GenerateReferenceLoadWithBakerReadBarrier(
+ invoke,
+ out_loc, // Unused, used only as a "temporary" within the read barrier.
+ base,
+ /* offset */ 0u,
+ /* index */ offset_loc,
+ ScaleFactor::TIMES_1,
+ tmp_ptr_loc,
+ /* needs_null_check */ false,
+ /* always_update_field */ true,
+ &tmp);
+ }
}
// Prevent reordering with prior memory operations.
@@ -942,12 +976,12 @@
__ add(tmp_ptr, base, ShifterOperand(offset));
if (kPoisonHeapReferences && type == Primitive::kPrimNot) {
- codegen->GetAssembler()->PoisonHeapReference(expected_lo);
- if (value_lo == expected_lo) {
- // Do not poison `value_lo`, as it is the same register as
- // `expected_lo`, which has just been poisoned.
+ __ PoisonHeapReference(expected);
+ if (value == expected) {
+ // Do not poison `value`, as it is the same register as
+ // `expected`, which has just been poisoned.
} else {
- codegen->GetAssembler()->PoisonHeapReference(value_lo);
+ __ PoisonHeapReference(value);
}
}
@@ -959,37 +993,29 @@
Label loop_head;
__ Bind(&loop_head);
- // 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 IntrinsicLocationsBuilderARM::VisitUnsafeCASObject).
- DCHECK(!(type == Primitive::kPrimNot && kEmitCompilerReadBarrier));
- __ ldrex(tmp_lo, tmp_ptr);
+ __ ldrex(tmp, tmp_ptr);
- __ subs(tmp_lo, tmp_lo, ShifterOperand(expected_lo));
+ __ subs(tmp, tmp, ShifterOperand(expected));
__ it(EQ, ItState::kItT);
- __ strex(tmp_lo, value_lo, tmp_ptr, EQ);
- __ cmp(tmp_lo, ShifterOperand(1), EQ);
+ __ strex(tmp, value, tmp_ptr, EQ);
+ __ cmp(tmp, ShifterOperand(1), EQ);
__ b(&loop_head, EQ);
__ dmb(ISH);
- __ rsbs(out, tmp_lo, ShifterOperand(1));
+ __ rsbs(out, tmp, ShifterOperand(1));
__ it(CC);
__ mov(out, ShifterOperand(0), CC);
if (kPoisonHeapReferences && type == Primitive::kPrimNot) {
- codegen->GetAssembler()->UnpoisonHeapReference(expected_lo);
- if (value_lo == expected_lo) {
- // Do not unpoison `value_lo`, as it is the same register as
- // `expected_lo`, which has just been unpoisoned.
+ __ UnpoisonHeapReference(expected);
+ if (value == expected) {
+ // Do not unpoison `value`, as it is the same register as
+ // `expected`, which has just been unpoisoned.
} else {
- codegen->GetAssembler()->UnpoisonHeapReference(value_lo);
+ __ UnpoisonHeapReference(value);
}
}
}
@@ -998,33 +1024,23 @@
CreateIntIntIntIntIntToIntPlusTemps(arena_, invoke, Primitive::kPrimInt);
}
void IntrinsicLocationsBuilderARM::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 (see TODO in GenCAS).
- //
- // TODO(rpl): Implement read barrier support in GenCAS and re-enable
- // this intrinsic.
- if (kEmitCompilerReadBarrier) {
+ // The only read barrier implementation supporting the
+ // UnsafeCASObject intrinsic is the Baker-style read barriers.
+ if (kEmitCompilerReadBarrier && !kUseBakerReadBarrier) {
return;
}
CreateIntIntIntIntIntToIntPlusTemps(arena_, invoke, Primitive::kPrimNot);
}
void IntrinsicCodeGeneratorARM::VisitUnsafeCASInt(HInvoke* invoke) {
- GenCas(invoke->GetLocations(), Primitive::kPrimInt, codegen_);
+ GenCas(invoke, Primitive::kPrimInt, codegen_);
}
void IntrinsicCodeGeneratorARM::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 (see TODO in GenCAS).
