RegisterScavenging.cpp File Reference

This file implements the machine register scavenger. More...

#include "llvm/CodeGen/RegisterScavenging.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/LiveRegUnits.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/TargetFrameLowering.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <iterator>
#include <limits>
#include <utility>

Go to the source code of this file.

Macros
#define	DEBUG_TYPE   "reg-scavenging"

Functions
	STATISTIC (NumScavengedRegs, "Number of frame index regs scavenged")
static std::pair< MCPhysReg, MachineBasicBlock::iterator >	findSurvivorBackwards (const MachineRegisterInfo &MRI, MachineBasicBlock::iterator From, MachineBasicBlock::iterator To, const LiveRegUnits &LiveOut, ArrayRef< MCPhysReg > AllocationOrder, bool RestoreAfter)
	Given the bitvector Available of free register units at position From.
static unsigned	getFrameIndexOperandNum (MachineInstr &MI)
static Register	scavengeVReg (MachineRegisterInfo &MRI, RegScavenger &RS, Register VReg, bool ReserveAfter)
	Allocate a register for the virtual register VReg.
static bool	scavengeFrameVirtualRegsInBlock (MachineRegisterInfo &MRI, RegScavenger &RS, MachineBasicBlock &MBB)
	Allocate (scavenge) vregs inside a single basic block.

Detailed Description

This file implements the machine register scavenger.

It can provide information, such as unused registers, at any point in a machine basic block. It also provides a mechanism to make registers available by evicting them to spill slots.

Definition in file RegisterScavenging.cpp.

Macro Definition Documentation

DEBUG_TYPE

#define DEBUG_TYPE   "reg-scavenging"

Definition at line 46 of file RegisterScavenging.cpp.

Function Documentation

findSurvivorBackwards()

static std::pair< MCPhysReg, MachineBasicBlock::iterator > findSurvivorBackwards ( const MachineRegisterInfo &  MRI, MachineBasicBlock::iterator  From, MachineBasicBlock::iterator  To, const LiveRegUnits &  LiveOut, ArrayRef< MCPhysReg >  AllocationOrder, bool  RestoreAfter  )

static

Given the bitvector Available of free register units at position From.

Search backwards to find a register that is part of Candidates and not used/clobbered until the point To. If there is multiple candidates continue searching and pick the one that is not used/ clobbered for the longest time. Returns the register and the earliest position we know it to be free or the position MBB.end() if no register is available.

Definition at line 127 of file RegisterScavenging.cpp.

References assert(), llvm::LiveRegUnits::available(), llvm::MachineBasicBlock::begin(), llvm::MachineBasicBlock::end(), llvm::MachineInstr::FrameSetup, From, I, InstrLimit, MBB, MI, MRI, and TRI.

Referenced by llvm::RegScavenger::scavengeRegisterBackwards().

getFrameIndexOperandNum()

static unsigned getFrameIndexOperandNum ( MachineInstr &  MI )

static

Definition at line 212 of file RegisterScavenging.cpp.

References assert(), and MI.

scavengeFrameVirtualRegsInBlock()

static bool scavengeFrameVirtualRegsInBlock ( MachineRegisterInfo &  MRI, RegScavenger &  RS, MachineBasicBlock &  MBB  )

static

Allocate (scavenge) vregs inside a single basic block.

Returns true if the target spill callback created new vregs and a 2nd pass is necessary.

Definition at line 391 of file RegisterScavenging.cpp.

References assert(), llvm::RegScavenger::backward(), llvm::MachineBasicBlock::begin(), llvm::MachineBasicBlock::end(), llvm::RegScavenger::enterBasicBlockEnd(), llvm::MachineBasicBlock::front(), I, MBB, MI, MRI, N, llvm::MachineInstr::operands(), scavengeVReg(), llvm::RegScavenger::setRegUsed(), TRI, and llvm::Register::virtReg2Index().

Referenced by llvm::scavengeFrameVirtualRegs().

scavengeVReg()

static Register scavengeVReg ( MachineRegisterInfo &  MRI, RegScavenger &  RS, Register  VReg, bool  ReserveAfter  )

static

Allocate a register for the virtual register VReg.

The last use of VReg is around the current position of the register scavenger RS. ReserveAfter controls whether the scavenged register needs to be reserved after the current instruction, otherwise it will only be reserved before the current instruction.

Definition at line 338 of file RegisterScavenging.cpp.

References assert(), DefMI, llvm::find_if(), llvm::MachineOperand::getParent(), llvm::MachineBasicBlock::getParent(), MBB, MI, MRI, llvm::RegScavenger::scavengeRegisterBackwards(), and TRI.

Referenced by scavengeFrameVirtualRegsInBlock().

STATISTIC()

STATISTIC	(	NumScavengedRegs	,
		"Number of frame index regs scavenged"
	)