[debugger] do not predict step in target for liveedit.

R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/1491743005

Cr-Commit-Position: refs/heads/master@{#32553}

src/arm/macro-assembler-arm.h

@@ -652,6 +652,10 @@ class MacroAssembler: public Assembler {
                           const ParameterCount& actual, InvokeFlag flag,
                           const CallWrapper& call_wrapper);
 
+  void FloodFunctionIfStepping(Register fun, Register new_target,
+                               const ParameterCount& expected,
+                               const ParameterCount& actual);
+
   // Invoke the JavaScript function in the given register. Changes the
   // current context to the context in the function before invoking.
   void InvokeFunction(Register function,
@@ -1454,10 +1458,6 @@ class MacroAssembler: public Assembler {
                       InvokeFlag flag,
                       const CallWrapper& call_wrapper);
 
-  void FloodFunctionIfStepping(Register fun, Register new_target,
-                               const ParameterCount& expected,
-                               const ParameterCount& actual);
-
   void InitializeNewString(Register string,
                            Register length,
                            Heap::RootListIndex map_index,

src/assembler.cc

@@ -1417,14 +1417,6 @@ ExternalReference ExternalReference::debug_after_break_target_address(
 }
 
 
-ExternalReference
-    ExternalReference::debug_restarter_frame_function_pointer_address(
-        Isolate* isolate) {
-  return ExternalReference(
-      isolate->debug()->restarter_frame_function_pointer_address());
-}
-
-
 ExternalReference ExternalReference::virtual_handler_register(
     Isolate* isolate) {
   return ExternalReference(isolate->virtual_handler_register_address());

src/assembler.h

@@ -976,8 +976,6 @@ class ExternalReference BASE_EMBEDDED {
 
   static ExternalReference debug_is_active_address(Isolate* isolate);
   static ExternalReference debug_after_break_target_address(Isolate* isolate);
-  static ExternalReference debug_restarter_frame_function_pointer_address(
-      Isolate* isolate);
 
   static ExternalReference is_profiling_address(Isolate* isolate);
   static ExternalReference invoke_function_callback(Isolate* isolate);

src/builtins.cc

@@ -2204,11 +2204,6 @@ static void Generate_Slot_DebugBreak(MacroAssembler* masm) {
 }
 
 
-static void Generate_PlainReturn_LiveEdit(MacroAssembler* masm) {
-  DebugCodegen::GeneratePlainReturnLiveEdit(masm);
-}
-
-
 static void Generate_FrameDropper_LiveEdit(MacroAssembler* masm) {
   DebugCodegen::GenerateFrameDropperLiveEdit(masm);
 }

src/builtins.h

@@ -196,7 +196,6 @@ inline bool operator&(BuiltinExtraArguments lhs, BuiltinExtraArguments rhs) {
 #define BUILTIN_LIST_DEBUG_A(V)                                 \
   V(Return_DebugBreak, BUILTIN, DEBUG_STUB, kNoExtraICState)    \
   V(Slot_DebugBreak, BUILTIN, DEBUG_STUB, kNoExtraICState)      \
-  V(PlainReturn_LiveEdit, BUILTIN, DEBUG_STUB, kNoExtraICState) \
   V(FrameDropper_LiveEdit, BUILTIN, DEBUG_STUB, kNoExtraICState)
 
 

src/debug/arm/debug-arm.cc

@@ -113,23 +113,14 @@ void DebugCodegen::GenerateDebugBreakStub(MacroAssembler* masm,
 }
 
 
-void DebugCodegen::GeneratePlainReturnLiveEdit(MacroAssembler* masm) {
-  __ Ret();
-}
-
-
 void DebugCodegen::GenerateFrameDropperLiveEdit(MacroAssembler* masm) {
-  ExternalReference restarter_frame_function_slot =
-      ExternalReference::debug_restarter_frame_function_pointer_address(
-          masm->isolate());
-  __ mov(ip, Operand(restarter_frame_function_slot));
-  __ mov(r1, Operand::Zero());
-  __ str(r1, MemOperand(ip, 0));
-
   // Load the function pointer off of our current stack frame.
   __ ldr(r1, MemOperand(fp,
          StandardFrameConstants::kConstantPoolOffset - kPointerSize));
 
