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llvm-project/llvm/lib/Target/ARM/ARMLoadStoreOptimizer.cpp

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//===-- ARMLoadStoreOptimizer.cpp - ARM load / store opt. pass ------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
/// \file This file contains a pass that performs load / store related peephole
/// optimizations. This pass should be run after register allocation.
//
//===----------------------------------------------------------------------===//
#include "ARM.h"
#include "ARMBaseInstrInfo.h"
#include "ARMBaseRegisterInfo.h"
#include "ARMISelLowering.h"
#include "ARMMachineFunctionInfo.h"
#include "ARMSubtarget.h"
#include "MCTargetDesc/ARMAddressingModes.h"
#include "ThumbRegisterInfo.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/RegisterClassInfo.h"
#include "llvm/CodeGen/SelectionDAGNodes.h"
#include "llvm/CodeGen/LivePhysRegs.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Function.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
using namespace llvm;
#define DEBUG_TYPE "arm-ldst-opt"
STATISTIC(NumLDMGened , "Number of ldm instructions generated");
STATISTIC(NumSTMGened , "Number of stm instructions generated");
STATISTIC(NumVLDMGened, "Number of vldm instructions generated");
STATISTIC(NumVSTMGened, "Number of vstm instructions generated");
STATISTIC(NumLdStMoved, "Number of load / store instructions moved");
STATISTIC(NumLDRDFormed,"Number of ldrd created before allocation");
STATISTIC(NumSTRDFormed,"Number of strd created before allocation");
STATISTIC(NumLDRD2LDM, "Number of ldrd instructions turned back into ldm");
STATISTIC(NumSTRD2STM, "Number of strd instructions turned back into stm");
STATISTIC(NumLDRD2LDR, "Number of ldrd instructions turned back into ldr's");
STATISTIC(NumSTRD2STR, "Number of strd instructions turned back into str's");
namespace llvm {
void initializeARMLoadStoreOptPass(PassRegistry &);
}
#define ARM_LOAD_STORE_OPT_NAME "ARM load / store optimization pass"
namespace {
/// Post- register allocation pass the combine load / store instructions to
/// form ldm / stm instructions.
struct ARMLoadStoreOpt : public MachineFunctionPass {
static char ID;
ARMLoadStoreOpt() : MachineFunctionPass(ID) {
initializeARMLoadStoreOptPass(*PassRegistry::getPassRegistry());
}
const MachineFunction *MF;
const TargetInstrInfo *TII;
const TargetRegisterInfo *TRI;
const ARMSubtarget *STI;
const TargetLowering *TL;
ARMFunctionInfo *AFI;
LivePhysRegs LiveRegs;
RegisterClassInfo RegClassInfo;
MachineBasicBlock::const_iterator LiveRegPos;
bool LiveRegsValid;
bool RegClassInfoValid;
bool isThumb1, isThumb2;
bool runOnMachineFunction(MachineFunction &Fn) override;
const char *getPassName() const override {
return ARM_LOAD_STORE_OPT_NAME;
}
private:
/// A set of load/store MachineInstrs with same base register sorted by
/// offset.
struct MemOpQueueEntry {
MachineInstr *MI;
int Offset; ///< Load/Store offset.
unsigned Position; ///< Position as counted from end of basic block.
MemOpQueueEntry(MachineInstr *MI, int Offset, unsigned Position)
: MI(MI), Offset(Offset), Position(Position) {}
};
typedef SmallVector<MemOpQueueEntry,8> MemOpQueue;
/// A set of MachineInstrs that fulfill (nearly all) conditions to get
/// merged into a LDM/STM.
struct MergeCandidate {
/// List of instructions ordered by load/store offset.
SmallVector<MachineInstr*, 4> Instrs;
/// Index in Instrs of the instruction being latest in the schedule.
unsigned LatestMIIdx;
/// Index in Instrs of the instruction being earliest in the schedule.
unsigned EarliestMIIdx;
/// Index into the basic block where the merged instruction will be
/// inserted. (See MemOpQueueEntry.Position)
unsigned InsertPos;
/// Whether the instructions can be merged into a ldm/stm instruction.
bool CanMergeToLSMulti;
/// Whether the instructions can be merged into a ldrd/strd instruction.
bool CanMergeToLSDouble;
};
SpecificBumpPtrAllocator<MergeCandidate> Allocator;
SmallVector<const MergeCandidate*,4> Candidates;
SmallVector<MachineInstr*,4> MergeBaseCandidates;
void moveLiveRegsBefore(const MachineBasicBlock &MBB,
MachineBasicBlock::const_iterator Before);
unsigned findFreeReg(const TargetRegisterClass &RegClass);
void UpdateBaseRegUses(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI,
DebugLoc DL, unsigned Base, unsigned WordOffset,
ARMCC::CondCodes Pred, unsigned PredReg);
MachineInstr *CreateLoadStoreMulti(MachineBasicBlock &MBB,
MachineBasicBlock::iterator InsertBefore, int Offset, unsigned Base,
bool BaseKill, unsigned Opcode, ARMCC::CondCodes Pred, unsigned PredReg,
DebugLoc DL, ArrayRef<std::pair<unsigned, bool>> Regs);
MachineInstr *CreateLoadStoreDouble(MachineBasicBlock &MBB,
MachineBasicBlock::iterator InsertBefore, int Offset, unsigned Base,
bool BaseKill, unsigned Opcode, ARMCC::CondCodes Pred, unsigned PredReg,
DebugLoc DL, ArrayRef<std::pair<unsigned, bool>> Regs) const;
void FormCandidates(const MemOpQueue &MemOps);
MachineInstr *MergeOpsUpdate(const MergeCandidate &Cand);
bool FixInvalidRegPairOp(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MBBI);
bool MergeBaseUpdateLoadStore(MachineInstr *MI);
bool MergeBaseUpdateLSMultiple(MachineInstr *MI);
bool MergeBaseUpdateLSDouble(MachineInstr &MI) const;
bool LoadStoreMultipleOpti(MachineBasicBlock &MBB);
bool MergeReturnIntoLDM(MachineBasicBlock &MBB);
};
char ARMLoadStoreOpt::ID = 0;
}
INITIALIZE_PASS(ARMLoadStoreOpt, "arm-load-store-opt", ARM_LOAD_STORE_OPT_NAME, false, false)
static bool definesCPSR(const MachineInstr *MI) {
for (const auto &MO : MI->operands()) {
if (!MO.isReg())
continue;
if (MO.isDef() && MO.getReg() == ARM::CPSR && !MO.isDead())
// If the instruction has live CPSR def, then it's not safe to fold it
// into load / store.
return true;
}
return false;
}
static int getMemoryOpOffset(const MachineInstr *MI) {
unsigned Opcode = MI->getOpcode();
bool isAM3 = Opcode == ARM::LDRD || Opcode == ARM::STRD;
unsigned NumOperands = MI->getDesc().getNumOperands();
unsigned OffField = MI->getOperand(NumOperands-3).getImm();
if (Opcode == ARM::t2LDRi12 || Opcode == ARM::t2LDRi8 ||
Opcode == ARM::t2STRi12 || Opcode == ARM::t2STRi8 ||
Opcode == ARM::t2LDRDi8 || Opcode == ARM::t2STRDi8 ||
Opcode == ARM::LDRi12 || Opcode == ARM::STRi12)
return OffField;
// Thumb1 immediate offsets are scaled by 4
if (Opcode == ARM::tLDRi || Opcode == ARM::tSTRi ||
Opcode == ARM::tLDRspi || Opcode == ARM::tSTRspi)
return OffField * 4;
int Offset = isAM3 ? ARM_AM::getAM3Offset(OffField)
: ARM_AM::getAM5Offset(OffField) * 4;
ARM_AM::AddrOpc Op = isAM3 ? ARM_AM::getAM3Op(OffField)
: ARM_AM::getAM5Op(OffField);
if (Op == ARM_AM::sub)
return -Offset;
return Offset;
}
static const MachineOperand &getLoadStoreBaseOp(const MachineInstr &MI) {
return MI.getOperand(1);
}
static const MachineOperand &getLoadStoreRegOp(const MachineInstr &MI) {
return MI.getOperand(0);
}
static int getLoadStoreMultipleOpcode(unsigned Opcode, ARM_AM::AMSubMode Mode) {
switch (Opcode) {
default: llvm_unreachable("Unhandled opcode!");
case ARM::LDRi12:
++NumLDMGened;
switch (Mode) {
default: llvm_unreachable("Unhandled submode!");
case ARM_AM::ia: return ARM::LDMIA;
case ARM_AM::da: return ARM::LDMDA;
case ARM_AM::db: return ARM::LDMDB;
case ARM_AM::ib: return ARM::LDMIB;
}
case ARM::STRi12:
++NumSTMGened;
switch (Mode) {
default: llvm_unreachable("Unhandled submode!");
case ARM_AM::ia: return ARM::STMIA;
case ARM_AM::da: return ARM::STMDA;
case ARM_AM::db: return ARM::STMDB;
case ARM_AM::ib: return ARM::STMIB;
}
case ARM::tLDRi:
case ARM::tLDRspi:
// tLDMIA is writeback-only - unless the base register is in the input
// reglist.
++NumLDMGened;
switch (Mode) {
default: llvm_unreachable("Unhandled submode!");
case ARM_AM::ia: return ARM::tLDMIA;
}
case ARM::tSTRi:
case ARM::tSTRspi:
// There is no non-writeback tSTMIA either.
++NumSTMGened;
switch (Mode) {
default: llvm_unreachable("Unhandled submode!");
case ARM_AM::ia: return ARM::tSTMIA_UPD;
}
case ARM::t2LDRi8:
case ARM::t2LDRi12:
++NumLDMGened;
switch (Mode) {
default: llvm_unreachable("Unhandled submode!");
case ARM_AM::ia: return ARM::t2LDMIA;
case ARM_AM::db: return ARM::t2LDMDB;
}
case ARM::t2STRi8:
case ARM::t2STRi12:
++NumSTMGened;
switch (Mode) {
default: llvm_unreachable("Unhandled submode!");
case ARM_AM::ia: return ARM::t2STMIA;
case ARM_AM::db: return ARM::t2STMDB;
}
case ARM::VLDRS:
++NumVLDMGened;
switch (Mode) {
default: llvm_unreachable("Unhandled submode!");
case ARM_AM::ia: return ARM::VLDMSIA;
case ARM_AM::db: return 0; // Only VLDMSDB_UPD exists.
}
case ARM::VSTRS:
++NumVSTMGened;
switch (Mode) {
default: llvm_unreachable("Unhandled submode!");
case ARM_AM::ia: return ARM::VSTMSIA;
case ARM_AM::db: return 0; // Only VSTMSDB_UPD exists.
}
case ARM::VLDRD:
++NumVLDMGened;
switch (Mode) {
default: llvm_unreachable("Unhandled submode!");
case ARM_AM::ia: return ARM::VLDMDIA;
case ARM_AM::db: return 0; // Only VLDMDDB_UPD exists.
}
case ARM::VSTRD:
++NumVSTMGened;
switch (Mode) {
default: llvm_unreachable("Unhandled submode!");
case ARM_AM::ia: return ARM::VSTMDIA;
case ARM_AM::db: return 0; // Only VSTMDDB_UPD exists.
