Moved escape analysis to reusable module
Rationale:
This prepares other optimizations that
want to do some simple escape analysis.
Also introduces ability for client
to inject a case-specific function.
Test: test-art-host
Change-Id: Ie38a1e24e4479dc40154673db589ec1c82fb73b9
diff --git a/compiler/optimizing/escape.cc b/compiler/optimizing/escape.cc
new file mode 100644
index 0000000..c80e19e
--- /dev/null
+++ b/compiler/optimizing/escape.cc
@@ -0,0 +1,100 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "escape.h"
+
+#include "nodes.h"
+
+namespace art {
+
+void CalculateEscape(HInstruction* reference,
+ bool (*no_escape)(HInstruction*, HInstruction*),
+ /*out*/ bool* is_singleton,
+ /*out*/ bool* is_singleton_and_non_escaping) {
+ // For references not allocated in the method, don't assume anything.
+ if (!reference->IsNewInstance() && !reference->IsNewArray()) {
+ *is_singleton = false;
+ *is_singleton_and_non_escaping = false;
+ return;
+ }
+ // Assume the best until proven otherwise.
+ *is_singleton = true;
+ *is_singleton_and_non_escaping = true;
+ // Visit all uses to determine if this reference can escape into the heap,
+ // a method call, an alias, etc.
+ for (const HUseListNode<HInstruction*>& use : reference->GetUses()) {
+ HInstruction* user = use.GetUser();
+ if (no_escape != nullptr && (*no_escape)(reference, user)) {
+ // Client supplied analysis says there is no escape.
+ continue;
+ } else if (user->IsBoundType() || user->IsNullCheck()) {
+ // BoundType shouldn't normally be necessary for an allocation. Just be conservative
+ // for the uncommon cases. Similarly, null checks are eventually eliminated for explicit
+ // allocations, but if we see one before it is simplified, assume an alias.
+ *is_singleton = false;
+ *is_singleton_and_non_escaping = false;
+ return;
+ } else if (user->IsPhi() || user->IsSelect() || user->IsInvoke() ||
+ (user->IsInstanceFieldSet() && (reference == user->InputAt(1))) ||
+ (user->IsUnresolvedInstanceFieldSet() && (reference == user->InputAt(1))) ||
+ (user->IsStaticFieldSet() && (reference == user->InputAt(1))) ||
+ (user->IsUnresolvedStaticFieldSet() && (reference == user->InputAt(0))) ||
+ (user->IsArraySet() && (reference == user->InputAt(2)))) {
+ // The reference is merged to HPhi/HSelect, passed to a callee, or stored to heap.
+ // Hence, the reference is no longer the only name that can refer to its value.
+ *is_singleton = false;
+ *is_singleton_and_non_escaping = false;
+ return;
+ } else if ((user->IsUnresolvedInstanceFieldGet() && (reference == user->InputAt(0))) ||
+ (user->IsUnresolvedInstanceFieldSet() && (reference == user->InputAt(0)))) {
+ // The field is accessed in an unresolved way. We mark the object as a non-singleton.
+ // Note that we could optimize this case and still perform some optimizations until
+ // we hit the unresolved access, but the conservative assumption is the simplest.
+ *is_singleton = false;
+ *is_singleton_and_non_escaping = false;
+ return;
+ } else if (user->IsReturn()) {
+ *is_singleton_and_non_escaping = false;
+ }
+ }
+
+ // Need for further analysis?
+ if (!*is_singleton_and_non_escaping) {
+ return;
+ }
+
+ // Look at the environment uses and if it's for HDeoptimize, it's treated the
+ // same as a return which escapes at the end of executing the compiled code.
+ // Other environment uses are fine, as long as all client optimizations that
+ // rely on this informations are disabled for debuggable.
+ for (const HUseListNode<HEnvironment*>& use : reference->GetEnvUses()) {
+ HEnvironment* user = use.GetUser();
+ if (user->GetHolder()->IsDeoptimize()) {
+ *is_singleton_and_non_escaping = false;
+ break;
+ }
+ }
+}
+
+bool IsNonEscapingSingleton(HInstruction* reference,
+ bool (*no_escape)(HInstruction*, HInstruction*)) {
+ bool is_singleton = true;
+ bool is_singleton_and_non_escaping = true;
+ CalculateEscape(reference, no_escape, &is_singleton, &is_singleton_and_non_escaping);
+ return is_singleton_and_non_escaping;
+}
+
+} // namespace art