ART: Create BoundType for CheckCast early
ReferenceTypePropagation creates a BoundType for each CheckCast and
replaces all dominated uses of the casted object with it. This does
not include Phi uses on the boundary of the dominated scope, reducing
typing precision. This patch creates the BoundType in Builder, causing
SsaBuilder to replace uses of the object automatically.
Bug: 26081304
Change-Id: I083979155cccb348071ff58cb9060a896ed7d2ac
diff --git a/compiler/optimizing/reference_type_propagation.cc b/compiler/optimizing/reference_type_propagation.cc
index 8113e65..e55061c 100644
--- a/compiler/optimizing/reference_type_propagation.cc
+++ b/compiler/optimizing/reference_type_propagation.cc
@@ -56,6 +56,7 @@
void VisitInvoke(HInvoke* instr) OVERRIDE;
void VisitArrayGet(HArrayGet* instr) OVERRIDE;
void VisitCheckCast(HCheckCast* instr) OVERRIDE;
+ void VisitBoundType(HBoundType* instr) OVERRIDE;
void VisitNullCheck(HNullCheck* instr) OVERRIDE;
void VisitFakeString(HFakeString* instr) OVERRIDE;
void UpdateReferenceTypeInfo(HInstruction* instr,
@@ -160,34 +161,6 @@
BoundTypeForIfInstanceOf(block);
}
-// Create a bound type for the given object narrowing the type as much as possible.
-// The BoundType upper values for the super type and can_be_null will be taken from
-// load_class.GetLoadedClassRTI() and upper_can_be_null.
-static HBoundType* CreateBoundType(ArenaAllocator* arena,
- HInstruction* obj,
- HLoadClass* load_class,
- bool upper_can_be_null)
- SHARED_REQUIRES(Locks::mutator_lock_) {
- ReferenceTypeInfo obj_rti = obj->GetReferenceTypeInfo();
- ReferenceTypeInfo class_rti = load_class->GetLoadedClassRTI();
- DCHECK(class_rti.IsValid());
- HBoundType* bound_type = new (arena) HBoundType(obj, class_rti, upper_can_be_null);
- // Narrow the type as much as possible.
- if (class_rti.GetTypeHandle()->CannotBeAssignedFromOtherTypes()) {
- bound_type->SetReferenceTypeInfo(
- ReferenceTypeInfo::Create(class_rti.GetTypeHandle(), /* is_exact */ true));
- } else if (obj_rti.IsValid() && class_rti.IsSupertypeOf(obj_rti)) {
- bound_type->SetReferenceTypeInfo(obj_rti);
- } else {
- bound_type->SetReferenceTypeInfo(
- ReferenceTypeInfo::Create(class_rti.GetTypeHandle(), /* is_exact */ false));
- }
- if (upper_can_be_null) {
- bound_type->SetCanBeNull(obj->CanBeNull());
- }
- return bound_type;
-}
-
// Check if we should create a bound type for the given object at the specified
// position. Because of inlining and the fact we run RTP more than once and we
// might have a HBoundType already. If we do, we should not create a new one.
@@ -273,8 +246,8 @@
ReferenceTypeInfo object_rti = ReferenceTypeInfo::Create(
object_class_handle_, /* is_exact */ true);
if (ShouldCreateBoundType(insert_point, obj, object_rti, nullptr, notNullBlock)) {
- bound_type = new (graph_->GetArena()) HBoundType(
- obj, object_rti, /* bound_can_be_null */ false);
+ bound_type = new (graph_->GetArena()) HBoundType(obj);
+ bound_type->SetUpperBound(object_rti, /* bound_can_be_null */ false);
if (obj->GetReferenceTypeInfo().IsValid()) {
bound_type->SetReferenceTypeInfo(obj->GetReferenceTypeInfo());
}
@@ -408,11 +381,8 @@
ScopedObjectAccess soa(Thread::Current());
HInstruction* insert_point = instanceOfTrueBlock->GetFirstInstruction();
if (ShouldCreateBoundType(insert_point, obj, class_rti, nullptr, instanceOfTrueBlock)) {
- bound_type = CreateBoundType(
- graph_->GetArena(),
- obj,
- load_class,
- false /* InstanceOf ensures the object is not null. */);
+ bound_type = new (graph_->GetArena()) HBoundType(obj);
+ bound_type->SetUpperBound(class_rti, /* InstanceOf fails for null. */ false);
instanceOfTrueBlock->InsertInstructionBefore(bound_type, insert_point);
} else {
// We already have a bound type on the position we would need to insert
@@ -602,43 +572,54 @@
instr->SetReferenceTypeInfo(ReferenceTypeInfo::Create(string_class_handle_, /* is_exact */ true));
}
+void RTPVisitor::VisitBoundType(HBoundType* instr) {
+ ScopedObjectAccess soa(Thread::Current());
+
+ ReferenceTypeInfo class_rti = instr->GetUpperBound();
+ if (class_rti.IsValid()) {
+ // Narrow the type as much as possible.
