More precise break points and stepping when debugging...

src/ia32/assembler-ia32-inl.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 34 matching lines @@
 
 Condition NegateCondition(Condition cc) {
   return static_cast<Condition>(cc ^ 1);
 }
 
 
 // The modes possibly affected by apply must be in kApplyMask.
 void RelocInfo::apply(intptr_t delta) {
   if (rmode_ == RUNTIME_ENTRY || IsCodeTarget(rmode_)) {
     int32_t* p = reinterpret_cast<int32_t*>(pc_);
-    *p -= delta;  // relocate entry
+    *p -= delta;  // Relocate entry.
   } else if (rmode_ == JS_RETURN && IsPatchedReturnSequence()) {
     // Special handling of js_return when a break point is set (call
     // instruction has been inserted).
     int32_t* p = reinterpret_cast<int32_t*>(pc_ + 1);
-    *p -= delta;  // relocate entry
+    *p -= delta;  // Relocate entry.
+  } else if (rmode_ == DEBUG_BREAK_SLOT && IsPatchedDebugBreakSlotSequence()) {
+    // Special handling of a debug break slot when a break point is set (call
+    // instruction has been inserted).
+    int32_t* p = reinterpret_cast<int32_t*>(pc_ + 1);
+    *p -= delta;  // Relocate entry.
   } else if (IsInternalReference(rmode_)) {
     // absolute code pointer inside code object moves with the code object.
     int32_t* p = reinterpret_cast<int32_t*>(pc_);
-    *p += delta;  // relocate entry
+    *p += delta;  // Relocate entry.
   }
 }
 
 
 Address RelocInfo::target_address() {
   ASSERT(IsCodeTarget(rmode_) || rmode_ == RUNTIME_ENTRY);
   return Assembler::target_address_at(pc_);
 }
 
 
@@ skipping 72 matching lines @@
   ASSERT(IsPatchedReturnSequence());
   *call_object_address() = target;
 }
 
 
 bool RelocInfo::IsPatchedReturnSequence() {
   return *pc_ == 0xE8;
 }
 
 
+bool RelocInfo::IsPatchedDebugBreakSlotSequence() {
+  return !Assembler::IsNop(pc());
+}
+
+
 void RelocInfo::Visit(ObjectVisitor* visitor) {
   RelocInfo::Mode mode = rmode();
   if (mode == RelocInfo::EMBEDDED_OBJECT) {
     visitor->VisitPointer(target_object_address());
   } else if (RelocInfo::IsCodeTarget(mode)) {
     visitor->VisitCodeTarget(this);
   } else if (mode == RelocInfo::EXTERNAL_REFERENCE) {
     visitor->VisitExternalReference(target_reference_address());
 #ifdef ENABLE_DEBUGGER_SUPPORT
   } else if (Debug::has_break_points() &&
-             RelocInfo::IsJSReturn(mode) &&
-             IsPatchedReturnSequence()) {
+             (RelocInfo::IsJSReturn(mode) &&
+              IsPatchedReturnSequence()) ||
+             (RelocInfo::IsDebugBreakSlot(mode) &&
+              IsPatchedDebugBreakSlotSequence())) {
     visitor->VisitDebugTarget(this);
 #endif
   } else if (mode == RelocInfo::RUNTIME_ENTRY) {
     visitor->VisitRuntimeEntry(this);
   }
 }
 
 
 Immediate::Immediate(int x)  {
   x_ = x;
@@ skipping 164 matching lines @@
 
 Operand::Operand(int32_t disp, RelocInfo::Mode rmode) {
   // [disp/r]
   set_modrm(0, ebp);
   set_dispr(disp, rmode);
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_IA32_ASSEMBLER_IA32_INL_H_