MipsLongBranch.cpp [plain text]
#define DEBUG_TYPE "mips-long-branch"
#include "Mips.h"
#include "MCTargetDesc/MipsBaseInfo.h"
#include "MipsTargetMachine.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/IR/Function.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
using namespace llvm;
STATISTIC(LongBranches, "Number of long branches.");
static cl::opt<bool> SkipLongBranch(
"skip-mips-long-branch",
cl::init(false),
cl::desc("MIPS: Skip long branch pass."),
cl::Hidden);
static cl::opt<bool> ForceLongBranch(
"force-mips-long-branch",
cl::init(false),
cl::desc("MIPS: Expand all branches to long format."),
cl::Hidden);
namespace {
typedef MachineBasicBlock::iterator Iter;
typedef MachineBasicBlock::reverse_iterator ReverseIter;
struct MBBInfo {
uint64_t Size, Address;
bool HasLongBranch;
MachineInstr *Br;
MBBInfo() : Size(0), HasLongBranch(false), Br(0) {}
};
class MipsLongBranch : public MachineFunctionPass {
public:
static char ID;
MipsLongBranch(TargetMachine &tm)
: MachineFunctionPass(ID), TM(tm),
TII(static_cast<const MipsInstrInfo*>(tm.getInstrInfo())),
IsPIC(TM.getRelocationModel() == Reloc::PIC_),
ABI(TM.getSubtarget<MipsSubtarget>().getTargetABI()),
LongBranchSeqSize(!IsPIC ? 2 : (ABI == MipsSubtarget::N64 ? 13 : 9)) {}
virtual const char *getPassName() const {
return "Mips Long Branch";
}
bool runOnMachineFunction(MachineFunction &F);
private:
void splitMBB(MachineBasicBlock *MBB);
void initMBBInfo();
int64_t computeOffset(const MachineInstr *Br);
void replaceBranch(MachineBasicBlock &MBB, Iter Br, DebugLoc DL,
MachineBasicBlock *MBBOpnd);
void expandToLongBranch(MBBInfo &Info);
const TargetMachine &TM;
const MipsInstrInfo *TII;
MachineFunction *MF;
SmallVector<MBBInfo, 16> MBBInfos;
bool IsPIC;
unsigned ABI;
unsigned LongBranchSeqSize;
};
char MipsLongBranch::ID = 0;
}
FunctionPass *llvm::createMipsLongBranchPass(MipsTargetMachine &tm) {
return new MipsLongBranch(tm);
}
static MachineBasicBlock *getTargetMBB(const MachineInstr &Br) {
for (unsigned I = 0, E = Br.getDesc().getNumOperands(); I < E; ++I) {
const MachineOperand &MO = Br.getOperand(I);
if (MO.isMBB())
return MO.getMBB();
}
assert(false && "This instruction does not have an MBB operand.");
return 0;
}
static ReverseIter getNonDebugInstr(ReverseIter B, ReverseIter E) {
for (; B != E; ++B)
if (!B->isDebugValue())
return B;
return E;
}
void MipsLongBranch::splitMBB(MachineBasicBlock *MBB) {
ReverseIter End = MBB->rend();
ReverseIter LastBr = getNonDebugInstr(MBB->rbegin(), End);
if ((LastBr == End) ||
(!LastBr->isConditionalBranch() && !LastBr->isUnconditionalBranch()))
return;
ReverseIter FirstBr = getNonDebugInstr(llvm::next(LastBr), End);
if ((FirstBr == End) ||
(!FirstBr->isConditionalBranch() && !FirstBr->isUnconditionalBranch()))
return;
assert(!FirstBr->isIndirectBranch() && "Unexpected indirect branch found.");
MachineBasicBlock *NewMBB =
MF->CreateMachineBasicBlock(MBB->getBasicBlock());
MachineBasicBlock *Tgt = getTargetMBB(*FirstBr);
NewMBB->transferSuccessors(MBB);
NewMBB->removeSuccessor(Tgt);
MBB->addSuccessor(NewMBB);
MBB->addSuccessor(Tgt);
MF->insert(llvm::next(MachineFunction::iterator(MBB)), NewMBB);
NewMBB->splice(NewMBB->end(), MBB, (++LastBr).base(), MBB->end());
}
void MipsLongBranch::initMBBInfo() {
for (MachineFunction::iterator I = MF->begin(), E = MF->end(); I != E;)
splitMBB(I++);
MF->RenumberBlocks();
MBBInfos.clear();
MBBInfos.resize(MF->size());
