Remove deoptimization by patching the call stack.

src/safepoint-table.h

 // Copyright 2011 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_SAFEPOINT_TABLE_H_
 #define V8_SAFEPOINT_TABLE_H_
 
 #include "src/allocation.h"
 #include "src/heap/heap.h"
 #include "src/v8memory.h"
 #include "src/zone.h"
 
 namespace v8 {
 namespace internal {
 
 struct Register;
 
 class SafepointEntry BASE_EMBEDDED {
  public:
-  SafepointEntry() : info_(0), deoptimization_pc_(0), bits_(NULL) {}
+  SafepointEntry() : info_(0), bits_(NULL) {}
 
-  SafepointEntry(unsigned info, unsigned deoptimization_pc, uint8_t* bits)
-      : info_(info), deoptimization_pc_(deoptimization_pc), bits_(bits) {
+  SafepointEntry(unsigned info, uint8_t* bits) : info_(info), bits_(bits) {
     DCHECK(is_valid());
   }
 
   bool is_valid() const { return bits_ != NULL; }
 
   bool Equals(const SafepointEntry& other) const {
     return info_ == other.info_ && bits_ == other.bits_;
   }
 
   void Reset() {
     info_ = 0;
     bits_ = NULL;
   }
 
   int deoptimization_index() const {
     DCHECK(is_valid());
     return DeoptimizationIndexField::decode(info_);
   }
 
-  unsigned deoptimization_pc() const {
-    DCHECK(is_valid());
-    return deoptimization_pc_;
-  }
-
   static const int kArgumentsFieldBits = 3;
   static const int kSaveDoublesFieldBits = 1;
   static const int kDeoptIndexBits =
       32 - kArgumentsFieldBits - kSaveDoublesFieldBits;
   class DeoptimizationIndexField:
     public BitField<int, 0, kDeoptIndexBits> {};  // NOLINT
   class ArgumentsField:
     public BitField<unsigned,
                     kDeoptIndexBits,
                     kArgumentsFieldBits> {};  // NOLINT
@@ skipping 15 matching lines @@
   uint8_t* bits() {
     DCHECK(is_valid());
     return bits_;
   }
 
   bool HasRegisters() const;
   bool HasRegisterAt(int reg_index) const;
 
  private:
   unsigned info_;
-  unsigned deoptimization_pc_;
   uint8_t* bits_;
 };
 
 
 class SafepointTable BASE_EMBEDDED {
  public:
   explicit SafepointTable(Code* code);
 
   int size() const {
     return kHeaderSize +
-           (length_ * (kPcAndDeoptimizationInfoSize + entry_size_));
+           (length_ * (kPcAndDeoptimizationIndexSize + entry_size_));
   }
   unsigned length() const { return length_; }
   unsigned entry_size() const { return entry_size_; }
 
   unsigned GetPcOffset(unsigned index) const {
     DCHECK(index < length_);
     return Memory::uint32_at(GetPcOffsetLocation(index));
   }
 
-  unsigned GetDeoptimizationPcOffset(unsigned index) const {
-    DCHECK(index < length_);
-    return Memory::uint32_at(GetDeoptimizationPcLocation(index));
-  }
-
   SafepointEntry GetEntry(unsigned index) const {
     DCHECK(index < length_);
     unsigned info = Memory::uint32_at(GetInfoLocation(index));
-    unsigned deopt_pc = Memory::uint32_at(GetDeoptimizationPcLocation(index));
     uint8_t* bits = &Memory::uint8_at(entries_ + (index * entry_size_));
-    return SafepointEntry(info, deopt_pc, bits);
+    return SafepointEntry(info, bits);
   }
 
   // Returns the entry for the given pc.
   SafepointEntry FindEntry(Address pc) const;
 
   void PrintEntry(unsigned index, OStream& os) const;  // NOLINT
 
  private:
   static const uint8_t kNoRegisters = 0xFF;
 
   static const int kLengthOffset = 0;
   static const int kEntrySizeOffset = kLengthOffset + kIntSize;
   static const int kHeaderSize = kEntrySizeOffset + kIntSize;
 
   static const int kPcSize = kIntSize;
   static const int kDeoptimizationIndexSize = kIntSize;
-  static const int kDeoptimizationPcSize = kIntSize;
-  static const int kPcAndDeoptimizationInfoSize =
-      kPcSize + kDeoptimizationIndexSize + kDeoptimizationPcSize;
+  static const int kPcAndDeoptimizationIndexSize =
+      kPcSize + kDeoptimizationIndexSize;
 