+  ParameterCount dummy(0);
+  __ FloodFunctionIfStepping(r1, no_reg, dummy, dummy);
+
   // Pop return address, frame and constant pool pointer (if
   // FLAG_enable_embedded_constant_pool).
   __ LeaveFrame(StackFrame::INTERNAL);

src/debug/arm64/debug-arm64.cc

@@ -124,26 +124,20 @@ void DebugCodegen::GenerateDebugBreakStub(MacroAssembler* masm,
 }
 
 
-void DebugCodegen::GeneratePlainReturnLiveEdit(MacroAssembler* masm) {
-  __ Ret();
-}
-
-
 void DebugCodegen::GenerateFrameDropperLiveEdit(MacroAssembler* masm) {
-  ExternalReference restarter_frame_function_slot =
-      ExternalReference::debug_restarter_frame_function_pointer_address(
-          masm->isolate());
-  UseScratchRegisterScope temps(masm);
-  Register scratch = temps.AcquireX();
-
-  __ Mov(scratch, restarter_frame_function_slot);
-  __ Str(xzr, MemOperand(scratch));
-
   // We do not know our frame height, but set sp based on fp.
   __ Sub(masm->StackPointer(), fp, kPointerSize);
   __ AssertStackConsistency();
 
-  __ Pop(x1, fp, lr);  // Function, Frame, Return address.
+  __ Pop(x1);  // Function.
+
+  ParameterCount dummy(0);
+  __ FloodFunctionIfStepping(x1, no_reg, dummy, dummy);
+
+  __ Pop(fp, lr);  // Frame, Return address.
+
+  UseScratchRegisterScope temps(masm);
+  Register scratch = temps.AcquireX();
 
   // Load context from the function.
   __ Ldr(cp, FieldMemOperand(x1, JSFunction::kContextOffset));

src/debug/debug.cc

@@ -336,7 +336,6 @@ void Debug::ThreadInit() {
   // TODO(isolates): frames_are_dropped_?
   base::NoBarrier_Store(&thread_local_.current_debug_scope_,
                         static_cast<base::AtomicWord>(0));
-  thread_local_.restarter_frame_function_pointer_ = NULL;
 }
 
 
@@ -931,17 +930,6 @@ void Debug::PrepareStep(StepAction step_action,
     return;
   }
 
-  STATIC_ASSERT(StepFrame > StepIn);
-  if (step_action >= StepIn) {
-    // If there's restarter frame on top of the stack, just get the pointer
-    // to function which is going to be restarted.
-    if (thread_local_.restarter_frame_function_pointer_ != NULL) {
-      Handle<JSFunction> restarted_function(
-          JSFunction::cast(*thread_local_.restarter_frame_function_pointer_));
-      FloodWithOneShot(restarted_function);
-    }
-  }
-
   // Fill the current function with one-shot break points even for step in on
   // a call target as the function called might be a native function for
   // which step in will not stop. It also prepares for stepping in
@@ -1522,14 +1510,11 @@ bool Debug::IsBreakAtReturn(JavaScriptFrame* frame) {
 
 
 void Debug::FramesHaveBeenDropped(StackFrame::Id new_break_frame_id,
-                                  LiveEdit::FrameDropMode mode,
-                                  Object** restarter_frame_function_pointer) {
+                                  LiveEdit::FrameDropMode mode) {
   if (mode != LiveEdit::CURRENTLY_SET_MODE) {
     thread_local_.frame_drop_mode_ = mode;
   }
   thread_local_.break_frame_id_ = new_break_frame_id;
-  thread_local_.restarter_frame_function_pointer_ =
-      restarter_frame_function_pointer;
 }
 
 

src/debug/debug.h

@@ -455,8 +455,7 @@ class Debug {
 
   // Support for LiveEdit
   void FramesHaveBeenDropped(StackFrame::Id new_break_frame_id,
-                             LiveEdit::FrameDropMode mode,
-                             Object** restarter_frame_function_pointer);
+                             LiveEdit::FrameDropMode mode);
 
   // Threading support.
   char* ArchiveDebug(char* to);
@@ -503,11 +502,6 @@ class Debug {
     return reinterpret_cast<Address>(&after_break_target_);
   }
 