for (unsigned I = 0, E = MBBInfos.size(); I < E; ++I) {
MachineBasicBlock *MBB = MF->getBlockNumbered(I);
for (MachineBasicBlock::instr_iterator MI = MBB->instr_begin();
MI != MBB->instr_end(); ++MI)
MBBInfos[I].Size += TII->GetInstSizeInBytes(&*MI);
ReverseIter End = MBB->rend();
ReverseIter Br = getNonDebugInstr(MBB->rbegin(), End);
if ((Br != End) && !Br->isIndirectBranch() &&
(Br->isConditionalBranch() ||
(Br->isUnconditionalBranch() &&
TM.getRelocationModel() == Reloc::PIC_)))
MBBInfos[I].Br = (++Br).base();
}
}
int64_t MipsLongBranch::computeOffset(const MachineInstr *Br) {
int64_t Offset = 0;
int ThisMBB = Br->getParent()->getNumber();
int TargetMBB = getTargetMBB(*Br)->getNumber();
if (ThisMBB < TargetMBB) {
for (int N = ThisMBB + 1; N < TargetMBB; ++N)
Offset += MBBInfos[N].Size;
return Offset + 4;
}
for (int N = ThisMBB; N >= TargetMBB; --N)
Offset += MBBInfos[N].Size;
return -Offset + 4;
}
void MipsLongBranch::replaceBranch(MachineBasicBlock &MBB, Iter Br,
DebugLoc DL, MachineBasicBlock *MBBOpnd) {
unsigned NewOpc = TII->GetOppositeBranchOpc(Br->getOpcode());
const MCInstrDesc &NewDesc = TII->get(NewOpc);
MachineInstrBuilder MIB = BuildMI(MBB, Br, DL, NewDesc);
for (unsigned I = 0, E = Br->getDesc().getNumOperands(); I < E; ++I) {
MachineOperand &MO = Br->getOperand(I);
if (!MO.isReg()) {
assert(MO.isMBB() && "MBB operand expected.");
break;
}
MIB.addReg(MO.getReg());
}
MIB.addMBB(MBBOpnd);
Br->eraseFromParent();
}
void MipsLongBranch::expandToLongBranch(MBBInfo &I) {
MachineBasicBlock::iterator Pos;
MachineBasicBlock *MBB = I.Br->getParent(), *TgtMBB = getTargetMBB(*I.Br);
DebugLoc DL = I.Br->getDebugLoc();
const BasicBlock *BB = MBB->getBasicBlock();
MachineFunction::iterator FallThroughMBB = ++MachineFunction::iterator(MBB);
MachineBasicBlock *LongBrMBB = MF->CreateMachineBasicBlock(BB);
MF->insert(FallThroughMBB, LongBrMBB);
MBB->removeSuccessor(TgtMBB);
MBB->addSuccessor(LongBrMBB);
if (IsPIC) {
MachineBasicBlock *BalTgtMBB = MF->CreateMachineBasicBlock(BB);
MF->insert(FallThroughMBB, BalTgtMBB);
LongBrMBB->addSuccessor(BalTgtMBB);
BalTgtMBB->addSuccessor(TgtMBB);
int64_t TgtAddress = MBBInfos[TgtMBB->getNumber()].Address;
unsigned BalTgtMBBSize = 5;
int64_t Offset = TgtAddress - (I.Address + I.Size - BalTgtMBBSize * 4);
int64_t Lo = SignExtend64<16>(Offset & 0xffff);
int64_t Hi = SignExtend64<16>(((Offset + 0x8000) >> 16) & 0xffff);
if (ABI != MipsSubtarget::N64) {
Pos = LongBrMBB->begin();
BuildMI(*LongBrMBB, Pos, DL, TII->get(Mips::ADDiu), Mips::SP)
.addReg(Mips::SP).addImm(-8);
BuildMI(*LongBrMBB, Pos, DL, TII->get(Mips::SW)).addReg(Mips::RA)
.addReg(Mips::SP).addImm(0);
MIBundleBuilder(*LongBrMBB, Pos)
.append(BuildMI(*MF, DL, TII->get(Mips::BAL_BR)).addMBB(BalTgtMBB))
.append(BuildMI(*MF, DL, TII->get(Mips::LUi), Mips::AT).addImm(Hi));
Pos = BalTgtMBB->begin();
BuildMI(*BalTgtMBB, Pos, DL, TII->get(Mips::ADDiu), Mips::AT)
.addReg(Mips::AT).addImm(Lo);
BuildMI(*BalTgtMBB, Pos, DL, TII->get(Mips::ADDu), Mips::AT)
.addReg(Mips::RA).addReg(Mips::AT);
BuildMI(*BalTgtMBB, Pos, DL, TII->get(Mips::LW), Mips::RA)
.addReg(Mips::SP).addImm(0);
MIBundleBuilder(*BalTgtMBB, Pos)
.append(BuildMI(*MF, DL, TII->get(Mips::JR)).addReg(Mips::AT))
.append(BuildMI(*MF, DL, TII->get(Mips::ADDiu), Mips::SP)
.addReg(Mips::SP).addImm(8));
} else {
int64_t Higher = SignExtend64<16>(((Offset + 0x80008000) >> 32) & 0xffff);
int64_t Highest =
