LCOV - code coverage report
Current view: top level - src/compiler - frame.h (source / functions) Hit Total Coverage
Test: app.info Lines: 25 26 96.2 %
Date: 2017-04-26 Functions: 1 1 100.0 %

          Line data    Source code
       1             : // Copyright 2014 the V8 project authors. All rights reserved.
       2             : // Use of this source code is governed by a BSD-style license that can be
       3             : // found in the LICENSE file.
       4             : 
       5             : #ifndef V8_COMPILER_FRAME_H_
       6             : #define V8_COMPILER_FRAME_H_
       7             : 
       8             : #include "src/bit-vector.h"
       9             : #include "src/frames.h"
      10             : 
      11             : namespace v8 {
      12             : namespace internal {
      13             : namespace compiler {
      14             : 
      15             : class CallDescriptor;
      16             : 
      17             : // Collects the spill slot and other frame slot requirements for a compiled
      18             : // function. Frames are usually populated by the register allocator and are used
      19             : // by Linkage to generate code for the prologue and epilogue to compiled
      20             : // code. Frame objects must be considered immutable once they've been
      21             : // instantiated and the basic information about the frame has been collected
      22             : // into them. Mutable state associated with the frame is stored separately in
      23             : // FrameAccessState.
      24             : //
      25             : // Frames are divided up into three regions.
      26             : // - The first is the fixed header, which always has a constant size and can be
      27             : //   predicted before code generation begins depending on the type of code being
      28             : //   generated.
      29             : // - The second is the region for spill slots, which is immediately below the
      30             : //   fixed header and grows as the register allocator needs to spill to the
      31             : //   stack and asks the frame for more space.
      32             : // - The third region, which contains the callee-saved registers must be
      33             : //   reserved after register allocation, since its size can only be precisely
      34             : //   determined after register allocation once the number of used callee-saved
      35             : //   register is certain.
      36             : //
      37             : // The frame region immediately below the fixed header contains spill slots
      38             : // starting at slot 4 for JSFunctions.  The callee-saved frame region below that
      39             : // starts at 4+spill_slot_count_.  Callee stack slots corresponding to
      40             : // parameters are accessible through negative slot ids.
      41             : //
      42             : // Every slot of a caller or callee frame is accessible by the register
      43             : // allocator and gap resolver with a SpillSlotOperand containing its
      44             : // corresponding slot id.
      45             : //
      46             : // Below an example JSFunction Frame with slot ids, frame regions and contents:
      47             : //
      48             : //  slot      JS frame
      49             : //       +-----------------+--------------------------------
      50             : //  -n-1 |   parameter 0   |                            ^
      51             : //       |- - - - - - - - -|                            |
      52             : //  -n   |                 |                          Caller
      53             : //  ...  |       ...       |                       frame slots
      54             : //  -2   |  parameter n-1  |                       (slot < 0)
      55             : //       |- - - - - - - - -|                            |
      56             : //  -1   |   parameter n   |                            v
      57             : //  -----+-----------------+--------------------------------
      58             : //   0   |   return addr   |   ^                        ^
      59             : //       |- - - - - - - - -|   |                        |
      60             : //   1   | saved frame ptr | Fixed                      |
      61             : //       |- - - - - - - - -| Header <-- frame ptr       |
      62             : //   2   |Context/Frm. Type|   |                        |
      63             : //       |- - - - - - - - -|   |                        |
      64             : //   3   |   [JSFunction]  |   v                        |
      65             : //       +-----------------+----                        |
      66             : //   4   |    spill 1      |   ^                      Callee
      67             : //       |- - - - - - - - -|   |                   frame slots
