More precise break points and stepping when debugging...

src/assembler.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 100 matching lines @@
   // code which are of interest when making stack traces to pin-point the source
   // location of a stack frame as close as possible. The "statement position" is
   // collected at the beginning at each statement, and is used to indicate
   // possible break locations. kNoPosition is used to indicate an
   // invalid/uninitialized position value.
   static const int kNoPosition = -1;
 
   enum Mode {
     // Please note the order is important (see IsCodeTarget, IsGCRelocMode).
     CONSTRUCT_CALL,  // code target that is a call to a JavaScript constructor.
-    CODE_TARGET_CONTEXT,  // code target used for contextual loads.
-    DEBUG_BREAK,
-    CODE_TARGET,         // code target which is not any of the above.
+    CODE_TARGET_CONTEXT,  // Code target used for contextual loads.
+    DEBUG_BREAK,  // Code target for the debugger statement.
+    CODE_TARGET,  // Code target which is not any of the above.
     EMBEDDED_OBJECT,
 
     // Everything after runtime_entry (inclusive) is not GC'ed.
     RUNTIME_ENTRY,
     JS_RETURN,  // Marks start of the ExitJSFrame code.
     COMMENT,
     POSITION,  // See comment for kNoPosition above.
     STATEMENT_POSITION,  // See comment for kNoPosition above.
+    DEBUG_BREAK_SLOT,  // Additional code inserted for debug break slot.
     EXTERNAL_REFERENCE,  // The address of an external C++ function.
     INTERNAL_REFERENCE,  // An address inside the same function.
 
     // add more as needed
     // Pseudo-types
     NUMBER_OF_MODES,  // must be no greater than 14 - see RelocInfoWriter
     NONE,  // never recorded
     LAST_CODE_ENUM = CODE_TARGET,
     LAST_GCED_ENUM = EMBEDDED_OBJECT
   };
@@ skipping 25 matching lines @@
   }
   static inline bool IsStatementPosition(Mode mode) {
     return mode == STATEMENT_POSITION;
   }
   static inline bool IsExternalReference(Mode mode) {
     return mode == EXTERNAL_REFERENCE;
   }
   static inline bool IsInternalReference(Mode mode) {
     return mode == INTERNAL_REFERENCE;
   }
+  static inline bool IsDebugBreakSlot(Mode mode) {
+    return mode == DEBUG_BREAK_SLOT;
+  }
   static inline int ModeMask(Mode mode) { return 1 << mode; }
 
   // Accessors
   byte* pc() const  { return pc_; }
   void set_pc(byte* pc) { pc_ = pc; }
   Mode rmode() const {  return rmode_; }
   intptr_t data() const  { return data_; }
 
   // Apply a relocation by delta bytes
   INLINE(void apply(intptr_t delta));
@@ skipping 49 matching lines @@
   // Patch the code with some other code.
   void PatchCode(byte* instructions, int instruction_count);
 
   // Patch the code with a call.
   void PatchCodeWithCall(Address target, int guard_bytes);
 
   // Check whether this return sequence has been patched
   // with a call to the debugger.
   INLINE(bool IsPatchedReturnSequence());
 
+  // Check whether this debug break slot has been patched with a call to the
+  // debugger.
+  INLINE(bool IsPatchedDebugBreakSlotSequence());
+
 #ifdef ENABLE_DISASSEMBLER
   // Printing
   static const char* RelocModeName(Mode rmode);
   void Print();
 #endif  // ENABLE_DISASSEMBLER
 #ifdef DEBUG
   // Debugging
   void Verify();
 #endif
 
@@ skipping 300 matching lines @@
   unsigned int num_bits_set;
   for (num_bits_set = 0; x; x >>= 1) {
     num_bits_set += x & 1;
   }
   return num_bits_set;
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_ASSEMBLER_H_