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 // Every pointer in a frame has a slot id. On 32-bit platforms, doubles consume 38 // two slots. 39 // 40 // Stack slot indices >= 0 access the callee stack with slot 0 corresponding to 41 // the callee's saved return address and 1 corresponding to the saved frame 42 // pointer. Some frames have additional information stored in the fixed header, 43 // for example JSFunctions store the function context and marker in the fixed 44 // header, with slot index 2 corresponding to the current function context and 3 45 // corresponding to the frame marker/JSFunction. The frame region immediately 46 // below the fixed header contains spill slots starting at 4 for JsFunctions. 47 // The callee-saved frame region below that starts at 4+spill_slot_count_. 48 // Callee stack slots corresponding to parameters are accessible through 49 // negative slot ids. 50 // 51 // Every slot of a caller or callee frame is accessible by the register 52 // allocator and gap resolver with a SpillSlotOperand containing its 53 // corresponding slot id. 54 // 55 // Below an example JSFunction Frame with slot ids, frame regions and contents: 56 // 57 // slot JS frame 58 // +-----------------+-------------------------------- 59 // -n-1 | parameter 0 | ^ 60 // |- - - - - - - - -| | 61 // -n | | Caller 62 // ... | ... | frame slots 63 // -2 | parameter n-1 | (slot < 0) 64 // |- - - - - - - - -| | 65 // -1 | parameter n | v 66 // -----+-----------------+-------------------------------- 67 // 0 | return addr | ^ ^ 68 // |- - - - - - - - -| | | 69 // 1 | saved frame ptr | Fixed | 70 // |- - - - - - - - -| Header <-- frame ptr | 71 // 2 | Context | | | 72 // |- - - - - - - - -| | | 73 // 3 |JSFunction/Marker| v | 74 // +-----------------+---- | 75 // 4 | spill 1 | ^ Callee 76 // |- - - - - - - - -| | frame slots 77 // ... | ... | Spill slots (slot >= 0) 78 // |- - - - - - - - -| | | 79 // m+4 | spill m | v | 80 // +-----------------+---- | 81 // m+5 | callee-saved 1 | ^ | 82 // |- - - - - - - - -| | | 83 // | ... | Callee-saved | 84 // |- - - - - - - - -| | | 85 // m+r+4 | callee-saved r | v v 86 // -----+-----------------+----- <-- stack ptr ------------- 87 // 88 class Frame : public ZoneObject { 89 public: 90 explicit Frame(int fixed_frame_size_in_slots, 91 const CallDescriptor* descriptor); 92 93 static int FPOffsetToSlot(int frame_offset) { 94 return StandardFrameConstants::kFixedSlotCountAboveFp - 1 - 95 frame_offset / kPointerSize; 96 } 97 98 static int SlotToFPOffset(int slot) { 99 return (StandardFrameConstants::kFixedSlotCountAboveFp - 1 - slot) * 100 kPointerSize; 101 } 102 103 inline bool needs_frame() const { return needs_frame_; } 104 inline void MarkNeedsFrame() { needs_frame_ = true; } 105 106 inline int GetTotalFrameSlotCount() const { return frame_slot_count_; } 107 108 inline int GetSpToFpSlotCount() const { 109 return GetTotalFrameSlotCount() - 110 StandardFrameConstants::kFixedSlotCountAboveFp; 111 } 112 inline int GetSavedCalleeRegisterSlotCount() const { 113 return callee_saved_slot_count_; 114 } 115 inline int GetSpillSlotCount() const { return spill_slot_count_; } 116 117 inline void SetElidedFrameSizeInSlots(int slots) { 118 DCHECK_EQ(0, callee_saved_slot_count_); 119 DCHECK_EQ(0, spill_slot_count_); 120 frame_slot_count_ = slots; 121 } 122 123 void SetAllocatedRegisters(BitVector* regs) { 124 DCHECK(allocated_registers_ == nullptr); 125 allocated_registers_ = regs; 126 } 127 128 void SetAllocatedDoubleRegisters(BitVector* regs) { 129 DCHECK(allocated_double_registers_ == nullptr); 130 allocated_double_registers_ = regs; 131 } 132 133 bool DidAllocateDoubleRegisters() const { 134 return !allocated_double_registers_->IsEmpty(); 135 } 136 137 int AlignSavedCalleeRegisterSlots() { 138 