Refactor BreakLocationIterator.

src/x64/debug-x64.cc

Index: src/x64/debug-x64.cc
diff --git a/src/x64/debug-x64.cc b/src/x64/debug-x64.cc
index c8f9456f75638501c74ba0d70b0ab62a25290cd9..ee2b5c526a449d74ed1fb30a9333aedfde2ab55d 100644
--- a/src/x64/debug-x64.cc
+++ b/src/x64/debug-x64.cc
@@ -14,58 +14,57 @@
 namespace v8 {
 namespace internal {
 
-bool BreakLocationIterator::IsDebugBreakAtReturn()  {
-  return Debug::IsDebugBreakAtReturn(rinfo());
-}
+// Patch the code at the current PC with a call to the target address.
+// Additional guard int3 instructions can be added if required.
+void PatchCodeWithCall(Address pc, Address target, int guard_bytes) {
+  int code_size = Assembler::kCallSequenceLength + guard_bytes;
 
+  // Create a code patcher.
+  CodePatcher patcher(pc, code_size);
 
-// Patch the JS frame exit code with a debug break call. See
-// CodeGenerator::VisitReturnStatement and VirtualFrame::Exit in codegen-x64.cc
-// for the precise return instructions sequence.
-void BreakLocationIterator::SetDebugBreakAtReturn()  {
-  DCHECK(Assembler::kJSReturnSequenceLength >= Assembler::kCallSequenceLength);
-  rinfo()->PatchCodeWithCall(
-      debug_info_->GetIsolate()->builtins()->Return_DebugBreak()->entry(),
-      Assembler::kJSReturnSequenceLength - Assembler::kCallSequenceLength);
-}
+// Add a label for checking the size of the code used for returning.
+#ifdef DEBUG
+  Label check_codesize;
+  patcher.masm()->bind(&check_codesize);
+#endif
 
+  // Patch the code.
+  patcher.masm()->movp(kScratchRegister, reinterpret_cast<void*>(target),
+                       Assembler::RelocInfoNone());
+  patcher.masm()->call(kScratchRegister);
 
-// Restore the JS frame exit code.
-void BreakLocationIterator::ClearDebugBreakAtReturn() {
-  rinfo()->PatchCode(original_rinfo()->pc(),
-                     Assembler::kJSReturnSequenceLength);
-}
+  // Check that the size of the code generated is as expected.
+  DCHECK_EQ(Assembler::kCallSequenceLength,
+            patcher.masm()->SizeOfCodeGeneratedSince(&check_codesize));
 
+  // Add the requested number of int3 instructions after the call.
+  for (int i = 0; i < guard_bytes; i++) {
+    patcher.masm()->int3();
+  }
 
-// A debug break in the frame exit code is identified by the JS frame exit code
-// having been patched with a call instruction.
-bool Debug::IsDebugBreakAtReturn(v8::internal::RelocInfo* rinfo) {
-  DCHECK(RelocInfo::IsJSReturn(rinfo->rmode()));
-  return rinfo->IsPatchedReturnSequence();
+  CpuFeatures::FlushICache(pc, code_size);
 }
 
 
-bool BreakLocationIterator::IsDebugBreakAtSlot() {
-  DCHECK(IsDebugBreakSlot());
-  // Check whether the debug break slot instructions have been patched.
-  return rinfo()->IsPatchedDebugBreakSlotSequence();
+// Patch the JS frame exit code with a debug break call. See
+// CodeGenerator::VisitReturnStatement and VirtualFrame::Exit in codegen-x64.cc
+// for the precise return instructions sequence.
+void BreakLocation::SetDebugBreakAtReturn() {
+  DCHECK(Assembler::kJSReturnSequenceLength >= Assembler::kCallSequenceLength);
+  PatchCodeWithCall(
+      pc(), debug_info_->GetIsolate()->builtins()->Return_DebugBreak()->entry(),
+      Assembler::kJSReturnSequenceLength - Assembler::kCallSequenceLength);
 }
 
 
-void BreakLocationIterator::SetDebugBreakAtSlot() {
+void BreakLocation::SetDebugBreakAtSlot() {
   DCHECK(IsDebugBreakSlot());
-  rinfo()->PatchCodeWithCall(
-      debug_info_->GetIsolate()->builtins()->Slot_DebugBreak()->entry(),
+  PatchCodeWithCall(
+      pc(), debug_info_->GetIsolate()->builtins()->Slot_DebugBreak()->entry(),
       Assembler::kDebugBreakSlotLength - Assembler::kCallSequenceLength);
 }
 
 
-void BreakLocationIterator::ClearDebugBreakAtSlot() {
-  DCHECK(IsDebugBreakSlot());
-  rinfo()->PatchCode(original_rinfo()->pc(), Assembler::kDebugBreakSlotLength);
-}
-
-
 #define __ ACCESS_MASM(masm)