Analysis that tracks defined/used subregister lanes across COPY instructions and instructions that get lowered to a COPY (PHI, REG_SEQUENCE, INSERT_SUBREG, EXTRACT_SUBREG). More...

#include "llvm/CodeGen/DetectDeadLanes.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"

Macros
#define	DEBUG_TYPE "detect-dead-lanes"

Functions
static bool	lowersToCopies (const MachineInstr &MI)
	Returns true if `MI` will get lowered to a series of COPY instructions.

static bool	isCrossCopy (const MachineRegisterInfo &MRI, const MachineInstr &MI, const TargetRegisterClass *DstRC, const MachineOperand &MO)

Detailed Description

Analysis that tracks defined/used subregister lanes across COPY instructions and instructions that get lowered to a COPY (PHI, REG_SEQUENCE, INSERT_SUBREG, EXTRACT_SUBREG).

The information is used to detect dead definitions and the usage of (completely) undefined values and mark the operands as such. This pass is necessary because the dead/undef status is not obvious anymore when subregisters are involved.

Example: %0 = some definition %1 = IMPLICIT_DEF %2 = REG_SEQUENCE %0, sub0, %1, sub1 %3 = EXTRACT_SUBREG %2, sub1 = use %3 The %0 definition is dead and %3 contains an undefined value.

Definition in file DetectDeadLanes.cpp.

Macro Definition Documentation

◆ DEBUG_TYPE

#define DEBUG_TYPE "detect-dead-lanes"

Definition at line 39 of file DetectDeadLanes.cpp.

Function Documentation

◆ isCrossCopy()

static bool isCrossCopy	(	const MachineRegisterInfo &	MRI,
		const MachineInstr &	MI,
		const TargetRegisterClass *	DstRC,
		const MachineOperand &	MO
	)

static

Definition at line 67 of file DetectDeadLanes.cpp.

References assert(), llvm::MachineOperand::getOperandNo(), llvm::MachineOperand::getReg(), llvm::MachineOperand::getSubReg(), lowersToCopies(), MI, MRI, SubReg, and TRI.

◆ lowersToCopies()

static bool lowersToCopies ( const MachineInstr & MI )

static

Returns true if MI will get lowered to a series of COPY instructions.

We call this a COPY-like instruction.

Definition at line 52 of file DetectDeadLanes.cpp.

References MI.

Referenced by isCrossCopy(), and llvm::DeadLaneDetector::transferUsedLanes().