1 /* 2 * Copyright (C) 2016 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #include "escape.h" 18 19 #include "nodes.h" 20 21 namespace art { 22 23 void CalculateEscape(HInstruction* reference, 24 bool (*no_escape)(HInstruction*, HInstruction*), 25 /*out*/ bool* is_singleton, 26 /*out*/ bool* is_singleton_and_not_returned, 27 /*out*/ bool* is_singleton_and_not_deopt_visible) { 28 // For references not allocated in the method, don't assume anything. 29 if (!reference->IsNewInstance() && !reference->IsNewArray()) { 30 *is_singleton = false; 31 *is_singleton_and_not_returned = false; 32 *is_singleton_and_not_deopt_visible = false; 33 return; 34 } 35 // Assume the best until proven otherwise. 36 *is_singleton = true; 37 *is_singleton_and_not_returned = true; 38 *is_singleton_and_not_deopt_visible = true; 39 // Visit all uses to determine if this reference can escape into the heap, 40 // a method call, an alias, etc. 41 for (const HUseListNode<HInstruction*>& use : reference->GetUses()) { 42 HInstruction* user = use.GetUser(); 43 if (no_escape != nullptr && (*no_escape)(reference, user)) { 44 // Client supplied analysis says there is no escape. 45 continue; 46 } else if (user->IsBoundType() || user->IsNullCheck()) { 47 // BoundType shouldn't normally be necessary for an allocation. Just be conservative 48 // for the uncommon cases. Similarly, null checks are eventually eliminated for explicit 49 // allocations, but if we see one before it is simplified, assume an alias. 50 *is_singleton = false; 51 *is_singleton_and_not_returned = false; 52 *is_singleton_and_not_deopt_visible = false; 53 return; 54 } else if (user->IsPhi() || user->IsSelect() || user->IsInvoke() || 55 (user->IsInstanceFieldSet() && (reference == user->InputAt(1))) || 56 (user->IsUnresolvedInstanceFieldSet() && (reference == user->InputAt(1))) || 57 (user->IsStaticFieldSet() && (reference == user->InputAt(1))) || 58 (user->IsUnresolvedStaticFieldSet() && (reference == user->InputAt(0))) || 59 (user->IsArraySet() && (reference == user->InputAt(2)))) { 60 // The reference is merged to HPhi/HSelect, passed to a callee, or stored to heap. 61 // Hence, the reference is no longer the only name that can refer to its value. 62 *is_singleton = false; 63 *is_singleton_and_not_returned = false; 64 *is_singleton_and_not_deopt_visible = false; 65 return; 66 } else if ((user->IsUnresolvedInstanceFieldGet() && (reference == user->InputAt(0))) || 67 (user->IsUnresolvedInstanceFieldSet() && (reference == user->InputAt(0)))) { 68 // The field is accessed in an unresolved way. We mark the object as a non-singleton. 69 // Note that we could optimize this case and still perform some optimizations until 70 // we hit the unresolved access, but the conservative assumption is the simplest. 71 *is_singleton = false; 72 *is_singleton_and_not_returned = false; 73 *is_singleton_and_not_deopt_visible = false; 74 return; 75 } else if (user->IsReturn()) { 76 *is_singleton_and_not_returned = false; 77 } 78 } 79 80 // Look at the environment uses if it's for HDeoptimize. Other environment uses are fine, 81 // as long as client optimizations that rely on this information are disabled for debuggable. 82 for (const HUseListNode<HEnvironment*>& use : reference->GetEnvUses()) { 83 HEnvironment* user = use.GetUser(); 84 if (user->GetHolder()->IsDeoptimize()) { 85 *is_singleton_and_not_deopt_visible = false; 86 break; 87 } 88 } 89 } 90 91 bool DoesNotEscape(HInstruction* reference, bool (*no_escape)(HInstruction*, HInstruction*)) { 92 bool is_singleton = false; 93 bool is_singleton_and_not_returned = false; 94 bool is_singleton_and_not_deopt_visible = false; // not relevant for escape 95 CalculateEscape(reference, 96 no_escape, 97 &is_singleton, 98 &is_singleton_and_not_returned, 99 &is_singleton_and_not_deopt_visible); 100 return is_singleton_and_not_returned; 101 } 102 103 } // namespace art 104
