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llvm-6502/lib/Target/ARM/ARMLoadStoreOptimizer.cpp
Jakob Stoklund Olesen 1dbc38f52e Move kill flags when the same register occurs more than once in a sequence. 
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92058 91177308-0d34-0410-b5e6-96231b3b80d8
2009-12-23 21:34:03 +00:00

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//===-- ARMLoadStoreOptimizer.cpp - ARM load / store opt. pass ----*- C++ -*-=//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains a pass that performs load / store related peephole
// optimizations. This pass should be run after register allocation.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "arm-ldst-opt"
#include "ARM.h"
#include "ARMAddressingModes.h"
#include "ARMBaseInstrInfo.h"
#include "ARMMachineFunctionInfo.h"
#include "ARMRegisterInfo.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.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/RegisterScavenging.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Support/ErrorHandling.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"
using namespace llvm;
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");
/// ARMAllocLoadStoreOpt - Post- register allocation pass the combine
/// load / store instructions to form ldm / stm instructions.
namespace {
struct ARMLoadStoreOpt : public MachineFunctionPass {
static char ID;
ARMLoadStoreOpt() : MachineFunctionPass(&ID) {}
const TargetInstrInfo *TII;
const TargetRegisterInfo *TRI;
ARMFunctionInfo *AFI;
RegScavenger *RS;
bool isThumb2;
virtual bool runOnMachineFunction(MachineFunction &Fn);
virtual const char *getPassName() const {
return "ARM load / store optimization pass";
}
private:
struct MemOpQueueEntry {
int Offset;
unsigned Position;
MachineBasicBlock::iterator MBBI;
bool Merged;
MemOpQueueEntry(int o, int p, MachineBasicBlock::iterator i)
: Offset(o), Position(p), MBBI(i), Merged(false) {}
};
typedef SmallVector<MemOpQueueEntry,8> MemOpQueue;
typedef MemOpQueue::iterator MemOpQueueIter;
bool MergeOps(MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
int Offset, unsigned Base, bool BaseKill, int Opcode,
ARMCC::CondCodes Pred, unsigned PredReg, unsigned Scratch,
DebugLoc dl, SmallVector<std::pair<unsigned, bool>, 8> &Regs);
void MergeOpsUpdate(MachineBasicBlock &MBB,
MemOpQueue &MemOps,
unsigned memOpsBegin,
unsigned memOpsEnd,
unsigned insertAfter,
int Offset,
unsigned Base,
bool BaseKill,
int Opcode,
ARMCC::CondCodes Pred,
unsigned PredReg,
unsigned Scratch,
DebugLoc dl,
SmallVector<MachineBasicBlock::iterator, 4> &Merges);
void MergeLDR_STR(MachineBasicBlock &MBB, unsigned SIndex, unsigned Base,
int Opcode, unsigned Size,
ARMCC::CondCodes Pred, unsigned PredReg,
unsigned Scratch, MemOpQueue &MemOps,
SmallVector<MachineBasicBlock::iterator, 4> &Merges);
void AdvanceRS(MachineBasicBlock &MBB, MemOpQueue &MemOps);
bool FixInvalidRegPairOp(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MBBI);
bool MergeBaseUpdateLoadStore(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI,
const TargetInstrInfo *TII,
bool &Advance,
MachineBasicBlock::iterator &I);
bool MergeBaseUpdateLSMultiple(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI,
bool &Advance,
MachineBasicBlock::iterator &I);
bool LoadStoreMultipleOpti(MachineBasicBlock &MBB);
bool MergeReturnIntoLDM(MachineBasicBlock &MBB);
};
char ARMLoadStoreOpt::ID = 0;
}
static int getLoadStoreMultipleOpcode(int Opcode) {
switch (Opcode) {
case ARM::LDR:
NumLDMGened++;
return ARM::LDM;
case ARM::STR:
NumSTMGened++;
return ARM::STM;
case ARM::t2LDRi8:
case ARM::t2LDRi12:
NumLDMGened++;
return ARM::t2LDM;
case ARM::t2STRi8:
case ARM::t2STRi12:
NumSTMGened++;
return ARM::t2STM;
case ARM::VLDRS:
NumVLDMGened++;
return ARM::VLDMS;
case ARM::VSTRS:
NumVSTMGened++;
return ARM::VSTMS;
case ARM::VLDRD:
NumVLDMGened++;
return ARM::VLDMD;
case ARM::VSTRD:
NumVSTMGened++;
return ARM::VSTMD;
default: llvm_unreachable("Unhandled opcode!");
}
return 0;
}
static bool isT2i32Load(unsigned Opc) {
return Opc == ARM::t2LDRi12 || Opc == ARM::t2LDRi8;
}
static bool isi32Load(unsigned Opc) {
return Opc == ARM::LDR || isT2i32Load(Opc);
}
static bool isT2i32Store(unsigned Opc) {
return Opc == ARM::t2STRi12 || Opc == ARM::t2STRi8;
}
static bool isi32Store(unsigned Opc) {
return Opc == ARM::STR || isT2i32Store(Opc);
}
/// MergeOps - 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.
bool
ARMLoadStoreOpt::MergeOps(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI,
int Offset, unsigned Base, bool BaseKill,
int Opcode, ARMCC::CondCodes Pred,
unsigned PredReg, unsigned Scratch, DebugLoc dl,
SmallVector<std::pair<unsigned, bool>, 8> &Regs) {
// Only a single register to load / store. Don't bother.
unsigned NumRegs = Regs.size();
if (NumRegs <= 1)
return false;
ARM_AM::AMSubMode Mode = ARM_AM::ia;
bool isAM4 = isi32Load(Opcode) || isi32Store(Opcode);
if (isAM4 && Offset == 4) {
if (isThumb2)
// Thumb2 does not support ldmib / stmib.
return false;
Mode = ARM_AM::ib;
} else if (isAM4 && Offset == -4 * (int)NumRegs + 4) {
if (isThumb2)
// Thumb2 does not support ldmda / stmda.
return false;
Mode = ARM_AM::da;
} else if (isAM4 && Offset == -4 * (int)NumRegs) {
Mode = ARM_AM::db;
} else if (Offset != 0) {
// 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 false;
unsigned NewBase;
if (isi32Load(Opcode))
// If it is a load, then just use one of the destination register to
// use as the new base.
