Revert of More simplification and unification of frame handling

src/compiler/frame.h

Index: src/compiler/frame.h
diff --git a/src/compiler/frame.h b/src/compiler/frame.h
index 011a0f02d5820e07c2064e528bbc0b2d1d8651c1..72f756b0dcd8e9693e21b9a5bf88f7ef3132d27f 100644
--- a/src/compiler/frame.h
+++ b/src/compiler/frame.h
@@ -34,10 +34,19 @@
 //   determined after register allocation once the number of used callee-saved
 //   register is certain.
 //
-// The frame region immediately below the fixed header contains spill slots
-// starting at slot 4 for JSFunctions.  The callee-saved frame region below that
-// starts at 4+spill_slot_count_.  Callee stack slots corresponding to
-// parameters are accessible through negative slot ids.
+// Every pointer in a frame has a slot id. On 32-bit platforms, doubles consume
+// two slots.
+//
+// Stack slot indices >= 0 access the callee stack with slot 0 corresponding to
+// the callee's saved return address and 1 corresponding to the saved frame
+// pointer. Some frames have additional information stored in the fixed header,
+// for example JSFunctions store the function context and marker in the fixed
+// header, with slot index 2 corresponding to the current function context and 3
+// corresponding to the frame marker/JSFunction. The frame region immediately
+// below the fixed header contains spill slots starting at 4 for JsFunctions.
+// The callee-saved frame region below that starts at 4+spill_slot_count_.
+// Callee stack slots corresponding to parameters are accessible through
+// negative slot ids.
 //
 // Every slot of a caller or callee frame is accessible by the register
 // allocator and gap resolver with a SpillSlotOperand containing its
@@ -67,19 +76,29 @@
 //       |- - - - - - - - -|   |                   frame slots
 //  ...  |      ...        | Spill slots           (slot >= 0)
 //       |- - - - - - - - -|   |                        |
-//  m+3  |    spill m      |   v                        |
+//  m+4  |    spill m      |   v                        |
 //       +-----------------+----                        |
-//  m+4  |  callee-saved 1 |   ^                        |
+//  m+5  |  callee-saved 1 |   ^                        |
 //       |- - - - - - - - -|   |                        |
 //       |      ...        | Callee-saved               |
 //       |- - - - - - - - -|   |                        |
-// m+r+3 |  callee-saved r |   v                        v
+// m+r+4 |  callee-saved r |   v                        v
 //  -----+-----------------+----- <-- stack ptr -------------
 //
 class Frame : public ZoneObject {
  public:
   explicit Frame(int fixed_frame_size_in_slots,
                  const CallDescriptor* descriptor);
+
+  static int FPOffsetToSlot(int frame_offset) {
+    return StandardFrameConstants::kFixedSlotCountAboveFp - 1 -
+           frame_offset / kPointerSize;
+  }
+
+  static int SlotToFPOffset(int slot) {
+    return (StandardFrameConstants::kFixedSlotCountAboveFp - 1 - slot) *
+           kPointerSize;
+  }
 
   inline bool needs_frame() const { return needs_frame_; }
   inline void MarkNeedsFrame() { needs_frame_ = true; }