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/frame-constants.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 four 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 : // - The fourth region is a scratch area for return values from other functions
37 : // called, if multiple returns cannot all be passed in registers. This region
38 : // Must be last in a stack frame, so that it is positioned immediately below
39 : // the stack frame of a callee to store to.
40 : //
41 : // The frame region immediately below the fixed header contains spill slots
42 : // starting at slot 4 for JSFunctions. The callee-saved frame region below that
43 : // starts at 4+spill_slot_count_. Callee stack slots correspond to
44 : // parameters that are accessible through negative slot ids.
45 : //
46 : // Every slot of a caller or callee frame is accessible by the register
47 : // allocator and gap resolver with a SpillSlotOperand containing its
48 : // corresponding slot id.
49 : //
50 : // Below an example JSFunction Frame with slot ids, frame regions and contents:
51 : //
52 : // slot JS frame
53 : // +-----------------+--------------------------------
54 : // -n-1 | parameter 0 | ^
55 : // |- - - - - - - - -| |
56 : // -n | | Caller
57 : // ... | ... | frame slots
58 : // -2 | parameter n-1 | (slot < 0)
59 : // |- - - - - - - - -| |
60 : // -1 | parameter n | v
61 : // -----+-----------------+--------------------------------
62 : // 0 | return addr | ^ ^
63 : // |- - - - - - - - -| | |
64 : // 1 | saved frame ptr | Fixed |
65 : // |- - - - - - - - -| Header <-- frame ptr |
66 : // 2 |Context/Frm. Type| | |
67 : // |- - - - - - - - -| | |
68 : // 3 | [JSFunction] | v |
69 : // +-----------------+---- |
70 : // 4 | spill 1 | ^ Callee
71 : // |- - - - - - - - -| | frame slots
72 : // ... | ... | Spill slots (slot >= 0)
73 : // |- - - - - - - - -| | |
74 : // m+3 | spill m | v |
75 : // +-----------------+---- |
76 : // m+4 | callee-saved 1 | ^ |
77 : // |- - - - - - - - -| | |
78 : // | ... | Callee-saved |
79 : // |- - - - - - - - -| | |
80 : // m+r+3 | callee-saved r | v |
81 : // +-----------------+---- |
82 : // m+r+4 | return 0 | ^ |
83 : // |- - - - - - - - -| | |
84 : // | ... | Return |
85 : // |- - - - - - - - -| | |
86 : // | return q-1 | v v
87 : // -----+-----------------+----- <-- stack ptr -------------
88 : //
89 : class Frame : public ZoneObject {
90 : public:
91 : explicit Frame(int fixed_frame_size_in_slots);
92 :
93 : inline int GetTotalFrameSlotCount() const { return frame_slot_count_; }
94 : inline int GetFixedSlotCount() const { return fixed_slot_count_; }
95 : inline int GetSpillSlotCount() const { return spill_slot_count_; }
96 : inline int GetReturnSlotCount() const { return return_slot_count_; }
97 :
98 : void SetAllocatedRegisters(BitVector* regs) {
99 : DCHECK_NULL(allocated_registers_);
100 2141568 : allocated_registers_ = regs;
101 : }
102 :
103 : void SetAllocatedDoubleRegisters(BitVector* regs) {
104 : DCHECK_NULL(allocated_double_registers_);
105 2141568 : allocated_double_registers_ = regs;
106 : }
107 :
108 : bool DidAllocateDoubleRegisters() const {
109 : return !allocated_double_registers_->IsEmpty();
110 : }
111 :
112 : void AlignSavedCalleeRegisterSlots(int alignment = kDoubleSize) {
113 : int alignment_slots = alignment / kSystemPointerSize;
114 : int delta = alignment_slots - (frame_slot_count_ & (alignment_slots - 1));
115 : if (delta != alignment_slots) {
116 : frame_slot_count_ += delta;
117 : }
118 0 : spill_slot_count_ += delta;
119 : }
120 :
121 : void AllocateSavedCalleeRegisterSlots(int count) {
122 904209 : frame_slot_count_ += count;
123 : }
124 :
125 2728015 : int AllocateSpillSlot(int width, int alignment = 0) {
126 : DCHECK_EQ(frame_slot_count_,
127 : fixed_slot_count_ + spill_slot_count_ + return_slot_count_);
128 2728015 : int frame_slot_count_before = frame_slot_count_;
129 2728015 : if (alignment > kSystemPointerSize) {
130 : // Slots are pointer sized, so alignment greater than a pointer size
131 : // requires allocating additional slots.