NewBase = Regs[NumRegs-1].first;
else {
// Use the scratch register to use as a new base.
NewBase = Scratch;
if (NewBase == 0)
return false;
}
int BaseOpc = !isThumb2
? ARM::ADDri
: ((Base == ARM::SP) ? ARM::t2ADDrSPi : ARM::t2ADDri);
if (Offset < 0) {
BaseOpc = !isThumb2
? ARM::SUBri
: ((Base == ARM::SP) ? ARM::t2SUBrSPi : ARM::t2SUBri);
Offset = - Offset;
}
int ImmedOffset = isThumb2
? ARM_AM::getT2SOImmVal(Offset) : ARM_AM::getSOImmVal(Offset);
if (ImmedOffset == -1)
// FIXME: Try t2ADDri12 or t2SUBri12?
return false; // Probably not worth it then.
BuildMI(MBB, MBBI, dl, TII->get(BaseOpc), NewBase)
.addReg(Base, getKillRegState(BaseKill)).addImm(Offset)
.addImm(Pred).addReg(PredReg).addReg(0);
Base = NewBase;
BaseKill = true; // New base is always killed right its use.
}
bool isDPR = Opcode == ARM::VLDRD || Opcode == ARM::VSTRD;
bool isDef = isi32Load(Opcode) || Opcode == ARM::VLDRS || Opcode == ARM::VLDRD;
Opcode = getLoadStoreMultipleOpcode(Opcode);
MachineInstrBuilder MIB = (isAM4)
? BuildMI(MBB, MBBI, dl, TII->get(Opcode))
.addReg(Base, getKillRegState(BaseKill))
.addImm(ARM_AM::getAM4ModeImm(Mode)).addImm(Pred).addReg(PredReg)
: BuildMI(MBB, MBBI, dl, TII->get(Opcode))
.addReg(Base, getKillRegState(BaseKill))
.addImm(ARM_AM::getAM5Opc(Mode, false, isDPR ? NumRegs<<1 : NumRegs))
.addImm(Pred).addReg(PredReg);
MIB.addReg(0); // Add optional writeback (0 for now).
for (unsigned i = 0; i != NumRegs; ++i)
MIB = MIB.addReg(Regs[i].first, getDefRegState(isDef)
| getKillRegState(Regs[i].second));
return true;
}
// MergeOpsUpdate - call MergeOps and update MemOps and merges accordingly on
// success.
void ARMLoadStoreOpt::
MergeOpsUpdate(MachineBasicBlock &MBB,
MemOpQueue &memOps,
unsigned memOpsBegin,
unsigned memOpsEnd,
unsigned insertAfter,
int Offset,
unsigned Base,
bool BaseKill,
int Opcode,
ARMCC::CondCodes Pred,
unsigned PredReg,
unsigned Scratch,
DebugLoc dl,
SmallVector<MachineBasicBlock::iterator, 4> &Merges) {
// First calculate which of the registers should be killed by the merged
// instruction.
SmallVector<std::pair<unsigned, bool>, 8> Regs;
const unsigned insertPos = memOps[insertAfter].Position;
for (unsigned i = memOpsBegin; i < memOpsEnd; ++i) {
const MachineOperand &MO = memOps[i].MBBI->getOperand(0);
unsigned Reg = MO.getReg();
bool isKill = MO.isKill();
// If we are inserting the merged operation after an unmerged operation that
// uses the same register, make sure to transfer any kill flag.
for (unsigned j = memOpsEnd, e = memOps.size(); !isKill && j != e; ++j)
if (memOps[j].Position<insertPos) {
const MachineOperand &MOJ = memOps[j].MBBI->getOperand(0);
if (MOJ.getReg() == Reg && MOJ.isKill())
isKill = true;
}
Regs.push_back(std::make_pair(Reg, isKill));
}
// Try to do the merge.
MachineBasicBlock::iterator Loc = memOps[insertAfter].MBBI;
Loc++;
if (!MergeOps(MBB, Loc, Offset, Base, BaseKill, Opcode,
Pred, PredReg, Scratch, dl, Regs))
return;
// Merge succeeded, update records.
Merges.push_back(prior(Loc));
for (unsigned i = memOpsBegin; i < memOpsEnd; ++i) {
// Remove kill flags from any unmerged memops that come before insertPos.
if (Regs[i-memOpsBegin].second)
for (unsigned j = memOpsEnd, e = memOps.size(); j != e; ++j)
if (memOps[j].Position<insertPos) {
MachineOperand &MOJ = memOps[j].MBBI->getOperand(0);
if (MOJ.getReg() == Regs[i-memOpsBegin].first && MOJ.isKill())
MOJ.setIsKill(false);
}
MBB.erase(memOps[i].MBBI);
memOps[i].Merged = true;
}
}
/// MergeLDR_STR - Merge a number of load / store instructions into one or more
/// load / store multiple instructions.
void
ARMLoadStoreOpt::MergeLDR_STR(MachineBasicBlock &MBB, unsigned SIndex,
unsigned Base, int Opcode, unsigned Size,
ARMCC::CondCodes Pred, unsigned PredReg,
unsigned Scratch, MemOpQueue &MemOps,
SmallVector<MachineBasicBlock::iterator, 4> &Merges) {
bool isAM4 = isi32Load(Opcode) || isi32Store(Opcode);
int Offset = MemOps[SIndex].Offset;
int SOffset = Offset;
unsigned insertAfter = SIndex;
MachineBasicBlock::iterator Loc = MemOps[SIndex].MBBI;
DebugLoc dl = Loc->getDebugLoc();
const MachineOperand &PMO = Loc->getOperand(0);
unsigned PReg = PMO.getReg();
unsigned PRegNum = PMO.isUndef() ? UINT_MAX
: ARMRegisterInfo::getRegisterNumbering(PReg);
for (unsigned i = SIndex+1, e = MemOps.size(); i != e; ++i) {
int NewOffset = MemOps[i].Offset;
const MachineOperand &MO = MemOps[i].MBBI->getOperand(0);
unsigned Reg = MO.getReg();
unsigned RegNum = MO.isUndef() ? UINT_MAX
: ARMRegisterInfo::getRegisterNumbering(Reg);
// AM4 - register numbers in ascending order.