+ HInstruction* obj = instr->InputAt(0);
+ ReferenceTypeInfo obj_rti = obj->GetReferenceTypeInfo();
+ if (class_rti.GetTypeHandle()->CannotBeAssignedFromOtherTypes()) {
+ instr->SetReferenceTypeInfo(
+ ReferenceTypeInfo::Create(class_rti.GetTypeHandle(), /* is_exact */ true));
+ } else if (obj_rti.IsValid() && class_rti.IsSupertypeOf(obj_rti)) {
+ instr->SetReferenceTypeInfo(obj_rti);
+ } else {
+ instr->SetReferenceTypeInfo(
+ ReferenceTypeInfo::Create(class_rti.GetTypeHandle(), /* is_exact */ false));
+ }
+ instr->SetCanBeNull(obj->CanBeNull() && instr->GetUpperCanBeNull());
+ } else {
+ // The owner of the BoundType was already visited. If the class is unresolved,
+ // the BoundType should have been removed from the data flow and this method
+ // should remove it from the graph.
+ DCHECK(!instr->HasUses());
+ instr->GetBlock()->RemoveInstruction(instr);
+ }
+}
+
void RTPVisitor::VisitCheckCast(HCheckCast* check_cast) {
+ ScopedObjectAccess soa(Thread::Current());
+
HLoadClass* load_class = check_cast->InputAt(1)->AsLoadClass();
ReferenceTypeInfo class_rti = load_class->GetLoadedClassRTI();
- {
- ScopedObjectAccess soa(Thread::Current());
- if (!class_rti.IsValid()) {
- // He have loaded an unresolved class. Don't bother bounding the type.
- return;
- }
+ HBoundType* bound_type = check_cast->GetNext()->AsBoundType();
+ if (bound_type == nullptr || bound_type->GetUpperBound().IsValid()) {
+ // The next instruction is not an uninitialized BoundType. This must be
+ // an RTP pass after SsaBuilder and we do not need to do anything.
+ return;
}
- HInstruction* obj = check_cast->InputAt(0);
- HBoundType* bound_type = nullptr;
- for (HUseIterator<HInstruction*> it(obj->GetUses()); !it.Done(); it.Advance()) {
- HInstruction* user = it.Current()->GetUser();
- if (check_cast->StrictlyDominates(user)) {
- if (bound_type == nullptr) {
- ScopedObjectAccess soa(Thread::Current());
- if (ShouldCreateBoundType(check_cast->GetNext(), obj, class_rti, check_cast, nullptr)) {
- bound_type = CreateBoundType(
- GetGraph()->GetArena(),
- obj,
- load_class,
- true /* CheckCast succeeds for nulls. */);
- check_cast->GetBlock()->InsertInstructionAfter(bound_type, check_cast);
- } else {
- // Update nullability of the existing bound type, which may not have known
- // that its input was not null when it was being created.
- bound_type = check_cast->GetNext()->AsBoundType();
- bound_type->SetCanBeNull(obj->CanBeNull());
- // We already have a bound type on the position we would need to insert
- // the new one. The existing bound type should dominate all the users
- // (dchecked) so there's no need to continue.
- break;
- }
- }
- user->ReplaceInput(bound_type, it.Current()->GetIndex());
- }
+ DCHECK_EQ(bound_type->InputAt(0), check_cast->InputAt(0));
+
+ if (class_rti.IsValid()) {
+ // This is the first run of RTP and class is resolved.
+ bound_type->SetUpperBound(class_rti, /* CheckCast succeeds for nulls. */ true);
+ } else {
+ // This is the first run of RTP and class is unresolved. Remove the binding.
+ // The instruction itself is removed in VisitBoundType so as to not
+ // invalidate HInstructionIterator.
+ bound_type->ReplaceWith(bound_type->InputAt(0));
}
}