MIPS: Long branch implementation and trampoline improvement.

src/mips/assembler-mips.h

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // All Rights Reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 // - Redistributions of source code must retain the above copyright notice,
 // this list of conditions and the following disclaimer.
 //
@@ skipping 463 matching lines @@
   //
   // Label L;    // unbound label
   // j(cc, &L);  // forward branch to unbound label
   // bind(&L);   // bind label to the current pc
   // j(cc, &L);  // backward branch to bound label
   // bind(&L);   // illegal: a label may be bound only once
   //
   // Note: The same Label can be used for forward and backward branches
   // but it may be bound only once.
   void bind(Label* L);  // Binds an unbound label L to current code position.
+  // Determines if Label is bound and near enough so that branch instruction
+  // can be used to reach it, instead of jump instruction.
+  bool is_near(Label* L);
 
   // Returns the branch offset to the given label from the current code
   // position. Links the label to the current position if it is still unbound.
   // Manages the jump elimination optimization if the second parameter is true.
   int32_t branch_offset(Label* L, bool jump_elimination_allowed);
   int32_t shifted_branch_offset(Label* L, bool jump_elimination_allowed) {
     int32_t o = branch_offset(L, jump_elimination_allowed);
     ASSERT((o & 3) == 0);   // Assert the offset is aligned.
     return o >> 2;
   }
+  uint32_t jump_address(Label* L);
 
   // Puts a labels target address at the given position.
   // The high 8 bits are set to zero.
   void label_at_put(Label* L, int at_offset);
 
   // Read/Modify the code target address in the branch/call instruction at pc.
   static Address target_address_at(Address pc);
   static void set_target_address_at(Address pc, Address target);
 
   // This sets the branch destination (which gets loaded at the call address).
@@ skipping 284 matching lines @@
     ~BlockTrampolinePoolScope() {
       assem_->EndBlockTrampolinePool();
     }
 
    private:
     Assembler* assem_;
 
     DISALLOW_IMPLICIT_CONSTRUCTORS(BlockTrampolinePoolScope);
   };
 
+  // Class for postponing the assembly buffer growth. Typically used for
+  // sequences of instructions that must be emitted as a unit, before
+  // buffer growth (and relocation) can occur.
+  // This blocking scope is not nestable.
+  class BlockGrowBufferScope {
+   public:
+    explicit BlockGrowBufferScope(Assembler* assem) : assem_(assem) {
+      assem_->StartBlockGrowBuffer();
+    }
+    ~BlockGrowBufferScope() {
+      assem_->EndBlockGrowBuffer();
+    }
+
+    private:
+     Assembler* assem_;
+
+     DISALLOW_IMPLICIT_CONSTRUCTORS(BlockGrowBufferScope);
+  };
+
   // Debugging.
 
   // Mark address of the ExitJSFrame code.
   void RecordJSReturn();
 
   // Mark address of a debug break slot.
   void RecordDebugBreakSlot();
 
   // Record the AST id of the CallIC being compiled, so that it can be placed
   // in the relocation information.
   void RecordAstId(unsigned ast_id) { ast_id_for_reloc_info_ = ast_id; }
 
   // Record a comment relocation entry that can be used by a disassembler.
   // Use --code-comments to enable.
   void RecordComment(const char* msg);
 
+  static int RelocateInternalReference(byte* pc, intptr_t pc_delta);
+
   // Writes a single byte or word of data in the code stream.  Used for
   // inline tables, e.g., jump-tables.
   void db(uint8_t data);
   void dd(uint32_t data);
 
   int32_t pc_offset() const { return pc_ - buffer_; }
 
   PositionsRecorder* positions_recorder() { return &positions_recorder_; }
 
   // Postpone the generation of the trampoline pool for the specified number of
@@ skipping 16 matching lines @@
   Instr instr_at(int pos) { return *reinterpret_cast<Instr*>(buffer_ + pos); }
   void instr_at_put(int pos, Instr instr) {
     *reinterpret_cast<Instr*>(buffer_ + pos) = instr;
   }
 
   // Check if an instruction is a branch of some kind.
   static bool IsBranch(Instr instr);
   static bool IsBeq(Instr instr);
   static bool IsBne(Instr instr);
 
