[es6] Tail calls support.

src/x64/builtins-x64.cc

Index: src/x64/builtins-x64.cc
diff --git a/src/x64/builtins-x64.cc b/src/x64/builtins-x64.cc
index 06fd59468dbc5b437538a0c0703e4a3384a786e7..60121a97bcf7c952ecc8a97a8ea128d76b930abb 100644
--- a/src/x64/builtins-x64.cc
+++ b/src/x64/builtins-x64.cc
@@ -2044,7 +2044,8 @@ void Builtins::Generate_Apply(MacroAssembler* masm) {
 
 // static
 void Builtins::Generate_CallFunction(MacroAssembler* masm,
-                                     ConvertReceiverMode mode) {
+                                     ConvertReceiverMode mode,
+                                     TailCallMode tail_call_mode) {
   // ----------- S t a t e -------------
   //  -- rax : the number of arguments (not including the receiver)
   //  -- rdi : the function to call (checked to be a JSFunction)
@@ -2140,6 +2141,10 @@ void Builtins::Generate_CallFunction(MacroAssembler* masm,
   //  -- rsi : the function context.
   // -----------------------------------
 
+  if (tail_call_mode == TailCallMode::kAllow) {
+    __ DropCurrentJSFrame(rax, rbx, rcx, r8);

[Benedikt Meurer, 2016/01/21 05:20:49]

We need to check whether the debugger is active, and if so don't eliminate the
frame(s), but do a normal call. See Yang's tail call+debugger document for
background.

[Igor Sheludko, 2016/01/21 14:37:08]

Done.

+  }
+
   __ LoadSharedFunctionInfoSpecialField(
       rbx, rdx, SharedFunctionInfo::kFormalParameterCountOffset);
   ParameterCount actual(rax);