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150 lines
6.0 KiB
150 lines
6.0 KiB
/*
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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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#ifndef ART_COMPILER_OPTIMIZING_ESCAPE_H_
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#define ART_COMPILER_OPTIMIZING_ESCAPE_H_
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namespace art {
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class HInstruction;
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/*
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* Methods related to escape analysis, i.e. determining whether an object
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* allocation is visible outside ('escapes') its immediate method context.
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*/
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// A visitor for seeing all instructions escape analysis considers escaping.
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// Called with each user of the reference passed to 'VisitEscapes'. Return true
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// to continue iteration and false to stop.
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class EscapeVisitor {
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public:
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virtual ~EscapeVisitor() {}
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virtual bool Visit(HInstruction* escape) = 0;
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bool operator()(HInstruction* user) {
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return Visit(user);
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}
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};
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// An explicit EscapeVisitor for lambdas
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template <typename F>
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class LambdaEscapeVisitor final : public EscapeVisitor {
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public:
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explicit LambdaEscapeVisitor(F f) : func_(f) {}
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bool Visit(HInstruction* escape) override {
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return func_(escape);
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}
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private:
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F func_;
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};
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// This functor is used with the escape-checking functions. If the NoEscape
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// function returns true escape analysis will consider 'user' to not have
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// escaped 'reference'. This allows clients with additional information to
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// supplement the escape-analysis. If the NoEscape function returns false then
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// the normal escape-checking code will be used to determine whether or not
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// 'reference' escapes.
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class NoEscapeCheck {
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public:
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virtual ~NoEscapeCheck() {}
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virtual bool NoEscape(HInstruction* reference, HInstruction* user) = 0;
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bool operator()(HInstruction* ref, HInstruction* user) {
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return NoEscape(ref, user);
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}
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};
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// An explicit NoEscapeCheck for use with c++ lambdas.
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template <typename F>
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class LambdaNoEscapeCheck final : public NoEscapeCheck {
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public:
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explicit LambdaNoEscapeCheck(F f) : func_(f) {}
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bool NoEscape(HInstruction* ref, HInstruction* user) override {
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return func_(ref, user);
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}
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private:
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F func_;
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};
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/*
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* Performs escape analysis on the given instruction, typically a reference to an
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* allocation. The method assigns true to parameter 'is_singleton' if the reference
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* is the only name that can refer to its value during the lifetime of the method,
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* meaning that the reference is not aliased with something else, is not stored to
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* heap memory, and not passed to another method. In addition, the method assigns
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* true to parameter 'is_singleton_and_not_returned' if the reference is a singleton
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* and not returned to the caller and to parameter 'is_singleton_and_not_deopt_visible'
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* if the reference is a singleton and not used as an environment local of an
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* HDeoptimize instruction (clients of the final value must run after BCE to ensure
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* all such instructions have been introduced already).
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*
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* Note that being visible to a HDeoptimize instruction does not count for ordinary
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* escape analysis, since switching between compiled code and interpreted code keeps
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* non escaping references restricted to the lifetime of the method and the thread
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* executing it. This property only concerns optimizations that are interested in
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* escape analysis with respect to the *compiled* code (such as LSE).
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*
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* When set, the no_escape function is applied to any use of the allocation instruction
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* prior to any built-in escape analysis. This allows clients to define better escape
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* analysis in certain case-specific circumstances. If 'no_escape(reference, user)'
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* returns true, the user is assumed *not* to cause any escape right away. The return
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* value false means the client cannot provide a definite answer and built-in escape
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* analysis is applied to the user instead.
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*/
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void CalculateEscape(HInstruction* reference,
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NoEscapeCheck& no_escape,
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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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inline void CalculateEscape(HInstruction* reference,
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bool (*no_escape_fn)(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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LambdaNoEscapeCheck esc(no_escape_fn);
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LambdaNoEscapeCheck noop_esc([](HInstruction*, HInstruction*) { return false; });
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CalculateEscape(reference,
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no_escape_fn == nullptr ? static_cast<NoEscapeCheck&>(noop_esc) : esc,
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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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}
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/*
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* Performs escape analysis and visits each escape of the reference. Does not try to calculate any
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* overall information about the method. Escapes are calculated in the same way as CalculateEscape.
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*
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* The escape_visitor should return true to continue visiting, false otherwise.
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*/
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void VisitEscapes(HInstruction* reference, EscapeVisitor& escape_visitor);
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/*
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* Convenience method for testing the singleton and not returned properties at once.
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* Callers should be aware that this method invokes the full analysis at each call.
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*/
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bool DoesNotEscape(HInstruction* reference, NoEscapeCheck& no_escape);
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inline bool DoesNotEscape(HInstruction* reference,
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bool (*no_escape_fn)(HInstruction*, HInstruction*)) {
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LambdaNoEscapeCheck<typeof(no_escape_fn)> esc(no_escape_fn);
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return DoesNotEscape(reference, esc);
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}
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} // namespace art
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#endif // ART_COMPILER_OPTIMIZING_ESCAPE_H_
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