   Address GetPcOffsetLocation(unsigned index) const {
     return pc_and_deoptimization_indexes_ +
-           (index * kPcAndDeoptimizationInfoSize);
+           (index * kPcAndDeoptimizationIndexSize);
   }
 
   Address GetInfoLocation(unsigned index) const {
     return GetPcOffsetLocation(index) + kPcSize;
   }
 
-  Address GetDeoptimizationPcLocation(unsigned index) const {
-    return GetInfoLocation(index) + kDeoptimizationIndexSize;
-  }
-
   static void PrintBits(OStream& os,  // NOLINT
                         uint8_t byte, int digits);
 
   DisallowHeapAllocation no_allocation_;
   Code* code_;
   unsigned length_;
   unsigned entry_size_;
 
   Address pc_and_deoptimization_indexes_;
   Address entries_;
@@ skipping 12 matching lines @@
     kWithRegisters = 1 << 0,
     kWithDoubles = 1 << 1,
     kWithRegistersAndDoubles = kWithRegisters | kWithDoubles
   } Kind;
 
   enum DeoptMode {
     kNoLazyDeopt,
     kLazyDeopt
   };
 
-  class Id {
-   private:
-    explicit Id(int id) : id_(id) {}
-
-    int id_;
-
-    friend class SafepointTableBuilder;
-    friend class Safepoint;
-  };
-
   static const int kNoDeoptimizationIndex =
       (1 << (SafepointEntry::kDeoptIndexBits)) - 1;
 
-  static const unsigned kNoDeoptimizationPc = ~0U;
-
   void DefinePointerSlot(int index, Zone* zone) { indexes_->Add(index, zone); }
   void DefinePointerRegister(Register reg, Zone* zone);
 
-  Id id() const { return Id(id_); }
-
  private:
-  Safepoint(int id, ZoneList<int>* indexes, ZoneList<int>* registers)
-      : id_(id), indexes_(indexes), registers_(registers) {}
-  int id_;
+  Safepoint(ZoneList<int>* indexes, ZoneList<int>* registers)
+      : indexes_(indexes), registers_(registers) {}
   ZoneList<int>* indexes_;
   ZoneList<int>* registers_;
 
   friend class SafepointTableBuilder;
 };
 
 
 class SafepointTableBuilder BASE_EMBEDDED {
  public:
   explicit SafepointTableBuilder(Zone* zone)
@@ skipping 13 matching lines @@
                             Safepoint::Kind kind,
                             int arguments,
                             Safepoint::DeoptMode mode);
 
   // Record deoptimization index for lazy deoptimization for the last
   // outstanding safepoints.
   void RecordLazyDeoptimizationIndex(int index);
   void BumpLastLazySafepointIndex() {
     last_lazy_safepoint_ = deopt_index_list_.length();
   }
-  void SetDeoptimizationPc(Safepoint::Id safepoint_id,
-                           unsigned deoptimization_pc) {
-    deoptimization_info_[safepoint_id.id_].deoptimization_pc =
-        deoptimization_pc;
-  }
 
   // Emit the safepoint table after the body. The number of bits per
   // entry must be enough to hold all the pointer indexes.
   void Emit(Assembler* assembler, int bits_per_entry);
 
 
  private:
   struct DeoptimizationInfo {
     unsigned pc;
     unsigned arguments;
     bool has_doubles;
-    unsigned deoptimization_pc;
   };
 
   uint32_t EncodeExceptPC(const DeoptimizationInfo& info, unsigned index);
 
   ZoneList<DeoptimizationInfo> deoptimization_info_;
   ZoneList<unsigned> deopt_index_list_;
   ZoneList<ZoneList<int>*> indexes_;
   ZoneList<ZoneList<int>*> registers_;
 
   unsigned offset_;
   bool emitted_;
   int last_lazy_safepoint_;
 
   Zone* zone_;
 
   DISALLOW_COPY_AND_ASSIGN(SafepointTableBuilder);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_SAFEPOINT_TABLE_H_