add context save for GenerateFastApiCall

src/x64/macro-assembler-x64.cc

Index: src/x64/macro-assembler-x64.cc
diff --git a/src/x64/macro-assembler-x64.cc b/src/x64/macro-assembler-x64.cc
index 0c605d826dd1f80fa4db3dec59fed95477c350c2..050b6a88a428719eefc8d1236894b07e950e4444 100644
--- a/src/x64/macro-assembler-x64.cc
+++ b/src/x64/macro-assembler-x64.cc
@@ -694,9 +694,11 @@ void MacroAssembler::CallApiFunctionAndReturn(Address function_address,
                                               Address thunk_address,
                                               Register thunk_last_arg,
                                               int stack_space,
-                                              int return_value_offset) {
+                                              int return_value_offset,
+                                              int restore_context_offset) {
   Label prologue;
   Label promote_scheduled_exception;
+  Label exception_handled;
   Label delete_allocated_handles;
   Label leave_exit_frame;
   Label write_back;
@@ -782,6 +784,7 @@ void MacroAssembler::CallApiFunctionAndReturn(Address function_address,
   movq(rsi, scheduled_exception_address);
   Cmp(Operand(rsi, 0), factory->the_hole_value());
   j(not_equal, &promote_scheduled_exception);
+  bind(&exception_handled);
 
 #if ENABLE_EXTRA_CHECKS
   // Check if the function returned a valid JavaScript value.
@@ -818,11 +821,16 @@ void MacroAssembler::CallApiFunctionAndReturn(Address function_address,
   bind(&ok);
 #endif
 
-  LeaveApiExitFrame();
+  bool restore_context = restore_context_offset != 0;

[Michael Starzinger, 2013/09/12 18:38:51]

Hmpf! The context is not restored when the offset is 0? That is not exactly
intuitive. Also I don't really understand why the CallIC for an API function
needs to restore the context of the callee at all. The context should be
restored by the caller IIUC.

So can't we just not restore Isolate::Context at all for API functions and just
always restore what's in the saved context slot?

+  if (restore_context) {
+    movq(rsi, Operand(rbp, restore_context_offset * kPointerSize));
+  }
+  LeaveApiExitFrame(!restore_context);
   ret(stack_space * kPointerSize);
 
   bind(&promote_scheduled_exception);
-  TailCallRuntime(Runtime::kPromoteScheduledException, 0, 1);
+  CallRuntime(Runtime::kPromoteScheduledException, 0);
+  jmp(&exception_handled);
 
   // HandleScope limit has changed. Delete allocated extensions.
   bind(&delete_allocated_handles);
@@ -3571,23 +3579,25 @@ void MacroAssembler::LeaveExitFrame(bool save_doubles) {
 
   PushReturnAddressFrom(rcx);
 
-  LeaveExitFrameEpilogue();
+  LeaveExitFrameEpilogue(true);
 }
 
 
-void MacroAssembler::LeaveApiExitFrame() {
+void MacroAssembler::LeaveApiExitFrame(bool restore_context) {
   movq(rsp, rbp);
   pop(rbp);
 
-  LeaveExitFrameEpilogue();
+  LeaveExitFrameEpilogue(restore_context);
 }
 
 
-void MacroAssembler::LeaveExitFrameEpilogue() {
+void MacroAssembler::LeaveExitFrameEpilogue(bool restore_context) {
   // Restore current context from top and clear it in debug mode.
   ExternalReference context_address(Isolate::kContextAddress, isolate());
   Operand context_operand = ExternalOperand(context_address);
-  movq(rsi, context_operand);
+  if (restore_context) {
+    movq(rsi, context_operand);
+  }
 #ifdef DEBUG
   movq(context_operand, Immediate(0));
 #endif