- //
- // TODO(rpl): Implement read barrier support in GenCAS and re-enable
- // this intrinsic.
- DCHECK(!kEmitCompilerReadBarrier);
+ // The only read barrier implementation supporting the
+ // UnsafeCASObject intrinsic is the Baker-style read barriers.
+ DCHECK(!kEmitCompilerReadBarrier || kUseBakerReadBarrier);
- GenCas(invoke->GetLocations(), Primitive::kPrimNot, codegen_);
+ GenCas(invoke, Primitive::kPrimNot, codegen_);
}
void IntrinsicLocationsBuilderARM::VisitStringCompareTo(HInvoke* invoke) {
diff --git a/compiler/optimizing/intrinsics_arm64.cc b/compiler/optimizing/intrinsics_arm64.cc
index e2c1802..db1c022 100644
--- a/compiler/optimizing/intrinsics_arm64.cc
+++ b/compiler/optimizing/intrinsics_arm64.cc
@@ -863,9 +863,9 @@
codegen->GenerateReferenceLoadWithBakerReadBarrier(invoke,
trg_loc,
base,
- /* offset */ 0U,
+ /* offset */ 0u,
/* index */ offset_loc,
- /* scale_factor */ 0U,
+ /* scale_factor */ 0u,
temp,
/* needs_null_check */ false,
is_volatile);
@@ -880,7 +880,7 @@
if (type == Primitive::kPrimNot) {
DCHECK(trg.IsW());
- codegen->MaybeGenerateReadBarrierSlow(invoke, trg_loc, trg_loc, base_loc, 0U, offset_loc);
+ codegen->MaybeGenerateReadBarrierSlow(invoke, trg_loc, trg_loc, base_loc, 0u, offset_loc);
}
}
}
@@ -890,9 +890,9 @@
(invoke->GetIntrinsic() == Intrinsics::kUnsafeGetObject ||
invoke->GetIntrinsic() == Intrinsics::kUnsafeGetObjectVolatile);
LocationSummary* locations = new (arena) LocationSummary(invoke,
- can_call ?
- LocationSummary::kCallOnSlowPath :
- LocationSummary::kNoCall,
+ (can_call
+ ? LocationSummary::kCallOnSlowPath
+ : LocationSummary::kNoCall),
kIntrinsified);
if (can_call && kUseBakerReadBarrier) {
locations->SetCustomSlowPathCallerSaves(RegisterSet::Empty()); // No caller-save registers.
@@ -901,7 +901,7 @@
locations->SetInAt(1, Location::RequiresRegister());
locations->SetInAt(2, Location::RequiresRegister());
locations->SetOut(Location::RequiresRegister(),
- can_call ? Location::kOutputOverlap : Location::kNoOutputOverlap);
+ (can_call ? Location::kOutputOverlap : Location::kNoOutputOverlap));
}
void IntrinsicLocationsBuilderARM64::VisitUnsafeGet(HInvoke* invoke) {
@@ -1086,8 +1086,13 @@
static void CreateIntIntIntIntIntToInt(ArenaAllocator* arena,
HInvoke* invoke,
Primitive::Type type) {
+ bool can_call = kEmitCompilerReadBarrier &&
+ kUseBakerReadBarrier &&
+ (invoke->GetIntrinsic() == Intrinsics::kUnsafeCASObject);
LocationSummary* locations = new (arena) LocationSummary(invoke,
- LocationSummary::kNoCall,
+ (can_call
+ ? LocationSummary::kCallOnSlowPath
+ : LocationSummary::kNoCall),
kIntrinsified);
locations->SetInAt(0, Location::NoLocation()); // Unused receiver.
locations->SetInAt(1, Location::RequiresRegister());
@@ -1096,20 +1101,29 @@
locations->SetInAt(4, Location::RequiresRegister());
// If heap poisoning is enabled, we don't want the unpoisoning
- // operations to potentially clobber the output.