-  Address restarter_frame_function_pointer_address() {
-    Object*** address = &thread_local_.restarter_frame_function_pointer_;
-    return reinterpret_cast<Address>(address);
-  }
-
   Address step_in_enabled_address() {
     return reinterpret_cast<Address>(&thread_local_.step_in_enabled_);
   }
@@ -656,11 +650,6 @@ class Debug {
     // Stores the way how LiveEdit has patched the stack. It is used when
     // debugger returns control back to user script.
     LiveEdit::FrameDropMode frame_drop_mode_;
-
-    // When restarter frame is on stack, stores the address
-    // of the pointer to function being restarted. Otherwise (most of the time)
-    // stores NULL. This pointer is used with 'step in' implementation.
-    Object** restarter_frame_function_pointer_;
   };
 
   // Storage location for registers when handling debug break calls
@@ -757,8 +746,6 @@ class DebugCodegen : public AllStatic {
   static void GenerateDebugBreakStub(MacroAssembler* masm,
                                      DebugBreakCallHelperMode mode);
 
-  static void GeneratePlainReturnLiveEdit(MacroAssembler* masm);
-
   // FrameDropper is a code replacement for a JavaScript frame with possibly
   // several frames above.
   // There is no calling conventions here, because it never actually gets

src/debug/ia32/debug-ia32.cc

@@ -105,21 +105,15 @@ void DebugCodegen::GenerateDebugBreakStub(MacroAssembler* masm,
 }
 
 
-void DebugCodegen::GeneratePlainReturnLiveEdit(MacroAssembler* masm) {
-  masm->ret(0);
-}
-
-
 void DebugCodegen::GenerateFrameDropperLiveEdit(MacroAssembler* masm) {
-  ExternalReference restarter_frame_function_slot =
-      ExternalReference::debug_restarter_frame_function_pointer_address(
-          masm->isolate());
-  __ mov(Operand::StaticVariable(restarter_frame_function_slot), Immediate(0));
-
   // We do not know our frame height, but set esp based on ebp.
   __ lea(esp, Operand(ebp, -1 * kPointerSize));
 
   __ pop(edi);  // Function.
+
+  ParameterCount dummy(0);
+  __ FloodFunctionIfStepping(edi, no_reg, dummy, dummy);
+
   __ pop(ebp);
 
   // Load context from the function.

src/debug/liveedit.cc

@@ -811,10 +811,6 @@ bool LiveEdit::SetAfterBreakTarget(Debug* debug) {
   switch (debug->thread_local_.frame_drop_mode_) {
     case FRAMES_UNTOUCHED:
       return false;
-    case FRAME_DROPPED_IN_IC_CALL:
-      // We must have been calling IC stub. Do not go there anymore.
-      code = isolate->builtins()->builtin(Builtins::kPlainReturn_LiveEdit);
-      break;
     case FRAME_DROPPED_IN_DEBUG_SLOT_CALL:
       // Debug break slot stub does not return normally, instead it manually
       // cleans the stack and jumps. We should patch the jump address.
@@ -1491,17 +1487,13 @@ static bool FixTryCatchHandler(StackFrame* top_frame,
 //  a. successful work of frame dropper code which eventually gets control,
 //  b. being compatible with regular stack structure for various stack
 //     iterators.
-// Returns address of stack allocated pointer to restarted function,
-// the value that is called 'restarter_frame_function_pointer'. The value
-// at this address (possibly updated by GC) may be used later when preparing
-// 'step in' operation.
 // Frame structure (conforms InternalFrame structure):
 //   -- code
 //   -- SMI maker
 //   -- function (slot is called "context")
 //   -- frame base
-static Object** SetUpFrameDropperFrame(StackFrame* bottom_js_frame,
-                                       Handle<Code> code) {
+static void SetUpFrameDropperFrame(StackFrame* bottom_js_frame,
+                                   Handle<Code> code) {
   DCHECK(bottom_js_frame->is_java_script());
 
   Address fp = bottom_js_frame->fp();
@@ -1513,9 +1505,6 @@ static Object** SetUpFrameDropperFrame(StackFrame* bottom_js_frame,
   Memory::Object_at(fp + InternalFrameConstants::kCodeOffset) = *code;
   Memory::Object_at(fp + StandardFrameConstants::kMarkerOffset) =
       Smi::FromInt(StackFrame::INTERNAL);
-
-  return reinterpret_cast<Object**>(&Memory::Object_at(
-      fp + StandardFrameConstants::kContextOffset));
 }
 