}
}
}
static ARM_AM::AMSubMode getLoadStoreMultipleSubMode(unsigned Opcode) {
switch (Opcode) {
default: llvm_unreachable("Unhandled opcode!");
case ARM::LDMIA_RET:
case ARM::LDMIA:
case ARM::LDMIA_UPD:
case ARM::STMIA:
case ARM::STMIA_UPD:
case ARM::tLDMIA:
case ARM::tLDMIA_UPD:
case ARM::tSTMIA_UPD:
case ARM::t2LDMIA_RET:
case ARM::t2LDMIA:
case ARM::t2LDMIA_UPD:
case ARM::t2STMIA:
case ARM::t2STMIA_UPD:
case ARM::VLDMSIA:
case ARM::VLDMSIA_UPD:
case ARM::VSTMSIA:
case ARM::VSTMSIA_UPD:
case ARM::VLDMDIA:
case ARM::VLDMDIA_UPD:
case ARM::VSTMDIA:
case ARM::VSTMDIA_UPD:
return ARM_AM::ia;
case ARM::LDMDA:
case ARM::LDMDA_UPD:
case ARM::STMDA:
case ARM::STMDA_UPD:
return ARM_AM::da;
case ARM::LDMDB:
case ARM::LDMDB_UPD:
case ARM::STMDB:
case ARM::STMDB_UPD:
case ARM::t2LDMDB:
case ARM::t2LDMDB_UPD:
case ARM::t2STMDB:
case ARM::t2STMDB_UPD:
case ARM::VLDMSDB_UPD:
case ARM::VSTMSDB_UPD:
case ARM::VLDMDDB_UPD:
case ARM::VSTMDDB_UPD:
return ARM_AM::db;
case ARM::LDMIB:
case ARM::LDMIB_UPD:
case ARM::STMIB:
case ARM::STMIB_UPD:
return ARM_AM::ib;
}
}
static bool isT1i32Load(unsigned Opc) {
return Opc == ARM::tLDRi || Opc == ARM::tLDRspi;
}
static bool isT2i32Load(unsigned Opc) {
return Opc == ARM::t2LDRi12 || Opc == ARM::t2LDRi8;
}
static bool isi32Load(unsigned Opc) {
return Opc == ARM::LDRi12 || isT1i32Load(Opc) || isT2i32Load(Opc) ;
}
static bool isT1i32Store(unsigned Opc) {
return Opc == ARM::tSTRi || Opc == ARM::tSTRspi;
}
static bool isT2i32Store(unsigned Opc) {
return Opc == ARM::t2STRi12 || Opc == ARM::t2STRi8;
}
static bool isi32Store(unsigned Opc) {
return Opc == ARM::STRi12 || isT1i32Store(Opc) || isT2i32Store(Opc);
}
static bool isLoadSingle(unsigned Opc) {
return isi32Load(Opc) || Opc == ARM::VLDRS || Opc == ARM::VLDRD;
}
static unsigned getImmScale(unsigned Opc) {
switch (Opc) {
default: llvm_unreachable("Unhandled opcode!");
case ARM::tLDRi:
case ARM::tSTRi:
case ARM::tLDRspi:
case ARM::tSTRspi:
return 1;
case ARM::tLDRHi:
case ARM::tSTRHi:
return 2;
case ARM::tLDRBi:
case ARM::tSTRBi:
return 4;
}
}
static unsigned getLSMultipleTransferSize(const MachineInstr *MI) {
switch (MI->getOpcode()) {
default: return 0;
case ARM::LDRi12:
case ARM::STRi12:
case ARM::tLDRi:
case ARM::tSTRi:
case ARM::tLDRspi:
case ARM::tSTRspi:
case ARM::t2LDRi8:
case ARM::t2LDRi12:
case ARM::t2STRi8:
case ARM::t2STRi12:
case ARM::VLDRS:
case ARM::VSTRS:
return 4;
case ARM::VLDRD:
case ARM::VSTRD:
return 8;
case ARM::LDMIA:
case ARM::LDMDA:
case ARM::LDMDB:
case ARM::LDMIB:
case ARM::STMIA:
case ARM::STMDA:
case ARM::STMDB:
case ARM::STMIB:
case ARM::tLDMIA:
case ARM::tLDMIA_UPD:
case ARM::tSTMIA_UPD:
case ARM::t2LDMIA:
case ARM::t2LDMDB:
case ARM::t2STMIA:
case ARM::t2STMDB:
case ARM::VLDMSIA:
case ARM::VSTMSIA:
return (MI->getNumOperands() - MI->getDesc().getNumOperands() + 1) * 4;
case ARM::VLDMDIA:
case ARM::VSTMDIA:
return (MI->getNumOperands() - MI->getDesc().getNumOperands() + 1) * 8;
}
}
/// Update future uses of the base register with the offset introduced
/// due to writeback. This function only works on Thumb1.
void
ARMLoadStoreOpt::UpdateBaseRegUses(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI,
DebugLoc DL, unsigned Base,
unsigned WordOffset,
ARMCC::CondCodes Pred, unsigned PredReg) {
assert(isThumb1 && "Can only update base register uses for Thumb1!");
// Start updating any instructions with immediate offsets. Insert a SUB before
// the first non-updateable instruction (if any).
for (; MBBI != MBB.end(); ++MBBI) {
bool InsertSub = false;
unsigned Opc = MBBI->getOpcode();
if (MBBI->readsRegister(Base)) {
int Offset;
bool IsLoad =
Opc == ARM::tLDRi || Opc == ARM::tLDRHi || Opc == ARM::tLDRBi;
bool IsStore =
Opc == ARM::tSTRi || Opc == ARM::tSTRHi || Opc == ARM::tSTRBi;
if (IsLoad || IsStore) {
// Loads and stores with immediate offsets can be updated, but only if
// the new offset isn't negative.
// The MachineOperand containing the offset immediate is the last one
// before predicates.
MachineOperand &MO =
MBBI->getOperand(MBBI->getDesc().getNumOperands() - 3);
// The offsets are scaled by 1, 2 or 4 depending on the Opcode.
Offset = MO.getImm() - WordOffset * getImmScale(Opc);
// If storing the base register, it needs to be reset first.
unsigned InstrSrcReg = getLoadStoreRegOp(*MBBI).getReg();
if (Offset >= 0 && !(IsStore && InstrSrcReg == Base))
MO.setImm(Offset);
else
InsertSub = true;
} else if ((Opc == ARM::tSUBi8 || Opc == ARM::tADDi8) &&
!definesCPSR(MBBI)) {
// SUBS/ADDS using this register, with a dead def of the CPSR.
// Merge it with the update; if the merged offset is too large,
// insert a new sub instead.
MachineOperand &MO =
MBBI->getOperand(MBBI->getDesc().getNumOperands() - 3);
Offset = (Opc == ARM::tSUBi8) ?
MO.getImm() + WordOffset * 4 :
MO.getImm() - WordOffset * 4 ;
if (Offset >= 0 && TL->isLegalAddImmediate(Offset)) {
// FIXME: Swap ADDS<->SUBS if Offset < 0, erase instruction if
// Offset == 0.
MO.setImm(Offset);
// The base register has now been reset, so exit early.
return;
} else {
InsertSub = true;
}
} else {
// Can't update the instruction.
InsertSub = true;
}
} else if (definesCPSR(MBBI) || MBBI->isCall() || MBBI->isBranch()) {
// Since SUBS sets the condition flags, we can't place the base reset
// after an instruction that has a live CPSR def.
// The base register might also contain an argument for a function call.
InsertSub = true;
}
if (InsertSub) {
// An instruction above couldn't be updated, so insert a sub.
AddDefaultT1CC(BuildMI(MBB, MBBI, DL, TII->get(ARM::tSUBi8), Base), true)
.addReg(Base).addImm(WordOffset * 4).addImm(Pred).addReg(PredReg);
return;
}
if (MBBI->killsRegister(Base) || MBBI->definesRegister(Base))
// Register got killed. Stop updating.
return;
}
// End of block was reached.
if (MBB.succ_size() > 0) {
// FIXME: Because of a bug, live registers are sometimes missing from
// the successor blocks' live-in sets. This means we can't trust that
// information and *always* have to reset at the end of a block.
// See PR21029.
if (MBBI != MBB.end()) --MBBI;
AddDefaultT1CC(
BuildMI(MBB, MBBI, DL, TII->get(ARM::tSUBi8), Base), true)
.addReg(Base).addImm(WordOffset * 4).addImm(Pred).addReg(PredReg);
}
}
/// Return the first register of class \p RegClass that is not in \p Regs.
unsigned ARMLoadStoreOpt::findFreeReg(const TargetRegisterClass &RegClass) {
if (!RegClassInfoValid) {
RegClassInfo.runOnMachineFunction(*MF);
RegClassInfoValid = true;
}
for (unsigned Reg : RegClassInfo.getOrder(&RegClass))
if (!LiveRegs.contains(Reg))
return Reg;
return 0;
}
/// Compute live registers just before instruction \p Before (in normal schedule
/// direction). Computes backwards so multiple queries in the same block must
/// come in reverse order.
void ARMLoadStoreOpt::moveLiveRegsBefore(const MachineBasicBlock &MBB,
MachineBasicBlock::const_iterator Before) {
// Initialize if we never queried in this block.
if (!LiveRegsValid) {
LiveRegs.init(TRI);
LiveRegs.addLiveOuts(&MBB, true);
LiveRegPos = MBB.end();
LiveRegsValid = true;
}
// Move backward just before the "Before" position.
while (LiveRegPos != Before) {
--LiveRegPos;
LiveRegs.stepBackward(*LiveRegPos);
}
}
static bool ContainsReg(const ArrayRef<std::pair<unsigned, bool>> &Regs,
unsigned Reg) {
for (const std::pair<unsigned, bool> &R : Regs)
if (R.first == Reg)
return true;
return false;
}
/// Create and insert a LDM or STM with Base as base register and registers in
/// Regs as the register operands that would be loaded / stored. It returns
/// true if the transformation is done.
MachineInstr *ARMLoadStoreOpt::CreateLoadStoreMulti(MachineBasicBlock &MBB,
MachineBasicBlock::iterator InsertBefore, int Offset, unsigned Base,
bool BaseKill, unsigned Opcode, ARMCC::CondCodes Pred, unsigned PredReg,
DebugLoc DL, ArrayRef<std::pair<unsigned, bool>> Regs) {
unsigned NumRegs = Regs.size();
assert(NumRegs > 1);
// For Thumb1 targets, it might be necessary to clobber the CPSR to merge.
// Compute liveness information for that register to make the decision.
bool SafeToClobberCPSR = !isThumb1 ||
(MBB.computeRegisterLiveness(TRI, ARM::CPSR, InsertBefore, 20) ==
MachineBasicBlock::LQR_Dead);
bool Writeback = isThumb1; // Thumb1 LDM/STM have base reg writeback.
// Exception: If the base register is in the input reglist, Thumb1 LDM is
// non-writeback.
// It's also not possible to merge an STR of the base register in Thumb1.
if (isThumb1 && isi32Load(Opcode) && ContainsReg(Regs, Base)) {
assert(Base != ARM::SP && "Thumb1 does not allow SP in register list");
if (Opcode == ARM::tLDRi) {
Writeback = false;
} else if (Opcode == ARM::tSTRi) {
return nullptr;
}
}
ARM_AM::AMSubMode Mode = ARM_AM::ia;
// VFP and Thumb2 do not support IB or DA modes. Thumb1 only supports IA.
bool isNotVFP = isi32Load(Opcode) || isi32Store(Opcode);
bool haveIBAndDA = isNotVFP && !isThumb2 && !isThumb1;
if (Offset == 4 && haveIBAndDA) {
Mode = ARM_AM::ib;
} else if (Offset == -4 * (int)NumRegs + 4 && haveIBAndDA) {
Mode = ARM_AM::da;
} else if (Offset == -4 * (int)NumRegs && isNotVFP && !isThumb1) {
// VLDM/VSTM do not support DB mode without also updating the base reg.
Mode = ARM_AM::db;
} else if (Offset != 0 || Opcode == ARM::tLDRspi || Opcode == ARM::tSTRspi) {
// Check if this is a supported opcode before inserting instructions to
// calculate a new base register.
if (!getLoadStoreMultipleOpcode(Opcode, Mode)) return nullptr;
// If starting offset isn't zero, insert a MI to materialize a new base.
