More precise break points and stepping when debugging...

src/arm/assembler-arm.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 611 matching lines @@
   // Call sequence is:
   //  mov  lr, pc
   //  ldr  pc, [pc, #...] @ call address
   //                      @ return address
   static const int kCallTargetAddressOffset = kInstrSize;
 #endif
 
   // Distance between start of patched return sequence and the emitted address
   // to jump to.
 #ifdef USE_BLX
-  // Return sequence is:
+  // Patched return sequence is:
   //  ldr  ip, [pc, #0]   @ emited address and start
   //  blx  ip
   static const int kPatchReturnSequenceAddressOffset =  0 * kInstrSize;
 #else
-  // Return sequence is:
+  // Patched return sequence is:
   //  mov  lr, pc         @ start of sequence
   //  ldr  pc, [pc, #-4]  @ emited address
   static const int kPatchReturnSequenceAddressOffset =  kInstrSize;
 #endif
 
+  // Distance between start of patched debug break slot and the emitted address
+  // to jump to.
+#ifdef USE_BLX
+  // Patched debug break slot code is:
+  //  ldr  ip, [pc, #0]   @ emited address and start
+  //  blx  ip
+  static const int kPatchDebugBreakSlotAddressOffset =  0 * kInstrSize;
+#else
+  // Patched debug break slot code is:
+  //  mov  lr, pc         @ start of sequence
+  //  ldr  pc, [pc, #-4]  @ emited address
+  static const int kPatchDebugBreakSlotAddressOffset =  kInstrSize;
+#endif
+
   // Difference between address of current opcode and value read from pc
   // register.
   static const int kPcLoadDelta = 8;
 
-  static const int kJSReturnSequenceLength = 4;
+  static const int kJSReturnSequenceInstructions = 4;
+  static const int kDebugBreakSlotInstructions = 3;
+  static const int kDebugBreakSlotLength =
+      kDebugBreakSlotInstructions * kInstrSize;
 
   // ---------------------------------------------------------------------------
   // Code generation
 
   // Insert the smallest number of nop instructions
   // possible to align the pc offset to a multiple
   // of m. m must be a power of 2 (>= 4).
   void Align(int m);
 
   // Branch instructions
@@ skipping 316 matching lines @@
 
   // Postpone the generation of the constant pool for the specified number of
   // instructions.
   void BlockConstPoolFor(int instructions);
 
   // Debugging
 
   // Mark address of the ExitJSFrame code.
   void RecordJSReturn();
 
+  // Mark address of a debug break slot.
+  void RecordDebugBreakSlot();
+
   // Record a comment relocation entry that can be used by a disassembler.
   // Use --debug_code to enable.
   void RecordComment(const char* msg);
 
   void RecordPosition(int pos);
   void RecordStatementPosition(int pos);
-  void WriteRecordedPositions();
+  bool WriteRecordedPositions();
 
   int pc_offset() const { return pc_ - buffer_; }
   int current_position() const { return current_position_; }
   int current_statement_position() const { return current_statement_position_; }
 
   bool can_peephole_optimize(int instructions) {
     if (!FLAG_peephole_optimization) return false;
     if (last_bound_pos_ > pc_offset() - instructions * kInstrSize) return false;
     return reloc_info_writer.last_pc() <= pc_ - instructions * kInstrSize;
   }
@@ skipping 150 matching lines @@
 
   friend class RegExpMacroAssemblerARM;
   friend class RelocInfo;
   friend class CodePatcher;
   friend class BlockConstPoolScope;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_ARM_ASSEMBLER_ARM_H_