 
@@ -1523,11 +1512,9 @@ static Object** SetUpFrameDropperFrame(StackFrame* bottom_js_frame,
 // frames in range. Anyway the bottom frame is restarted rather than dropped,
 // and therefore has to be a JavaScript frame.
 // Returns error message or NULL.
-static const char* DropFrames(Vector<StackFrame*> frames,
-                              int top_frame_index,
+static const char* DropFrames(Vector<StackFrame*> frames, int top_frame_index,
                               int bottom_js_frame_index,
-                              LiveEdit::FrameDropMode* mode,
-                              Object*** restarter_frame_function_pointer) {
+                              LiveEdit::FrameDropMode* mode) {
   if (!LiveEdit::kFrameDropperSupported) {
     return "Stack manipulations are not supported in this architecture.";
   }
@@ -1542,12 +1529,8 @@ static const char* DropFrames(Vector<StackFrame*> frames,
   Isolate* isolate = bottom_js_frame->isolate();
   Code* pre_top_frame_code = pre_top_frame->LookupCode();
   bool frame_has_padding = true;
-  if (pre_top_frame_code->is_inline_cache_stub() &&
-      pre_top_frame_code->is_debug_stub()) {
-    // OK, we can drop inline cache calls.
-    *mode = LiveEdit::FRAME_DROPPED_IN_IC_CALL;
-  } else if (pre_top_frame_code ==
-             isolate->builtins()->builtin(Builtins::kSlot_DebugBreak)) {
+  if (pre_top_frame_code ==
+      isolate->builtins()->builtin(Builtins::kSlot_DebugBreak)) {
     // OK, we can drop debug break slot.
     *mode = LiveEdit::FRAME_DROPPED_IN_DEBUG_SLOT_CALL;
   } else if (pre_top_frame_code ==
@@ -1641,10 +1624,7 @@ static const char* DropFrames(Vector<StackFrame*> frames,
   *top_frame_pc_address = code->entry();
   pre_top_frame->SetCallerFp(bottom_js_frame->fp());
 
-  *restarter_frame_function_pointer =
-      SetUpFrameDropperFrame(bottom_js_frame, code);
-
-  DCHECK((**restarter_frame_function_pointer)->IsJSFunction());
+  SetUpFrameDropperFrame(bottom_js_frame, code);
 
   for (Address a = unused_stack_top;
       a < unused_stack_bottom;
@@ -1759,10 +1739,8 @@ static const char* DropActivationsInActiveThreadImpl(Isolate* isolate,
   }
 
   LiveEdit::FrameDropMode drop_mode = LiveEdit::FRAMES_UNTOUCHED;
-  Object** restarter_frame_function_pointer = NULL;
-  const char* error_message = DropFrames(frames, top_frame_index,
-                                         bottom_js_frame_index, &drop_mode,
-                                         &restarter_frame_function_pointer);
+  const char* error_message =
+      DropFrames(frames, top_frame_index, bottom_js_frame_index, &drop_mode);
 
   if (error_message != NULL) {
     return error_message;
@@ -1776,8 +1754,7 @@ static const char* DropActivationsInActiveThreadImpl(Isolate* isolate,
       break;
     }
   }
-  debug->FramesHaveBeenDropped(
-      new_id, drop_mode, restarter_frame_function_pointer);
+  debug->FramesHaveBeenDropped(new_id, drop_mode);
   return NULL;
 }
 

src/debug/liveedit.h

@@ -61,8 +61,6 @@ class LiveEdit : AllStatic {
   enum FrameDropMode {
     // No frame has been dropped.
     FRAMES_UNTOUCHED,
-    // The top JS frame had been calling IC stub. IC stub mustn't be called now.
-    FRAME_DROPPED_IN_IC_CALL,
     // The top JS frame had been calling debug break slot stub. Patch the
     // address this stub jumps to in the end.
     FRAME_DROPPED_IN_DEBUG_SLOT_CALL,

src/debug/mips/debug-mips.cc

@@ -108,22 +108,16 @@ void DebugCodegen::GenerateDebugBreakStub(MacroAssembler* masm,
 }
 