DCHECK_EQ(0, callee_saved_slot_count_); 139 needs_frame_ = true; 140 int delta = frame_slot_count_ & 1; 141 frame_slot_count_ += delta; 142 return delta; 143 } 144 145 void AllocateSavedCalleeRegisterSlots(int count) { 146 needs_frame_ = true; 147 frame_slot_count_ += count; 148 callee_saved_slot_count_ += count; 149 } 150 151 int AllocateSpillSlot(int width) { 152 DCHECK_EQ(0, callee_saved_slot_count_); 153 needs_frame_ = true; 154 int frame_slot_count_before = frame_slot_count_; 155 int slot = AllocateAlignedFrameSlot(width); 156 spill_slot_count_ += (frame_slot_count_ - frame_slot_count_before); 157 return slot; 158 } 159 160 int ReserveSpillSlots(size_t slot_count) { 161 DCHECK_EQ(0, callee_saved_slot_count_); 162 DCHECK_EQ(0, spill_slot_count_); 163 needs_frame_ = true; 164 spill_slot_count_ += static_cast<int>(slot_count); 165 frame_slot_count_ += static_cast<int>(slot_count); 166 return frame_slot_count_ - 1; 167 } 168 169 static const int kContextSlot = 2 + StandardFrameConstants::kCPSlotCount; 170 static const int kJSFunctionSlot = 3 + StandardFrameConstants::kCPSlotCount; 171 172 private: 173 int AllocateAlignedFrameSlot(int width) { 174 DCHECK(width == 4 || width == 8); 175 // Skip one slot if necessary. 176 if (width > kPointerSize) { 177 DCHECK(width == kPointerSize * 2); 178 frame_slot_count_++; 179 frame_slot_count_ |= 1; 180 } 181 return frame_slot_count_++; 182 } 183 184 private: 185 bool needs_frame_; 186 int frame_slot_count_; 187 int callee_saved_slot_count_; 188 int spill_slot_count_; 189 BitVector* allocated_registers_; 190 BitVector* allocated_double_registers_; 191 192 DISALLOW_COPY_AND_ASSIGN(Frame); 193 }; 194 195 196 // Represents an offset from either the stack pointer or frame pointer. 197 class FrameOffset { 198 public: 199 inline bool from_stack_pointer() { return (offset_ & 1) == kFromSp; } 200 inline bool from_frame_pointer() { return (offset_ & 1) == kFromFp; } 201 inline int offset() { return offset_ & ~1; } 202 203 inline static FrameOffset FromStackPointer(int offset) { 204 DCHECK((offset & 1) == 0); 205 return FrameOffset(offset | kFromSp); 206 } 207 208 inline static FrameOffset FromFramePointer(int offset) { 209 DCHECK((offset & 1) == 0); 210 return FrameOffset(offset | kFromFp); 211 } 212 213 private: 214 explicit FrameOffset(int offset) : offset_(offset) {} 215 216 int offset_; // Encodes SP or FP in the low order bit. 217 218 static const int kFromSp = 1; 219 static const int kFromFp = 0; 220 }; 221 222 // Encapsulates the mutable state maintained during code generation about the 223 // current function's frame. 224 class FrameAccessState : public ZoneObject { 225 public: 226 explicit FrameAccessState(Frame* const frame) 227 : frame_(frame), access_frame_with_fp_(false), sp_delta_(0) { 228 SetFrameAccessToDefault(); 229 } 230 231 Frame* frame() const { return frame_; } 232 233 int sp_delta() const { return sp_delta_; } 234 void ClearSPDelta() { sp_delta_ = 0; } 235 void IncreaseSPDelta(int amount) { sp_delta_ += amount; } 236 237 bool access_frame_with_fp() const { return access_frame_with_fp_; } 238 void SetFrameAccessToDefault(); 239 void SetFrameAccessToFP() { access_frame_with_fp_ = true; } 240 void SetFrameAccessToSP() { access_frame_with_fp_ = false; } 241 242 // Get the frame offset for a given spill slot. The location depends on the 243 // calling convention and the specific frame layout, and may thus be 244 // architecture-specific. Negative spill slots indicate arguments on the 245 // caller's frame. 246 FrameOffset GetFrameOffset(int spill_slot) const; 247 248 private: 249 Frame* const frame_; 250 bool access_frame_with_fp_; 251 int sp_delta_; 252 }; 253 } // namespace compiler 254 } // namespace internal 255 } // namespace v8 256 257 #endif // V8_COMPILER_FRAME_H_ 258