// AM5 - consecutive register numbers in ascending order.
if (NewOffset == Offset + (int)Size &&
((isAM4 && RegNum > PRegNum) || RegNum == PRegNum+1)) {
Offset += Size;
PRegNum = RegNum;
} else {
// Can't merge this in. Try merge the earlier ones first.
MergeOpsUpdate(MBB, MemOps, SIndex, i, insertAfter, SOffset,
Base, false, Opcode, Pred, PredReg, Scratch, dl, Merges);
MergeLDR_STR(MBB, i, Base, Opcode, Size, Pred, PredReg, Scratch,
MemOps, Merges);
return;
}
if (MemOps[i].Position > MemOps[insertAfter].Position)
insertAfter = i;
}
bool BaseKill = Loc->findRegisterUseOperandIdx(Base, true) != -1;
MergeOpsUpdate(MBB, MemOps, SIndex, MemOps.size(), insertAfter, SOffset,
Base, BaseKill, Opcode, Pred, PredReg, Scratch, dl, Merges);
return;
}
static inline bool isMatchingDecrement(MachineInstr *MI, unsigned Base,
unsigned Bytes, unsigned Limit,
ARMCC::CondCodes Pred, unsigned PredReg){
unsigned MyPredReg = 0;
if (!MI)
return false;
if (MI->getOpcode() != ARM::t2SUBri &&
MI->getOpcode() != ARM::t2SUBrSPi &&
MI->getOpcode() != ARM::t2SUBrSPi12 &&
MI->getOpcode() != ARM::tSUBspi &&
MI->getOpcode() != ARM::SUBri)
return false;
// Make sure the offset fits in 8 bits.
if (Bytes <= 0 || (Limit && Bytes >= Limit))
return false;
unsigned Scale = (MI->getOpcode() == ARM::tSUBspi) ? 4 : 1; // FIXME
return (MI->getOperand(0).getReg() == Base &&
MI->getOperand(1).getReg() == Base &&
(MI->getOperand(2).getImm()*Scale) == Bytes &&
llvm::getInstrPredicate(MI, MyPredReg) == Pred &&
MyPredReg == PredReg);
}
static inline bool isMatchingIncrement(MachineInstr *MI, unsigned Base,
unsigned Bytes, unsigned Limit,
ARMCC::CondCodes Pred, unsigned PredReg){
unsigned MyPredReg = 0;
if (!MI)
return false;
if (MI->getOpcode() != ARM::t2ADDri &&
MI->getOpcode() != ARM::t2ADDrSPi &&
MI->getOpcode() != ARM::t2ADDrSPi12 &&
MI->getOpcode() != ARM::tADDspi &&
MI->getOpcode() != ARM::ADDri)
return false;
if (Bytes <= 0 || (Limit && Bytes >= Limit))
// Make sure the offset fits in 8 bits.
return false;
unsigned Scale = (MI->getOpcode() == ARM::tADDspi) ? 4 : 1; // FIXME
return (MI->getOperand(0).getReg() == Base &&
MI->getOperand(1).getReg() == Base &&
(MI->getOperand(2).getImm()*Scale) == Bytes &&
llvm::getInstrPredicate(MI, MyPredReg) == Pred &&
MyPredReg == PredReg);
}
static inline unsigned getLSMultipleTransferSize(MachineInstr *MI) {
switch (MI->getOpcode()) {
default: return 0;
case ARM::LDR:
case ARM::STR:
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::LDM:
case ARM::STM:
case ARM::t2LDM:
case ARM::t2STM:
return (MI->getNumOperands() - 5) * 4;
case ARM::VLDMS:
case ARM::VSTMS:
case ARM::VLDMD:
case ARM::VSTMD:
return ARM_AM::getAM5Offset(MI->getOperand(1).getImm()) * 4;
}
}
/// MergeBaseUpdateLSMultiple - 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(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI,
bool &Advance,
MachineBasicBlock::iterator &I) {
MachineInstr *MI = MBBI;
unsigned Base = MI->getOperand(0).getReg();
unsigned Bytes = getLSMultipleTransferSize(MI);
unsigned PredReg = 0;
ARMCC::CondCodes Pred = llvm::getInstrPredicate(MI, PredReg);
int Opcode = MI->getOpcode();
bool isAM4 = Opcode == ARM::LDM || Opcode == ARM::t2LDM ||
Opcode == ARM::STM || Opcode == ARM::t2STM;
if (isAM4) {
if (ARM_AM::getAM4WBFlag(MI->getOperand(1).getImm()))
return false;
// Can't use the updating AM4 sub-mode if the base register is also a dest
// register. e.g. ldmdb r0!, {r0, r1, r2}. The behavior is undefined.
for (unsigned i = 3, e = MI->getNumOperands(); i != e; ++i) {
if (MI->getOperand(i).getReg() == Base)
return false;
}
ARM_AM::AMSubMode Mode = ARM_AM::getAM4SubMode(MI->getOperand(1).getImm());
if (MBBI != MBB.begin()) {
MachineBasicBlock::iterator PrevMBBI = prior(MBBI);
if (Mode == ARM_AM::ia &&
isMatchingDecrement(PrevMBBI, Base, Bytes, 0, Pred, PredReg)) {
MI->getOperand(1).setImm(ARM_AM::getAM4ModeImm(ARM_AM::db, true));
MI->getOperand(4).setReg(Base);
MI->getOperand(4).setIsDef();
MBB.erase(PrevMBBI);
return true;
} else if (Mode == ARM_AM::ib &&
isMatchingDecrement(PrevMBBI, Base, Bytes, 0, Pred, PredReg)) {
MI->getOperand(1).setImm(ARM_AM::getAM4ModeImm(ARM_AM::da, true));
MI->getOperand(4).setReg(Base); // WB to base
MI->getOperand(4).setIsDef();
MBB.erase(PrevMBBI);
return true;
}
}
if (MBBI != MBB.end()) {
MachineBasicBlock::iterator NextMBBI = llvm::next(MBBI);
if ((Mode == ARM_AM::ia || Mode == ARM_AM::ib) &&
isMatchingIncrement(NextMBBI, Base, Bytes, 0, Pred, PredReg)) {
MI->getOperand(1).setImm(ARM_AM::getAM4ModeImm(Mode, true));
MI->getOperand(4).setReg(Base); // WB to base
MI->getOperand(4).setIsDef();
if (NextMBBI == I) {
Advance = true;
++I;
}
MBB.erase(NextMBBI);
return true;
} else if ((Mode == ARM_AM::da || Mode == ARM_AM::db) &&
isMatchingDecrement(NextMBBI, Base, Bytes, 0, Pred, PredReg)) {
MI->getOperand(1).setImm(ARM_AM::getAM4ModeImm(Mode, true));
MI->getOperand(4).setReg(Base); // WB to base
MI->getOperand(4).setIsDef();
if (NextMBBI == I) {
Advance = true;
++I;
}
MBB.erase(NextMBBI);
return true;
}
}
} else {
// VLDM{D|S}, VSTM{D|S} addressing mode 5 ops.