      68             : //  ...  |      ...        | Spill slots           (slot >= 0)
      69             : //       |- - - - - - - - -|   |                        |
      70             : //  m+3  |    spill m      |   v                        |
      71             : //       +-----------------+----                        |
      72             : //  m+4  |  callee-saved 1 |   ^                        |
      73             : //       |- - - - - - - - -|   |                        |
      74             : //       |      ...        | Callee-saved               |
      75             : //       |- - - - - - - - -|   |                        |
      76             : // m+r+3 |  callee-saved r |   v                        v
      77             : //  -----+-----------------+----- <-- stack ptr -------------
      78             : //
      79             : class Frame : public ZoneObject {
      80             :  public:
      81             :   explicit Frame(int fixed_frame_size_in_slots);
      82             : 
      83             :   inline int GetTotalFrameSlotCount() const { return frame_slot_count_; }
      84             : 
      85             :   inline int GetSpillSlotCount() const { return spill_slot_count_; }
      86             : 
      87             :   void SetAllocatedRegisters(BitVector* regs) {
      88             :     DCHECK(allocated_registers_ == nullptr);
      89      915919 :     allocated_registers_ = regs;
      90             :   }
      91             : 
      92             :   void SetAllocatedDoubleRegisters(BitVector* regs) {
      93             :     DCHECK(allocated_double_registers_ == nullptr);
      94      915919 :     allocated_double_registers_ = regs;
      95             :   }
      96             : 
      97             :   bool DidAllocateDoubleRegisters() const {
      98      345680 :     return !allocated_double_registers_->IsEmpty();
      99             :   }
     100             : 
     101             :   void AlignSavedCalleeRegisterSlots(int alignment = kDoubleSize) {
     102             :     int alignment_slots = alignment / kPointerSize;
     103             :     int delta = alignment_slots - (frame_slot_count_ & (alignment_slots - 1));
     104             :     if (delta != alignment_slots) {
     105             :       frame_slot_count_ += delta;
     106             :     }
     107           0 :     spill_slot_count_ += delta;
     108             :   }
     109             : 
     110             :   void AllocateSavedCalleeRegisterSlots(int count) {
     111      251808 :     frame_slot_count_ += count;
     112             :   }
     113             : 
     114     1061861 :   int AllocateSpillSlot(int width) {
     115     1061861 :     int frame_slot_count_before = frame_slot_count_;
     116             :     AllocateAlignedFrameSlots(width);
     117     1061861 :     spill_slot_count_ += frame_slot_count_ - frame_slot_count_before;
     118     1061861 :     return frame_slot_count_ - 1;
     119             :   }
     120             : 
     121             :   int AlignFrame(int alignment = kDoubleSize);
     122             : 
     123             :   int ReserveSpillSlots(size_t slot_count) {
     124             :     DCHECK_EQ(0, spill_slot_count_);
     125        5813 :     spill_slot_count_ += static_cast<int>(slot_count);
     126        5813 :     frame_slot_count_ += static_cast<int>(slot_count);
     127             :     return frame_slot_count_ - 1;
     128             :   }
     129             : 
     130             :   static const int kContextSlot = 2 + StandardFrameConstants::kCPSlotCount;
     131             :   static const int kJSFunctionSlot = 3 + StandardFrameConstants::kCPSlotCount;
     132             : 
     133             :  private:
     134             :   void AllocateAlignedFrameSlots(int width) {
     135             :     DCHECK_LT(0, width);
     136     1061861 :     int new_frame_slots = (width + kPointerSize - 1) / kPointerSize;
     137             :     // Align to 8 bytes if width is a multiple of 8 bytes, and to 16 bytes if
     138             :     // multiple of 16.
     139     1061861 :     int align_to = (width & 15) == 0 ? 16 : (width & 7) == 0 ? 8 : kPointerSize;
     140             :     frame_slot_count_ =
     141     2123722 :         RoundUp(frame_slot_count_ + new_frame_slots, align_to / kPointerSize);
     142             :     DCHECK_LT(0, frame_slot_count_);
     143             :   }
     144             : 
     145             :  private:
     146             :   int frame_slot_count_;
     147             :   int spill_slot_count_;
     148             :   BitVector* allocated_registers_;
     149             :   BitVector* allocated_double_registers_;
     150             : 
     151             :   DISALLOW_COPY_AND_ASSIGN(Frame);
     152             : };
     153             : 
     154             : 
     155             : // Represents an offset from either the stack pointer or frame pointer.