// But only do so if it is cost effective, i.e. merging more than two
// loads / stores.
if (NumRegs <= 2)
return nullptr;
// On Thumb1, it's not worth materializing a new base register without
// clobbering the CPSR (i.e. not using ADDS/SUBS).
if (!SafeToClobberCPSR)
return nullptr;
unsigned NewBase;
if (isi32Load(Opcode)) {
// If it is a load, then just use one of the destination registers
// as the new base. Will no longer be writeback in Thumb1.
NewBase = Regs[NumRegs-1].first;
Writeback = false;
} else {
// Find a free register that we can use as scratch register.
moveLiveRegsBefore(MBB, InsertBefore);
// The merged instruction does not exist yet but will use several Regs if
// it is a Store.
if (!isLoadSingle(Opcode))
for (const std::pair<unsigned, bool> &R : Regs)
LiveRegs.addReg(R.first);
NewBase = findFreeReg(isThumb1 ? ARM::tGPRRegClass : ARM::GPRRegClass);
if (NewBase == 0)
return nullptr;
}
int BaseOpc =
isThumb2 ? ARM::t2ADDri :
(isThumb1 && Base == ARM::SP) ? ARM::tADDrSPi :
(isThumb1 && Offset < 8) ? ARM::tADDi3 :
isThumb1 ? ARM::tADDi8 : ARM::ADDri;
if (Offset < 0) {
Offset = - Offset;
BaseOpc =
isThumb2 ? ARM::t2SUBri :
(isThumb1 && Offset < 8 && Base != ARM::SP) ? ARM::tSUBi3 :
isThumb1 ? ARM::tSUBi8 : ARM::SUBri;
}
if (!TL->isLegalAddImmediate(Offset))
// FIXME: Try add with register operand?
return nullptr; // Probably not worth it then.
// We can only append a kill flag to the add/sub input if the value is not
// used in the register list of the stm as well.
bool KillOldBase = BaseKill &&
(!isi32Store(Opcode) || !ContainsReg(Regs, Base));
if (isThumb1) {
// Thumb1: depending on immediate size, use either
// ADDS NewBase, Base, #imm3
// or
// MOV NewBase, Base
// ADDS NewBase, #imm8.
if (Base != NewBase &&
(BaseOpc == ARM::tADDi8 || BaseOpc == ARM::tSUBi8)) {
// Need to insert a MOV to the new base first.
if (isARMLowRegister(NewBase) && isARMLowRegister(Base) &&
!STI->hasV6Ops()) {
// thumbv4t doesn't have lo->lo copies, and we can't predicate tMOVSr
if (Pred != ARMCC::AL)
return nullptr;
BuildMI(MBB, InsertBefore, DL, TII->get(ARM::tMOVSr), NewBase)
.addReg(Base, getKillRegState(KillOldBase));
} else
BuildMI(MBB, InsertBefore, DL, TII->get(ARM::tMOVr), NewBase)
.addReg(Base, getKillRegState(KillOldBase))
.addImm(Pred).addReg(PredReg);
// The following ADDS/SUBS becomes an update.
Base = NewBase;
KillOldBase = true;
}
if (BaseOpc == ARM::tADDrSPi) {
assert(Offset % 4 == 0 && "tADDrSPi offset is scaled by 4");
BuildMI(MBB, InsertBefore, DL, TII->get(BaseOpc), NewBase)
.addReg(Base, getKillRegState(KillOldBase)).addImm(Offset/4)
.addImm(Pred).addReg(PredReg);
} else
AddDefaultT1CC(
BuildMI(MBB, InsertBefore, DL, TII->get(BaseOpc), NewBase), true)
.addReg(Base, getKillRegState(KillOldBase)).addImm(Offset)
.addImm(Pred).addReg(PredReg);
} else {
BuildMI(MBB, InsertBefore, DL, TII->get(BaseOpc), NewBase)
.addReg(Base, getKillRegState(KillOldBase)).addImm(Offset)
.addImm(Pred).addReg(PredReg).addReg(0);
}
Base = NewBase;
BaseKill = true; // New base is always killed straight away.
}
bool isDef = isLoadSingle(Opcode);
// Get LS multiple opcode. Note that for Thumb1 this might be an opcode with
// base register writeback.
Opcode = getLoadStoreMultipleOpcode(Opcode, Mode);
if (!Opcode)
return nullptr;
// Check if a Thumb1 LDM/STM merge is safe. This is the case if:
// - There is no writeback (LDM of base register),
// - the base register is killed by the merged instruction,
// - or it's safe to overwrite the condition flags, i.e. to insert a SUBS
// to reset the base register.
// Otherwise, don't merge.
// It's safe to return here since the code to materialize a new base register
// above is also conditional on SafeToClobberCPSR.
if (isThumb1 && !SafeToClobberCPSR && Writeback && !BaseKill)
return nullptr;
MachineInstrBuilder MIB;
if (Writeback) {
assert(isThumb1 && "expected Writeback only inThumb1");
if (Opcode == ARM::tLDMIA) {
assert(!(ContainsReg(Regs, Base)) && "Thumb1 can't LDM ! with Base in Regs");
// Update tLDMIA with writeback if necessary.
Opcode = ARM::tLDMIA_UPD;
}
MIB = BuildMI(MBB, InsertBefore, DL, TII->get(Opcode));
// Thumb1: we might need to set base writeback when building the MI.
MIB.addReg(Base, getDefRegState(true))
.addReg(Base, getKillRegState(BaseKill));
// The base isn't dead after a merged instruction with writeback.
// Insert a sub instruction after the newly formed instruction to reset.
if (!BaseKill)
UpdateBaseRegUses(MBB, InsertBefore, DL, Base, NumRegs, Pred, PredReg);
} else {
// No writeback, simply build the MachineInstr.
MIB = BuildMI(MBB, InsertBefore, DL, TII->get(Opcode));
MIB.addReg(Base, getKillRegState(BaseKill));
}
MIB.addImm(Pred).addReg(PredReg);
for (const std::pair<unsigned, bool> &R : Regs)
MIB.addReg(R.first, getDefRegState(isDef) | getKillRegState(R.second));
return MIB.getInstr();
}
MachineInstr *ARMLoadStoreOpt::CreateLoadStoreDouble(MachineBasicBlock &MBB,
MachineBasicBlock::iterator InsertBefore, int Offset, unsigned Base,
bool BaseKill, unsigned Opcode, ARMCC::CondCodes Pred, unsigned PredReg,
DebugLoc DL, ArrayRef<std::pair<unsigned, bool>> Regs) const {
bool IsLoad = isi32Load(Opcode);
assert((IsLoad || isi32Store(Opcode)) && "Must have integer load or store");
unsigned LoadStoreOpcode = IsLoad ? ARM::t2LDRDi8 : ARM::t2STRDi8;
assert(Regs.size() == 2);
MachineInstrBuilder MIB = BuildMI(MBB, InsertBefore, DL,
TII->get(LoadStoreOpcode));
if (IsLoad) {
MIB.addReg(Regs[0].first, RegState::Define)
.addReg(Regs[1].first, RegState::Define);
} else {
MIB.addReg(Regs[0].first, getKillRegState(Regs[0].second))
.addReg(Regs[1].first, getKillRegState(Regs[1].second));
}
MIB.addReg(Base).addImm(Offset).addImm(Pred).addReg(PredReg);
return MIB.getInstr();
}
/// Call MergeOps and update MemOps and merges accordingly on success.
MachineInstr *ARMLoadStoreOpt::MergeOpsUpdate(const MergeCandidate &Cand) {
const MachineInstr *First = Cand.Instrs.front();
unsigned Opcode = First->getOpcode();
bool IsLoad = isLoadSingle(Opcode);
SmallVector<std::pair<unsigned, bool>, 8> Regs;
SmallVector<unsigned, 4> ImpDefs;
DenseSet<unsigned> KilledRegs;
DenseSet<unsigned> UsedRegs;
// Determine list of registers and list of implicit super-register defs.
for (const MachineInstr *MI : Cand.Instrs) {
const MachineOperand &MO = getLoadStoreRegOp(*MI);
unsigned Reg = MO.getReg();
bool IsKill = MO.isKill();
if (IsKill)
KilledRegs.insert(Reg);
Regs.push_back(std::make_pair(Reg, IsKill));
UsedRegs.insert(Reg);
if (IsLoad) {
// Collect any implicit defs of super-registers, after merging we can't
// be sure anymore that we properly preserved these live ranges and must
// removed these implicit operands.
for (const MachineOperand &MO : MI->implicit_operands()) {
if (!MO.isReg() || !MO.isDef() || MO.isDead())
continue;
assert(MO.isImplicit());
unsigned DefReg = MO.getReg();
if (std::find(ImpDefs.begin(), ImpDefs.end(), DefReg) != ImpDefs.end())
continue;
// We can ignore cases where the super-reg is read and written.
if (MI->readsRegister(DefReg))
continue;
ImpDefs.push_back(DefReg);
}
}
}
// Attempt the merge.
typedef MachineBasicBlock::iterator iterator;
MachineInstr *LatestMI = Cand.Instrs[Cand.LatestMIIdx];
iterator InsertBefore = std::next(iterator(LatestMI));
MachineBasicBlock &MBB = *LatestMI->getParent();
unsigned Offset = getMemoryOpOffset(First);
unsigned Base = getLoadStoreBaseOp(*First).getReg();
bool BaseKill = LatestMI->killsRegister(Base);
unsigned PredReg = 0;
ARMCC::CondCodes Pred = getInstrPredicate(First, PredReg);
DebugLoc DL = First->getDebugLoc();
MachineInstr *Merged = nullptr;
if (Cand.CanMergeToLSDouble)
Merged = CreateLoadStoreDouble(MBB, InsertBefore, Offset, Base, BaseKill,
Opcode, Pred, PredReg, DL, Regs);
if (!Merged && Cand.CanMergeToLSMulti)
Merged = CreateLoadStoreMulti(MBB, InsertBefore, Offset, Base, BaseKill,
Opcode, Pred, PredReg, DL, Regs);
if (!Merged)
return nullptr;
// Determine earliest instruction that will get removed. We then keep an
// iterator just above it so the following erases don't invalidated it.
iterator EarliestI(Cand.Instrs[Cand.EarliestMIIdx]);
bool EarliestAtBegin = false;
if (EarliestI == MBB.begin()) {
EarliestAtBegin = true;
} else {
EarliestI = std::prev(EarliestI);
}
// Remove instructions which have been merged.
for (MachineInstr *MI : Cand.Instrs)
MBB.erase(MI);
// Determine range between the earliest removed instruction and the new one.
if (EarliestAtBegin)
EarliestI = MBB.begin();
else
EarliestI = std::next(EarliestI);
auto FixupRange = make_range(EarliestI, iterator(Merged));
if (isLoadSingle(Opcode)) {
// If the previous loads defined a super-reg, then we have to mark earlier
// operands undef; Replicate the super-reg def on the merged instruction.
for (MachineInstr &MI : FixupRange) {
for (unsigned &ImpDefReg : ImpDefs) {
for (MachineOperand &MO : MI.implicit_operands()) {
if (!MO.isReg() || MO.getReg() != ImpDefReg)
continue;
if (MO.readsReg())
MO.setIsUndef();
else if (MO.isDef())
ImpDefReg = 0;
}
}
}
MachineInstrBuilder MIB(*Merged->getParent()->getParent(), Merged);
for (unsigned ImpDef : ImpDefs)
MIB.addReg(ImpDef, RegState::ImplicitDefine);
} else {
// Remove kill flags: We are possibly storing the values later now.
