llvm-6502/lib/Target/Mips/MipsDelaySlotFiller.cpp

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//===-- MipsDelaySlotFiller.cpp - Mips Delay Slot Filler ------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Simple pass to fill delay slots with useful instructions.
//
//===----------------------------------------------------------------------===//
#include "MCTargetDesc/MipsMCNaCl.h"
#include "Mips.h"
#include "MipsInstrInfo.h"
#include "MipsTargetMachine.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/PseudoSourceValue.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
using namespace llvm;
#define DEBUG_TYPE "delay-slot-filler"
STATISTIC(FilledSlots, "Number of delay slots filled");
STATISTIC(UsefulSlots, "Number of delay slots filled with instructions that"
" are not NOP.");
static cl::opt<bool> DisableDelaySlotFiller(
"disable-mips-delay-filler",
cl::init(false),
cl::desc("Fill all delay slots with NOPs."),
cl::Hidden);
static cl::opt<bool> DisableForwardSearch(
"disable-mips-df-forward-search",
cl::init(true),
cl::desc("Disallow MIPS delay filler to search forward."),
cl::Hidden);
static cl::opt<bool> DisableSuccBBSearch(
"disable-mips-df-succbb-search",
cl::init(true),
cl::desc("Disallow MIPS delay filler to search successor basic blocks."),
cl::Hidden);
static cl::opt<bool> DisableBackwardSearch(
"disable-mips-df-backward-search",
cl::init(false),
cl::desc("Disallow MIPS delay filler to search backward."),
cl::Hidden);
namespace {
typedef MachineBasicBlock::iterator Iter;
typedef MachineBasicBlock::reverse_iterator ReverseIter;
typedef SmallDenseMap<MachineBasicBlock*, MachineInstr*, 2> BB2BrMap;
class RegDefsUses {
public:
RegDefsUses(const TargetRegisterInfo &TRI);
void init(const MachineInstr &MI);
/// This function sets all caller-saved registers in Defs.
void setCallerSaved(const MachineInstr &MI);
/// This function sets all unallocatable registers in Defs.
void setUnallocatableRegs(const MachineFunction &MF);
/// Set bits in Uses corresponding to MBB's live-out registers except for
/// the registers that are live-in to SuccBB.
void addLiveOut(const MachineBasicBlock &MBB,
const MachineBasicBlock &SuccBB);
bool update(const MachineInstr &MI, unsigned Begin, unsigned End);
private:
bool checkRegDefsUses(BitVector &NewDefs, BitVector &NewUses, unsigned Reg,
bool IsDef) const;
/// Returns true if Reg or its alias is in RegSet.
bool isRegInSet(const BitVector &RegSet, unsigned Reg) const;
const TargetRegisterInfo &TRI;
BitVector Defs, Uses;
};
/// Base class for inspecting loads and stores.
class InspectMemInstr {
public:
InspectMemInstr(bool ForbidMemInstr_)
: OrigSeenLoad(false), OrigSeenStore(false), SeenLoad(false),
SeenStore(false), ForbidMemInstr(ForbidMemInstr_) {}
/// Return true if MI cannot be moved to delay slot.
bool hasHazard(const MachineInstr &MI);
virtual ~InspectMemInstr() {}
protected:
/// Flags indicating whether loads or stores have been seen.
bool OrigSeenLoad, OrigSeenStore, SeenLoad, SeenStore;
/// Memory instructions are not allowed to move to delay slot if this flag
/// is true.
bool ForbidMemInstr;
private:
virtual bool hasHazard_(const MachineInstr &MI) = 0;
};
/// This subclass rejects any memory instructions.
class NoMemInstr : public InspectMemInstr {
public:
NoMemInstr() : InspectMemInstr(true) {}
private:
bool hasHazard_(const MachineInstr &MI) override { return true; }
};
/// This subclass accepts loads from stacks and constant loads.
class LoadFromStackOrConst : public InspectMemInstr {
public:
LoadFromStackOrConst() : InspectMemInstr(false) {}
private:
bool hasHazard_(const MachineInstr &MI) override;
};
/// This subclass uses memory dependence information to determine whether a
/// memory instruction can be moved to a delay slot.
class MemDefsUses : public InspectMemInstr {
public:
MemDefsUses(const DataLayout &DL, const MachineFrameInfo *MFI);
private:
typedef PointerUnion<const Value *, const PseudoSourceValue *> ValueType;
bool hasHazard_(const MachineInstr &MI) override;
/// Update Defs and Uses. Return true if there exist dependences that
/// disqualify the delay slot candidate between V and values in Uses and
/// Defs.