if (ARM_AM::getAM5WBFlag(MI->getOperand(1).getImm()))
return false;
ARM_AM::AMSubMode Mode = ARM_AM::getAM5SubMode(MI->getOperand(1).getImm());
unsigned Offset = ARM_AM::getAM5Offset(MI->getOperand(1).getImm());
if (MBBI != MBB.begin()) {
MachineBasicBlock::iterator PrevMBBI = prior(MBBI);
if (Mode == ARM_AM::ia &&
isMatchingDecrement(PrevMBBI, Base, Bytes, 0, Pred, PredReg)) {
MI->getOperand(1).setImm(ARM_AM::getAM5Opc(ARM_AM::db, true, Offset));
MI->getOperand(4).setReg(Base); // WB to base
MI->getOperand(4).setIsDef();
MBB.erase(PrevMBBI);
return true;
}
}
if (MBBI != MBB.end()) {
MachineBasicBlock::iterator NextMBBI = llvm::next(MBBI);
if (Mode == ARM_AM::ia &&
isMatchingIncrement(NextMBBI, Base, Bytes, 0, Pred, PredReg)) {
MI->getOperand(1).setImm(ARM_AM::getAM5Opc(ARM_AM::ia, true, Offset));
MI->getOperand(4).setReg(Base); // WB to base
MI->getOperand(4).setIsDef();
if (NextMBBI == I) {
Advance = true;
++I;
}
MBB.erase(NextMBBI);
}
return true;
}
}
return false;
}
static unsigned getPreIndexedLoadStoreOpcode(unsigned Opc) {
switch (Opc) {
case ARM::LDR: return ARM::LDR_PRE;
case ARM::STR: return ARM::STR_PRE;
case ARM::VLDRS: return ARM::VLDMS;
case ARM::VLDRD: return ARM::VLDMD;
case ARM::VSTRS: return ARM::VSTMS;
case ARM::VSTRD: return ARM::VSTMD;
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!");
}
return 0;
}
static unsigned getPostIndexedLoadStoreOpcode(unsigned Opc) {
switch (Opc) {
case ARM::LDR: return ARM::LDR_POST;
case ARM::STR: return ARM::STR_POST;
case ARM::VLDRS: return ARM::VLDMS;
case ARM::VLDRD: return ARM::VLDMD;
case ARM::VSTRS: return ARM::VSTMS;
case ARM::VSTRD: return ARM::VSTMD;
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!");
}
return 0;
}
/// MergeBaseUpdateLoadStore - Fold proceeding/trailing inc/dec of base
/// register into the LDR/STR/FLD{D|S}/FST{D|S} op when possible:
bool ARMLoadStoreOpt::MergeBaseUpdateLoadStore(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI,
const TargetInstrInfo *TII,
bool &Advance,
MachineBasicBlock::iterator &I) {
MachineInstr *MI = MBBI;
unsigned Base = MI->getOperand(1).getReg();
bool BaseKill = MI->getOperand(1).isKill();
unsigned Bytes = getLSMultipleTransferSize(MI);
int 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::LDR || Opcode == ARM::STR;
if (isAM2 && ARM_AM::getAM2Offset(MI->getOperand(3).getImm()) != 0)
return false;
else if (isAM5 && ARM_AM::getAM5Offset(MI->getOperand(2).getImm()) != 0)
return false;
else if (isT2i32Load(Opcode) || isT2i32Store(Opcode))
if (MI->getOperand(2).getImm() != 0)
return false;
bool isLd = isi32Load(Opcode) || Opcode == ARM::VLDRS || Opcode == ARM::VLDRD;
// Can't do the merge if the destination register is the same as the would-be
// writeback register.
if (isLd && MI->getOperand(0).getReg() == Base)
return false;
unsigned PredReg = 0;
ARMCC::CondCodes Pred = llvm::getInstrPredicate(MI, PredReg);
bool DoMerge = false;
ARM_AM::AddrOpc AddSub = ARM_AM::add;
unsigned NewOpc = 0;
// AM2 - 12 bits, thumb2 - 8 bits.