- Location::OutputOverlap overlaps = (kPoisonHeapReferences && type == Primitive::kPrimNot)
+ // operations to potentially clobber the output. Likewise when
+ // emitting a (Baker) read barrier, which may call.
+ Location::OutputOverlap overlaps =
+ ((kPoisonHeapReferences && type == Primitive::kPrimNot) || can_call)
? Location::kOutputOverlap
: Location::kNoOutputOverlap;
locations->SetOut(Location::RequiresRegister(), overlaps);
+ if (type == Primitive::kPrimNot && kEmitCompilerReadBarrier && kUseBakerReadBarrier) {
+ // Temporary register for (Baker) read barrier.
+ locations->AddTemp(Location::RequiresRegister());
+ }
}
-static void GenCas(LocationSummary* locations, Primitive::Type type, CodeGeneratorARM64* codegen) {
+static void GenCas(HInvoke* invoke, Primitive::Type type, CodeGeneratorARM64* codegen) {
MacroAssembler* masm = codegen->GetVIXLAssembler();
+ LocationSummary* locations = invoke->GetLocations();
- Register out = WRegisterFrom(locations->Out()); // Boolean result.
+ Location out_loc = locations->Out();
+ Register out = WRegisterFrom(out_loc); // Boolean result.
Register base = WRegisterFrom(locations->InAt(1)); // Object pointer.
- Register offset = XRegisterFrom(locations->InAt(2)); // Long offset.
+ Location offset_loc = locations->InAt(2);
+ Register offset = XRegisterFrom(offset_loc); // Long offset.
Register expected = RegisterFrom(locations->InAt(3), type); // Expected.
Register value = RegisterFrom(locations->InAt(4), type); // Value.
@@ -1118,6 +1132,27 @@
// Mark card for object assuming new value is stored.
bool value_can_be_null = true; // TODO: Worth finding out this information?
codegen->MarkGCCard(base, value, value_can_be_null);
+
+ // The only read barrier implementation supporting the
+ // UnsafeCASObject intrinsic is the Baker-style read barriers.
+ DCHECK(!kEmitCompilerReadBarrier || kUseBakerReadBarrier);
+
+ if (kEmitCompilerReadBarrier && kUseBakerReadBarrier) {
+ Register temp = WRegisterFrom(locations->GetTemp(0));
+ // Need to make sure the reference stored in the field is a to-space
+ // one before attempting the CAS or the CAS could fail incorrectly.
+ codegen->GenerateReferenceLoadWithBakerReadBarrier(
+ invoke,
+ out_loc, // Unused, used only as a "temporary" within the read barrier.
+ base,
+ /* offset */ 0u,
+ /* index */ offset_loc,
+ /* scale_factor */ 0u,
+ temp,
+ /* needs_null_check */ false,
+ /* use_load_acquire */ false,
+ /* always_update_field */ true);
+ }
}
UseScratchRegisterScope temps(masm);
@@ -1145,14 +1180,6 @@
vixl::aarch64::Label loop_head, exit_loop;
__ Bind(&loop_head);
- // 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));
__ Ldaxr(tmp_value, MemOperand(tmp_ptr));
__ Cmp(tmp_value, expected);
__ B(&exit_loop, ne);
@@ -1179,14 +1206,9 @@
CreateIntIntIntIntIntToInt(arena_, invoke, Primitive::kPrimLong);
}
void IntrinsicLocationsBuilderARM64::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 (see TODO in GenCAS).
- //
- // TODO(rpl): Implement read barrier support in GenCAS and re-enable
- // this intrinsic.
- if (kEmitCompilerReadBarrier) {
+ // The only read barrier implementation supporting the
+ // UnsafeCASObject intrinsic is the Baker-style read barriers.
