56a486c322
- this avoids using relative include paths which are forbidden by the style guide - makes the code more readable since it's clear which header is meant - allows for starting to use checkdeps BUG=none R=jkummerow@chromium.org, danno@chromium.org LOG=n Review URL: https://codereview.chromium.org/304153016 git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21625 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
74 lines
2.3 KiB
C++
74 lines
2.3 KiB
C++
// Copyright 2013 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef V8_HYDROGEN_ALIAS_ANALYSIS_H_
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#define V8_HYDROGEN_ALIAS_ANALYSIS_H_
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#include "src/hydrogen.h"
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namespace v8 {
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namespace internal {
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enum HAliasing {
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kMustAlias,
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kMayAlias,
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kNoAlias
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};
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// Defines the interface to alias analysis for the rest of the compiler.
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// A simple implementation can use only local reasoning, but a more powerful
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// analysis might employ points-to analysis.
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class HAliasAnalyzer : public ZoneObject {
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public:
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// Simple alias analysis distinguishes allocations, parameters,
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// and constants using only local reasoning.
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HAliasing Query(HValue* a, HValue* b) {
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// The same SSA value always references the same object.
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if (a == b) return kMustAlias;
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if (a->IsAllocate() || a->IsInnerAllocatedObject()) {
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// Two non-identical allocations can never be aliases.
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if (b->IsAllocate()) return kNoAlias;
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if (b->IsInnerAllocatedObject()) return kNoAlias;
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// An allocation can never alias a parameter or a constant.
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if (b->IsParameter()) return kNoAlias;
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if (b->IsConstant()) return kNoAlias;
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}
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if (b->IsAllocate() || b->IsInnerAllocatedObject()) {
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// An allocation can never alias a parameter or a constant.
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if (a->IsParameter()) return kNoAlias;
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if (a->IsConstant()) return kNoAlias;
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}
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// Constant objects can be distinguished statically.
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if (a->IsConstant()) {
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// TODO(titzer): DataEquals() is more efficient, but that's protected.
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return a->Equals(b) ? kMustAlias : kNoAlias;
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}
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return kMayAlias;
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}
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// Checks whether the objects referred to by the given instructions may
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// ever be aliases. Note that this is more conservative than checking
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// {Query(a, b) == kMayAlias}, since this method considers kMustAlias
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// objects to also be may-aliasing.
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inline bool MayAlias(HValue* a, HValue* b) {
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return Query(a, b) != kNoAlias;
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}
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inline bool MustAlias(HValue* a, HValue* b) {
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return Query(a, b) == kMustAlias;
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}
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inline bool NoAlias(HValue* a, HValue* b) {
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return Query(a, b) == kNoAlias;
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}
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};
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} } // namespace v8::internal
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#endif // V8_HYDROGEN_ALIAS_ANALYSIS_H_
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