unsigned Limit = isAM5 ? 0 : (isAM2 ? 0x1000 : 0x100);
if (MBBI != MBB.begin()) {
MachineBasicBlock::iterator PrevMBBI = prior(MBBI);
if (isMatchingDecrement(PrevMBBI, Base, Bytes, Limit, Pred, PredReg)) {
DoMerge = true;
AddSub = ARM_AM::sub;
NewOpc = getPreIndexedLoadStoreOpcode(Opcode);
} else if (!isAM5 &&
isMatchingIncrement(PrevMBBI, Base, Bytes, Limit,Pred,PredReg)) {
DoMerge = true;
NewOpc = getPreIndexedLoadStoreOpcode(Opcode);
}
if (DoMerge)
MBB.erase(PrevMBBI);
}
if (!DoMerge && MBBI != MBB.end()) {
MachineBasicBlock::iterator NextMBBI = llvm::next(MBBI);
if (!isAM5 &&
isMatchingDecrement(NextMBBI, Base, Bytes, Limit, Pred, PredReg)) {
DoMerge = true;
AddSub = ARM_AM::sub;
NewOpc = getPostIndexedLoadStoreOpcode(Opcode);
} else if (isMatchingIncrement(NextMBBI, Base, Bytes, Limit,Pred,PredReg)) {
DoMerge = true;
NewOpc = getPostIndexedLoadStoreOpcode(Opcode);
}
if (DoMerge) {
if (NextMBBI == I) {
Advance = true;
++I;
}
MBB.erase(NextMBBI);
}
}
if (!DoMerge)
return false;
bool isDPR = NewOpc == ARM::VLDMD || NewOpc == ARM::VSTMD;
unsigned Offset = 0;
if (isAM5)
Offset = ARM_AM::getAM5Opc((AddSub == ARM_AM::sub)
? ARM_AM::db
: ARM_AM::ia, true, (isDPR ? 2 : 1));
else if (isAM2)
Offset = ARM_AM::getAM2Opc(AddSub, Bytes, ARM_AM::no_shift);
else
Offset = AddSub == ARM_AM::sub ? -Bytes : Bytes;
if (isLd) {
if (isAM5)
// VLDMS, VLDMD
BuildMI(MBB, MBBI, dl, TII->get(NewOpc))
.addReg(Base, getKillRegState(BaseKill))
.addImm(Offset).addImm(Pred).addReg(PredReg)
.addReg(Base, getDefRegState(true)) // WB base register
.addReg(MI->getOperand(0).getReg(), RegState::Define);
else if (isAM2)
// LDR_PRE, LDR_POST,
BuildMI(MBB, MBBI, dl, TII->get(NewOpc), MI->getOperand(0).getReg())
.addReg(Base, RegState::Define)
.addReg(Base).addReg(0).addImm(Offset).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);
if (isAM5)
// VSTMS, VSTMD
BuildMI(MBB, MBBI, dl, TII->get(NewOpc)).addReg(Base).addImm(Offset)
.addImm(Pred).addReg(PredReg)
.addReg(Base, getDefRegState(true)) // WB base register
.addReg(MO.getReg(), getKillRegState(MO.isKill()));
else if (isAM2)
// STR_PRE, STR_POST
BuildMI(MBB, MBBI, dl, TII->get(NewOpc), Base)
.addReg(MO.getReg(), getKillRegState(MO.isKill()))
.addReg(Base).addReg(0).addImm(Offset).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;
}
/// isMemoryOp - Returns true if instruction is a memory operations (that this
/// pass is capable of operating on).
static bool isMemoryOp(const MachineInstr *MI) {
int Opcode = MI->getOpcode();
switch (Opcode) {
default: break;
case ARM::LDR:
case ARM::STR:
return MI->getOperand(1).isReg() && MI->getOperand(2).getReg() == 0;
case ARM::VLDRS:
case ARM::VSTRS:
return MI->getOperand(1).isReg();
case ARM::VLDRD:
case ARM::VSTRD:
return MI->getOperand(1).isReg();
case ARM::t2LDRi8:
case ARM::t2LDRi12:
case ARM::t2STRi8:
case ARM::t2STRi12:
return MI->getOperand(1).isReg();
}
return false;
}
/// AdvanceRS - Advance register scavenger to just before the earliest memory
/// op that is being merged.
void ARMLoadStoreOpt::AdvanceRS(MachineBasicBlock &MBB, MemOpQueue &MemOps) {
MachineBasicBlock::iterator Loc = MemOps[0].MBBI;
unsigned Position = MemOps[0].Position;
for (unsigned i = 1, e = MemOps.size(); i != e; ++i) {
if (MemOps[i].Position < Position) {
Position = MemOps[i].Position;
Loc = MemOps[i].MBBI;
}
}
if (Loc != MBB.begin())
RS->forward(prior(Loc));
}
static int getMemoryOpOffset(const MachineInstr *MI) {
int Opcode = MI->getOpcode();
bool isAM2 = Opcode == ARM::LDR || Opcode == ARM::STR;
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)
return OffField;
int Offset = isAM2
? ARM_AM::getAM2Offset(OffField)
: (isAM3 ? ARM_AM::getAM3Offset(OffField)
: ARM_AM::getAM5Offset(OffField) * 4);
if (isAM2) {
if (ARM_AM::getAM2Op(OffField) == ARM_AM::sub)
Offset = -Offset;
} else if (isAM3) {
if (ARM_AM::getAM3Op(OffField) == ARM_AM::sub)
Offset = -Offset;
} else {
if (ARM_AM::getAM5Op(OffField) == ARM_AM::sub)
Offset = -Offset;
}
return Offset;
}
static void InsertLDR_STR(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MBBI,
int OffImm, bool isDef,
DebugLoc dl, unsigned NewOpc,
unsigned Reg, bool RegDeadKill, bool RegUndef,
unsigned BaseReg, bool BaseKill, bool BaseUndef,
unsigned OffReg, bool OffKill, bool OffUndef,
ARMCC::CondCodes Pred, unsigned PredReg,
const TargetInstrInfo *TII, bool isT2) {
int Offset = OffImm;
if (!isT2) {
if (OffImm < 0)
Offset = ARM_AM::getAM2Opc(ARM_AM::sub, -OffImm, ARM_AM::no_shift);
else
Offset = ARM_AM::getAM2Opc(ARM_AM::add, OffImm, ARM_AM::no_shift);
}
if (isDef) {
MachineInstrBuilder MIB = BuildMI(MBB, MBBI, MBBI->getDebugLoc(),
TII->get(NewOpc))
.addReg(Reg, getDefRegState(true) | getDeadRegState(RegDeadKill))
.addReg(BaseReg, getKillRegState(BaseKill)|getUndefRegState(BaseUndef));
if (!isT2)
MIB.addReg(OffReg, getKillRegState(OffKill)|getUndefRegState(OffUndef));
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));
if (!isT2)
MIB.addReg(OffReg, getKillRegState(OffKill)|getUndefRegState(OffUndef));
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 || Opcode == ARM::t2STRDi8) {
unsigned EvenReg = MI->getOperand(0).getReg();
unsigned OddReg = MI->getOperand(1).getReg();
unsigned EvenRegNum = TRI->getDwarfRegNum(EvenReg, false);
unsigned OddRegNum = TRI->getDwarfRegNum(OddReg, false);
if ((EvenRegNum & 1) == 0 && (EvenRegNum + 1) == OddRegNum)
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();
const MachineOperand &BaseOp = MI->getOperand(2);
unsigned BaseReg = BaseOp.getReg();
bool BaseKill = BaseOp.isKill();
bool BaseUndef = BaseOp.isUndef();
unsigned OffReg = isT2 ? 0 : MI->getOperand(3).getReg();
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 = llvm::getInstrPredicate(MI, PredReg);
if (OddRegNum > EvenRegNum && OffReg == 0 && OffImm == 0) {
// Ascending register numbers and no offset. It's safe to change it to a
// ldm or stm.
