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