     156             : class FrameOffset {
     157             :  public:
     158     9271217 :   inline bool from_stack_pointer() { return (offset_ & 1) == kFromSp; }
     159             :   inline bool from_frame_pointer() { return (offset_ & 1) == kFromFp; }
     160     9271217 :   inline int offset() { return offset_ & ~1; }
     161             : 
     162             :   inline static FrameOffset FromStackPointer(int offset) {
     163             :     DCHECK((offset & 1) == 0);
     164       72693 :     return FrameOffset(offset | kFromSp);
     165             :   }
     166             : 
     167             :   inline static FrameOffset FromFramePointer(int offset) {
     168             :     DCHECK((offset & 1) == 0);
     169             :     return FrameOffset(offset | kFromFp);
     170             :   }
     171             : 
     172             :  private:
     173             :   explicit FrameOffset(int offset) : offset_(offset) {}
     174             : 
     175             :   int offset_;  // Encodes SP or FP in the low order bit.
     176             : 
     177             :   static const int kFromSp = 1;
     178             :   static const int kFromFp = 0;
     179             : };
     180             : 
     181             : // Encapsulates the mutable state maintained during code generation about the
     182             : // current function's frame.
     183             : class FrameAccessState : public ZoneObject {
     184             :  public:
     185             :   explicit FrameAccessState(const Frame* const frame)
     186             :       : frame_(frame),
     187             :         access_frame_with_fp_(false),
     188             :         sp_delta_(0),
     189      912392 :         has_frame_(false) {}
     190             : 
     191             :   const Frame* frame() const { return frame_; }
     192             :   void MarkHasFrame(bool state);
     193             : 
     194             :   int sp_delta() const { return sp_delta_; }
     195     3530225 :   void ClearSPDelta() { sp_delta_ = 0; }
     196     3736987 :   void IncreaseSPDelta(int amount) { sp_delta_ += amount; }
     197             : 
     198             :   bool access_frame_with_fp() const { return access_frame_with_fp_; }
     199             : 
     200             :   // Regardless of how we access slots on the stack - using sp or fp - do we
     201             :   // have a frame, at the current stage in code generation.
     202             :   bool has_frame() const { return has_frame_; }
     203             : 
     204             :   void SetFrameAccessToDefault();
     205     9177434 :   void SetFrameAccessToFP() { access_frame_with_fp_ = true; }
     206     2522532 :   void SetFrameAccessToSP() { access_frame_with_fp_ = false; }
     207             : 
     208      892450 :   int GetSPToFPSlotCount() const {
     209             :     int frame_slot_count =
     210      479474 :         (has_frame() ? frame()->GetTotalFrameSlotCount() : kElidedFrameSlots) -
     211             :         StandardFrameConstants::kFixedSlotCountAboveFp;
     212      412976 :     return frame_slot_count + sp_delta();
     213             :   }
     214       72693 :   int GetSPToFPOffset() const { return GetSPToFPSlotCount() * kPointerSize; }
     215             : 
     216             :   // Get the frame offset for a given spill slot. The location depends on the
     217             :   // calling convention and the specific frame layout, and may thus be
     218             :   // architecture-specific. Negative spill slots indicate arguments on the
     219             :   // caller's frame.
     220             :   FrameOffset GetFrameOffset(int spill_slot) const;
     221             : 
     222             :  private:
     223             :   const Frame* const frame_;
     224             :   bool access_frame_with_fp_;
     225             :   int sp_delta_;
     226             :   bool has_frame_;
     227             : };
     228             : }  // namespace compiler
     229             : }  // namespace internal
     230             : }  // namespace v8
     231             : 
     232             : #endif  // V8_COMPILER_FRAME_H_

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