1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
|
// Copyright 2014 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_COMPILER_FRAME_H_
#define V8_COMPILER_FRAME_H_
#include "src/bit-vector.h"
#include "src/frames.h"
namespace v8 {
namespace internal {
namespace compiler {
// 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:
explicit Frame(int fixed_frame_size_in_slots);
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);
allocated_registers_ = regs;
}
void SetAllocatedDoubleRegisters(BitVector* regs) {
DCHECK(allocated_double_registers_ == NULL);
allocated_double_registers_ = regs;
}
bool DidAllocateDoubleRegisters() {
return !allocated_double_registers_->IsEmpty();
}
int AlignSavedCalleeRegisterSlots() {
DCHECK_EQ(0, spilled_callee_register_slot_count_);
int delta = frame_slot_count_ & 1;
frame_slot_count_ += delta;
return delta;
}
void AllocateSavedCalleeRegisterSlots(int count) {
frame_slot_count_ += count;
spilled_callee_register_slot_count_ += count;
}
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 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;
}
private:
int AllocateAlignedFrameSlot(int width) {
DCHECK(width == 4 || width == 8);
// Skip one slot if necessary.
if (width > kPointerSize) {
DCHECK(width == kPointerSize * 2);
frame_slot_count_++;
frame_slot_count_ |= 1;
}
return frame_slot_count_++;
}
private:
int frame_slot_count_;
int spilled_callee_register_slot_count_;
int stack_slot_count_;
BitVector* allocated_registers_;
BitVector* allocated_double_registers_;
DISALLOW_COPY_AND_ASSIGN(Frame);
};
// Represents an offset from either the stack pointer or frame pointer.
class FrameOffset {
public:
inline bool from_stack_pointer() { return (offset_ & 1) == kFromSp; }
inline bool from_frame_pointer() { return (offset_ & 1) == kFromFp; }
inline int offset() { return offset_ & ~1; }
inline static FrameOffset FromStackPointer(int offset) {
DCHECK((offset & 1) == 0);
return FrameOffset(offset | kFromSp);
}
inline static FrameOffset FromFramePointer(int offset) {
DCHECK((offset & 1) == 0);
return FrameOffset(offset | kFromFp);
}
private:
explicit FrameOffset(int offset) : offset_(offset) {}
int offset_; // Encodes SP or FP in the low order bit.
static const int kFromSp = 1;
static const int kFromFp = 0;
};
} // namespace compiler
} // namespace internal
} // namespace v8
#endif // V8_COMPILER_FRAME_H_
|