 
-void DebugCodegen::GeneratePlainReturnLiveEdit(MacroAssembler* masm) {
-  __ Ret();
-}
-
-
 void DebugCodegen::GenerateFrameDropperLiveEdit(MacroAssembler* masm) {
-  ExternalReference restarter_frame_function_slot =
-      ExternalReference::debug_restarter_frame_function_pointer_address(
-          masm->isolate());
-  __ li(at, Operand(restarter_frame_function_slot));
-  __ sw(zero_reg, MemOperand(at, 0));
-
   // We do not know our frame height, but set sp based on fp.
   __ Subu(sp, fp, Operand(kPointerSize));
 
-  __ Pop(ra, fp, a1);  // Return address, Frame, Function.
+  __ Pop(a1);  // Function.
+
+  ParameterCount dummy(0);
+  __ FloodFunctionIfStepping(a1, no_reg, dummy, dummy);
+
+  __ Pop(ra, fp);  // Return address, Frame.
 
   // Load context from the function.
   __ lw(cp, FieldMemOperand(a1, JSFunction::kContextOffset));

src/debug/mips64/debug-mips64.cc

@@ -110,22 +110,16 @@ void DebugCodegen::GenerateDebugBreakStub(MacroAssembler* masm,
 }
 
 
-void DebugCodegen::GeneratePlainReturnLiveEdit(MacroAssembler* masm) {
-  __ Ret();
-}
-
-
 void DebugCodegen::GenerateFrameDropperLiveEdit(MacroAssembler* masm) {
-  ExternalReference restarter_frame_function_slot =
-      ExternalReference::debug_restarter_frame_function_pointer_address(
-          masm->isolate());
-  __ li(at, Operand(restarter_frame_function_slot));
-  __ sw(zero_reg, MemOperand(at, 0));
-
   // We do not know our frame height, but set sp based on fp.
   __ Dsubu(sp, fp, Operand(kPointerSize));
 
-  __ Pop(ra, fp, a1);  // Return address, Frame, Function.
+  __ Pop(a1);  // Function.
+
+  ParameterCount dummy(0);
+  __ FloodFunctionIfStepping(a1, no_reg, dummy, dummy);
+
+  __ Pop(ra, fp);  // Return address, Frame.
 
   // Load context from the function.
   __ ld(cp, FieldMemOperand(a1, JSFunction::kContextOffset));

src/debug/x64/debug-x64.cc

@@ -106,22 +106,15 @@ void DebugCodegen::GenerateDebugBreakStub(MacroAssembler* masm,
 }
 
 
-void DebugCodegen::GeneratePlainReturnLiveEdit(MacroAssembler* masm) {
-  masm->ret(0);
-}
-
-
 void DebugCodegen::GenerateFrameDropperLiveEdit(MacroAssembler* masm) {
-  ExternalReference restarter_frame_function_slot =
-      ExternalReference::debug_restarter_frame_function_pointer_address(
-          masm->isolate());
-  __ Move(rax, restarter_frame_function_slot);
-  __ movp(Operand(rax, 0), Immediate(0));
-
   // We do not know our frame height, but set rsp based on rbp.
   __ leap(rsp, Operand(rbp, -1 * kPointerSize));
 
   __ Pop(rdi);  // Function.
+
+  ParameterCount dummy(0);
+  __ FloodFunctionIfStepping(rdi, no_reg, dummy, dummy);
+
   __ popq(rbp);
 
   // Load context from the function.

src/ia32/macro-assembler-ia32.h

@@ -315,6 +315,10 @@ class MacroAssembler: public Assembler {
                           const ParameterCount& actual, InvokeFlag flag,
                           const CallWrapper& call_wrapper);
 
+  void FloodFunctionIfStepping(Register fun, Register new_target,
+                               const ParameterCount& expected,
+                               const ParameterCount& actual);
+
   // Invoke the JavaScript function in the given register. Changes the
   // current context to the context in the function before invoking.
   void InvokeFunction(Register function, Register new_target,
@@ -897,10 +901,6 @@ class MacroAssembler: public Assembler {
                       Label::Distance done_distance,
                       const CallWrapper& call_wrapper);
 
-  void FloodFunctionIfStepping(Register fun, Register new_target,
-                               const ParameterCount& expected,
-                               const ParameterCount& actual);
-
   void EnterExitFramePrologue();
   void EnterExitFrameEpilogue(int argc, bool save_doubles);
 

src/mips/macro-assembler-mips.h

@@ -979,6 +979,10 @@ class MacroAssembler: public Assembler {
                           const ParameterCount& actual, InvokeFlag flag,
                           const CallWrapper& call_wrapper);
 