bool updateDefsUses(ValueType V, bool MayStore);
/// Get the list of underlying objects of MI's memory operand.
bool getUnderlyingObjects(const MachineInstr &MI,
SmallVectorImpl<ValueType> &Objects) const;
const MachineFrameInfo *MFI;
SmallPtrSet<ValueType, 4> Uses, Defs;
const DataLayout &DL;
/// Flags indicating whether loads or stores with no underlying objects have
/// been seen.
bool SeenNoObjLoad, SeenNoObjStore;
};
class Filler : public MachineFunctionPass {
public:
Filler(TargetMachine &tm)
: MachineFunctionPass(ID), TM(tm) { }
const char *getPassName() const override {
return "Mips Delay Slot Filler";
}
bool runOnMachineFunction(MachineFunction &F) override {
bool Changed = false;
for (MachineFunction::iterator FI = F.begin(), FE = F.end();
FI != FE; ++FI)
Changed |= runOnMachineBasicBlock(*FI);
// This pass invalidates liveness information when it reorders
// instructions to fill delay slot. Without this, -verify-machineinstrs
// will fail.
if (Changed)
F.getRegInfo().invalidateLiveness();
return Changed;
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<MachineBranchProbabilityInfo>();
MachineFunctionPass::getAnalysisUsage(AU);
}
private:
bool runOnMachineBasicBlock(MachineBasicBlock &MBB);
Iter replaceWithCompactBranch(MachineBasicBlock &MBB,
Iter Branch, DebugLoc DL);
Iter replaceWithCompactJump(MachineBasicBlock &MBB,
Iter Jump, DebugLoc DL);
/// This function checks if it is valid to move Candidate to the delay slot
/// and returns true if it isn't. It also updates memory and register
/// dependence information.
bool delayHasHazard(const MachineInstr &Candidate, RegDefsUses &RegDU,
InspectMemInstr &IM) const;
/// This function searches range [Begin, End) for an instruction that can be
/// moved to the delay slot. Returns true on success.
template<typename IterTy>
bool searchRange(MachineBasicBlock &MBB, IterTy Begin, IterTy End,
RegDefsUses &RegDU, InspectMemInstr &IM, Iter Slot,
IterTy &Filler) const;
/// This function searches in the backward direction for an instruction that
/// can be moved to the delay slot. Returns true on success.
bool searchBackward(MachineBasicBlock &MBB, Iter Slot) const;
/// This function searches MBB in the forward direction for an instruction
/// that can be moved to the delay slot. Returns true on success.
bool searchForward(MachineBasicBlock &MBB, Iter Slot) const;
/// This function searches one of MBB's successor blocks for an instruction
/// that can be moved to the delay slot and inserts clones of the
/// instruction into the successor's predecessor blocks.
bool searchSuccBBs(MachineBasicBlock &MBB, Iter Slot) const;
/// Pick a successor block of MBB. Return NULL if MBB doesn't have a
/// successor block that is not a landing pad.
MachineBasicBlock *selectSuccBB(MachineBasicBlock &B) const;
/// This function analyzes MBB and returns an instruction with an unoccupied
/// slot that branches to Dst.
std::pair<MipsInstrInfo::BranchType, MachineInstr *>
getBranch(MachineBasicBlock &MBB, const MachineBasicBlock &Dst) const;
/// Examine Pred and see if it is possible to insert an instruction into
/// one of its branches delay slot or its end.
bool examinePred(MachineBasicBlock &Pred, const MachineBasicBlock &Succ,
RegDefsUses &RegDU, bool &HasMultipleSuccs,
BB2BrMap &BrMap) const;
bool terminateSearch(const MachineInstr &Candidate) const;
TargetMachine &TM;
static char ID;
};
char Filler::ID = 0;
} // end of anonymous namespace
static bool hasUnoccupiedSlot(const MachineInstr *MI) {
return MI->hasDelaySlot() && !MI->isBundledWithSucc();
}
/// This function inserts clones of Filler into predecessor blocks.
