PPC: [crankshaft] Support ES6 tail call elimination.

src/ppc/macro-assembler-ppc.h

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_PPC_MACRO_ASSEMBLER_PPC_H_
 #define V8_PPC_MACRO_ASSEMBLER_PPC_H_
 
 #include "src/assembler.h"
 #include "src/bailout-reason.h"
 #include "src/frames.h"
@@ skipping 138 matching lines @@
   void Drop(int count);
   void Drop(Register count, Register scratch = r0);
 
   void Ret(int drop) {
     Drop(drop);
     blr();
   }
 
   void Call(Label* target);
 
-  // Emit call to the code we are currently generating.
-  void CallSelf() {
-    Handle<Code> self(reinterpret_cast<Code**>(CodeObject().location()));
-    Call(self, RelocInfo::CODE_TARGET);
-  }
-
   // Register move. May do nothing if the registers are identical.
   void Move(Register dst, Smi* smi) { LoadSmiLiteral(dst, smi); }
   void Move(Register dst, Handle<Object> value);
   void Move(Register dst, Register src, Condition cond = al);
   void Move(DoubleRegister dst, DoubleRegister src);
 
   void MultiPush(RegList regs, Register location = sp);
   void MultiPop(RegList regs, Register location = sp);
 
   void MultiPushDoubles(RegList dregs, Register location = sp);
@@ skipping 382 matching lines @@
   // reset rounding mode to default (kRoundToNearest)
   void ResetRoundingMode();
 
   // These exist to provide portability between 32 and 64bit
   void LoadP(Register dst, const MemOperand& mem, Register scratch = no_reg);
   void StoreP(Register src, const MemOperand& mem, Register scratch = no_reg);
 
   // ---------------------------------------------------------------------------
   // 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.
+  // 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);
+
   // Invoke the JavaScript function code by either calling or jumping.
   void InvokeFunctionCode(Register function, Register new_target,
                           const ParameterCount& expected,
                           const ParameterCount& actual, InvokeFlag flag,
                           const CallWrapper& call_wrapper);
 
   void FloodFunctionIfStepping(Register fun, Register new_target,
                                const ParameterCount& expected,
                                const ParameterCount& actual);
 
@@ skipping 1033 matching lines @@
 #define ACCESS_MASM(masm)    \
   masm->stop(__FILE_LINE__); \
   masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PPC_MACRO_ASSEMBLER_PPC_H_