+ if (kEmitCompilerReadBarrier && !kUseBakerReadBarrier) {
return;
}
@@ -1194,22 +1216,17 @@
}
void IntrinsicCodeGeneratorARM64::VisitUnsafeCASInt(HInvoke* invoke) {
- GenCas(invoke->GetLocations(), Primitive::kPrimInt, codegen_);
+ GenCas(invoke, Primitive::kPrimInt, codegen_);
}
void IntrinsicCodeGeneratorARM64::VisitUnsafeCASLong(HInvoke* invoke) {
- GenCas(invoke->GetLocations(), Primitive::kPrimLong, codegen_);
+ GenCas(invoke, Primitive::kPrimLong, codegen_);
}
void IntrinsicCodeGeneratorARM64::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 (see TODO in GenCAS).
- //
- // TODO(rpl): Implement read barrier support in GenCAS and re-enable
- // this intrinsic.
- DCHECK(!kEmitCompilerReadBarrier);
+ // The only read barrier implementation supporting the
+ // UnsafeCASObject intrinsic is the Baker-style read barriers.
+ DCHECK(!kEmitCompilerReadBarrier || kUseBakerReadBarrier);
- GenCas(invoke->GetLocations(), Primitive::kPrimNot, codegen_);
+ GenCas(invoke, Primitive::kPrimNot, codegen_);
}
void IntrinsicLocationsBuilderARM64::VisitStringCompareTo(HInvoke* invoke) {
diff --git a/compiler/optimizing/intrinsics_x86.cc b/compiler/optimizing/intrinsics_x86.cc
index f41e4d9..aae3899 100644
--- a/compiler/optimizing/intrinsics_x86.cc
+++ b/compiler/optimizing/intrinsics_x86.cc
@@ -2056,9 +2056,9 @@
(invoke->GetIntrinsic() == Intrinsics::kUnsafeGetObject ||
invoke->GetIntrinsic() == Intrinsics::kUnsafeGetObjectVolatile);
LocationSummary* locations = new (arena) LocationSummary(invoke,
- can_call ?
- LocationSummary::kCallOnSlowPath :
- LocationSummary::kNoCall,
+ (can_call
+ ? LocationSummary::kCallOnSlowPath
+ : LocationSummary::kNoCall),
kIntrinsified);
if (can_call && kUseBakerReadBarrier) {
locations->SetCustomSlowPathCallerSaves(RegisterSet::Empty()); // No caller-save registers.
@@ -2076,7 +2076,7 @@
}
} else {
locations->SetOut(Location::RequiresRegister(),
- can_call ? Location::kOutputOverlap : Location::kNoOutputOverlap);
+ (can_call ? Location::kOutputOverlap : Location::kNoOutputOverlap));
}
}
@@ -2255,10 +2255,16 @@
GenUnsafePut(invoke->GetLocations(), Primitive::kPrimLong, /* is_volatile */ true, codegen_);
}
-static void CreateIntIntIntIntIntToInt(ArenaAllocator* arena, Primitive::Type type,
+static void CreateIntIntIntIntIntToInt(ArenaAllocator* arena,
+ Primitive::Type type,
HInvoke* invoke) {
+ bool can_call = kEmitCompilerReadBarrier &&
+ kUseBakerReadBarrier &&
+ (invoke->GetIntrinsic() == Intrinsics::kUnsafeCASObject);
LocationSummary* locations = new (arena) LocationSummary(invoke,
- LocationSummary::kNoCall,
+ (can_call
+ ? LocationSummary::kCallOnSlowPath
+ : LocationSummary::kNoCall),
kIntrinsified);
locations->SetInAt(0, Location::NoLocation()); // Unused receiver.
locations->SetInAt(1, Location::RequiresRegister());
@@ -2278,7 +2284,8 @@
// Force a byte register for the output.
locations->SetOut(Location::RegisterLocation(EAX));
if (type == Primitive::kPrimNot) {
- // Need temp registers for card-marking.