static void insertDelayFiller(Iter Filler, const BB2BrMap &BrMap) {
MachineFunction *MF = Filler->getParent()->getParent();
for (BB2BrMap::const_iterator I = BrMap.begin(); I != BrMap.end(); ++I) {
if (I->second) {
MIBundleBuilder(I->second).append(MF->CloneMachineInstr(&*Filler));
++UsefulSlots;
} else {
I->first->insert(I->first->end(), MF->CloneMachineInstr(&*Filler));
}
}
}
/// This function adds registers Filler defines to MBB's live-in register list.
static void addLiveInRegs(Iter Filler, MachineBasicBlock &MBB) {
for (unsigned I = 0, E = Filler->getNumOperands(); I != E; ++I) {
const MachineOperand &MO = Filler->getOperand(I);
unsigned R;
if (!MO.isReg() || !MO.isDef() || !(R = MO.getReg()))
continue;
#ifndef NDEBUG
const MachineFunction &MF = *MBB.getParent();
assert(MF.getSubtarget().getRegisterInfo()->getAllocatableSet(MF).test(R) &&
"Shouldn't move an instruction with unallocatable registers across "
"basic block boundaries.");
#endif
if (!MBB.isLiveIn(R))
MBB.addLiveIn(R);
}
}
RegDefsUses::RegDefsUses(const TargetRegisterInfo &TRI)
: TRI(TRI), Defs(TRI.getNumRegs(), false), Uses(TRI.getNumRegs(), false) {}
void RegDefsUses::init(const MachineInstr &MI) {
// Add all register operands which are explicit and non-variadic.
update(MI, 0, MI.getDesc().getNumOperands());
// If MI is a call, add RA to Defs to prevent users of RA from going into
// delay slot.
if (MI.isCall())
Defs.set(Mips::RA);
// Add all implicit register operands of branch instructions except
// register AT.
if (MI.isBranch()) {
update(MI, MI.getDesc().getNumOperands(), MI.getNumOperands());
Defs.reset(Mips::AT);
}
}
void RegDefsUses::setCallerSaved(const MachineInstr &MI) {
assert(MI.isCall());
// If MI is a call, add all caller-saved registers to Defs.
BitVector CallerSavedRegs(TRI.getNumRegs(), true);
CallerSavedRegs.reset(Mips::ZERO);
CallerSavedRegs.reset(Mips::ZERO_64);
for (const MCPhysReg *R = TRI.getCalleeSavedRegs(MI.getParent()->getParent());
*R; ++R)
for (MCRegAliasIterator AI(*R, &TRI, true); AI.isValid(); ++AI)
CallerSavedRegs.reset(*AI);
Defs |= CallerSavedRegs;
}
void RegDefsUses::setUnallocatableRegs(const MachineFunction &MF) {
BitVector AllocSet = TRI.getAllocatableSet(MF);
for (int R = AllocSet.find_first(); R != -1; R = AllocSet.find_next(R))
for (MCRegAliasIterator AI(R, &TRI, false); AI.isValid(); ++AI)
AllocSet.set(*AI);
AllocSet.set(Mips::ZERO);
AllocSet.set(Mips::ZERO_64);
Defs |= AllocSet.flip();
}
void RegDefsUses::addLiveOut(const MachineBasicBlock &MBB,
const MachineBasicBlock &SuccBB) {
for (MachineBasicBlock::const_succ_iterator SI = MBB.succ_begin(),
SE = MBB.succ_end(); SI != SE; ++SI)
if (*SI != &SuccBB)
for (MachineBasicBlock::livein_iterator LI = (*SI)->livein_begin(),
LE = (*SI)->livein_end(); LI != LE; ++LI)
Uses.set(*LI);
}
bool RegDefsUses::update(const MachineInstr &MI, unsigned Begin, unsigned End) {
BitVector NewDefs(TRI.getNumRegs()), NewUses(TRI.getNumRegs());
bool HasHazard = false;
for (unsigned I = Begin; I != End; ++I) {
const MachineOperand &MO = MI.getOperand(I);
if (MO.isReg() && MO.getReg())
HasHazard |= checkRegDefsUses(NewDefs, NewUses, MO.getReg(), MO.isDef());
}
Defs |= NewDefs;
Uses |= NewUses;
return HasHazard;
}
bool RegDefsUses::checkRegDefsUses(BitVector &NewDefs, BitVector &NewUses,
unsigned Reg, bool IsDef) const {
if (IsDef) {
NewDefs.set(Reg);
// check whether Reg has already been defined or used.
return (isRegInSet(Defs, Reg) || isRegInSet(Uses, Reg));
}
NewUses.set(Reg);
// check whether Reg has already been defined.