unsigned NewOpc = (isLd)
? (isT2 ? ARM::t2LDM : ARM::LDM)
: (isT2 ? ARM::t2STM : ARM::STM);
if (isLd) {
BuildMI(MBB, MBBI, MBBI->getDebugLoc(), TII->get(NewOpc))
.addReg(BaseReg, getKillRegState(BaseKill))
.addImm(ARM_AM::getAM4ModeImm(ARM_AM::ia))
.addImm(Pred).addReg(PredReg)
.addReg(0)
.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(ARM_AM::getAM4ModeImm(ARM_AM::ia))
.addImm(Pred).addReg(PredReg)
.addReg(0)
.addReg(EvenReg,
getKillRegState(EvenDeadKill) | getUndefRegState(EvenUndef))
.addReg(OddReg,
getKillRegState(OddDeadKill) | getUndefRegState(OddUndef));
++NumSTRD2STM;
}
} else {
// Split into two instructions.
assert((!isT2 || !OffReg) &&
"Thumb2 ldrd / strd does not encode offset register!");
unsigned NewOpc = (isLd)
? (isT2 ? (OffImm < 0 ? ARM::t2LDRi8 : ARM::t2LDRi12) : ARM::LDR)
: (isT2 ? (OffImm < 0 ? ARM::t2STRi8 : ARM::t2STRi12) : ARM::STR);
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) ||
(OffReg && TRI->regsOverlap(EvenReg, OffReg)))) {
assert(!TRI->regsOverlap(OddReg, BaseReg) &&
(!OffReg || !TRI->regsOverlap(OddReg, OffReg)));
InsertLDR_STR(MBB, MBBI, OffImm+4, isLd, dl, NewOpc,
OddReg, OddDeadKill, false,
BaseReg, false, BaseUndef, OffReg, false, OffUndef,
Pred, PredReg, TII, isT2);
InsertLDR_STR(MBB, MBBI, OffImm, isLd, dl, NewOpc,
EvenReg, EvenDeadKill, false,
BaseReg, BaseKill, BaseUndef, OffReg, 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;
}
InsertLDR_STR(MBB, MBBI, OffImm, isLd, dl, NewOpc,
EvenReg, EvenDeadKill, EvenUndef,
BaseReg, false, BaseUndef, OffReg, false, OffUndef,
Pred, PredReg, TII, isT2);
InsertLDR_STR(MBB, MBBI, OffImm+4, isLd, dl, NewOpc,
OddReg, OddDeadKill, OddUndef,
BaseReg, BaseKill, BaseUndef, OffReg, OffKill, OffUndef,
Pred, PredReg, TII, isT2);
}
if (isLd)
++NumLDRD2LDR;
else
++NumSTRD2STR;
}
MBBI = prior(MBBI);
MBB.erase(MI);
}
return false;
}
/// LoadStoreMultipleOpti - 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) {
unsigned NumMerges = 0;
unsigned NumMemOps = 0;
MemOpQueue MemOps;
unsigned CurrBase = 0;
int CurrOpc = -1;
unsigned CurrSize = 0;
ARMCC::CondCodes CurrPred = ARMCC::AL;
unsigned CurrPredReg = 0;
unsigned Position = 0;
SmallVector<MachineBasicBlock::iterator,4> Merges;
RS->enterBasicBlock(&MBB);
MachineBasicBlock::iterator MBBI = MBB.begin(), E = MBB.end();
while (MBBI != E) {
if (FixInvalidRegPairOp(MBB, MBBI))
continue;
bool Advance = false;
bool TryMerge = false;
bool Clobber = false;
bool isMemOp = isMemoryOp(MBBI);
if (isMemOp) {
int Opcode = MBBI->getOpcode();
unsigned Size = getLSMultipleTransferSize(MBBI);
unsigned Base = MBBI->getOperand(1).getReg();
unsigned PredReg = 0;
ARMCC::CondCodes Pred = llvm::getInstrPredicate(MBBI, PredReg);
int Offset = getMemoryOpOffset(MBBI);
// Watch out for:
// r4 := ldr [r5]
// r5 := ldr [r5, #4]
// r6 := ldr [r5, #8]
//
// The second ldr has effectively broken the chain even though it
// looks like the later ldr(s) use the same base register. Try to
// merge the ldr's so far, including this one. But don't try to
// combine the following ldr(s).
Clobber = (isi32Load(Opcode) && Base == MBBI->getOperand(0).getReg());
if (CurrBase == 0 && !Clobber) {
// Start of a new chain.
CurrBase = Base;
CurrOpc = Opcode;
CurrSize = Size;
CurrPred = Pred;
CurrPredReg = PredReg;
MemOps.push_back(MemOpQueueEntry(Offset, Position, MBBI));
NumMemOps++;
Advance = true;
} else {
if (Clobber) {
TryMerge = true;
Advance = true;
}
if (CurrOpc == Opcode && CurrBase == Base && CurrPred == Pred) {
// No need to match PredReg.
// Continue adding to the queue.
if (Offset > MemOps.back().Offset) {
MemOps.push_back(MemOpQueueEntry(Offset, Position, MBBI));
NumMemOps++;
Advance = true;
} else {
for (MemOpQueueIter I = MemOps.begin(), E = MemOps.end();
I != E; ++I) {
if (Offset < I->Offset) {
MemOps.insert(I, MemOpQueueEntry(Offset, Position, MBBI));
NumMemOps++;
Advance = true;
break;
} else if (Offset == I->Offset) {
// Collision! This can't be merged!
break;
}
}
}
}
}
}
if (Advance) {
++Position;
++MBBI;
if (MBBI == E)
// Reach the end of the block, try merging the memory instructions.