+ // Need temporary registers for card-marking, and possibly for
+ // (Baker) read barrier.
locations->AddTemp(Location::RequiresRegister()); // Possibly used for reference poisoning too.
// Need a byte register for marking.
locations->AddTemp(Location::RegisterLocation(ECX));
@@ -2294,14 +2301,9 @@
}
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 (see TODO in GenCAS).
- //
- // TODO(rpl): Implement read barrier support in GenCAS and re-enable
- // this intrinsic.
- if (kEmitCompilerReadBarrier) {
+ // The only read barrier implementation supporting the
+ // UnsafeCASObject intrinsic is the Baker-style read barriers.
+ if (kEmitCompilerReadBarrier && !kUseBakerReadBarrier) {
return;
}
@@ -2317,7 +2319,18 @@
Location out = locations->Out();
DCHECK_EQ(out.AsRegister<Register>(), EAX);
+ // The address of the field within the holding object.
+ Address field_addr(base, offset, ScaleFactor::TIMES_1, 0);
+
if (type == Primitive::kPrimNot) {
+ // The only read barrier implementation supporting the
+ // UnsafeCASObject intrinsic is the Baker-style read barriers.
+ DCHECK(!kEmitCompilerReadBarrier || kUseBakerReadBarrier);
+
+ Location temp1_loc = locations->GetTemp(0);
+ Register temp1 = temp1_loc.AsRegister<Register>();
+ Register temp2 = locations->GetTemp(1).AsRegister<Register>();
+
Register expected = locations->InAt(3).AsRegister<Register>();
// Ensure `expected` is in EAX (required by the CMPXCHG instruction).
DCHECK_EQ(expected, EAX);
@@ -2325,11 +2338,20 @@
// Mark card for object assuming new value is stored.
bool value_can_be_null = true; // TODO: Worth finding out this information?
- codegen->MarkGCCard(locations->GetTemp(0).AsRegister<Register>(),
- locations->GetTemp(1).AsRegister<Register>(),
- base,
- value,
- value_can_be_null);
+ codegen->MarkGCCard(temp1, temp2, base, value, value_can_be_null);
+
+ if (kEmitCompilerReadBarrier && kUseBakerReadBarrier) {
+ // Need to make sure the reference stored in the field is a to-space
+ // one before attempting the CAS or the CAS could fail incorrectly.
+ codegen->GenerateReferenceLoadWithBakerReadBarrier(
+ invoke,
+ temp1_loc, // Unused, used only as a "temporary" within the read barrier.
+ base,
+ field_addr,
+ /* needs_null_check */ false,
+ /* always_update_field */ true,
+ &temp2);
+ }
bool base_equals_value = (base == value);
if (kPoisonHeapReferences) {
@@ -2337,7 +2359,7 @@
// If `base` and `value` are the same register location, move
// `value` to a temporary register. This way, poisoning
// `value` won't invalidate `base`.
- value = locations->GetTemp(0).AsRegister<Register>();
+ value = temp1;
__ movl(value, base);
}
@@ -2356,19 +2378,12 @@
__ 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);
+ __ LockCmpxchgl(field_addr, value);
// LOCK CMPXCHG has full barrier semantics, and we don't need
// scheduling barriers at this time.
- // Convert ZF into the boolean result.
+ // Convert ZF into the Boolean result.
__ setb(kZero, out.AsRegister<Register>());
__ movzxb(out.AsRegister<Register>(), out.AsRegister<ByteRegister>());
@@ -2392,8 +2407,7 @@
// Ensure the expected value is in EAX (required by the CMPXCHG
// instruction).
DCHECK_EQ(locations->InAt(3).AsRegister<Register>(), EAX);
- __ LockCmpxchgl(Address(base, offset, TIMES_1, 0),
- locations->InAt(4).AsRegister<Register>());
+ __ LockCmpxchgl(field_addr, locations->InAt(4).AsRegister<Register>());
} else if (type == Primitive::kPrimLong) {
// Ensure the expected value is in EAX:EDX and that the new
// value is in EBX:ECX (required by the CMPXCHG8B instruction).
