[turbofan] Unify referencing of stack slots

src/compiler/frame.h

Index: src/compiler/frame.h
diff --git a/src/compiler/frame.h b/src/compiler/frame.h
index f901b1e2b3402bc662023b1618cefa4702cc7cc5..aa823b6ba8ad0f885c68ed6dfe91f460a48e11c2 100644
--- a/src/compiler/frame.h
+++ b/src/compiler/frame.h
@@ -6,26 +6,93 @@
 #define V8_COMPILER_FRAME_H_
 
 #include "src/bit-vector.h"
+#include "src/frames.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
-// Collects the spill slot requirements and the allocated general and double
-// registers for a compiled function. Frames are usually populated by the
-// register allocator and are used by Linkage to generate code for the prologue
-// and epilogue to compiled code.
+// Collects the spill slot and other frame slot requirements for a compiled
+// function. Frames are usually populated by the register allocator and are used
+// by Linkage to generate code for the prologue and epilogue to compiled code.
+//
+// Frames are divided up into three regions. The first is the fixed header,
+// which always has a constant size and can be predicted before code generation
+// begins depending on the type of code being generated. The second is the
+// region for spill slots, which is immediately below the fixed header and grows
+// as the register allocator needs to spill to the stack and asks the frame for
+// more space. The third region, which contains the callee-saved registers must
+// be reserved after register allocation, since its size can only be precisely
+// determined after register allocation once the number of used callee-saved
+// register is certain.
+//
+// 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 a 4 for JsFunctions. The
+// callee-saved frame region below that starts at 4+spilled_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
+// corresponding slot id.
+//
+// Below an example JSFunction Frame with slot ids, frame regions and contents:
+//
+//  slot      JS frame
+//       +-----------------+----------------------------
+//  -n-1 |   parameter 0   |                        ^
+//       |- - - - - - - - -|                        |
+//  -n   |                 |                      Caller
+//  ...  |       ...       |                   frame slots
+//  -2   |  parameter n-1  |                   (slot < 0)
+//       |- - - - - - - - -|                        |
+//  -1   |   parameter n   |                        v
+//  -----+-----------------+----------------------------
+//   0   |   return addr   |   ^                    ^
+//       |- - - - - - - - -|   |                    |
+//   1   | saved frame ptr | Fixed                  |
+//       |- - - - - - - - -| Header <-- frame ptr   |
+//   2   |     Context     |   |                    |
+//       |- - - - - - - - -|   |                    |
+//   3   |JSFunction/Marker|   v                    |
+//       +-----------------+----                    |
+//   4   |    spill 1      |   ^                  Callee
+//       |- - - - - - - - -|   |               frame slots
+//  ...  |      ...        | Spill slots       (slot >= 0)
+//       |- - - - - - - - -|   |                    |
+//  m+4  |    spill m      |   v                    |
+//       +-----------------+----                    |
+//  m+5  |  callee-saved 1 |   ^                    |
+//       |- - - - - - - - -|   |                    |
+//       |      ...        | Callee-saved           |
+//       |- - - - - - - - -|   |                    |
+// m+r+4 |  callee-saved r |   v                    v
+//  -----+-----------------+----- <-- stack ptr ---------
+//
 class Frame : public ZoneObject {
  public:
-  Frame()
-      : register_save_area_size_(0),
-        spill_slot_count_(0),
-        osr_stack_slot_count_(0),
-        allocated_registers_(NULL),
-        allocated_double_registers_(NULL),
-        pc_on_stack_(true) {}
+  explicit Frame(int fixed_frame_size_in_slots);
 
-  inline int GetSpillSlotCount() { return spill_slot_count_; }
+  inline int GetTotalFrameSlotCount() { return frame_slot_count_; }
+
+  inline int GetSavedCalleeRegisterSlotCount() {
+    return spilled_callee_register_slot_count_;
+  }
+  inline int GetSpillSlotCount() { return stack_slot_count_; }
+
+  inline void SetElidedFrameSizeInSlots(int slots) {
+    DCHECK_EQ(0, spilled_callee_register_slot_count_);
+    DCHECK_EQ(0, stack_slot_count_);
+    frame_slot_count_ = slots;
+  }
 
   void SetAllocatedRegisters(BitVector* regs) {
     DCHECK(allocated_registers_ == NULL);
@@ -41,48 +108,52 @@ class Frame : public ZoneObject {
     return !allocated_double_registers_->IsEmpty();
   }
 
-  void SetRegisterSaveAreaSize(int size) {
-    DCHECK(IsAligned(size, kPointerSize));
-    register_save_area_size_ = size;
+  int AlignSavedCalleeRegisterSlots() {
+    DCHECK_EQ(0, spilled_callee_register_slot_count_);
+    int frame_slot_count_before = frame_slot_count_;
+    frame_slot_count_ = RoundUp(frame_slot_count_, 2);
+    return frame_slot_count_before - frame_slot_count_;
   }
 
-  int GetRegisterSaveAreaSize() { return register_save_area_size_; }
+  void AllocateSavedCalleeRegisterSlots(int count) {
+    frame_slot_count_ += count;
+    spilled_callee_register_slot_count_ += count;
+  }
 
-  // OSR stack slots, including locals and expression stack slots.
-  void SetOsrStackSlotCount(int slots) {
-    DCHECK(slots >= 0);
-    osr_stack_slot_count_ = slots;
+  int AllocateSpillSlot(int width) {
+    DCHECK_EQ(0, spilled_callee_register_slot_count_);
+    int frame_slot_count_before = frame_slot_count_;
+    int slot = AllocateAlignedFrameSlot(width);
+    stack_slot_count_ += (frame_slot_count_ - frame_slot_count_before);
+    return slot;
   }
 
-  int GetOsrStackSlotCount() { return osr_stack_slot_count_; }
+  int ReserveSpillSlots(size_t slot_count) {
+    DCHECK_EQ(0, spilled_callee_register_slot_count_);
+    DCHECK_EQ(0, stack_slot_count_);
+    stack_slot_count_ += static_cast<int>(slot_count);
+    frame_slot_count_ += static_cast<int>(slot_count);
+    return frame_slot_count_ - 1;
+  }
 
-  int AllocateSpillSlot(int width) {
+ private:
+  int AllocateAlignedFrameSlot(int width) {
     DCHECK(width == 4 || width == 8);
     // Skip one slot if necessary.
     if (width > kPointerSize) {
       DCHECK(width == kPointerSize * 2);
-      spill_slot_count_++;
-      spill_slot_count_ |= 1;
+      frame_slot_count_++;
+      frame_slot_count_ |= 1;
     }
-    return spill_slot_count_++;
-  }
-
-  void ReserveSpillSlots(size_t slot_count) {
-    DCHECK_EQ(0, spill_slot_count_);  // can only reserve before allocation.
-    spill_slot_count_ = static_cast<int>(slot_count);
+    return frame_slot_count_++;
   }
 
-  void SetPCOnStack(bool val) { pc_on_stack_ = val; }
-
-  int PCOnStackSize() { return pc_on_stack_ ? kRegisterSize : 0; }
-
  private:
-  int register_save_area_size_;
-  int spill_slot_count_;
-  int osr_stack_slot_count_;
+  int frame_slot_count_;
+  int spilled_callee_register_slot_count_;
+  int stack_slot_count_;
   BitVector* allocated_registers_;
   BitVector* allocated_double_registers_;
-  bool pc_on_stack_;
 
   DISALLOW_COPY_AND_ASSIGN(Frame);
 };