[arm64] Share constant pool entries in snapshot.

src/arm64/assembler-arm64.h

 // 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_ARM64_ASSEMBLER_ARM64_H_
 #define V8_ARM64_ASSEMBLER_ARM64_H_
 
 #include <deque>
 #include <list>
 #include <map>
@@ skipping 784 matching lines @@
   int64_t offset_;
   AddrMode addrmode_;
   Shift shift_;
   Extend extend_;
   unsigned shift_amount_;
 };
 
 
 class ConstPool {
  public:
-  explicit ConstPool(Assembler* assm)
-      : assm_(assm),
-        first_use_(-1),
-        shared_entries_count(0) {}
-  void RecordEntry(intptr_t data, RelocInfo::Mode mode);
-  int EntryCount() const {
-    return shared_entries_count + static_cast<int>(unique_entries_.size());
-  }
-  bool IsEmpty() const {
-    return shared_entries_.empty() && unique_entries_.empty();
-  }
+  explicit ConstPool(Assembler* assm) : assm_(assm), first_use_(-1) {}
+  // Returns true when we need to write RelocInfo and false when we do not.
+  bool RecordEntry(intptr_t data, RelocInfo::Mode mode);
+  int EntryCount() const { return static_cast<int>(entries_.size()); }
+  bool IsEmpty() const { return entries_.empty(); }
   // Distance in bytes between the current pc and the first instruction
   // using the pool. If there are no pending entries return kMaxInt.
   int DistanceToFirstUse();
   // Offset after which instructions using the pool will be out of range.
   int MaxPcOffset();
   // Maximum size the constant pool can be with current entries. It always
   // includes alignment padding and branch over.
   int WorstCaseSize();
   // Size in bytes of the literal pool *if* it is emitted at the current
   // pc. The size will include the branch over the pool if it was requested.
   int SizeIfEmittedAtCurrentPc(bool require_jump);
   // Emit the literal pool at the current pc with a branch over the pool if
   // requested.
   void Emit(bool require_jump);
   // Discard any pending pool entries.
   void Clear();
 
  private:
   bool CanBeShared(RelocInfo::Mode mode);
   void EmitMarker();
   void EmitGuard();
   void EmitEntries();
 
+  typedef std::map<uint64_t, int> SharedEntryMap;
+  // Adds a shared entry to entries_, using 'entry_map' to determine whether we
+  // already track this entry. Returns true if this is the first time we add
+  // this entry, false otherwise.
+  bool AddSharedEntry(SharedEntryMap& entry_map, uint64_t data, int offset);
+
   Assembler* assm_;
   // Keep track of the first instruction requiring a constant pool entry
   // since the previous constant pool was emitted.
   int first_use_;
-  // values, pc offset(s) of entries which can be shared.
-  std::multimap<uint64_t, int> shared_entries_;
-  // Number of distinct literal in shared entries.
-  int shared_entries_count;
-  // values, pc offset of entries which cannot be shared.
-  std::vector<std::pair<uint64_t, int> > unique_entries_;
+
+  // Map of data to index in entries_ for shared entries.
+  SharedEntryMap shared_entries_;
+
+  // Map of address of handle to index in entries_. We need to keep track of
+  // code targets separately from other shared entries, as they can be
+  // relocated.
+  SharedEntryMap handle_to_index_map_;
+
+  // Values, pc offset(s) of entries. Use a vector to preserve the order of
+  // insertion, as the serializer expects code target RelocInfo to point to
+  // constant pool addresses in an ascending order.
+  std::vector<std::pair<uint64_t, std::vector<int> > > entries_;
 };
 
 
 // -----------------------------------------------------------------------------
 // Assembler.
 
 class Assembler : public AssemblerBase {
  public:
   // Create an assembler. Instructions and relocation information are emitted
   // into a buffer, with the instructions starting from the beginning and the
@@ skipping 141 matching lines @@
 
   static constexpr int kPatchDebugBreakSlotAddressOffset = 0;
 
   // Number of instructions necessary to be able to later patch it to a call.
   static constexpr int kDebugBreakSlotInstructions = 5;
   static constexpr int kDebugBreakSlotLength =
       kDebugBreakSlotInstructions * kInstructionSize;
 
   // Prevent contant pool emission until EndBlockConstPool is called.
   // Call to this function can be nested but must be followed by an equal
-  // number of call to EndBlockConstpool.
+  // number of calls to EndBlockConstpool.
   void StartBlockConstPool();
 
   // Resume constant pool emission. Need to be called as many time as
   // StartBlockConstPool to have an effect.
   void EndBlockConstPool();
 
   bool is_const_pool_blocked() const;
   static bool IsConstantPoolAt(Instruction* instr);
   static int ConstantPoolSizeAt(Instruction* instr);
   // See Assembler::CheckConstPool for more info.
   void EmitPoolGuard();
 