@@ -2401,7 +2415,7 @@
DCHECK_EQ(locations->InAt(3).AsRegisterPairHigh<Register>(), EDX);
DCHECK_EQ(locations->InAt(4).AsRegisterPairLow<Register>(), EBX);
DCHECK_EQ(locations->InAt(4).AsRegisterPairHigh<Register>(), ECX);
- __ LockCmpxchg8b(Address(base, offset, TIMES_1, 0));
+ __ LockCmpxchg8b(field_addr);
} else {
LOG(FATAL) << "Unexpected CAS type " << type;
}
@@ -2409,7 +2423,7 @@
// LOCK CMPXCHG/LOCK CMPXCHG8B have full barrier semantics, and we
// don't need scheduling barriers at this time.
- // Convert ZF into the boolean result.
+ // Convert ZF into the Boolean result.
__ setb(kZero, out.AsRegister<Register>());
__ movzxb(out.AsRegister<Register>(), out.AsRegister<ByteRegister>());
}
@@ -2424,14 +2438,9 @@
}
void IntrinsicCodeGeneratorX86::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 (see TODO in GenCAS).
- //
- // TODO(rpl): Implement read barrier support in GenCAS and re-enable
- // this intrinsic.
- DCHECK(!kEmitCompilerReadBarrier);
+ // The only read barrier implementation supporting the
+ // UnsafeCASObject intrinsic is the Baker-style read barriers.
+ DCHECK(!kEmitCompilerReadBarrier || kUseBakerReadBarrier);
GenCAS(Primitive::kPrimNot, invoke, codegen_);
}
diff --git a/compiler/optimizing/intrinsics_x86_64.cc b/compiler/optimizing/intrinsics_x86_64.cc
index 4b0afca..cdef22f 100644
--- a/compiler/optimizing/intrinsics_x86_64.cc
+++ b/compiler/optimizing/intrinsics_x86_64.cc
@@ -2172,9 +2172,9 @@
(invoke->GetIntrinsic() == Intrinsics::kUnsafeGetObject ||
invoke->GetIntrinsic() == Intrinsics::kUnsafeGetObjectVolatile);
LocationSummary* locations = new (arena) LocationSummary(invoke,
- can_call ?
- LocationSummary::kCallOnSlowPath :
- LocationSummary::kNoCall,
+ (can_call
+ ? LocationSummary::kCallOnSlowPath
+ : LocationSummary::kNoCall),
kIntrinsified);
if (can_call && kUseBakerReadBarrier) {
locations->SetCustomSlowPathCallerSaves(RegisterSet::Empty()); // No caller-save registers.
@@ -2183,7 +2183,7 @@
locations->SetInAt(1, Location::RequiresRegister());
locations->SetInAt(2, Location::RequiresRegister());
locations->SetOut(Location::RequiresRegister(),
- can_call ? Location::kOutputOverlap : Location::kNoOutputOverlap);
+ (can_call ? Location::kOutputOverlap : Location::kNoOutputOverlap));
}
void IntrinsicLocationsBuilderX86_64::VisitUnsafeGet(HInvoke* invoke) {
@@ -2333,10 +2333,16 @@
GenUnsafePut(invoke->GetLocations(), Primitive::kPrimLong, /* is_volatile */ true, codegen_);
}
-static void CreateIntIntIntIntIntToInt(ArenaAllocator* arena, Primitive::Type type,
+static void CreateIntIntIntIntIntToInt(ArenaAllocator* arena,
+ Primitive::Type type,
HInvoke* invoke) {
+ bool can_call = kEmitCompilerReadBarrier &&
+ kUseBakerReadBarrier &&
+ (invoke->GetIntrinsic() == Intrinsics::kUnsafeCASObject);
LocationSummary* locations = new (arena) LocationSummary(invoke,
- LocationSummary::kNoCall,
+ (can_call
+ ? LocationSummary::kCallOnSlowPath
+ : LocationSummary::kNoCall),
kIntrinsified);
locations->SetInAt(0, Location::NoLocation()); // Unused receiver.
locations->SetInAt(1, Location::RequiresRegister());
@@ -2347,7 +2353,8 @@
locations->SetOut(Location::RequiresRegister());
if (type == Primitive::kPrimNot) {
- // Need temp registers for card-marking.
