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>

Include dependency graph for X86FlagsCopyLowering.cpp:

Go to the source code of this file.

Namespaces
	llvm
	This class represents lattice values for constants.

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)

Enumerations
enum	FlagArithMnemonic
	An enumeration of the arithmetic instruction mnemonics which have interesting flag semantics. More...

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")
void	llvm::initializeX86FlagsCopyLoweringPassPass (PassRegistry &)
	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)

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 67 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:

Referenced by getMnemonicFromOpcode().

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:

Referenced by getMnemonicFromOpcode().

PASS_KEY

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

Definition at line 66 of file X86FlagsCopyLowering.cpp.

Enumeration Type Documentation

FlagArithMnemonic

enum FlagArithMnemonic

strong

An enumeration of the arithmetic instruction mnemonics which have interesting flag semantics.

We can map instruction opcodes into these mnemonics to make it easy to dispatch with specific functionality.

Definition at line 166 of file X86FlagsCopyLowering.cpp.

Function Documentation

getMnemonicFromOpcode()

static FlagArithMnemonic getMnemonicFromOpcode ( unsigned  Opcode )

static

Definition at line 176 of file X86FlagsCopyLowering.cpp.

References llvm::AArch64ISD::ADC, LLVM_EXPAND_ADC_SBB_INSTR, LLVM_EXPAND_INSTR_SIZES, r1(), llvm::report_fatal_error(), and llvm::X86ISD::SBB.

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 246 of file X86FlagsCopyLowering.cpp.

References llvm::any_of(), assert(), llvm::MachineFunction::begin(), llvm::X86::COND_INVALID, Copies, llvm::MachineBasicBlock::copySuccessor(), llvm::MachineFunction::CreateMachineBasicBlock(), llvm::MachineOperand::CreateMBB(), llvm::dbgs(), llvm::MachineBasicBlock::end(), llvm::MachineFunction::end(), llvm::X86::getCondFromBranchOpc(), llvm::MachineBasicBlock::getFallThrough(), llvm::ilist_node_impl< OptionsT >::getIterator(), llvm::MachineOperand::getMBB(), llvm::MachineFunction::getName(), llvm::MachineInstr::getOpcode(), llvm::MachineInstr::getOperand(), llvm::MachineBasicBlock::getParent(), llvm::MachineInstr::getParent(), llvm::MachineOperand::getReg(), llvm::MachineFunction::getRegInfo(), llvm::MachineFunction::getSubtarget(), llvm::MachineFunction::insert(), llvm::MachineBasicBlock::instr_end(), llvm::MachineInstr::isBranch(), llvm::MachineOperand::isMBB(), llvm::MachineOperand::isReg(), llvm::MachineBasicBlock::isSuccessor(), LLVM_DEBUG, llvm::make_scope_exit(), MI, MRI, llvm::MachineBasicBlock::normalizeSuccProbs(), llvm::SmallVectorTemplateBase< T, bool >::push_back(), llvm::MachineBasicBlock::replaceSuccessor(), llvm::report_fatal_error(), llvm::MachineOperand::setMBB(), SI, llvm::MachineBasicBlock::splice(), llvm::MachineBasicBlock::succ_begin(), llvm::MachineBasicBlock::succ_end(), llvm::MachineBasicBlock::successors(), TII, and TRI.

STATISTIC() [1/4]

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

STATISTIC() [2/4]

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

STATISTIC() [3/4]

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

STATISTIC() [4/4]

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

Variable Documentation

DEBUG_TYPE

DEBUG_TYPE

Definition at line 146 of file X86FlagsCopyLowering.cpp.

false

X86 EFLAGS copy false

Definition at line 146 of file X86FlagsCopyLowering.cpp.

lowering

X86 EFLAGS copy lowering

Definition at line 146 of file X86FlagsCopyLowering.cpp.