TryMerge = true;
} else
TryMerge = true;
if (TryMerge) {
if (NumMemOps > 1) {
// Try to find a free register to use as a new base in case it's needed.
// First advance to the instruction just before the start of the chain.
AdvanceRS(MBB, MemOps);
// Find a scratch register.
unsigned Scratch = RS->FindUnusedReg(ARM::GPRRegisterClass);
// Process the load / store instructions.
RS->forward(prior(MBBI));
// Merge ops.
Merges.clear();
MergeLDR_STR(MBB, 0, CurrBase, CurrOpc, CurrSize,
CurrPred, CurrPredReg, Scratch, MemOps, Merges);
// Try folding preceeding/trailing base inc/dec into the generated
// LDM/STM ops.
for (unsigned i = 0, e = Merges.size(); i < e; ++i)
if (MergeBaseUpdateLSMultiple(MBB, Merges[i], Advance, MBBI))
++NumMerges;
NumMerges += Merges.size();
// Try folding preceeding/trailing base inc/dec into those load/store
// that were not merged to form LDM/STM ops.
for (unsigned i = 0; i != NumMemOps; ++i)
if (!MemOps[i].Merged)
if (MergeBaseUpdateLoadStore(MBB, MemOps[i].MBBI, TII,Advance,MBBI))
++NumMerges;
// RS may be pointing to an instruction that's deleted.
RS->skipTo(prior(MBBI));
} else if (NumMemOps == 1) {
// Try folding preceeding/trailing base inc/dec into the single
// load/store.
if (MergeBaseUpdateLoadStore(MBB, MemOps[0].MBBI, TII, Advance, MBBI)) {
++NumMerges;
RS->forward(prior(MBBI));
}
}
CurrBase = 0;
CurrOpc = -1;
CurrSize = 0;
CurrPred = ARMCC::AL;
CurrPredReg = 0;
if (NumMemOps) {
MemOps.clear();
NumMemOps = 0;
}
// If iterator hasn't been advanced and this is not a memory op, skip it.
// It can't start a new chain anyway.
if (!Advance && !isMemOp && MBBI != E) {
++Position;
++MBBI;
}
}
}
return NumMerges > 0;
}
namespace {
struct OffsetCompare {
bool operator()(const MachineInstr *LHS, const MachineInstr *RHS) const {
int LOffset = getMemoryOpOffset(LHS);
int ROffset = getMemoryOpOffset(RHS);
assert(LHS == RHS || LOffset != ROffset);
return LOffset > ROffset;
}
};
}
/// MergeReturnIntoLDM - If this is a exit BB, try merging the return op
/// (bx lr) into the preceeding stack restore so it directly restore the value
/// of LR into pc.
/// ldmfd sp!, {r7, lr}
/// bx lr
/// =>
/// ldmfd sp!, {r7, pc}
bool ARMLoadStoreOpt::MergeReturnIntoLDM(MachineBasicBlock &MBB) {
if (MBB.empty()) return false;
MachineBasicBlock::iterator MBBI = prior(MBB.end());
if (MBBI != MBB.begin() &&
(MBBI->getOpcode() == ARM::BX_RET || MBBI->getOpcode() == ARM::tBX_RET)) {
MachineInstr *PrevMI = prior(MBBI);
if (PrevMI->getOpcode() == ARM::LDM || PrevMI->getOpcode() == ARM::t2LDM) {
MachineOperand &MO = PrevMI->getOperand(PrevMI->getNumOperands()-1);
if (MO.getReg() != ARM::LR)
return false;
unsigned NewOpc = isThumb2 ? ARM::t2LDM_RET : ARM::LDM_RET;
PrevMI->setDesc(TII->get(NewOpc));
MO.setReg(ARM::PC);
MBB.erase(MBBI);
return true;
}
}
return false;
}
bool ARMLoadStoreOpt::runOnMachineFunction(MachineFunction &Fn) {
const TargetMachine &TM = Fn.getTarget();
AFI = Fn.getInfo<ARMFunctionInfo>();
TII = TM.getInstrInfo();
TRI = TM.getRegisterInfo();
RS = new RegScavenger();
isThumb2 = AFI->isThumb2Function();
bool Modified = false;
for (MachineFunction::iterator MFI = Fn.begin(), E = Fn.end(); MFI != E;
++MFI) {
MachineBasicBlock &MBB = *MFI;
Modified |= LoadStoreMultipleOpti(MBB);
Modified |= MergeReturnIntoLDM(MBB);
}
delete RS;
return Modified;
}
/// ARMPreAllocLoadStoreOpt - Pre- register allocation pass that move
/// load / stores from consecutive locations close to make it more
/// likely they will be combined later.
namespace {
struct ARMPreAllocLoadStoreOpt : public MachineFunctionPass{
static char ID;
ARMPreAllocLoadStoreOpt() : MachineFunctionPass(&ID) {}
const TargetData *TD;
const TargetInstrInfo *TII;
const TargetRegisterInfo *TRI;
const ARMSubtarget *STI;
MachineRegisterInfo *MRI;
MachineFunction *MF;
virtual bool runOnMachineFunction(MachineFunction &Fn);
virtual const char *getPassName() const {
return "ARM pre- register allocation load / store optimization pass";
}
private:
bool CanFormLdStDWord(MachineInstr *Op0, MachineInstr *Op1, DebugLoc &dl,
unsigned &NewOpc, unsigned &EvenReg,
unsigned &OddReg, unsigned &BaseReg,
unsigned &OffReg, int &Offset,
unsigned &PredReg, ARMCC::CondCodes &Pred,
bool &isT2);
bool RescheduleOps(MachineBasicBlock *MBB,
SmallVector<MachineInstr*, 4> &Ops,
unsigned Base, bool isLd,
DenseMap<MachineInstr*, unsigned> &MI2LocMap);
bool RescheduleLoadStoreInstrs(MachineBasicBlock *MBB);
};
char ARMPreAllocLoadStoreOpt::ID = 0;
}
bool ARMPreAllocLoadStoreOpt::runOnMachineFunction(MachineFunction &Fn) {
TD = Fn.getTarget().getTargetData();
TII = Fn.getTarget().getInstrInfo();
TRI = Fn.getTarget().getRegisterInfo();
STI = &Fn.getTarget().getSubtarget<ARMSubtarget>();
MRI = &Fn.getRegInfo();
MF = &Fn;
bool Modified = false;
for (MachineFunction::iterator MFI = Fn.begin(), E = Fn.end(); MFI != E;
++MFI)
Modified |= RescheduleLoadStoreInstrs(MFI);
return Modified;
}
static bool IsSafeAndProfitableToMove(bool isLd, unsigned Base,
MachineBasicBlock::iterator I,
MachineBasicBlock::iterator E,
SmallPtrSet<MachineInstr*, 4> &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 (MemOps.count(&*I))
continue;
const TargetInstrDesc &TID = I->getDesc();
if (TID.isCall() || TID.isTerminator() || TID.hasUnmodeledSideEffects())
return false;
if (isLd && TID.mayStore())
return false;
if (!isLd) {
if (TID.mayLoad())
return false;
// It's not safe to move the first 'str' down.
