[interpreter] Add a safety-net for interpreter entry.

src/ppc/builtins-ppc.cc

 // 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.
 
 #if V8_TARGET_ARCH_PPC
 
 #include "src/codegen.h"
 #include "src/debug/debug.h"
 #include "src/deoptimizer.h"
 #include "src/full-codegen/full-codegen.h"
@@ skipping 848 matching lines @@
 //
 // The live registers are:
 //   o r4: the JS function object being called.
 //   o r6: the new target
 //   o cp: our context
 //   o pp: the caller's constant pool pointer (if enabled)
 //   o fp: the caller's frame pointer
 //   o sp: stack pointer
 //   o lr: return address
 //
-// The function builds a JS frame.  Please see JavaScriptFrameConstants in
-// frames-ppc.h for its layout.
-// TODO(rmcilroy): We will need to include the current bytecode pointer in the
-// frame.
+// The function builds an interpreter frame.  See InterpreterFrameConstants in
+// frames.h for its layout.
 void Builtins::Generate_InterpreterEntryTrampoline(MacroAssembler* masm) {
   // Open a frame scope to indicate that there is a frame on the stack.  The
   // MANUAL indicates that the scope shouldn't actually generate code to set up
   // the frame (that is done below).
   FrameScope frame_scope(masm, StackFrame::MANUAL);
   __ PushFixedFrame(r4);
   __ addi(fp, sp, Operand(StandardFrameConstants::kFixedFrameSizeFromFp));
   __ push(r6);
 
   // Push zero for bytecode array offset.
@@ skipping 76 matching lines @@
 
   // Dispatch to the first bytecode handler for the function.
   __ lbzx(r4, MemOperand(kInterpreterBytecodeArrayRegister,
                          kInterpreterBytecodeOffsetRegister));
   __ ShiftLeftImm(ip, r4, Operand(kPointerSizeLog2));
   __ LoadPX(ip, MemOperand(kInterpreterDispatchTableRegister, ip));
   // TODO(rmcilroy): Make dispatch table point to code entrys to avoid untagging
   // and header removal.
   __ addi(ip, ip, Operand(Code::kHeaderSize - kHeapObjectTag));
   __ Call(ip);
-  __ bkpt(0);  // Does not return here.
+
+  // Even though the first bytecode handler was called, we will never return.
+  __ Abort(kUnexpectedReturnFromBytecodeHandler);
 }
 
 
 void Builtins::Generate_InterpreterExitTrampoline(MacroAssembler* masm) {
   // TODO(rmcilroy): List of things not currently dealt with here but done in
   // fullcodegen's EmitReturnSequence.
   //  - Supporting FLAG_trace for Runtime::TraceExit.
   //  - Support profiler (specifically decrementing profiling_counter
   //    appropriately and calling out to HandleInterrupts if necessary).
 
@@ skipping 1688 matching lines @@
     __ bkpt(0);
   }
 }
 
 
 #undef __
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_PPC