assert(isi32Store(Opcode) || Opcode == ARM::VSTRS || Opcode == ARM::VSTRD);
for (MachineInstr &MI : FixupRange) {
for (MachineOperand &MO : MI.uses()) {
if (!MO.isReg() || !MO.isKill())
continue;
if (UsedRegs.count(MO.getReg()))
MO.setIsKill(false);
}
}
assert(ImpDefs.empty());
}
return Merged;
}
static bool isValidLSDoubleOffset(int Offset) {
unsigned Value = abs(Offset);
// t2LDRDi8/t2STRDi8 supports an 8 bit immediate which is internally
// multiplied by 4.
return (Value % 4) == 0 && Value < 1024;
}
/// Find candidates for load/store multiple merge in list of MemOpQueueEntries.
void ARMLoadStoreOpt::FormCandidates(const MemOpQueue &MemOps) {
const MachineInstr *FirstMI = MemOps[0].MI;
unsigned Opcode = FirstMI->getOpcode();
bool isNotVFP = isi32Load(Opcode) || isi32Store(Opcode);
unsigned Size = getLSMultipleTransferSize(FirstMI);
unsigned SIndex = 0;
unsigned EIndex = MemOps.size();
do {
// Look at the first instruction.
const MachineInstr *MI = MemOps[SIndex].MI;
int Offset = MemOps[SIndex].Offset;
const MachineOperand &PMO = getLoadStoreRegOp(*MI);
unsigned PReg = PMO.getReg();
unsigned PRegNum = PMO.isUndef() ? UINT_MAX : TRI->getEncodingValue(PReg);
unsigned Latest = SIndex;
unsigned Earliest = SIndex;
unsigned Count = 1;
bool CanMergeToLSDouble =
STI->isThumb2() && isNotVFP && isValidLSDoubleOffset(Offset);
// ARM errata 602117: LDRD with base in list may result in incorrect base
// register when interrupted or faulted.
if (STI->isCortexM3() && isi32Load(Opcode) &&
PReg == getLoadStoreBaseOp(*MI).getReg())
CanMergeToLSDouble = false;
bool CanMergeToLSMulti = true;
// On swift vldm/vstm starting with an odd register number as that needs
// more uops than single vldrs.
if (STI->isSwift() && !isNotVFP && (PRegNum % 2) == 1)
CanMergeToLSMulti = false;
// LDRD/STRD do not allow SP/PC. LDM/STM do not support it or have it
// deprecated; LDM to PC is fine but cannot happen here.
if (PReg == ARM::SP || PReg == ARM::PC)
CanMergeToLSMulti = CanMergeToLSDouble = false;
// Merge following instructions where possible.
for (unsigned I = SIndex+1; I < EIndex; ++I, ++Count) {
int NewOffset = MemOps[I].Offset;
if (NewOffset != Offset + (int)Size)
break;
const MachineOperand &MO = getLoadStoreRegOp(*MemOps[I].MI);
unsigned Reg = MO.getReg();
if (Reg == ARM::SP || Reg == ARM::PC)
break;
// See if the current load/store may be part of a multi load/store.
unsigned RegNum = MO.isUndef() ? UINT_MAX : TRI->getEncodingValue(Reg);
bool PartOfLSMulti = CanMergeToLSMulti;
if (PartOfLSMulti) {
// Register numbers must be in ascending order.
if (RegNum <= PRegNum)
PartOfLSMulti = false;
// For VFP / NEON load/store multiples, the registers must be
// consecutive and within the limit on the number of registers per
// instruction.
else if (!isNotVFP && RegNum != PRegNum+1)
PartOfLSMulti = false;
}
// See if the current load/store may be part of a double load/store.
bool PartOfLSDouble = CanMergeToLSDouble && Count <= 1;
if (!PartOfLSMulti && !PartOfLSDouble)
break;
CanMergeToLSMulti &= PartOfLSMulti;
CanMergeToLSDouble &= PartOfLSDouble;
// Track MemOp with latest and earliest position (Positions are
// counted in reverse).
unsigned Position = MemOps[I].Position;
if (Position < MemOps[Latest].Position)
Latest = I;
else if (Position > MemOps[Earliest].Position)
Earliest = I;
// Prepare for next MemOp.
Offset += Size;
PRegNum = RegNum;
}
// Form a candidate from the Ops collected so far.
MergeCandidate *Candidate = new(Allocator.Allocate()) MergeCandidate;
for (unsigned C = SIndex, CE = SIndex + Count; C < CE; ++C)
Candidate->Instrs.push_back(MemOps[C].MI);
Candidate->LatestMIIdx = Latest - SIndex;
Candidate->EarliestMIIdx = Earliest - SIndex;
Candidate->InsertPos = MemOps[Latest].Position;
if (Count == 1)
CanMergeToLSMulti = CanMergeToLSDouble = false;
Candidate->CanMergeToLSMulti = CanMergeToLSMulti;
Candidate->CanMergeToLSDouble = CanMergeToLSDouble;
Candidates.push_back(Candidate);
// Continue after the chain.
SIndex += Count;
} while (SIndex < EIndex);
}
static unsigned getUpdatingLSMultipleOpcode(unsigned Opc,
ARM_AM::AMSubMode Mode) {
switch (Opc) {
default: llvm_unreachable("Unhandled opcode!");
case ARM::LDMIA:
case ARM::LDMDA:
case ARM::LDMDB:
case ARM::LDMIB:
switch (Mode) {
default: llvm_unreachable("Unhandled submode!");
case ARM_AM::ia: return ARM::LDMIA_UPD;
case ARM_AM::ib: return ARM::LDMIB_UPD;
case ARM_AM::da: return ARM::LDMDA_UPD;
case ARM_AM::db: return ARM::LDMDB_UPD;
}
case ARM::STMIA:
case ARM::STMDA:
case ARM::STMDB:
case ARM::STMIB:
switch (Mode) {
default: llvm_unreachable("Unhandled submode!");
case ARM_AM::ia: return ARM::STMIA_UPD;
case ARM_AM::ib: return ARM::STMIB_UPD;
case ARM_AM::da: return ARM::STMDA_UPD;
case ARM_AM::db: return ARM::STMDB_UPD;
}
case ARM::t2LDMIA:
case ARM::t2LDMDB:
switch (Mode) {
default: llvm_unreachable("Unhandled submode!");
case ARM_AM::ia: return ARM::t2LDMIA_UPD;
case ARM_AM::db: return ARM::t2LDMDB_UPD;
}
case ARM::t2STMIA:
case ARM::t2STMDB:
switch (Mode) {
default: llvm_unreachable("Unhandled submode!");
case ARM_AM::ia: return ARM::t2STMIA_UPD;
case ARM_AM::db: return ARM::t2STMDB_UPD;
}
case ARM::VLDMSIA:
switch (Mode) {
default: llvm_unreachable("Unhandled submode!");
case ARM_AM::ia: return ARM::VLDMSIA_UPD;
case ARM_AM::db: return ARM::VLDMSDB_UPD;
}
case ARM::VLDMDIA:
switch (Mode) {
default: llvm_unreachable("Unhandled submode!");
case ARM_AM::ia: return ARM::VLDMDIA_UPD;
case ARM_AM::db: return ARM::VLDMDDB_UPD;
}
case ARM::VSTMSIA:
switch (Mode) {
default: llvm_unreachable("Unhandled submode!");
case ARM_AM::ia: return ARM::VSTMSIA_UPD;
case ARM_AM::db: return ARM::VSTMSDB_UPD;
}
case ARM::VSTMDIA:
switch (Mode) {
default: llvm_unreachable("Unhandled submode!");
case ARM_AM::ia: return ARM::VSTMDIA_UPD;
case ARM_AM::db: return ARM::VSTMDDB_UPD;
}
}
}
/// Check if the given instruction increments or decrements a register and
/// return the amount it is incremented/decremented. Returns 0 if the CPSR flags
/// generated by the instruction are possibly read as well.
static int isIncrementOrDecrement(const MachineInstr &MI, unsigned Reg,
ARMCC::CondCodes Pred, unsigned PredReg) {
bool CheckCPSRDef;
int Scale;
switch (MI.getOpcode()) {
case ARM::tADDi8: Scale = 4; CheckCPSRDef = true; break;
case ARM::tSUBi8: Scale = -4; CheckCPSRDef = true; break;
case ARM::t2SUBri:
case ARM::SUBri: Scale = -1; CheckCPSRDef = true; break;
case ARM::t2ADDri:
case ARM::ADDri: Scale = 1; CheckCPSRDef = true; break;
case ARM::tADDspi: Scale = 4; CheckCPSRDef = false; break;
case ARM::tSUBspi: Scale = -4; CheckCPSRDef = false; break;
default: return 0;
}
unsigned MIPredReg;
if (MI.getOperand(0).getReg() != Reg ||
MI.getOperand(1).getReg() != Reg ||
getInstrPredicate(&MI, MIPredReg) != Pred ||
MIPredReg != PredReg)
return 0;
if (CheckCPSRDef && definesCPSR(&MI))
return 0;
return MI.getOperand(2).getImm() * Scale;
}
/// Searches for an increment or decrement of \p Reg before \p MBBI.
static MachineBasicBlock::iterator
findIncDecBefore(MachineBasicBlock::iterator MBBI, unsigned Reg,
ARMCC::CondCodes Pred, unsigned PredReg, int &Offset) {
Offset = 0;
MachineBasicBlock &MBB = *MBBI->getParent();
MachineBasicBlock::iterator BeginMBBI = MBB.begin();
MachineBasicBlock::iterator EndMBBI = MBB.end();
if (MBBI == BeginMBBI)
return EndMBBI;
// Skip debug values.
MachineBasicBlock::iterator PrevMBBI = std::prev(MBBI);
while (PrevMBBI->isDebugValue() && PrevMBBI != BeginMBBI)
--PrevMBBI;
Offset = isIncrementOrDecrement(*PrevMBBI, Reg, Pred, PredReg);
return Offset == 0 ? EndMBBI : PrevMBBI;
}
/// Searches for a increment or decrement of \p Reg after \p MBBI.
static MachineBasicBlock::iterator
findIncDecAfter(MachineBasicBlock::iterator MBBI, unsigned Reg,
ARMCC::CondCodes Pred, unsigned PredReg, int &Offset) {
Offset = 0;
MachineBasicBlock &MBB = *MBBI->getParent();
MachineBasicBlock::iterator EndMBBI = MBB.end();
MachineBasicBlock::iterator NextMBBI = std::next(MBBI);
// Skip debug values.
while (NextMBBI != EndMBBI && NextMBBI->isDebugValue())
++NextMBBI;
if (NextMBBI == EndMBBI)
return EndMBBI;
Offset = isIncrementOrDecrement(*NextMBBI, Reg, Pred, PredReg);
return Offset == 0 ? EndMBBI : NextMBBI;
}
/// Fold proceeding/trailing inc/dec of base register into the
/// LDM/STM/VLDM{D|S}/VSTM{D|S} op when possible:
///
/// stmia rn, <ra, rb, rc>
/// rn := rn + 4 * 3;
/// =>
/// stmia rn!, <ra, rb, rc>
///
/// rn := rn - 4 * 3;
/// ldmia rn, <ra, rb, rc>
/// =>
/// ldmdb rn!, <ra, rb, rc>
bool ARMLoadStoreOpt::MergeBaseUpdateLSMultiple(MachineInstr *MI) {
// Thumb1 is already using updating loads/stores.
if (isThumb1) return false;
const MachineOperand &BaseOP = MI->getOperand(0);
unsigned Base = BaseOP.getReg();
bool BaseKill = BaseOP.isKill();
unsigned PredReg = 0;
ARMCC::CondCodes Pred = getInstrPredicate(MI, PredReg);
unsigned Opcode = MI->getOpcode();
DebugLoc DL = MI->getDebugLoc();
// Can't use an updating ld/st if the base register is also a dest
// register. e.g. ldmdb r0!, {r0, r1, r2}. The behavior is undefined.
for (unsigned i = 2, e = MI->getNumOperands(); i != e; ++i)
if (MI->getOperand(i).getReg() == Base)
return false;
int Bytes = getLSMultipleTransferSize(MI);
MachineBasicBlock &MBB = *MI->getParent();
MachineBasicBlock::iterator MBBI(MI);
int Offset;
MachineBasicBlock::iterator MergeInstr
= findIncDecBefore(MBBI, Base, Pred, PredReg, Offset);
ARM_AM::AMSubMode Mode = getLoadStoreMultipleSubMode(Opcode);
if (Mode == ARM_AM::ia && Offset == -Bytes) {
Mode = ARM_AM::db;
} else if (Mode == ARM_AM::ib && Offset == -Bytes) {
Mode = ARM_AM::da;
} else {
MergeInstr = findIncDecAfter(MBBI, Base, Pred, PredReg, Offset);
if (((Mode != ARM_AM::ia && Mode != ARM_AM::ib) || Offset != Bytes) &&
((Mode != ARM_AM::da && Mode != ARM_AM::db) || Offset != -Bytes))
return false;
}
MBB.erase(MergeInstr);
unsigned NewOpc = getUpdatingLSMultipleOpcode(Opcode, Mode);
MachineInstrBuilder MIB = BuildMI(MBB, MBBI, DL, TII->get(NewOpc))
.addReg(Base, getDefRegState(true)) // WB base register
.addReg(Base, getKillRegState(BaseKill))
.addImm(Pred).addReg(PredReg);
// Transfer the rest of operands.
for (unsigned OpNum = 3, e = MI->getNumOperands(); OpNum != e; ++OpNum)
MIB.addOperand(MI->getOperand(OpNum));
// Transfer memoperands.