return isRegInSet(Defs, Reg);
}
bool RegDefsUses::isRegInSet(const BitVector &RegSet, unsigned Reg) const {
// Check Reg and all aliased Registers.
for (MCRegAliasIterator AI(Reg, &TRI, true); AI.isValid(); ++AI)
if (RegSet.test(*AI))
return true;
return false;
}
bool InspectMemInstr::hasHazard(const MachineInstr &MI) {
if (!MI.mayStore() && !MI.mayLoad())
return false;
if (ForbidMemInstr)
return true;
OrigSeenLoad = SeenLoad;
OrigSeenStore = SeenStore;
SeenLoad |= MI.mayLoad();
SeenStore |= MI.mayStore();
// If MI is an ordered or volatile memory reference, disallow moving
// subsequent loads and stores to delay slot.
if (MI.hasOrderedMemoryRef() && (OrigSeenLoad || OrigSeenStore)) {
ForbidMemInstr = true;
return true;
}
return hasHazard_(MI);
}
bool LoadFromStackOrConst::hasHazard_(const MachineInstr &MI) {
if (MI.mayStore())
return true;
if (!MI.hasOneMemOperand() || !(*MI.memoperands_begin())->getPseudoValue())
return true;
if (const PseudoSourceValue *PSV =
(*MI.memoperands_begin())->getPseudoValue()) {
if (isa<FixedStackPseudoSourceValue>(PSV))
return false;
return !PSV->isConstant(nullptr) && PSV != PseudoSourceValue::getStack();
}
return true;
}
MemDefsUses::MemDefsUses(const DataLayout &DL, const MachineFrameInfo *MFI_)
: InspectMemInstr(false), MFI(MFI_), DL(DL), SeenNoObjLoad(false),
SeenNoObjStore(false) {}
bool MemDefsUses::hasHazard_(const MachineInstr &MI) {
bool HasHazard = false;
SmallVector<ValueType, 4> Objs;
// Check underlying object list.
if (getUnderlyingObjects(MI, Objs)) {
for (SmallVectorImpl<ValueType>::const_iterator I = Objs.begin();
I != Objs.end(); ++I)
HasHazard |= updateDefsUses(*I, MI.mayStore());
return HasHazard;
}
// No underlying objects found.
HasHazard = MI.mayStore() && (OrigSeenLoad || OrigSeenStore);
HasHazard |= MI.mayLoad() || OrigSeenStore;
SeenNoObjLoad |= MI.mayLoad();
SeenNoObjStore |= MI.mayStore();
return HasHazard;
}
bool MemDefsUses::updateDefsUses(ValueType V, bool MayStore) {
if (MayStore)
return !Defs.insert(V).second || Uses.count(V) || SeenNoObjStore ||
SeenNoObjLoad;
Uses.insert(V);
return Defs.count(V) || SeenNoObjStore;
}
bool MemDefsUses::
getUnderlyingObjects(const MachineInstr &MI,
SmallVectorImpl<ValueType> &Objects) const {
if (!MI.hasOneMemOperand() ||
(!(*MI.memoperands_begin())->getValue() &&
!(*MI.memoperands_begin())->getPseudoValue()))
return false;
if (const PseudoSourceValue *PSV =
(*MI.memoperands_begin())->getPseudoValue()) {
if (!PSV->isAliased(MFI))
return false;
Objects.push_back(PSV);
return true;
}
const Value *V = (*MI.memoperands_begin())->getValue();
SmallVector<Value *, 4> Objs;
GetUnderlyingObjects(const_cast<Value *>(V), Objs, DL);
for (SmallVectorImpl<Value *>::iterator I = Objs.begin(), E = Objs.end();
I != E; ++I) {
if (!isIdentifiedObject(V))
return false;
Objects.push_back(*I);
}
return true;
}
// Replace Branch with the compact branch instruction.
Iter Filler::replaceWithCompactBranch(MachineBasicBlock &MBB,
Iter Branch, DebugLoc DL) {
const MipsInstrInfo *TII =
MBB.getParent()->getSubtarget<MipsSubtarget>().getInstrInfo();
unsigned NewOpcode =
(((unsigned) Branch->getOpcode()) == Mips::BEQ) ? Mips::BEQZC_MM
: Mips::BNEZC_MM;
const MCInstrDesc &NewDesc = TII->get(NewOpcode);
MachineInstrBuilder MIB = BuildMI(MBB, Branch, DL, NewDesc);
MIB.addReg(Branch->getOperand(0).getReg());
MIB.addMBB(Branch->getOperand(2).getMBB());
Iter tmpIter = Branch;
Branch = std::prev(Branch);
MBB.erase(tmpIter);
return Branch;
}
// Replace Jumps with the compact jump instruction.