132 0 : width += alignment - kSystemPointerSize;
133 : }
134 : AllocateAlignedFrameSlots(width);
135 2728015 : spill_slot_count_ += frame_slot_count_ - frame_slot_count_before;
136 2728015 : return frame_slot_count_ - return_slot_count_ - 1;
137 : }
138 :
139 : void EnsureReturnSlots(int count) {
140 5284 : if (count > return_slot_count_) {
141 672 : count -= return_slot_count_;
142 672 : frame_slot_count_ += count;
143 672 : return_slot_count_ += count;
144 : }
145 : }
146 :
147 : int AlignFrame(int alignment = kDoubleSize);
148 :
149 : int ReserveSpillSlots(size_t slot_count) {
150 : DCHECK_EQ(0, spill_slot_count_);
151 4991 : spill_slot_count_ += static_cast<int>(slot_count);
152 4991 : frame_slot_count_ += static_cast<int>(slot_count);
153 : return frame_slot_count_ - 1;
154 : }
155 :
156 : private:
157 : void AllocateAlignedFrameSlots(int width) {
158 : DCHECK_LT(0, width);
159 2728015 : int new_frame_slots = (width + kSystemPointerSize - 1) / kSystemPointerSize;
160 : // Align to 8 bytes if width is a multiple of 8 bytes, and to 16 bytes if
161 : // multiple of 16.
162 : int align_to =
163 2728015 : (width & 15) == 0 ? 16 : (width & 7) == 0 ? 8 : kSystemPointerSize;
164 : frame_slot_count_ = RoundUp(frame_slot_count_ + new_frame_slots,
165 5456030 : align_to / kSystemPointerSize);
166 : DCHECK_LT(0, frame_slot_count_);
167 : }
168 :
169 : private:
170 : int fixed_slot_count_;
171 : int frame_slot_count_;
172 : int spill_slot_count_;
173 : int return_slot_count_;
174 : BitVector* allocated_registers_;
175 : BitVector* allocated_double_registers_;
176 :
177 : DISALLOW_COPY_AND_ASSIGN(Frame);
178 : };
179 :
180 :
181 : // Represents an offset from either the stack pointer or frame pointer.
182 : class FrameOffset {
183 : public:
184 14368519 : inline bool from_stack_pointer() { return (offset_ & 1) == kFromSp; }
185 : inline bool from_frame_pointer() { return (offset_ & 1) == kFromFp; }
186 14368519 : inline int offset() { return offset_ & ~1; }
187 :
188 : inline static FrameOffset FromStackPointer(int offset) {
189 : DCHECK_EQ(0, offset & 1);
190 115484 : return FrameOffset(offset | kFromSp);
191 : }
192 :
193 : inline static FrameOffset FromFramePointer(int offset) {
194 : DCHECK_EQ(0, offset & 1);
195 : return FrameOffset(offset | kFromFp);
196 : }
197 :
198 : private:
199 : explicit FrameOffset(int offset) : offset_(offset) {}
200 :
201 : int offset_; // Encodes SP or FP in the low order bit.
202 :
203 : static const int kFromSp = 1;
204 : static const int kFromFp = 0;
205 : };
206 :
207 : // Encapsulates the mutable state maintained during code generation about the
208 : // current function's frame.
209 : class FrameAccessState : public ZoneObject {
210 : public:
211 : explicit FrameAccessState(const Frame* const frame)
212 : : frame_(frame),
213 : access_frame_with_fp_(false),
214 : sp_delta_(0),
215 2141466 : has_frame_(false) {}
216 :
217 : const Frame* frame() const { return frame_; }
218 : void MarkHasFrame(bool state);
219 :
220 : int sp_delta() const { return sp_delta_; }
221 5839978 : void ClearSPDelta() { sp_delta_ = 0; }
222 3194611 : void IncreaseSPDelta(int amount) { sp_delta_ += amount; }
223 :
224 : bool access_frame_with_fp() const { return access_frame_with_fp_; }
225 :
226 : // Regardless of how we access slots on the stack - using sp or fp - do we
227 : // have a frame, at the current stage in code generation.
228 : bool has_frame() const { return has_frame_; }
229 :
230 : void SetFrameAccessToDefault();
231 16831629 : void SetFrameAccessToFP() { access_frame_with_fp_ = true; }
232 2900444 : void SetFrameAccessToSP() { access_frame_with_fp_ = false; }
233 :
234 991816 : int GetSPToFPSlotCount() const {
235 : int frame_slot_count =
236 608724 : (has_frame() ? frame()->GetTotalFrameSlotCount() : kElidedFrameSlots) -
237 : StandardFrameConstants::kFixedSlotCountAboveFp;
238 383092 : return frame_slot_count + sp_delta();
239 : }
240 : int GetSPToFPOffset() const {
241 115484 : return GetSPToFPSlotCount() * kSystemPointerSize;
242 : }
243 :
244 : // Get the frame offset for a given spill slot. The location depends on the
245 : // calling convention and the specific frame layout, and may thus be
246 : // architecture-specific. Negative spill slots indicate arguments on the
247 : // caller's frame.
248 : FrameOffset GetFrameOffset(int spill_slot) const;
249 :
250 : private:
251 : const Frame* const frame_;
252 : bool access_frame_with_fp_;
253 : int sp_delta_;
254 : bool has_frame_;
255 : };
256 : } // namespace compiler
257 : } // namespace internal
258 : } // namespace v8
259 :
260 : #endif // V8_COMPILER_FRAME_H_
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