// str r1, [r0]
// strh r5, [r0]
// str r4, [r0, #+4]
if (TID.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;
}
bool
ARMPreAllocLoadStoreOpt::CanFormLdStDWord(MachineInstr *Op0, MachineInstr *Op1,
DebugLoc &dl,
unsigned &NewOpc, unsigned &EvenReg,
unsigned &OddReg, unsigned &BaseReg,
unsigned &OffReg, 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::LDR)
NewOpc = ARM::LDRD;
else if (Opcode == ARM::STR)
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 offset registers match.
if (!isT2 &&
(Op0->getOperand(2).getReg() != Op1->getOperand(2).getReg()))
return false;
// Must sure the base address satisfies i64 ld / st alignment requirement.
if (!Op0->hasOneMemOperand() ||
!(*Op0->memoperands_begin())->getValue() ||
(*Op0->memoperands_begin())->isVolatile())
return false;
unsigned Align = (*Op0->memoperands_begin())->getAlignment();
Function *Func = MF->getFunction();
unsigned ReqAlign = STI->hasV6Ops()
? TD->getPrefTypeAlignment(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) {
if (OffImm < 0) {
if (OffImm < -255)
// Can't fall back to t2LDRi8 / t2STRi8.
return false;
} else {
int Limit = (1 << 8) * Scale;
if (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);
}
EvenReg = Op0->getOperand(0).getReg();
OddReg = Op1->getOperand(0).getReg();
if (EvenReg == OddReg)
return false;
BaseReg = Op0->getOperand(1).getReg();
if (!isT2)
OffReg = Op0->getOperand(2).getReg();
Pred = llvm::getInstrPredicate(Op0, PredReg);
dl = Op0->getDebugLoc();
return true;
}
bool ARMPreAllocLoadStoreOpt::RescheduleOps(MachineBasicBlock *MBB,
SmallVector<MachineInstr*, 4> &Ops,
unsigned Base, bool isLd,
DenseMap<MachineInstr*, unsigned> &MI2LocMap) {
bool RetVal = false;
// Sort by offset (in reverse order).
std::sort(Ops.begin(), Ops.end(), OffsetCompare());
// The loads / stores of the same base are in order. Scan them from first to
// last and check for the followins:
// 1. Any def of base.
// 2. Any gaps.
while (Ops.size() > 1) {
unsigned FirstLoc = ~0U;
unsigned LastLoc = 0;
MachineInstr *FirstOp = 0;
MachineInstr *LastOp = 0;
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 Opcode = Op->getOpcode();
if (LastOpcode && Opcode != 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 = Opcode;
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;
// 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 EvenReg = 0, OddReg = 0;
unsigned BaseReg = 0, OffReg = 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,
EvenReg, OddReg, BaseReg, OffReg,
Offset, PredReg, Pred, isT2)) {
Ops.pop_back();
Ops.pop_back();
// Form the pair instruction.
if (isLd) {
MachineInstrBuilder MIB = BuildMI(*MBB, InsertPos,
dl, TII->get(NewOpc))
.addReg(EvenReg, RegState::Define)
.addReg(OddReg, RegState::Define)
.addReg(BaseReg);
if (!isT2)
MIB.addReg(OffReg);
MIB.addImm(Offset).addImm(Pred).addReg(PredReg);
++NumLDRDFormed;
} else {
MachineInstrBuilder MIB = BuildMI(*MBB, InsertPos,
dl, TII->get(NewOpc))
.addReg(EvenReg)
.addReg(OddReg)
.addReg(BaseReg);
if (!isT2)
MIB.addReg(OffReg);
MIB.addImm(Offset).addImm(Pred).addReg(PredReg);
++NumSTRDFormed;
}
MBB->erase(Op0);
MBB->erase(Op1);
// Add register allocation hints to form register pairs.
MRI->setRegAllocationHint(EvenReg, ARMRI::RegPairEven, OddReg);
MRI->setRegAllocationHint(OddReg, ARMRI::RegPairOdd, EvenReg);
} 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;
const TargetInstrDesc &TID = MI->getDesc();
if (TID.isCall() || TID.isTerminator()) {
// Stop at barriers.
++MBBI;
break;
}
MI2LocMap[MI] = Loc++;
if (!isMemoryOp(MI))
continue;
unsigned PredReg = 0;
if (llvm::getInstrPredicate(MI, PredReg) != ARMCC::AL)
continue;
int Opc = MI->getOpcode();
bool isLd = isi32Load(Opc) || Opc == ARM::VLDRS || Opc == ARM::VLDRD;
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 {
SmallVector<MachineInstr*, 4> MIs;
MIs.push_back(MI);
Base2LdsMap[Base] = MIs;
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 {
SmallVector<MachineInstr*, 4> MIs;
MIs.push_back(MI);
Base2StsMap[Base] = MIs;
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];
SmallVector<MachineInstr*, 4> &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];
SmallVector<MachineInstr*, 4> &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;
}
/// createARMLoadStoreOptimizationPass - 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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