MIB->setMemRefs(MI->memoperands_begin(), MI->memoperands_end());
MBB.erase(MBBI);
return true;
}
static unsigned getPreIndexedLoadStoreOpcode(unsigned Opc,
ARM_AM::AddrOpc Mode) {
switch (Opc) {
case ARM::LDRi12:
return ARM::LDR_PRE_IMM;
case ARM::STRi12:
return ARM::STR_PRE_IMM;
case ARM::VLDRS:
return Mode == ARM_AM::add ? ARM::VLDMSIA_UPD : ARM::VLDMSDB_UPD;
case ARM::VLDRD:
return Mode == ARM_AM::add ? ARM::VLDMDIA_UPD : ARM::VLDMDDB_UPD;
case ARM::VSTRS:
return Mode == ARM_AM::add ? ARM::VSTMSIA_UPD : ARM::VSTMSDB_UPD;
case ARM::VSTRD:
return Mode == ARM_AM::add ? ARM::VSTMDIA_UPD : ARM::VSTMDDB_UPD;
case ARM::t2LDRi8:
case ARM::t2LDRi12:
return ARM::t2LDR_PRE;
case ARM::t2STRi8:
case ARM::t2STRi12:
return ARM::t2STR_PRE;
default: llvm_unreachable("Unhandled opcode!");
}
}
static unsigned getPostIndexedLoadStoreOpcode(unsigned Opc,
ARM_AM::AddrOpc Mode) {
switch (Opc) {
case ARM::LDRi12:
return ARM::LDR_POST_IMM;
case ARM::STRi12:
return ARM::STR_POST_IMM;
case ARM::VLDRS:
return Mode == ARM_AM::add ? ARM::VLDMSIA_UPD : ARM::VLDMSDB_UPD;
case ARM::VLDRD:
return Mode == ARM_AM::add ? ARM::VLDMDIA_UPD : ARM::VLDMDDB_UPD;
case ARM::VSTRS:
return Mode == ARM_AM::add ? ARM::VSTMSIA_UPD : ARM::VSTMSDB_UPD;
case ARM::VSTRD:
return Mode == ARM_AM::add ? ARM::VSTMDIA_UPD : ARM::VSTMDDB_UPD;
case ARM::t2LDRi8:
case ARM::t2LDRi12:
return ARM::t2LDR_POST;
case ARM::t2STRi8:
case ARM::t2STRi12:
return ARM::t2STR_POST;
default: llvm_unreachable("Unhandled opcode!");
}
}
/// Fold proceeding/trailing inc/dec of base register into the
/// LDR/STR/FLD{D|S}/FST{D|S} op when possible:
bool ARMLoadStoreOpt::MergeBaseUpdateLoadStore(MachineInstr *MI) {
// Thumb1 doesn't have updating LDR/STR.
// FIXME: Use LDM/STM with single register instead.
if (isThumb1) return false;
unsigned Base = getLoadStoreBaseOp(*MI).getReg();
bool BaseKill = getLoadStoreBaseOp(*MI).isKill();
unsigned Opcode = MI->getOpcode();
DebugLoc DL = MI->getDebugLoc();
bool isAM5 = (Opcode == ARM::VLDRD || Opcode == ARM::VLDRS ||
Opcode == ARM::VSTRD || Opcode == ARM::VSTRS);
bool isAM2 = (Opcode == ARM::LDRi12 || Opcode == ARM::STRi12);
if (isi32Load(Opcode) || isi32Store(Opcode))
if (MI->getOperand(2).getImm() != 0)
return false;
if (isAM5 && ARM_AM::getAM5Offset(MI->getOperand(2).getImm()) != 0)
return false;
// Can't do the merge if the destination register is the same as the would-be
// writeback register.
if (MI->getOperand(0).getReg() == Base)
return false;
unsigned PredReg = 0;
ARMCC::CondCodes Pred = getInstrPredicate(MI, PredReg);
int Bytes = getLSMultipleTransferSize(MI);
MachineBasicBlock &MBB = *MI->getParent();
MachineBasicBlock::iterator MBBI(MI);
int Offset;
MachineBasicBlock::iterator MergeInstr
= findIncDecBefore(MBBI, Base, Pred, PredReg, Offset);
unsigned NewOpc;
if (!isAM5 && Offset == Bytes) {
NewOpc = getPreIndexedLoadStoreOpcode(Opcode, ARM_AM::add);
} else if (Offset == -Bytes) {
NewOpc = getPreIndexedLoadStoreOpcode(Opcode, ARM_AM::sub);
} else {
MergeInstr = findIncDecAfter(MBBI, Base, Pred, PredReg, Offset);
if (Offset == Bytes) {
NewOpc = getPostIndexedLoadStoreOpcode(Opcode, ARM_AM::add);
} else if (!isAM5 && Offset == -Bytes) {
NewOpc = getPostIndexedLoadStoreOpcode(Opcode, ARM_AM::sub);
} else
return false;
}
MBB.erase(MergeInstr);
ARM_AM::AddrOpc AddSub = Offset < 0 ? ARM_AM::sub : ARM_AM::add;
bool isLd = isLoadSingle(Opcode);
if (isAM5) {
// VLDM[SD]_UPD, VSTM[SD]_UPD
// (There are no base-updating versions of VLDR/VSTR instructions, but the
// updating load/store-multiple instructions can be used with only one
// register.)
MachineOperand &MO = MI->getOperand(0);
BuildMI(MBB, MBBI, DL, TII->get(NewOpc))
.addReg(Base, getDefRegState(true)) // WB base register
.addReg(Base, getKillRegState(isLd ? BaseKill : false))
.addImm(Pred).addReg(PredReg)
.addReg(MO.getReg(), (isLd ? getDefRegState(true) :
getKillRegState(MO.isKill())));
} else if (isLd) {
if (isAM2) {
// LDR_PRE, LDR_POST
if (NewOpc == ARM::LDR_PRE_IMM || NewOpc == ARM::LDRB_PRE_IMM) {
BuildMI(MBB, MBBI, DL, TII->get(NewOpc), MI->getOperand(0).getReg())
.addReg(Base, RegState::Define)
.addReg(Base).addImm(Offset).addImm(Pred).addReg(PredReg);
} else {
int Imm = ARM_AM::getAM2Opc(AddSub, Bytes, ARM_AM::no_shift);
BuildMI(MBB, MBBI, DL, TII->get(NewOpc), MI->getOperand(0).getReg())
.addReg(Base, RegState::Define)
.addReg(Base).addReg(0).addImm(Imm).addImm(Pred).addReg(PredReg);
}
} else {
// t2LDR_PRE, t2LDR_POST
BuildMI(MBB, MBBI, DL, TII->get(NewOpc), MI->getOperand(0).getReg())
.addReg(Base, RegState::Define)
.addReg(Base).addImm(Offset).addImm(Pred).addReg(PredReg);
}
} else {
MachineOperand &MO = MI->getOperand(0);
// FIXME: post-indexed stores use am2offset_imm, which still encodes
// the vestigal zero-reg offset register. When that's fixed, this clause
// can be removed entirely.
if (isAM2 && NewOpc == ARM::STR_POST_IMM) {
int Imm = ARM_AM::getAM2Opc(AddSub, Bytes, ARM_AM::no_shift);
// STR_PRE, STR_POST
BuildMI(MBB, MBBI, DL, TII->get(NewOpc), Base)
.addReg(MO.getReg(), getKillRegState(MO.isKill()))
.addReg(Base).addReg(0).addImm(Imm).addImm(Pred).addReg(PredReg);
} else {
// t2STR_PRE, t2STR_POST
BuildMI(MBB, MBBI, DL, TII->get(NewOpc), Base)
.addReg(MO.getReg(), getKillRegState(MO.isKill()))
.addReg(Base).addImm(Offset).addImm(Pred).addReg(PredReg);
}
}
MBB.erase(MBBI);
return true;
}
bool ARMLoadStoreOpt::MergeBaseUpdateLSDouble(MachineInstr &MI) const {
unsigned Opcode = MI.getOpcode();
assert((Opcode == ARM::t2LDRDi8 || Opcode == ARM::t2STRDi8) &&
"Must have t2STRDi8 or t2LDRDi8");
if (MI.getOperand(3).getImm() != 0)
return false;
// Behaviour for writeback is undefined if base register is the same as one
// of the others.
const MachineOperand &BaseOp = MI.getOperand(2);
unsigned Base = BaseOp.getReg();
const MachineOperand &Reg0Op = MI.getOperand(0);
const MachineOperand &Reg1Op = MI.getOperand(1);
if (Reg0Op.getReg() == Base || Reg1Op.getReg() == Base)
return false;
unsigned PredReg;
ARMCC::CondCodes Pred = getInstrPredicate(&MI, PredReg);
MachineBasicBlock::iterator MBBI(MI);
MachineBasicBlock &MBB = *MI.getParent();
int Offset;
MachineBasicBlock::iterator MergeInstr = findIncDecBefore(MBBI, Base, Pred,
PredReg, Offset);
unsigned NewOpc;
if (Offset == 8 || Offset == -8) {
NewOpc = Opcode == ARM::t2LDRDi8 ? ARM::t2LDRD_PRE : ARM::t2STRD_PRE;
} else {
MergeInstr = findIncDecAfter(MBBI, Base, Pred, PredReg, Offset);
if (Offset == 8 || Offset == -8) {
NewOpc = Opcode == ARM::t2LDRDi8 ? ARM::t2LDRD_POST : ARM::t2STRD_POST;
} else
return false;
}
MBB.erase(MergeInstr);
DebugLoc DL = MI.getDebugLoc();
MachineInstrBuilder MIB = BuildMI(MBB, MBBI, DL, TII->get(NewOpc));
if (NewOpc == ARM::t2LDRD_PRE || NewOpc == ARM::t2LDRD_POST) {
MIB.addOperand(Reg0Op).addOperand(Reg1Op)
.addReg(BaseOp.getReg(), RegState::Define);
} else {
assert(NewOpc == ARM::t2STRD_PRE || NewOpc == ARM::t2STRD_POST);
MIB.addReg(BaseOp.getReg(), RegState::Define)
.addOperand(Reg0Op).addOperand(Reg1Op);
}
MIB.addReg(BaseOp.getReg(), RegState::Kill)
.addImm(Offset).addImm(Pred).addReg(PredReg);
assert(TII->get(Opcode).getNumOperands() == 6 &&
TII->get(NewOpc).getNumOperands() == 7 &&
"Unexpected number of operands in Opcode specification.");
// Transfer implicit operands.
