// 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 {
class CallDescriptor;
// 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. Frame objects must be considered immutable once they've been
// instantiated and the basic information about the frame has been collected
// into them. Mutable state associated with the frame is stored separately in
// FrameAccessState.
//
// 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.
//
// The frame region immediately below the fixed header contains spill slots
// starting at slot 4 for JSFunctions. The callee-saved frame region below that
// starts at 4+spill_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/Frm. Type| | |
// |- - - - - - - - -| | |
// 3 | [JSFunction] | v |
// +-----------------+---- |
// 4 | spill 1 | ^ Callee
// |- - - - - - - - -| | frame slots
// ... | ... | Spill slots (slot >= 0)
// |- - - - - - - - -| | |
// m+3 | spill m | v |
// +-----------------+---- |
// m+4 | callee-saved 1 | ^ |
// |- - - - - - - - -| | |
// | ... | Callee-saved |
// |- - - - - - - - -| | |
// m+r+3 | callee-saved r | v v
// -----+-----------------+----- <-- stack ptr -------------
//
class Frame : public ZoneObject {
public:
explicit Frame(int fixed_frame_size_in_slots);
inline int GetTotalFrameSlotCount() const { return frame_slot_count_; }
inline int GetSpillSlotCount() const { return spill_slot_count_; }
void SetAllocatedRegisters(BitVector* regs) {
DCHECK(allocated_registers_ == nullptr);
allocated_registers_ = regs;
}
void SetAllocatedDoubleRegisters(BitVector* regs) {
DCHECK(allocated_double_registers_ == nullptr);
allocated_double_registers_ = regs;
}
bool DidAllocateDoubleRegisters() const {
return !allocated_double_registers_->IsEmpty();
}
void AlignSavedCalleeRegisterSlots(int alignment = kDoubleSize) {
int alignment_slots = alignment / kPointerSize;
int delta = alignment_slots - (frame_slot_count_ & (alignment_slots - 1));
if (delta != alignment_slots) {
frame_slot_count_ += delta;
}
spill_slot_count_ += delta;
}
void AllocateSavedCalleeRegisterSlots(int count) {
frame_slot_count_ += count;
}
int AllocateSpillSlot(int width) {
int frame_slot_count_before = frame_slot_count_;
int slot = AllocateAlignedFrameSlot(width);
spill_slot_count_ += (frame_slot_count_ - frame_slot_count_before);
return slot;
}
int AlignFrame(int alignment = kDoubleSize);
int ReserveSpillSlots(size_t slot_count) {
DCHECK_EQ(0, spill_slot_count_);
spill_slot_count_ += static_cast<int>(slot_count);
frame_slot_count_ += static_cast<int>(slot_count);
return frame_slot_count_ - 1;
}
static const int kContextSlot = 2 + StandardFrameConstants::kCPSlotCount;
static const int kJSFunctionSlot = 3 + StandardFrameConstants::kCPSlotCount;
private:
int AllocateAlignedFrameSlot(int width) {
DCHECK(width == 4 || width == 8 || width == 16);
if (kPointerSize == 4) {
// Skip one slot if necessary.
if (width > kPointerSize) {
frame_slot_count_++;
frame_slot_count_ |= 1;
// 2 extra slots if width == 16.
frame_slot_count_ += (width & 16) / 8;
}
} else {
// No alignment when slots are 8 bytes.
DCHECK_EQ(8, kPointerSize);
// 1 extra slot if width == 16.
frame_slot_count_ += (width & 16) / 16;
}
return frame_slot_count_++;
}
private:
int frame_slot_count_;
int spill_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;
};
// Encapsulates the mutable state maintained during code generation about the
// current function's frame.
class FrameAccessState : public ZoneObject {
public:
explicit FrameAccessState(const Frame* const frame)
: frame_(frame),
access_frame_with_fp_(false),
sp_delta_(0),
has_frame_(false) {}
const Frame* frame() const { return frame_; }
void MarkHasFrame(bool state);
int sp_delta() const { return sp_delta_; }
void ClearSPDelta() { sp_delta_ = 0; }
void IncreaseSPDelta(int amount) { sp_delta_ += amount; }
bool access_frame_with_fp() const { return access_frame_with_fp_; }
// Regardless of how we access slots on the stack - using sp or fp - do we
// have a frame, at the current stage in code generation.
bool has_frame() const { return has_frame_; }
void SetFrameAccessToDefault();
void SetFrameAccessToFP() { access_frame_with_fp_ = true; }
void SetFrameAccessToSP() { access_frame_with_fp_ = false; }
int GetSPToFPSlotCount() const {
int frame_slot_count =
(has_frame() ? frame()->GetTotalFrameSlotCount() : kElidedFrameSlots) -
StandardFrameConstants::kFixedSlotCountAboveFp;
return frame_slot_count + sp_delta();
}
int GetSPToFPOffset() const { return GetSPToFPSlotCount() * kPointerSize; }
// Get the frame offset for a given spill slot. The location depends on the
// calling convention and the specific frame layout, and may thus be
// architecture-specific. Negative spill slots indicate arguments on the
// caller's frame.
FrameOffset GetFrameOffset(int spill_slot) const;
private:
const Frame* const frame_;
bool access_frame_with_fp_;
int sp_delta_;
bool has_frame_;
};
} // namespace compiler
} // namespace internal
} // namespace v8
#endif // V8_COMPILER_FRAME_H_