SignExtend64<16>(((Offset + 0x800080008000LL) >> 48) & 0xffff);
Pos = LongBrMBB->begin();
BuildMI(*LongBrMBB, Pos, DL, TII->get(Mips::DADDiu), Mips::SP_64)
.addReg(Mips::SP_64).addImm(-16);
BuildMI(*LongBrMBB, Pos, DL, TII->get(Mips::SD)).addReg(Mips::RA_64)
.addReg(Mips::SP_64).addImm(0);
BuildMI(*LongBrMBB, Pos, DL, TII->get(Mips::LUi64), Mips::AT_64)
.addImm(Highest);
BuildMI(*LongBrMBB, Pos, DL, TII->get(Mips::DADDiu), Mips::AT_64)
.addReg(Mips::AT_64).addImm(Higher);
BuildMI(*LongBrMBB, Pos, DL, TII->get(Mips::DSLL), Mips::AT_64)
.addReg(Mips::AT_64).addImm(16);
BuildMI(*LongBrMBB, Pos, DL, TII->get(Mips::DADDiu), Mips::AT_64)
.addReg(Mips::AT_64).addImm(Hi);
MIBundleBuilder(*LongBrMBB, Pos)
.append(BuildMI(*MF, DL, TII->get(Mips::BAL_BR)).addMBB(BalTgtMBB))
.append(BuildMI(*MF, DL, TII->get(Mips::DSLL), Mips::AT_64)
.addReg(Mips::AT_64).addImm(16));
Pos = BalTgtMBB->begin();
BuildMI(*BalTgtMBB, Pos, DL, TII->get(Mips::DADDiu), Mips::AT_64)
.addReg(Mips::AT_64).addImm(Lo);
BuildMI(*BalTgtMBB, Pos, DL, TII->get(Mips::DADDu), Mips::AT_64)
.addReg(Mips::RA_64).addReg(Mips::AT_64);
BuildMI(*BalTgtMBB, Pos, DL, TII->get(Mips::LD), Mips::RA_64)
.addReg(Mips::SP_64).addImm(0);
MIBundleBuilder(*BalTgtMBB, Pos)
.append(BuildMI(*MF, DL, TII->get(Mips::JR64)).addReg(Mips::AT_64))
.append(BuildMI(*MF, DL, TII->get(Mips::DADDiu), Mips::SP_64)
.addReg(Mips::SP_64).addImm(16));
}
assert(BalTgtMBBSize == BalTgtMBB->size());
assert(LongBrMBB->size() + BalTgtMBBSize == LongBranchSeqSize);
} else {
Pos = LongBrMBB->begin();
LongBrMBB->addSuccessor(TgtMBB);
MIBundleBuilder(*LongBrMBB, Pos)
.append(BuildMI(*MF, DL, TII->get(Mips::J)).addMBB(TgtMBB))
.append(BuildMI(*MF, DL, TII->get(Mips::NOP)));
assert(LongBrMBB->size() == LongBranchSeqSize);
}
if (I.Br->isUnconditionalBranch()) {
assert(I.Br->getDesc().getNumOperands() == 1);
I.Br->RemoveOperand(0);
I.Br->addOperand(MachineOperand::CreateMBB(LongBrMBB));
} else
replaceBranch(*MBB, I.Br, DL, FallThroughMBB);
}
static void emitGPDisp(MachineFunction &F, const MipsInstrInfo *TII) {
MachineBasicBlock &MBB = F.front();
MachineBasicBlock::iterator I = MBB.begin();
DebugLoc DL = MBB.findDebugLoc(MBB.begin());
BuildMI(MBB, I, DL, TII->get(Mips::LUi), Mips::V0)
.addExternalSymbol("_gp_disp", MipsII::MO_ABS_HI);
BuildMI(MBB, I, DL, TII->get(Mips::ADDiu), Mips::V0)
.addReg(Mips::V0).addExternalSymbol("_gp_disp", MipsII::MO_ABS_LO);
MBB.removeLiveIn(Mips::V0);
}
bool MipsLongBranch::runOnMachineFunction(MachineFunction &F) {
if ((TM.getRelocationModel() == Reloc::PIC_) &&
TM.getSubtarget<MipsSubtarget>().isABI_O32() &&
F.getInfo<MipsFunctionInfo>()->globalBaseRegSet())
emitGPDisp(F, TII);
if (SkipLongBranch)
return true;
MF = &F;
initMBBInfo();
SmallVector<MBBInfo, 16>::iterator I, E = MBBInfos.end();
bool EverMadeChange = false, MadeChange = true;
while (MadeChange) {
MadeChange = false;
for (I = MBBInfos.begin(); I != E; ++I) {
if (!I->Br || I->HasLongBranch)
continue;
if (!ForceLongBranch && isInt<16>(computeOffset(I->Br) / 4))
continue;
I->HasLongBranch = true;
I->Size += LongBranchSeqSize * 4;
++LongBranches;
EverMadeChange = MadeChange = true;
}
}
if (!EverMadeChange)
return true;
if (TM.getRelocationModel() == Reloc::PIC_) {
uint64_t Address = 0;
for (I = MBBInfos.begin(); I != E; Address += I->Size, ++I)
I->Address = Address;
}
for (I = MBBInfos.begin(); I != E; ++I)
if (I->HasLongBranch)
expandToLongBranch(*I);
MF->RenumberBlocks();
return true;
}