| // Copyright 2013 the V8 project authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef V8_CRANKSHAFT_HYDROGEN_ALIAS_ANALYSIS_H_ |
| #define V8_CRANKSHAFT_HYDROGEN_ALIAS_ANALYSIS_H_ |
| |
| #include "src/crankshaft/hydrogen.h" |
| |
| namespace v8 { |
| namespace internal { |
| |
| enum HAliasing { |
| kMustAlias, |
| kMayAlias, |
| kNoAlias |
| }; |
| |
| |
| // Defines the interface to alias analysis for the rest of the compiler. |
| // A simple implementation can use only local reasoning, but a more powerful |
| // analysis might employ points-to analysis. |
| class HAliasAnalyzer : public ZoneObject { |
| public: |
| // Simple alias analysis distinguishes allocations, parameters, |
| // and constants using only local reasoning. |
| HAliasing Query(HValue* a, HValue* b) { |
| // The same SSA value always references the same object. |
| if (a == b) return kMustAlias; |
| |
| if (a->IsAllocate() || a->IsInnerAllocatedObject()) { |
| // Two non-identical allocations can never be aliases. |
| if (b->IsAllocate()) return kNoAlias; |
| if (b->IsInnerAllocatedObject()) return kNoAlias; |
| // An allocation can never alias a parameter or a constant. |
| if (b->IsParameter()) return kNoAlias; |
| if (b->IsConstant()) return kNoAlias; |
| } |
| if (b->IsAllocate() || b->IsInnerAllocatedObject()) { |
| // An allocation can never alias a parameter or a constant. |
| if (a->IsParameter()) return kNoAlias; |
| if (a->IsConstant()) return kNoAlias; |
| } |
| |
| // Constant objects can be distinguished statically. |
| if (a->IsConstant()) { |
| return a->Equals(b) ? kMustAlias : kNoAlias; |
| } |
| return kMayAlias; |
| } |
| |
| // Checks whether the objects referred to by the given instructions may |
| // ever be aliases. Note that this is more conservative than checking |
| // {Query(a, b) == kMayAlias}, since this method considers kMustAlias |
| // objects to also be may-aliasing. |
| inline bool MayAlias(HValue* a, HValue* b) { |
| return Query(a, b) != kNoAlias; |
| } |
| |
| inline bool MustAlias(HValue* a, HValue* b) { |
| return Query(a, b) == kMustAlias; |
| } |
| |
| inline bool NoAlias(HValue* a, HValue* b) { |
| return Query(a, b) == kNoAlias; |
| } |
| }; |
| |
| |
| } // namespace internal |
| } // namespace v8 |
| |
| #endif // V8_CRANKSHAFT_HYDROGEN_ALIAS_ANALYSIS_H_ |