[crankshaft] Support ES6 tail call elimination.

src/x64/macro-assembler-x64.h

Index: src/x64/macro-assembler-x64.h
diff --git a/src/x64/macro-assembler-x64.h b/src/x64/macro-assembler-x64.h
index 9c0b7964b3441f4c575989ee4aae10bcf7ba9965..ac5ea8f6ca9448585b1352475e885067408485e2 100644
--- a/src/x64/macro-assembler-x64.h
+++ b/src/x64/macro-assembler-x64.h
@@ -56,6 +56,8 @@ enum class SmiOperationConstraint {
   kBailoutOnOverflow = 1 << 2
 };
 
+enum class ReturnAddressState { kOnStack, kNotOnStack };
+
 typedef base::Flags<SmiOperationConstraint> SmiOperationConstraints;
 
 DEFINE_OPERATORS_FOR_FLAGS(SmiOperationConstraints)
@@ -370,6 +372,16 @@ class MacroAssembler: public Assembler {
   // ---------------------------------------------------------------------------
   // JavaScript invokes
 
+  // Removes current frame and its arguments from the stack preserving
+  // the arguments and a return address pushed to the stack for the next call.
+  // |ra_state| defines whether return address is already pushed to stack or
+  // not. Both |callee_args_count| and |caller_args_count_reg| do not include
+  // receiver. |callee_args_count| is not modified, |caller_args_count_reg|
+  // is trashed.
+  void PrepareForTailCall(const ParameterCount& callee_args_count,
+                          Register caller_args_count_reg, Register scratch0,
+                          Register scratch1, ReturnAddressState ra_state);
+
   // Invoke the JavaScript function code by either calling or jumping.
   void InvokeFunctionCode(Register function, Register new_target,
                           const ParameterCount& expected,
@@ -1014,12 +1026,6 @@ class MacroAssembler: public Assembler {
     return (target.requires_rex() ? 2 : 1) + target.operand_size();
   }
 
-  // Emit call to the code we are currently generating.
-  void CallSelf() {
-    Handle<Code> self(reinterpret_cast<Code**>(CodeObject().location()));
-    Call(self, RelocInfo::CODE_TARGET);
-  }
-
   // Non-SSE2 instructions.
   void Pextrd(Register dst, XMMRegister src, int8_t imm8);
   void Pinsrd(XMMRegister dst, Register src, int8_t imm8);