X86FlagsCopyLowering.cpp File Reference

Lowers COPY nodes of EFLAGS by directly extracting and preserving individual flag bits. More...

#include "X86.h"
#include "X86InstrBuilder.h"
#include "X86InstrInfo.h"
#include "X86Subtarget.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/ScopeExit.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/MachineSSAUpdater.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/CodeGen/TargetSchedule.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/MC/MCSchedule.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cassert>
#include <iterator>
#include <utility>

Go to the source code of this file.

Macros
#define	PASS_KEY   "x86-flags-copy-lowering"
#define	DEBUG_TYPE   PASS_KEY
#define	FROM_TO(A, B)
#define	CASE(A)

Enumerations
enum	EFLAGSClobber { NoClobber , EvitableClobber , InevitableClobber }

Functions
	STATISTIC (NumCopiesEliminated, "Number of copies of EFLAGS eliminated")
	STATISTIC (NumSetCCsInserted, "Number of setCC instructions inserted")
	STATISTIC (NumTestsInserted, "Number of test instructions inserted")
	STATISTIC (NumAddsInserted, "Number of adds instructions inserted")
	STATISTIC (NumNFsConvertedTo, "Number of NF instructions converted to")
	INITIALIZE_PASS_BEGIN (X86FlagsCopyLoweringPass, DEBUG_TYPE, "X86 EFLAGS copy lowering", false, false) INITIALIZE_PASS_END(X86FlagsCopyLoweringPass
static bool	isArithmeticOp (unsigned Opc)
static MachineBasicBlock &	splitBlock (MachineBasicBlock &MBB, MachineInstr &SplitI, const X86InstrInfo &TII)
static EFLAGSClobber	getClobberType (const MachineInstr &MI)
static X86::CondCode	getImplicitCondFromMI (unsigned Opc)
static unsigned	getOpcodeWithCC (unsigned Opc, X86::CondCode CC)

Variables
	DEBUG_TYPE
X86 EFLAGS copy	lowering
X86 EFLAGS copy	false

Detailed Description

Lowers COPY nodes of EFLAGS by directly extracting and preserving individual flag bits.

We have to do this by carefully analyzing and rewriting the usage of the copied EFLAGS register because there is no general way to rematerialize the entire EFLAGS register safely and efficiently. Using popf both forces dynamic stack adjustment and can create correctness issues due to IF, TF, and other non-status flags being overwritten. Using sequences involving SAHF don't work on all x86 processors and are often quite slow compared to directly testing a single status preserved in its own GPR.

Definition in file X86FlagsCopyLowering.cpp.

Macro Definition Documentation

CASE

#define CASE

(

A

)

Value:

  case X86::CMOVB_##A:                                                         \
  case X86::CMOVE_##A:                                                         \
  case X86::CMOVP_##A:                                                         \
  case X86::CMOVBE_##A:                                                        \
  case X86::CMOVNB_##A:                                                        \
  case X86::CMOVNE_##A:                                                        \
  case X86::CMOVNP_##A:                                                        \
  case X86::CMOVNBE_##A:                                                       \
    return (CC == X86::COND_E) ? X86::CMOVE_##A : X86::CMOVNE_##A;

DEBUG_TYPE

#define DEBUG_TYPE   PASS_KEY

Definition at line 63 of file X86FlagsCopyLowering.cpp.

FROM_TO

#define FROM_TO	(		A,
			B
	)

Value:

  case X86::CMOV##A##_Fp32:                                                    \
  case X86::CMOV##A##_Fp64:                                                    \
  case X86::CMOV##A##_Fp80:                                                    \
    return X86::COND_##B;

PASS_KEY

#define PASS_KEY   "x86-flags-copy-lowering"

Definition at line 62 of file X86FlagsCopyLowering.cpp.

Enumeration Type Documentation

EFLAGSClobber

enum EFLAGSClobber

Enumerator
NoClobber
EvitableClobber
InevitableClobber

Definition at line 240 of file X86FlagsCopyLowering.cpp.

Function Documentation

getClobberType()

static EFLAGSClobber getClobberType ( const MachineInstr &  MI )

static

Definition at line 242 of file X86FlagsCopyLowering.cpp.

References EvitableClobber, llvm::X86::getNFVariant(), InevitableClobber, llvm::MachineOperand::isDead(), MI, and NoClobber.

getImplicitCondFromMI()

static X86::CondCode getImplicitCondFromMI ( unsigned  Opc )

static

Definition at line 844 of file X86FlagsCopyLowering.cpp.

References A, B, llvm::X86::COND_INVALID, FROM_TO, and P.

getOpcodeWithCC()

static unsigned getOpcodeWithCC ( unsigned  Opc, X86::CondCode  CC  )

static

Definition at line 866 of file X86FlagsCopyLowering.cpp.

References assert(), CASE, CC, llvm::X86::COND_E, llvm::X86::COND_NE, and llvm_unreachable.

INITIALIZE_PASS_BEGIN()

INITIALIZE_PASS_BEGIN	(	X86FlagsCopyLoweringPass	,
		DEBUG_TYPE	,
		"X86 EFLAGS copy lowering"	,
		false	,
		false
	)

isArithmeticOp()

static bool isArithmeticOp ( unsigned  Opc )

static

Definition at line 135 of file X86FlagsCopyLowering.cpp.

splitBlock()

static MachineBasicBlock & splitBlock ( MachineBasicBlock &  MBB, MachineInstr &  SplitI, const X86InstrInfo &  TII  )

static

Definition at line 140 of file X86FlagsCopyLowering.cpp.

References assert(), llvm::X86::COND_INVALID, llvm::X86::getCondFromBranch(), llvm::ilist_node_impl< OptionsT >::getIterator(), llvm::MachineOperand::getMBB(), llvm::MachineInstr::getOperand(), llvm::MachineBasicBlock::getParent(), llvm::MachineInstr::getParent(), llvm::MachineBasicBlock::instr_end(), llvm::MachineInstr::isBranch(), MBB, and MI.

STATISTIC() [1/5]

STATISTIC	(	NumAddsInserted	,
		"Number of adds instructions inserted"
	)

STATISTIC() [2/5]

STATISTIC	(	NumCopiesEliminated	,
		"Number of copies of EFLAGS eliminated"
	)

STATISTIC() [3/5]

STATISTIC	(	NumNFsConvertedTo	,
		"Number of NF instructions converted to"
	)

STATISTIC() [4/5]

STATISTIC	(	NumSetCCsInserted	,
		"Number of setCC instructions inserted"
	)

STATISTIC() [5/5]

STATISTIC	(	NumTestsInserted	,
		"Number of test instructions inserted"
	)

Variable Documentation

DEBUG_TYPE

DEBUG_TYPE

Definition at line 121 of file X86FlagsCopyLowering.cpp.

false

X86 EFLAGS copy false

Definition at line 122 of file X86FlagsCopyLowering.cpp.

lowering

X86 EFLAGS copy lowering

Definition at line 122 of file X86FlagsCopyLowering.cpp.