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/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/ScopeExit.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/SparseBitVector.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	LLVM_EXPAND_INSTR_SIZES(MNEMONIC, SUFFIX)
#define	LLVM_EXPAND_ADC_SBB_INSTR(MNEMONIC)

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")
	INITIALIZE_PASS_BEGIN (X86FlagsCopyLoweringPass, DEBUG_TYPE, "X86 EFLAGS copy lowering", false, false) INITIALIZE_PASS_END(X86FlagsCopyLoweringPass
static FlagArithMnemonic	getMnemonicFromOpcode (unsigned Opcode)
static MachineBasicBlock &	splitBlock (MachineBasicBlock &MBB, MachineInstr &SplitI, const X86InstrInfo &TII)
static X86::CondCode	getCondFromFCMOV (unsigned Opcode)

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

DEBUG_TYPE

#define DEBUG_TYPE   PASS_KEY

Definition at line 66 of file X86FlagsCopyLowering.cpp.

LLVM_EXPAND_ADC_SBB_INSTR

#define LLVM_EXPAND_ADC_SBB_INSTR

(

MNEMONIC

)

Value:

  LLVM_EXPAND_INSTR_SIZES(MNEMONIC, rr)                                        \
  LLVM_EXPAND_INSTR_SIZES(MNEMONIC, rr_REV)                                    \
  LLVM_EXPAND_INSTR_SIZES(MNEMONIC, rm)                                        \
  LLVM_EXPAND_INSTR_SIZES(MNEMONIC, mr)                                        \
  case X86::MNEMONIC##8ri:                                                     \
  case X86::MNEMONIC##16ri8:                                                   \
  case X86::MNEMONIC##32ri8:                                                   \
  case X86::MNEMONIC##64ri8:                                                   \
  case X86::MNEMONIC##16ri:                                                    \
  case X86::MNEMONIC##32ri:                                                    \
  case X86::MNEMONIC##64ri32:                                                  \
  case X86::MNEMONIC##8mi:                                                     \
  case X86::MNEMONIC##16mi8:                                                   \
  case X86::MNEMONIC##32mi8:                                                   \
  case X86::MNEMONIC##64mi8:                                                   \
  case X86::MNEMONIC##16mi:                                                    \
  case X86::MNEMONIC##32mi:                                                    \
  case X86::MNEMONIC##64mi32:                                                  \
  case X86::MNEMONIC##8i8:                                                     \
  case X86::MNEMONIC##16i16:                                                   \
  case X86::MNEMONIC##32i32:                                                   \
  case X86::MNEMONIC##64i32:

LLVM_EXPAND_INSTR_SIZES

#define LLVM_EXPAND_INSTR_SIZES	(		MNEMONIC,
			SUFFIX
	)

Value:

  case X86::MNEMONIC##8##SUFFIX:                                               \
  case X86::MNEMONIC##16##SUFFIX:                                              \
  case X86::MNEMONIC##32##SUFFIX:                                              \
  case X86::MNEMONIC##64##SUFFIX:

PASS_KEY

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

Definition at line 65 of file X86FlagsCopyLowering.cpp.

Function Documentation

getCondFromFCMOV()

static X86::CondCode getCondFromFCMOV ( unsigned  Opcode )

static

Definition at line 328 of file X86FlagsCopyLowering.cpp.

References llvm::X86::COND_A, llvm::X86::COND_AE, llvm::X86::COND_B, llvm::X86::COND_BE, llvm::X86::COND_E, llvm::X86::COND_INVALID, llvm::X86::COND_NE, llvm::X86::COND_NP, and llvm::X86::COND_P.

getMnemonicFromOpcode()

static FlagArithMnemonic getMnemonicFromOpcode ( unsigned  Opcode )

static

Definition at line 166 of file X86FlagsCopyLowering.cpp.

References LLVM_EXPAND_ADC_SBB_INSTR, LLVM_EXPAND_INSTR_SIZES, r1(), and llvm::report_fatal_error().

INITIALIZE_PASS_BEGIN()

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

splitBlock()

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

static

Definition at line 228 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() [1/4]

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

STATISTIC() [2/4]

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

STATISTIC() [3/4]

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

STATISTIC() [4/4]

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

Variable Documentation

DEBUG_TYPE

DEBUG_TYPE

Definition at line 137 of file X86FlagsCopyLowering.cpp.

false

X86 EFLAGS copy false

Definition at line 138 of file X86FlagsCopyLowering.cpp.

lowering

X86 EFLAGS copy lowering

Definition at line 138 of file X86FlagsCopyLowering.cpp.