for (const MachineOperand &MO : MI.implicit_operands())
MIB.addOperand(MO);
MIB->setMemRefs(MI.memoperands_begin(), MI.memoperands_end());
MBB.erase(MBBI);
return true;
}
/// Returns true if instruction is a memory operation that this pass is capable
/// of operating on.
static bool isMemoryOp(const MachineInstr &MI) {
unsigned Opcode = MI.getOpcode();
switch (Opcode) {
case ARM::VLDRS:
case ARM::VSTRS:
case ARM::VLDRD:
case ARM::VSTRD:
case ARM::LDRi12:
case ARM::STRi12:
case ARM::tLDRi:
case ARM::tSTRi:
case ARM::tLDRspi:
case ARM::tSTRspi:
case ARM::t2LDRi8:
case ARM::t2LDRi12:
case ARM::t2STRi8:
case ARM::t2STRi12:
break;
default:
return false;
}
if (!MI.getOperand(1).isReg())
return false;
// When no memory operands are present, conservatively assume unaligned,
// volatile, unfoldable.
if (!MI.hasOneMemOperand())
return false;
const MachineMemOperand &MMO = **MI.memoperands_begin();
// Don't touch volatile memory accesses - we may be changing their order.
if (MMO.isVolatile())
return false;
// Unaligned ldr/str is emulated by some kernels, but unaligned ldm/stm is
// not.
if (MMO.getAlignment() < 4)
return false;
// str <undef> could probably be eliminated entirely, but for now we just want
// to avoid making a mess of it.
// FIXME: Use str <undef> as a wildcard to enable better stm folding.
if (MI.getOperand(0).isReg() && MI.getOperand(0).isUndef())
return false;
// Likewise don't mess with references to undefined addresses.
if (MI.getOperand(1).isUndef())
return false;
return true;
}
static void InsertLDR_STR(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MBBI,
int Offset, bool isDef,
DebugLoc DL, unsigned NewOpc,
unsigned Reg, bool RegDeadKill, bool RegUndef,
unsigned BaseReg, bool BaseKill, bool BaseUndef,
bool OffKill, bool OffUndef,
ARMCC::CondCodes Pred, unsigned PredReg,
const TargetInstrInfo *TII, bool isT2) {
if (isDef) {
MachineInstrBuilder MIB = BuildMI(MBB, MBBI, MBBI->getDebugLoc(),
TII->get(NewOpc))
.addReg(Reg, getDefRegState(true) | getDeadRegState(RegDeadKill))
.addReg(BaseReg, getKillRegState(BaseKill)|getUndefRegState(BaseUndef));
MIB.addImm(Offset).addImm(Pred).addReg(PredReg);
} else {
MachineInstrBuilder MIB = BuildMI(MBB, MBBI, MBBI->getDebugLoc(),
TII->get(NewOpc))
.addReg(Reg, getKillRegState(RegDeadKill) | getUndefRegState(RegUndef))
.addReg(BaseReg, getKillRegState(BaseKill)|getUndefRegState(BaseUndef));
MIB.addImm(Offset).addImm(Pred).addReg(PredReg);
}
}
bool ARMLoadStoreOpt::FixInvalidRegPairOp(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MBBI) {
MachineInstr *MI = &*MBBI;
unsigned Opcode = MI->getOpcode();
if (Opcode != ARM::LDRD && Opcode != ARM::STRD && Opcode != ARM::t2LDRDi8)
return false;
const MachineOperand &BaseOp = MI->getOperand(2);
unsigned BaseReg = BaseOp.getReg();
unsigned EvenReg = MI->getOperand(0).getReg();
unsigned OddReg = MI->getOperand(1).getReg();
unsigned EvenRegNum = TRI->getDwarfRegNum(EvenReg, false);
unsigned OddRegNum = TRI->getDwarfRegNum(OddReg, false);
// ARM errata 602117: LDRD with base in list may result in incorrect base
// register when interrupted or faulted.
bool Errata602117 = EvenReg == BaseReg &&
(Opcode == ARM::LDRD || Opcode == ARM::t2LDRDi8) && STI->isCortexM3();
// ARM LDRD/STRD needs consecutive registers.
bool NonConsecutiveRegs = (Opcode == ARM::LDRD || Opcode == ARM::STRD) &&
(EvenRegNum % 2 != 0 || EvenRegNum + 1 != OddRegNum);
if (!Errata602117 && !NonConsecutiveRegs)
return false;
bool isT2 = Opcode == ARM::t2LDRDi8 || Opcode == ARM::t2STRDi8;
bool isLd = Opcode == ARM::LDRD || Opcode == ARM::t2LDRDi8;
bool EvenDeadKill = isLd ?
MI->getOperand(0).isDead() : MI->getOperand(0).isKill();
bool EvenUndef = MI->getOperand(0).isUndef();
bool OddDeadKill = isLd ?
MI->getOperand(1).isDead() : MI->getOperand(1).isKill();
bool OddUndef = MI->getOperand(1).isUndef();
bool BaseKill = BaseOp.isKill();
bool BaseUndef = BaseOp.isUndef();
bool OffKill = isT2 ? false : MI->getOperand(3).isKill();
bool OffUndef = isT2 ? false : MI->getOperand(3).isUndef();
int OffImm = getMemoryOpOffset(MI);
unsigned PredReg = 0;
ARMCC::CondCodes Pred = getInstrPredicate(MI, PredReg);
if (OddRegNum > EvenRegNum && OffImm == 0) {
// Ascending register numbers and no offset. It's safe to change it to a
// ldm or stm.
unsigned NewOpc = (isLd)
? (isT2 ? ARM::t2LDMIA : ARM::LDMIA)
: (isT2 ? ARM::t2STMIA : ARM::STMIA);
if (isLd) {
BuildMI(MBB, MBBI, MBBI->getDebugLoc(), TII->get(NewOpc))
.addReg(BaseReg, getKillRegState(BaseKill))
.addImm(Pred).addReg(PredReg)
.addReg(EvenReg, getDefRegState(isLd) | getDeadRegState(EvenDeadKill))
.addReg(OddReg, getDefRegState(isLd) | getDeadRegState(OddDeadKill));
++NumLDRD2LDM;
} else {
BuildMI(MBB, MBBI, MBBI->getDebugLoc(), TII->get(NewOpc))
.addReg(BaseReg, getKillRegState(BaseKill))
.addImm(Pred).addReg(PredReg)
.addReg(EvenReg,
getKillRegState(EvenDeadKill) | getUndefRegState(EvenUndef))
.addReg(OddReg,
getKillRegState(OddDeadKill) | getUndefRegState(OddUndef));
++NumSTRD2STM;
}
} else {
// Split into two instructions.
unsigned NewOpc = (isLd)
? (isT2 ? (OffImm < 0 ? ARM::t2LDRi8 : ARM::t2LDRi12) : ARM::LDRi12)
: (isT2 ? (OffImm < 0 ? ARM::t2STRi8 : ARM::t2STRi12) : ARM::STRi12);
// Be extra careful for thumb2. t2LDRi8 can't reference a zero offset,
// so adjust and use t2LDRi12 here for that.
unsigned NewOpc2 = (isLd)
? (isT2 ? (OffImm+4 < 0 ? ARM::t2LDRi8 : ARM::t2LDRi12) : ARM::LDRi12)
: (isT2 ? (OffImm+4 < 0 ? ARM::t2STRi8 : ARM::t2STRi12) : ARM::STRi12);
DebugLoc dl = MBBI->getDebugLoc();
// If this is a load and base register is killed, it may have been
// re-defed by the load, make sure the first load does not clobber it.
if (isLd &&
(BaseKill || OffKill) &&
(TRI->regsOverlap(EvenReg, BaseReg))) {
assert(!TRI->regsOverlap(OddReg, BaseReg));
InsertLDR_STR(MBB, MBBI, OffImm+4, isLd, dl, NewOpc2,
OddReg, OddDeadKill, false,
BaseReg, false, BaseUndef, false, OffUndef,
Pred, PredReg, TII, isT2);
InsertLDR_STR(MBB, MBBI, OffImm, isLd, dl, NewOpc,
EvenReg, EvenDeadKill, false,
BaseReg, BaseKill, BaseUndef, OffKill, OffUndef,
Pred, PredReg, TII, isT2);
} else {
if (OddReg == EvenReg && EvenDeadKill) {
// If the two source operands are the same, the kill marker is
// probably on the first one. e.g.
// t2STRDi8 %R5<kill>, %R5, %R9<kill>, 0, 14, %reg0
EvenDeadKill = false;
OddDeadKill = true;
}
// Never kill the base register in the first instruction.
if (EvenReg == BaseReg)
EvenDeadKill = false;
InsertLDR_STR(MBB, MBBI, OffImm, isLd, dl, NewOpc,
EvenReg, EvenDeadKill, EvenUndef,
BaseReg, false, BaseUndef, false, OffUndef,
Pred, PredReg, TII, isT2);
InsertLDR_STR(MBB, MBBI, OffImm+4, isLd, dl, NewOpc2,
OddReg, OddDeadKill, OddUndef,
BaseReg, BaseKill, BaseUndef, OffKill, OffUndef,
Pred, PredReg, TII, isT2);
}
if (isLd)
++NumLDRD2LDR;
else
++NumSTRD2STR;
}
MBBI = MBB.erase(MBBI);
return true;
}
/// An optimization pass to turn multiple LDR / STR ops of the same base and
/// incrementing offset into LDM / STM ops.
bool ARMLoadStoreOpt::LoadStoreMultipleOpti(MachineBasicBlock &MBB) {
MemOpQueue MemOps;
unsigned CurrBase = 0;
unsigned CurrOpc = ~0u;
ARMCC::CondCodes CurrPred = ARMCC::AL;
unsigned Position = 0;
assert(Candidates.size() == 0);
assert(MergeBaseCandidates.size() == 0);
LiveRegsValid = false;
for (MachineBasicBlock::iterator I = MBB.end(), MBBI; I != MBB.begin();
I = MBBI) {
// The instruction in front of the iterator is the one we look at.
MBBI = std::prev(I);
if (FixInvalidRegPairOp(MBB, MBBI))
continue;
++Position;
if (isMemoryOp(*MBBI)) {
unsigned Opcode = MBBI->getOpcode();
const MachineOperand &MO = MBBI->getOperand(0);
unsigned Reg = MO.getReg();
unsigned Base = getLoadStoreBaseOp(*MBBI).getReg();
unsigned PredReg = 0;
ARMCC::CondCodes Pred = getInstrPredicate(MBBI, PredReg);
int Offset = getMemoryOpOffset(MBBI);
if (CurrBase == 0) {
// Start of a new chain.
CurrBase = Base;
CurrOpc = Opcode;
CurrPred = Pred;
MemOps.push_back(MemOpQueueEntry(MBBI, Offset, Position));
continue;
}
// Note: No need to match PredReg in the next if.
if (CurrOpc == Opcode && CurrBase == Base && CurrPred == Pred) {
// Watch out for:
// r4 := ldr [r0, #8]
// r4 := ldr [r0, #4]
// or
// r0 := ldr [r0]
// If a load overrides the base register or a register loaded by
// another load in our chain, we cannot take this instruction.
bool Overlap = false;
if (isLoadSingle(Opcode)) {
Overlap = (Base == Reg);
if (!Overlap) {
for (const MemOpQueueEntry &E : MemOps) {
if (TRI->regsOverlap(Reg, E.MI->getOperand(0).getReg())) {
Overlap = true;
break;
}
}
}
}
if (!Overlap) {
// Check offset and sort memory operation into the current chain.
if (Offset > MemOps.back().Offset) {
MemOps.push_back(MemOpQueueEntry(MBBI, Offset, Position));
continue;
} else {
MemOpQueue::iterator MI, ME;
for (MI = MemOps.begin(), ME = MemOps.end(); MI != ME; ++MI) {
if (Offset < MI->Offset) {
// Found a place to insert.
break;
}
if (Offset == MI->Offset) {
// Collision, abort.