+  static bool IsJump(Instr instr);
+  static bool IsJ(Instr instr);
+  static bool IsLui(Instr instr);
+  static bool IsOri(Instr instr);
+
   static bool IsNop(Instr instr, unsigned int type);
   static bool IsPop(Instr instr);
   static bool IsPush(Instr instr);
   static bool IsLwRegFpOffset(Instr instr);
   static bool IsSwRegFpOffset(Instr instr);
   static bool IsLwRegFpNegOffset(Instr instr);
   static bool IsSwRegFpNegOffset(Instr instr);
 
   static Register GetRtReg(Instr instr);
   static Register GetRsReg(Instr instr);
   static Register GetRdReg(Instr instr);
 
   static uint32_t GetRt(Instr instr);
   static uint32_t GetRtField(Instr instr);
   static uint32_t GetRs(Instr instr);
   static uint32_t GetRsField(Instr instr);
   static uint32_t GetRd(Instr instr);
   static uint32_t GetRdField(Instr instr);
   static uint32_t GetSa(Instr instr);
   static uint32_t GetSaField(Instr instr);
   static uint32_t GetOpcodeField(Instr instr);
+  static uint32_t GetFunction(Instr instr);
+  static uint32_t GetFunctionField(Instr instr);
   static uint32_t GetImmediate16(Instr instr);
   static uint32_t GetLabelConst(Instr instr);
 
   static int32_t GetBranchOffset(Instr instr);
   static bool IsLw(Instr instr);
   static int16_t GetLwOffset(Instr instr);
   static Instr SetLwOffset(Instr instr, int16_t offset);
 
   static bool IsSw(Instr instr);
   static Instr SetSwOffset(Instr instr, int16_t offset);
   static bool IsAddImmediate(Instr instr);
   static Instr SetAddImmediateOffset(Instr instr, int16_t offset);
 
   static bool IsAndImmediate(Instr instr);
 
-  void CheckTrampolinePool(bool force_emit = false);
+  void CheckTrampolinePool();
 
  protected:
   // Relocation for a type-recording IC has the AST id added to it.  This
   // member variable is a way to pass the information from the call site to
   // the relocation info.
   unsigned ast_id_for_reloc_info_;
 
   bool emit_debug_code() const { return emit_debug_code_; }
 
   int32_t buffer_space() const { return reloc_info_writer.pos() - pc_; }
@@ skipping 12 matching lines @@
 
   // Block the emission of the trampoline pool before pc_offset.
   void BlockTrampolinePoolBefore(int pc_offset) {
     if (no_trampoline_pool_before_ < pc_offset)
       no_trampoline_pool_before_ = pc_offset;
   }
 
   void StartBlockTrampolinePool() {
     trampoline_pool_blocked_nesting_++;
   }
+
   void EndBlockTrampolinePool() {
     trampoline_pool_blocked_nesting_--;
   }
 
   bool is_trampoline_pool_blocked() const {
     return trampoline_pool_blocked_nesting_ > 0;
   }
 
   bool has_exception() const {
     return internal_trampoline_exception_;
   }
 
+  bool is_trampoline_emitted() const {
+    return trampoline_emitted_;
+  }
+
+  // Temporarily block automatic assembly buffer growth.
+  void StartBlockGrowBuffer() {
+    ASSERT(!block_buffer_growth_);
+    block_buffer_growth_ = true;
+  }
+
+  void EndBlockGrowBuffer() {
+    ASSERT(block_buffer_growth_);
+    block_buffer_growth_ = false;
+  }
+
+  bool is_buffer_growth_blocked() const {
+    return block_buffer_growth_;
+  }
+
  private:
   // Code buffer:
   // The buffer into which code and relocation info are generated.
   byte* buffer_;
   int buffer_size_;
   // True if the assembler owns the buffer, false if buffer is external.
   bool own_buffer_;
 
   // Buffer size and constant pool distance are checked together at regular
   // intervals of kBufferCheckInterval emitted bytes.
@@ skipping 16 matching lines @@
 
   int next_buffer_check_;  // pc offset of next buffer check.
 
   // Emission of the trampoline pool may be blocked in some code sequences.
   int trampoline_pool_blocked_nesting_;  // Block emission if this is not zero.
   int no_trampoline_pool_before_;  // Block emission before this pc offset.
 
   // Keep track of the last emitted pool to guarantee a maximal distance.
   int last_trampoline_pool_end_;  // pc offset of the end of the last pool.
 