+ // Need temporary registers for card-marking, and possibly for
+ // (Baker) read barrier.
locations->AddTemp(Location::RequiresRegister()); // Possibly used for reference poisoning too.
locations->AddTemp(Location::RequiresRegister());
}
@@ -2362,14 +2369,9 @@
}
void IntrinsicLocationsBuilderX86_64::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 (see TODO in GenCAS).
- //
- // TODO(rpl): Implement read barrier support in GenCAS and re-enable
- // this intrinsic.
- if (kEmitCompilerReadBarrier) {
+ // The only read barrier implementation supporting the
+ // UnsafeCASObject intrinsic is the Baker-style read barriers.
+ if (kEmitCompilerReadBarrier && !kUseBakerReadBarrier) {
return;
}
@@ -2386,16 +2388,37 @@
// Ensure `expected` is in RAX (required by the CMPXCHG instruction).
DCHECK_EQ(expected.AsRegister(), RAX);
CpuRegister value = locations->InAt(4).AsRegister<CpuRegister>();
- CpuRegister out = locations->Out().AsRegister<CpuRegister>();
+ Location out_loc = locations->Out();
+ CpuRegister out = out_loc.AsRegister<CpuRegister>();
if (type == Primitive::kPrimNot) {
+ // The only read barrier implementation supporting the
+ // UnsafeCASObject intrinsic is the Baker-style read barriers.
+ DCHECK(!kEmitCompilerReadBarrier || kUseBakerReadBarrier);
+
+ CpuRegister temp1 = locations->GetTemp(0).AsRegister<CpuRegister>();
+ CpuRegister temp2 = locations->GetTemp(1).AsRegister<CpuRegister>();
+
// Mark card for object assuming new value is stored.
bool value_can_be_null = true; // TODO: Worth finding out this information?
- codegen->MarkGCCard(locations->GetTemp(0).AsRegister<CpuRegister>(),
- locations->GetTemp(1).AsRegister<CpuRegister>(),
- base,
- value,
- value_can_be_null);
+ codegen->MarkGCCard(temp1, temp2, base, value, value_can_be_null);
+
+ // The address of the field within the holding object.
+ Address field_addr(base, offset, ScaleFactor::TIMES_1, 0);
+
+ if (kEmitCompilerReadBarrier && kUseBakerReadBarrier) {
+ // Need to make sure the reference stored in the field is a to-space
+ // one before attempting the CAS or the CAS could fail incorrectly.
+ codegen->GenerateReferenceLoadWithBakerReadBarrier(
+ invoke,
+ out_loc, // Unused, used only as a "temporary" within the read barrier.
+ base,
+ field_addr,
+ /* needs_null_check */ false,
+ /* always_update_field */ true,
+ &temp1,
+ &temp2);
+ }
bool base_equals_value = (base.AsRegister() == value.AsRegister());
Register value_reg = value.AsRegister();
@@ -2404,7 +2427,7 @@
// If `base` and `value` are the same register location, move
// `value_reg` to a temporary register. This way, poisoning
// `value_reg` won't invalidate `base`.
- value_reg = locations->GetTemp(0).AsRegister<CpuRegister>().AsRegister();
+ value_reg = temp1.AsRegister();
__ movl(CpuRegister(value_reg), base);
}
@@ -2423,19 +2446,12 @@
__ PoisonHeapReference(CpuRegister(value_reg));
}
- // 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_64::VisitUnsafeCASObject).