MI = ME;
break;
}
}
if (MI != MemOps.end()) {
MemOps.insert(MI, MemOpQueueEntry(MBBI, Offset, Position));
continue;
}
}
}
}
// Don't advance the iterator; The op will start a new chain next.
MBBI = I;
--Position;
// Fallthrough to look into existing chain.
} else if (MBBI->isDebugValue()) {
continue;
} else if (MBBI->getOpcode() == ARM::t2LDRDi8 ||
MBBI->getOpcode() == ARM::t2STRDi8) {
// ARMPreAllocLoadStoreOpt has already formed some LDRD/STRD instructions
// remember them because we may still be able to merge add/sub into them.
MergeBaseCandidates.push_back(MBBI);
}
// If we are here then the chain is broken; Extract candidates for a merge.
if (MemOps.size() > 0) {
FormCandidates(MemOps);
// Reset for the next chain.
CurrBase = 0;
CurrOpc = ~0u;
CurrPred = ARMCC::AL;
MemOps.clear();
}
}
if (MemOps.size() > 0)
FormCandidates(MemOps);
// Sort candidates so they get processed from end to begin of the basic
// block later; This is necessary for liveness calculation.
auto LessThan = [](const MergeCandidate* M0, const MergeCandidate *M1) {
return M0->InsertPos < M1->InsertPos;
};
std::sort(Candidates.begin(), Candidates.end(), LessThan);
// Go through list of candidates and merge.
bool Changed = false;
for (const MergeCandidate *Candidate : Candidates) {
if (Candidate->CanMergeToLSMulti || Candidate->CanMergeToLSDouble) {
MachineInstr *Merged = MergeOpsUpdate(*Candidate);
// Merge preceding/trailing base inc/dec into the merged op.
if (Merged) {
Changed = true;
unsigned Opcode = Merged->getOpcode();
if (Opcode == ARM::t2STRDi8 || Opcode == ARM::t2LDRDi8)
MergeBaseUpdateLSDouble(*Merged);
else
MergeBaseUpdateLSMultiple(Merged);
} else {
for (MachineInstr *MI : Candidate->Instrs) {
if (MergeBaseUpdateLoadStore(MI))
Changed = true;
}
}
} else {
assert(Candidate->Instrs.size() == 1);
if (MergeBaseUpdateLoadStore(Candidate->Instrs.front()))
Changed = true;
}
}
Candidates.clear();
// Try to fold add/sub into the LDRD/STRD formed by ARMPreAllocLoadStoreOpt.
for (MachineInstr *MI : MergeBaseCandidates)
MergeBaseUpdateLSDouble(*MI);
MergeBaseCandidates.clear();
return Changed;
}
/// If this is a exit BB, try merging the return ops ("bx lr" and "mov pc, lr")
/// into the preceding stack restore so it directly restore the value of LR
/// into pc.
/// ldmfd sp!, {..., lr}
/// bx lr
/// or
/// ldmfd sp!, {..., lr}
/// mov pc, lr
/// =>
/// ldmfd sp!, {..., pc}
bool ARMLoadStoreOpt::MergeReturnIntoLDM(MachineBasicBlock &MBB) {
// Thumb1 LDM doesn't allow high registers.
if (isThumb1) return false;
if (MBB.empty()) return false;
MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
if (MBBI != MBB.begin() &&
(MBBI->getOpcode() == ARM::BX_RET ||
MBBI->getOpcode() == ARM::tBX_RET ||
MBBI->getOpcode() == ARM::MOVPCLR)) {
MachineInstr *PrevMI = std::prev(MBBI);
unsigned Opcode = PrevMI->getOpcode();
if (Opcode == ARM::LDMIA_UPD || Opcode == ARM::LDMDA_UPD ||
Opcode == ARM::LDMDB_UPD || Opcode == ARM::LDMIB_UPD ||
Opcode == ARM::t2LDMIA_UPD || Opcode == ARM::t2LDMDB_UPD) {
MachineOperand &MO = PrevMI->getOperand(PrevMI->getNumOperands()-1);
if (MO.getReg() != ARM::LR)
return false;
unsigned NewOpc = (isThumb2 ? ARM::t2LDMIA_RET : ARM::LDMIA_RET);
assert(((isThumb2 && Opcode == ARM::t2LDMIA_UPD) ||
Opcode == ARM::LDMIA_UPD) && "Unsupported multiple load-return!");
PrevMI->setDesc(TII->get(NewOpc));
MO.setReg(ARM::PC);
PrevMI->copyImplicitOps(*MBB.getParent(), &*MBBI);
MBB.erase(MBBI);
return true;
}
}
return false;
}
bool ARMLoadStoreOpt::runOnMachineFunction(MachineFunction &Fn) {
MF = &Fn;
STI = &static_cast<const ARMSubtarget &>(Fn.getSubtarget());
TL = STI->getTargetLowering();
AFI = Fn.getInfo<ARMFunctionInfo>();
TII = STI->getInstrInfo();
TRI = STI->getRegisterInfo();
RegClassInfoValid = false;
isThumb2 = AFI->isThumb2Function();
isThumb1 = AFI->isThumbFunction() && !isThumb2;
bool Modified = false;
for (MachineFunction::iterator MFI = Fn.begin(), E = Fn.end(); MFI != E;
++MFI) {
MachineBasicBlock &MBB = *MFI;
Modified |= LoadStoreMultipleOpti(MBB);
if (STI->hasV5TOps())
Modified |= MergeReturnIntoLDM(MBB);
}
Allocator.DestroyAll();
return Modified;
}
namespace llvm {
void initializeARMPreAllocLoadStoreOptPass(PassRegistry &);
}
#define ARM_PREALLOC_LOAD_STORE_OPT_NAME \
"ARM pre- register allocation load / store optimization pass"
namespace {
/// Pre- register allocation pass that move load / stores from consecutive
/// locations close to make it more likely they will be combined later.
struct ARMPreAllocLoadStoreOpt : public MachineFunctionPass{
static char ID;
ARMPreAllocLoadStoreOpt() : MachineFunctionPass(ID) {
initializeARMPreAllocLoadStoreOptPass(*PassRegistry::getPassRegistry());
}
const DataLayout *TD;
const TargetInstrInfo *TII;
const TargetRegisterInfo *TRI;
const ARMSubtarget *STI;
MachineRegisterInfo *MRI;
MachineFunction *MF;
bool runOnMachineFunction(MachineFunction &Fn) override;
const char *getPassName() const override {
return ARM_PREALLOC_LOAD_STORE_OPT_NAME;
}
private:
bool CanFormLdStDWord(MachineInstr *Op0, MachineInstr *Op1, DebugLoc &dl,
unsigned &NewOpc, unsigned &EvenReg,
unsigned &OddReg, unsigned &BaseReg,
int &Offset,
unsigned &PredReg, ARMCC::CondCodes &Pred,
bool &isT2);
bool RescheduleOps(MachineBasicBlock *MBB,
SmallVectorImpl<MachineInstr *> &Ops,
unsigned Base, bool isLd,
DenseMap<MachineInstr*, unsigned> &MI2LocMap);
bool RescheduleLoadStoreInstrs(MachineBasicBlock *MBB);
};
char ARMPreAllocLoadStoreOpt::ID = 0;
}
INITIALIZE_PASS(ARMPreAllocLoadStoreOpt, "arm-prera-load-store-opt",
ARM_PREALLOC_LOAD_STORE_OPT_NAME, false, false)
bool ARMPreAllocLoadStoreOpt::runOnMachineFunction(MachineFunction &Fn) {
TD = &Fn.getDataLayout();
STI = &static_cast<const ARMSubtarget &>(Fn.getSubtarget());
TII = STI->getInstrInfo();
TRI = STI->getRegisterInfo();
MRI = &Fn.getRegInfo();
MF = &Fn;
bool Modified = false;
for (MachineBasicBlock &MFI : Fn)
Modified |= RescheduleLoadStoreInstrs(&MFI);
return Modified;
}
static bool IsSafeAndProfitableToMove(bool isLd, unsigned Base,
MachineBasicBlock::iterator I,
MachineBasicBlock::iterator E,
SmallPtrSetImpl<MachineInstr*> &MemOps,
SmallSet<unsigned, 4> &MemRegs,
const TargetRegisterInfo *TRI) {
// Are there stores / loads / calls between them?
// FIXME: This is overly conservative. We should make use of alias information
// some day.
SmallSet<unsigned, 4> AddedRegPressure;
while (++I != E) {
if (I->isDebugValue() || MemOps.count(&*I))
continue;
if (I->isCall() || I->isTerminator() || I->hasUnmodeledSideEffects())
return false;
if (isLd && I->mayStore())
return false;
if (!isLd) {
if (I->mayLoad())
return false;
// It's not safe to move the first 'str' down.
// str r1, [r0]
// strh r5, [r0]
// str r4, [r0, #+4]
if (I->mayStore())
return false;
}
for (unsigned j = 0, NumOps = I->getNumOperands(); j != NumOps; ++j) {
MachineOperand &MO = I->getOperand(j);
if (!MO.isReg())
continue;
unsigned Reg = MO.getReg();
if (MO.isDef() && TRI->regsOverlap(Reg, Base))
return false;
if (Reg != Base && !MemRegs.count(Reg))
AddedRegPressure.insert(Reg);
}
}
// Estimate register pressure increase due to the transformation.
if (MemRegs.size() <= 4)
// Ok if we are moving small number of instructions.
return true;
return AddedRegPressure.size() <= MemRegs.size() * 2;
}
/// Copy \p Op0 and \p Op1 operands into a new array assigned to MI.
static void concatenateMemOperands(MachineInstr *MI, MachineInstr *Op0,
MachineInstr *Op1) {
assert(MI->memoperands_empty() && "expected a new machineinstr");
size_t numMemRefs = (Op0->memoperands_end() - Op0->memoperands_begin())
+ (Op1->memoperands_end() - Op1->memoperands_begin());
MachineFunction *MF = MI->getParent()->getParent();
MachineSDNode::mmo_iterator MemBegin = MF->allocateMemRefsArray(numMemRefs);
MachineSDNode::mmo_iterator MemEnd =
std::copy(Op0->memoperands_begin(), Op0->memoperands_end(), MemBegin);
MemEnd =
std::copy(Op1->memoperands_begin(), Op1->memoperands_end(), MemEnd);
MI->setMemRefs(MemBegin, MemEnd);
}
bool
ARMPreAllocLoadStoreOpt::CanFormLdStDWord(MachineInstr *Op0, MachineInstr *Op1,
DebugLoc &dl, unsigned &NewOpc,
unsigned &FirstReg,
unsigned &SecondReg,
unsigned &BaseReg, int &Offset,
unsigned &PredReg,
ARMCC::CondCodes &Pred,
bool &isT2) {
// Make sure we're allowed to generate LDRD/STRD.
if (!STI->hasV5TEOps())
return false;
// FIXME: VLDRS / VSTRS -> VLDRD / VSTRD
unsigned Scale = 1;
unsigned Opcode = Op0->getOpcode();
if (Opcode == ARM::LDRi12) {
NewOpc = ARM::LDRD;
} else if (Opcode == ARM::STRi12) {
NewOpc = ARM::STRD;
} else if (Opcode == ARM::t2LDRi8 || Opcode == ARM::t2LDRi12) {
NewOpc = ARM::t2LDRDi8;
Scale = 4;
isT2 = true;
} else if (Opcode == ARM::t2STRi8 || Opcode == ARM::t2STRi12) {
NewOpc = ARM::t2STRDi8;
Scale = 4;
isT2 = true;
} else {
return false;
}
// Make sure the base address satisfies i64 ld / st alignment requirement.
