[turbofan] Unify referencing of stack slots

src/frames.cc

 // Copyright 2012 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.
 
 #include "src/frames.h"
 
 #include <sstream>
 
 #include "src/ast.h"
 #include "src/base/bits.h"
@@ skipping 1061 matching lines @@
       } else {
         CHECK_EQ(Translation::JS_FRAME_FUNCTION, opcode);
         function = this->function();
       }
       functions->Add(JSFunction::cast(function));
     }
   }
 }
 
 
+int OptimizedFrame::StackSlotOffsetRelativeToFp(int slot_index) {
+  return StandardFrameConstants::kCallerSPOffset -
+         ((slot_index + 1) * kPointerSize);
+}
+
+
 Object* OptimizedFrame::StackSlotAt(int index) const {
-  // Positive index means the value is spilled to the locals
-  // area. Negative means it is stored in the incoming parameter
-  // area.
-  if (index >= 0) return GetExpression(index);
-
-  // Index -1 overlaps with last parameter, -n with the first parameter,
-  // (-n - 1) with the receiver with n being the number of parameters
-  // of the outermost, optimized frame.
-  int const parameter_count = ComputeParametersCount();
-  int const parameter_index = index + parameter_count;
-  return (parameter_index == -1) ? receiver() : GetParameter(parameter_index);
+  return Memory::Object_at(fp() + StackSlotOffsetRelativeToFp(index));
 }
 
 
 int ArgumentsAdaptorFrame::GetNumberOfIncomingArguments() const {
   return Smi::cast(GetExpression(0))->value();
 }
 
 
 Address ArgumentsAdaptorFrame::GetCallerStackPointer() const {
   return fp() + StandardFrameConstants::kCallerSPOffset;
@@ skipping 447 matching lines @@
   for (StackFrameIterator it(isolate); !it.done(); it.Advance()) {
     StackFrame* frame = AllocateFrameCopy(it.frame(), zone);
     list.Add(frame, zone);
   }
   return list.ToVector();
 }
 
 
 }  // namespace internal
 }  // namespace v8