- DCHECK(!kEmitCompilerReadBarrier);
- __ LockCmpxchgl(Address(base, offset, TIMES_1, 0), CpuRegister(value_reg));
+ __ LockCmpxchgl(field_addr, CpuRegister(value_reg));
// LOCK CMPXCHG has full barrier semantics, and we don't need
// scheduling barriers at this time.
- // Convert ZF into the boolean result.
+ // Convert ZF into the Boolean result.
__ setcc(kZero, out);
__ movzxb(out, out);
@@ -2468,7 +2484,7 @@
// LOCK CMPXCHG has full barrier semantics, and we don't need
// scheduling barriers at this time.
- // Convert ZF into the boolean result.
+ // Convert ZF into the Boolean result.
__ setcc(kZero, out);
__ movzxb(out, out);
}
@@ -2483,14 +2499,9 @@
}
void IntrinsicCodeGeneratorX86_64::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 (see TODO in GenCAS).
- //
- // TODO(rpl): Implement read barrier support in GenCAS and re-enable
- // this intrinsic.
- DCHECK(!kEmitCompilerReadBarrier);
+ // The only read barrier implementation supporting the
+ // UnsafeCASObject intrinsic is the Baker-style read barriers.
+ DCHECK(!kEmitCompilerReadBarrier || kUseBakerReadBarrier);
GenCAS(Primitive::kPrimNot, invoke, codegen_);
}
diff --git a/runtime/interpreter/unstarted_runtime.cc b/runtime/interpreter/unstarted_runtime.cc
index 75b91b1..6bf7e15 100644
--- a/runtime/interpreter/unstarted_runtime.cc
+++ b/runtime/interpreter/unstarted_runtime.cc
@@ -1272,7 +1272,7 @@
mirror::HeapReference<mirror::Object>* field_addr =
reinterpret_cast<mirror::HeapReference<mirror::Object>*>(
reinterpret_cast<uint8_t*>(obj) + static_cast<size_t>(offset));
- ReadBarrier::Barrier<mirror::Object, kWithReadBarrier, /*kAlwaysUpdateField*/true>(
+ ReadBarrier::Barrier<mirror::Object, kWithReadBarrier, /* kAlwaysUpdateField */ true>(
obj,
MemberOffset(offset),
field_addr);
diff --git a/runtime/native/sun_misc_Unsafe.cc b/runtime/native/sun_misc_Unsafe.cc
index cdf4b14..644df07 100644
--- a/runtime/native/sun_misc_Unsafe.cc
+++ b/runtime/native/sun_misc_Unsafe.cc
@@ -65,7 +65,7 @@
mirror::HeapReference<mirror::Object>* field_addr =
reinterpret_cast<mirror::HeapReference<mirror::Object>*>(
reinterpret_cast<uint8_t*>(obj.Ptr()) + static_cast<size_t>(offset));
- ReadBarrier::Barrier<mirror::Object, kWithReadBarrier, /*kAlwaysUpdateField*/true>(
+ ReadBarrier::Barrier<mirror::Object, kWithReadBarrier, /* kAlwaysUpdateField */ true>(
obj.Ptr(),
MemberOffset(offset),
field_addr);
diff --git a/runtime/read_barrier-inl.h b/runtime/read_barrier-inl.h
index 67e5a81..be95600 100644
--- a/runtime/read_barrier-inl.h
+++ b/runtime/read_barrier-inl.h
@@ -54,7 +54,7 @@
// Slow-path.
ref = reinterpret_cast<MirrorType*>(Mark(ref));
// If kAlwaysUpdateField is true, update the field atomically. This may fail if mutator
- // updates before us, but it's ok.
+ // updates before us, but it's OK.
if (kAlwaysUpdateField && ref != old_ref) {
obj->CasFieldStrongRelaxedObjectWithoutWriteBarrier<false, false>(
offset, old_ref, ref);