// At the moment, we ignore the memoryoperand's value.
// If we want to use AliasAnalysis, we should check it accordingly.
if (!Op0->hasOneMemOperand() ||
(*Op0->memoperands_begin())->isVolatile())
return false;
unsigned Align = (*Op0->memoperands_begin())->getAlignment();
const Function *Func = MF->getFunction();
unsigned ReqAlign = STI->hasV6Ops()
? TD->getABITypeAlignment(Type::getInt64Ty(Func->getContext()))
: 8; // Pre-v6 need 8-byte align
if (Align < ReqAlign)
return false;
// Then make sure the immediate offset fits.
int OffImm = getMemoryOpOffset(Op0);
if (isT2) {
int Limit = (1 << 8) * Scale;
if (OffImm >= Limit || (OffImm <= -Limit) || (OffImm & (Scale-1)))
return false;
Offset = OffImm;
} else {
ARM_AM::AddrOpc AddSub = ARM_AM::add;
if (OffImm < 0) {
AddSub = ARM_AM::sub;
OffImm = - OffImm;
}
int Limit = (1 << 8) * Scale;
if (OffImm >= Limit || (OffImm & (Scale-1)))
return false;
Offset = ARM_AM::getAM3Opc(AddSub, OffImm);
}
FirstReg = Op0->getOperand(0).getReg();
SecondReg = Op1->getOperand(0).getReg();
if (FirstReg == SecondReg)
return false;
BaseReg = Op0->getOperand(1).getReg();
Pred = getInstrPredicate(Op0, PredReg);
dl = Op0->getDebugLoc();
return true;
}
bool ARMPreAllocLoadStoreOpt::RescheduleOps(MachineBasicBlock *MBB,
SmallVectorImpl<MachineInstr *> &Ops,
unsigned Base, bool isLd,
DenseMap<MachineInstr*, unsigned> &MI2LocMap) {
bool RetVal = false;
// Sort by offset (in reverse order).
std::sort(Ops.begin(), Ops.end(),
[](const MachineInstr *LHS, const MachineInstr *RHS) {
int LOffset = getMemoryOpOffset(LHS);
int ROffset = getMemoryOpOffset(RHS);
assert(LHS == RHS || LOffset != ROffset);
return LOffset > ROffset;
});
// The loads / stores of the same base are in order. Scan them from first to
// last and check for the following:
// 1. Any def of base.
// 2. Any gaps.
while (Ops.size() > 1) {
unsigned FirstLoc = ~0U;
unsigned LastLoc = 0;
MachineInstr *FirstOp = nullptr;
MachineInstr *LastOp = nullptr;
int LastOffset = 0;
unsigned LastOpcode = 0;
unsigned LastBytes = 0;
unsigned NumMove = 0;
for (int i = Ops.size() - 1; i >= 0; --i) {
MachineInstr *Op = Ops[i];
unsigned Loc = MI2LocMap[Op];
if (Loc <= FirstLoc) {
FirstLoc = Loc;
FirstOp = Op;
}
if (Loc >= LastLoc) {
LastLoc = Loc;
LastOp = Op;
}
unsigned LSMOpcode
= getLoadStoreMultipleOpcode(Op->getOpcode(), ARM_AM::ia);
if (LastOpcode && LSMOpcode != LastOpcode)
break;
int Offset = getMemoryOpOffset(Op);
unsigned Bytes = getLSMultipleTransferSize(Op);
if (LastBytes) {
if (Bytes != LastBytes || Offset != (LastOffset + (int)Bytes))
break;
}
LastOffset = Offset;
LastBytes = Bytes;
LastOpcode = LSMOpcode;
if (++NumMove == 8) // FIXME: Tune this limit.
break;
}
if (NumMove <= 1)
Ops.pop_back();
else {
SmallPtrSet<MachineInstr*, 4> MemOps;
SmallSet<unsigned, 4> MemRegs;
for (int i = NumMove-1; i >= 0; --i) {
MemOps.insert(Ops[i]);
MemRegs.insert(Ops[i]->getOperand(0).getReg());
}
// Be conservative, if the instructions are too far apart, don't
// move them. We want to limit the increase of register pressure.
bool DoMove = (LastLoc - FirstLoc) <= NumMove*4; // FIXME: Tune this.
if (DoMove)
DoMove = IsSafeAndProfitableToMove(isLd, Base, FirstOp, LastOp,
MemOps, MemRegs, TRI);
if (!DoMove) {
for (unsigned i = 0; i != NumMove; ++i)
Ops.pop_back();
} else {
// This is the new location for the loads / stores.
MachineBasicBlock::iterator InsertPos = isLd ? FirstOp : LastOp;
while (InsertPos != MBB->end()
&& (MemOps.count(InsertPos) || InsertPos->isDebugValue()))
++InsertPos;
// If we are moving a pair of loads / stores, see if it makes sense
// to try to allocate a pair of registers that can form register pairs.
MachineInstr *Op0 = Ops.back();
MachineInstr *Op1 = Ops[Ops.size()-2];
unsigned FirstReg = 0, SecondReg = 0;
unsigned BaseReg = 0, PredReg = 0;
ARMCC::CondCodes Pred = ARMCC::AL;
bool isT2 = false;
unsigned NewOpc = 0;
int Offset = 0;
DebugLoc dl;
if (NumMove == 2 && CanFormLdStDWord(Op0, Op1, dl, NewOpc,
FirstReg, SecondReg, BaseReg,
Offset, PredReg, Pred, isT2)) {
Ops.pop_back();
Ops.pop_back();
const MCInstrDesc &MCID = TII->get(NewOpc);
const TargetRegisterClass *TRC = TII->getRegClass(MCID, 0, TRI, *MF);
MRI->constrainRegClass(FirstReg, TRC);
MRI->constrainRegClass(SecondReg, TRC);
// Form the pair instruction.
if (isLd) {
MachineInstrBuilder MIB = BuildMI(*MBB, InsertPos, dl, MCID)
.addReg(FirstReg, RegState::Define)
.addReg(SecondReg, RegState::Define)
.addReg(BaseReg);
// FIXME: We're converting from LDRi12 to an insn that still
// uses addrmode2, so we need an explicit offset reg. It should
// always by reg0 since we're transforming LDRi12s.
if (!isT2)
MIB.addReg(0);
MIB.addImm(Offset).addImm(Pred).addReg(PredReg);
concatenateMemOperands(MIB, Op0, Op1);
DEBUG(dbgs() << "Formed " << *MIB << "\n");
++NumLDRDFormed;
} else {
MachineInstrBuilder MIB = BuildMI(*MBB, InsertPos, dl, MCID)
.addReg(FirstReg)
.addReg(SecondReg)
.addReg(BaseReg);
// FIXME: We're converting from LDRi12 to an insn that still
// uses addrmode2, so we need an explicit offset reg. It should
// always by reg0 since we're transforming STRi12s.
if (!isT2)
MIB.addReg(0);
MIB.addImm(Offset).addImm(Pred).addReg(PredReg);
concatenateMemOperands(MIB, Op0, Op1);
DEBUG(dbgs() << "Formed " << *MIB << "\n");
++NumSTRDFormed;
}
MBB->erase(Op0);
MBB->erase(Op1);
if (!isT2) {
// Add register allocation hints to form register pairs.
MRI->setRegAllocationHint(FirstReg, ARMRI::RegPairEven, SecondReg);
MRI->setRegAllocationHint(SecondReg, ARMRI::RegPairOdd, FirstReg);
}
} else {
for (unsigned i = 0; i != NumMove; ++i) {
MachineInstr *Op = Ops.back();
Ops.pop_back();
MBB->splice(InsertPos, MBB, Op);
}
}
NumLdStMoved += NumMove;
RetVal = true;
}
}
}
return RetVal;
}
bool
ARMPreAllocLoadStoreOpt::RescheduleLoadStoreInstrs(MachineBasicBlock *MBB) {
bool RetVal = false;
DenseMap<MachineInstr*, unsigned> MI2LocMap;
DenseMap<unsigned, SmallVector<MachineInstr*, 4> > Base2LdsMap;
DenseMap<unsigned, SmallVector<MachineInstr*, 4> > Base2StsMap;
SmallVector<unsigned, 4> LdBases;
SmallVector<unsigned, 4> StBases;
unsigned Loc = 0;
MachineBasicBlock::iterator MBBI = MBB->begin();
MachineBasicBlock::iterator E = MBB->end();
while (MBBI != E) {
for (; MBBI != E; ++MBBI) {
MachineInstr *MI = MBBI;
if (MI->isCall() || MI->isTerminator()) {
// Stop at barriers.
++MBBI;
break;
}
if (!MI->isDebugValue())
MI2LocMap[MI] = ++Loc;
if (!isMemoryOp(*MI))
continue;
unsigned PredReg = 0;
if (getInstrPredicate(MI, PredReg) != ARMCC::AL)
continue;
int Opc = MI->getOpcode();
bool isLd = isLoadSingle(Opc);
unsigned Base = MI->getOperand(1).getReg();
int Offset = getMemoryOpOffset(MI);
bool StopHere = false;
if (isLd) {
DenseMap<unsigned, SmallVector<MachineInstr*, 4> >::iterator BI =
Base2LdsMap.find(Base);
if (BI != Base2LdsMap.end()) {
for (unsigned i = 0, e = BI->second.size(); i != e; ++i) {
if (Offset == getMemoryOpOffset(BI->second[i])) {
StopHere = true;
break;
}
}
if (!StopHere)
BI->second.push_back(MI);
} else {
Base2LdsMap[Base].push_back(MI);
LdBases.push_back(Base);
}
} else {
DenseMap<unsigned, SmallVector<MachineInstr*, 4> >::iterator BI =
Base2StsMap.find(Base);
if (BI != Base2StsMap.end()) {
for (unsigned i = 0, e = BI->second.size(); i != e; ++i) {
if (Offset == getMemoryOpOffset(BI->second[i])) {
StopHere = true;
break;
}
}
if (!StopHere)
BI->second.push_back(MI);
} else {
Base2StsMap[Base].push_back(MI);
StBases.push_back(Base);
}
}
if (StopHere) {
// Found a duplicate (a base+offset combination that's seen earlier).
// Backtrack.
--Loc;
break;
}
}
// Re-schedule loads.
for (unsigned i = 0, e = LdBases.size(); i != e; ++i) {
unsigned Base = LdBases[i];
SmallVectorImpl<MachineInstr *> &Lds = Base2LdsMap[Base];
if (Lds.size() > 1)
RetVal |= RescheduleOps(MBB, Lds, Base, true, MI2LocMap);
}
// Re-schedule stores.
for (unsigned i = 0, e = StBases.size(); i != e; ++i) {
unsigned Base = StBases[i];
SmallVectorImpl<MachineInstr *> &Sts = Base2StsMap[Base];
if (Sts.size() > 1)
RetVal |= RescheduleOps(MBB, Sts, Base, false, MI2LocMap);
}
if (MBBI != E) {
Base2LdsMap.clear();
Base2StsMap.clear();
LdBases.clear();
StBases.clear();
}
}
return RetVal;
}
/// Returns an instance of the load / store optimization pass.
FunctionPass *llvm::createARMLoadStoreOptimizationPass(bool PreAlloc) {
if (PreAlloc)
return new ARMPreAllocLoadStoreOpt();
return new ARMLoadStoreOpt();
}
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