+  // Automatic growth of the assembly buffer may be blocked for some sequences.
+  bool block_buffer_growth_;  // Block growth when true.
+
   // Relocation information generation.
   // Each relocation is encoded as a variable size value.
   static const int kMaxRelocSize = RelocInfoWriter::kMaxSize;
   RelocInfoWriter reloc_info_writer;
 
   // The bound position, before this we cannot do instruction elimination.
   int last_bound_pos_;
 
   // Code emission.
   inline void CheckBuffer();
@@ skipping 60 matching lines @@
 
   void GenInstrJump(Opcode opcode,
                      uint32_t address);
 
   // Helpers.
   void LoadRegPlusOffsetToAt(const MemOperand& src);
 
   // Labels.
   void print(Label* L);
   void bind_to(Label* L, int pos);
-  void link_to(Label* L, Label* appendix);
   void next(Label* L);
 
   // One trampoline consists of:
   // - space for trampoline slots,
   // - space for labels.
   //
   // Space for trampoline slots is equal to slot_count * 2 * kInstrSize.
   // Space for trampoline slots preceeds space for labels. Each label is of one
   // instruction size, so total amount for labels is equal to
   // label_count *  kInstrSize.
   class Trampoline {
    public:
-    Trampoline(int start, int slot_count, int label_count) {
+    Trampoline() {
+      start_ = 0;
+      next_slot_ = 0;
+      free_slot_count_ = 0;
+      end_ = 0;
+    }
+    Trampoline(int start, int slot_count) {
       start_ = start;
       next_slot_ = start;
       free_slot_count_ = slot_count;
-      next_label_ = start + slot_count * 2 * kInstrSize;
-      free_label_count_ = label_count;
-      end_ = next_label_ + (label_count - 1) * kInstrSize;
+      end_ = start + slot_count * kTrampolineSlotsSize;
     }
     int start() {
       return start_;
     }
     int end() {
       return end_;
     }
     int take_slot() {
       int trampoline_slot = kInvalidSlotPos;
       if (free_slot_count_ <= 0) {
         // We have run out of space on trampolines.
         // Make sure we fail in debug mode, so we become aware of each case
         // when this happens.
         ASSERT(0);
         // Internal exception will be caught.
       } else {
         trampoline_slot = next_slot_;
         free_slot_count_--;
-        next_slot_ += 2*kInstrSize;
+        next_slot_ += kTrampolineSlotsSize;
       }
       return trampoline_slot;
     }
-    int take_label() {
-      int label_pos = next_label_;
-      ASSERT(free_label_count_ > 0);
-      free_label_count_--;
-      next_label_ += kInstrSize;
-      return label_pos;
-    }
-
    private:
     int start_;
     int end_;
     int next_slot_;
     int free_slot_count_;
-    int next_label_;
-    int free_label_count_;
   };
 
-  int32_t get_label_entry(int32_t pos, bool next_pool = true);
-  int32_t get_trampoline_entry(int32_t pos, bool next_pool = true);
-
-  static const int kSlotsPerTrampoline = 2304;
-  static const int kLabelsPerTrampoline = 8;
-  static const int kTrampolineInst =
-      2 * kSlotsPerTrampoline + kLabelsPerTrampoline;
-  static const int kTrampolineSize = kTrampolineInst * kInstrSize;
+  int32_t get_trampoline_entry(int32_t pos);
+  int unbound_labels_count_;
+  // If trampoline is emitted, generated code is becoming large. As this is
+  // already a slow case which can possibly break our code generation for the
+  // extreme case, we use this information to trigger different mode of
+  // branch instruction generation, where we use jump instructions rather
+  // than regular branch instructions.
+  bool trampoline_emitted_;
+  static const int kTrampolineSlotsSize = 4 * kInstrSize;
   static const int kMaxBranchOffset = (1 << (18 - 1)) - 1;
-  static const int kMaxDistBetweenPools =
-      kMaxBranchOffset - 2 * kTrampolineSize;
   static const int kInvalidSlotPos = -1;
 
-  List<Trampoline> trampolines_;
+  Trampoline trampoline_;
   bool internal_trampoline_exception_;
 
   friend class RegExpMacroAssemblerMIPS;
   friend class RelocInfo;
   friend class CodePatcher;
   friend class BlockTrampolinePoolScope;
 
   PositionsRecorder positions_recorder_;
   bool emit_debug_code_;
   friend class PositionsRecorder;
   friend class EnsureSpace;
 };
 
 
 class EnsureSpace BASE_EMBEDDED {
  public:
   explicit EnsureSpace(Assembler* assembler) {
     assembler->CheckBuffer();
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_ARM_ASSEMBLER_MIPS_H_