+  void FloodFunctionIfStepping(Register fun, Register new_target,
+                               const ParameterCount& expected,
+                               const ParameterCount& actual);
+
   // Invoke the JavaScript function in the given register. Changes the
   // current context to the context in the function before invoking.
   void InvokeFunction(Register function,
@@ -1669,10 +1673,6 @@ const Operand& rt = Operand(zero_reg), BranchDelaySlot bd = PROTECT
                       InvokeFlag flag,
                       const CallWrapper& call_wrapper);
 
-  void FloodFunctionIfStepping(Register fun, Register new_target,
-                               const ParameterCount& expected,
-                               const ParameterCount& actual);
-
   void InitializeNewString(Register string,
                            Register length,
                            Heap::RootListIndex map_index,

src/mips64/macro-assembler-mips64.h

@@ -1034,6 +1034,10 @@ class MacroAssembler: public Assembler {
                           const ParameterCount& actual, InvokeFlag flag,
                           const CallWrapper& call_wrapper);
 
+  void FloodFunctionIfStepping(Register fun, Register new_target,
+                               const ParameterCount& expected,
+                               const ParameterCount& actual);
+
   // Invoke the JavaScript function in the given register. Changes the
   // current context to the context in the function before invoking.
   void InvokeFunction(Register function,
@@ -1765,10 +1769,6 @@ const Operand& rt = Operand(zero_reg), BranchDelaySlot bd = PROTECT
                       InvokeFlag flag,
                       const CallWrapper& call_wrapper);
 
-  void FloodFunctionIfStepping(Register fun, Register new_target,
-                               const ParameterCount& expected,
-                               const ParameterCount& actual);
-
   void InitializeNewString(Register string,
                            Register length,
                            Heap::RootListIndex map_index,

src/snapshot/serialize.cc

@@ -60,8 +60,6 @@ ExternalReferenceTable::ExternalReferenceTable(Isolate* isolate) {
       "Heap::NewSpaceAllocationLimitAddress()");
   Add(ExternalReference::new_space_allocation_top_address(isolate).address(),
       "Heap::NewSpaceAllocationTopAddress()");
-  Add(ExternalReference::debug_step_in_enabled_address(isolate).address(),
-      "Debug::step_in_enabled_address()");
   Add(ExternalReference::mod_two_doubles_operation(isolate).address(),
       "mod_two_doubles");
   // Keyed lookup cache.
@@ -139,11 +137,10 @@ ExternalReferenceTable::ExternalReferenceTable(Isolate* isolate) {
   // Debug addresses
   Add(ExternalReference::debug_after_break_target_address(isolate).address(),
       "Debug::after_break_target_address()");
-  Add(ExternalReference::debug_restarter_frame_function_pointer_address(isolate)
-          .address(),
-      "Debug::restarter_frame_function_pointer_address()");
   Add(ExternalReference::debug_is_active_address(isolate).address(),
       "Debug::is_active_address()");
+  Add(ExternalReference::debug_step_in_enabled_address(isolate).address(),
+      "Debug::step_in_enabled_address()");
 
 #ifndef V8_INTERPRETED_REGEXP
   Add(ExternalReference::re_case_insensitive_compare_uc16(isolate).address(),

src/x64/macro-assembler-x64.h

@@ -385,6 +385,10 @@ class MacroAssembler: public Assembler {
                           const ParameterCount& actual, InvokeFlag flag,
                           const CallWrapper& call_wrapper);
 
+  void FloodFunctionIfStepping(Register fun, Register new_target,
+                               const ParameterCount& expected,
+                               const ParameterCount& actual);
+
   // Invoke the JavaScript function in the given register. Changes the
   // current context to the context in the function before invoking.
   void InvokeFunction(Register function,
@@ -1604,10 +1608,6 @@ class MacroAssembler: public Assembler {
                       Label::Distance near_jump,
                       const CallWrapper& call_wrapper);
 
-  void FloodFunctionIfStepping(Register fun, Register new_target,
-                               const ParameterCount& expected,
-                               const ParameterCount& actual);
-
   void EnterExitFramePrologue(bool save_rax);
 
   // Allocates arg_stack_space * kPointerSize memory (not GCed) on the stack