   // Prevent veneer pool emission until EndBlockVeneerPool is called.
   // Call to this function can be nested but must be followed by an equal
-  // number of call to EndBlockConstpool.
+  // number of calls to EndBlockConstpool.
   void StartBlockVeneerPool();
 
   // Resume constant pool emission. Need to be called as many time as
   // StartBlockVeneerPool to have an effect.
   void EndBlockVeneerPool();
 
   bool is_veneer_pool_blocked() const {
     return veneer_pool_blocked_nesting_ > 0;
   }
 
@@ skipping 2140 matching lines @@
     ~BlockPoolsScope() {
       assem_->EndBlockPools();
     }
 
    private:
     Assembler* assem_;
 
     DISALLOW_IMPLICIT_CONSTRUCTORS(BlockPoolsScope);
   };
 
+  // Class for blocking sharing of code targets in constant pool.
+  class BlockCodeTargetSharingScope {
+   public:
+    explicit BlockCodeTargetSharingScope(Assembler* assem) : assem_(nullptr) {
+      Open(assem);
+    }
+    // This constructor does not initialize the scope. The user needs to
+    // explicitly call Open() before using it.
+    BlockCodeTargetSharingScope() : assem_(nullptr) {}
+    ~BlockCodeTargetSharingScope() { Close(); }
+    void Open(Assembler* assem) {
+      DCHECK_NULL(assem_);
+      DCHECK_NOT_NULL(assem);
+      assem_ = assem;
+      assem_->StartBlockCodeTargetSharing();
+    }
+
+   private:
+    void Close() {
+      if (assem_ != nullptr) {
+        assem_->EndBlockCodeTargetSharing();
+      }
+    }
+    Assembler* assem_;
+
+    DISALLOW_COPY_AND_ASSIGN(BlockCodeTargetSharingScope);
+  };
+
  protected:
   inline const Register& AppropriateZeroRegFor(const CPURegister& reg) const;
 
   void LoadStore(const CPURegister& rt,
                  const MemOperand& addr,
                  LoadStoreOp op);
   void LoadStorePair(const CPURegister& rt, const CPURegister& rt2,
                      const MemOperand& addr, LoadStorePairOp op);
   void LoadStoreStruct(const VRegister& vt, const MemOperand& addr,
                        NEONLoadStoreMultiStructOp op);
@@ skipping 65 matching lines @@
                                                const CPURegister& rt2);
   static inline LoadLiteralOp LoadLiteralOpFor(const CPURegister& rt);
 
   // Remove the specified branch from the unbound label link chain.
   // If available, a veneer for this label can be used for other branches in the
   // chain if the link chain cannot be fixed up without this branch.
   void RemoveBranchFromLabelLinkChain(Instruction* branch,
                                       Label* label,
                                       Instruction* label_veneer = NULL);
 
+  // Prevent sharing of code target constant pool entries until
+  // EndBlockCodeTargetSharing is called. Calls to this function can be nested
+  // but must be followed by an equal number of call to
+  // EndBlockCodeTargetSharing.
+  void StartBlockCodeTargetSharing() { ++code_target_sharing_blocked_nesting_; }
+
+  // Resume sharing of constant pool code target entries. Needs to be called
+  // as many times as StartBlockCodeTargetSharing to have an effect.
+  void EndBlockCodeTargetSharing() { --code_target_sharing_blocked_nesting_; }
+
  private:
   static uint32_t FPToImm8(double imm);
 
   // Instruction helpers.
   void MoveWide(const Register& rd,
                 uint64_t imm,
                 int shift,
                 MoveWideImmediateOp mov_op);
   void DataProcShiftedRegister(const Register& rd,
                                const Register& rn,
@@ skipping 161 matching lines @@
   // pool emission checks are interval based this value is an approximation.
   static constexpr int kApproxMaxPoolEntryCount = 512;
 
   // Emission of the constant pool may be blocked in some code sequences.
   int const_pool_blocked_nesting_;  // Block emission if this is not zero.
   int no_const_pool_before_;  // Block emission before this pc offset.
 
   // Emission of the veneer pools may be blocked in some code sequences.
   int veneer_pool_blocked_nesting_;  // Block emission if this is not zero.
 
+  // Sharing of code target entries may be blocked in some code sequences.
+  int code_target_sharing_blocked_nesting_;
+  bool IsCodeTargetSharingAllowed() const {
+    return code_target_sharing_blocked_nesting_ == 0;
+  }
+
   // Relocation info generation
   // Each relocation is encoded as a variable size value
   static constexpr int kMaxRelocSize = RelocInfoWriter::kMaxSize;
   RelocInfoWriter reloc_info_writer;
 
   // Internal reference positions, required for (potential) patching in
   // GrowBuffer(); contains only those internal references whose labels
   // are already bound.
   std::deque<int> internal_reference_positions_;
 
@@ skipping 165 matching lines @@
  public:
   explicit EnsureSpace(Assembler* assembler) {
     assembler->CheckBufferSpace();
   }
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_ARM64_ASSEMBLER_ARM64_H_