Iter Filler::replaceWithCompactJump(MachineBasicBlock &MBB,
Iter Jump, DebugLoc DL) {
const MipsInstrInfo *TII =
MBB.getParent()->getSubtarget<MipsSubtarget>().getInstrInfo();
const MCInstrDesc &NewDesc = TII->get(Mips::JRC16_MM);
MachineInstrBuilder MIB = BuildMI(MBB, Jump, DL, NewDesc);
MIB.addReg(Jump->getOperand(0).getReg());
Iter tmpIter = Jump;
Jump = std::prev(Jump);
MBB.erase(tmpIter);
return Jump;
}
// For given opcode returns opcode of corresponding instruction with short
// delay slot.
static int getEquivalentCallShort(int Opcode) {
switch (Opcode) {
case Mips::BGEZAL:
return Mips::BGEZALS_MM;
case Mips::BLTZAL:
return Mips::BLTZALS_MM;
case Mips::JAL:
return Mips::JALS_MM;
case Mips::JALR:
return Mips::JALRS_MM;
case Mips::JALR16_MM:
return Mips::JALRS16_MM;
default:
llvm_unreachable("Unexpected call instruction for microMIPS.");
}
}
/// runOnMachineBasicBlock - Fill in delay slots for the given basic block.
/// We assume there is only one delay slot per delayed instruction.
bool Filler::runOnMachineBasicBlock(MachineBasicBlock &MBB) {
bool Changed = false;
const MipsSubtarget &STI = MBB.getParent()->getSubtarget<MipsSubtarget>();
bool InMicroMipsMode = STI.inMicroMipsMode();
const MipsInstrInfo *TII = STI.getInstrInfo();
for (Iter I = MBB.begin(); I != MBB.end(); ++I) {
if (!hasUnoccupiedSlot(&*I))
continue;
++FilledSlots;
Changed = true;
// Delay slot filling is disabled at -O0.
if (!DisableDelaySlotFiller && (TM.getOptLevel() != CodeGenOpt::None)) {
bool Filled = false;
if (searchBackward(MBB, I)) {
Filled = true;
} else if (I->isTerminator()) {
if (searchSuccBBs(MBB, I)) {
Filled = true;
}
} else if (searchForward(MBB, I)) {
Filled = true;
}
if (Filled) {
// Get instruction with delay slot.
MachineBasicBlock::instr_iterator DSI(I);
if (InMicroMipsMode && TII->GetInstSizeInBytes(std::next(DSI)) == 2 &&
DSI->isCall()) {
// If instruction in delay slot is 16b change opcode to
// corresponding instruction with short delay slot.
DSI->setDesc(TII->get(getEquivalentCallShort(DSI->getOpcode())));
}
continue;
}
}
// If instruction is BEQ or BNE with one ZERO register, then instead of
// adding NOP replace this instruction with the corresponding compact
// branch instruction, i.e. BEQZC or BNEZC.
unsigned Opcode = I->getOpcode();
if (InMicroMipsMode) {
switch (Opcode) {
case Mips::BEQ:
case Mips::BNE:
if (((unsigned) I->getOperand(1).getReg()) == Mips::ZERO) {
I = replaceWithCompactBranch(MBB, I, I->getDebugLoc());
continue;
}
break;
case Mips::JR:
case Mips::PseudoReturn:
case Mips::PseudoIndirectBranch:
// For microMIPS the PseudoReturn and PseudoIndirectBranch are allways
// expanded to JR_MM, so they can be replaced with JRC16_MM.
I = replaceWithCompactJump(MBB, I, I->getDebugLoc());
continue;
default:
break;
}
}
// Bundle the NOP to the instruction with the delay slot.
BuildMI(MBB, std::next(I), I->getDebugLoc(), TII->get(Mips::NOP));
MIBundleBuilder(MBB, I, std::next(I, 2));
}
return Changed;
}
/// createMipsDelaySlotFillerPass - Returns a pass that fills in delay
/// slots in Mips MachineFunctions
FunctionPass *llvm::createMipsDelaySlotFillerPass(MipsTargetMachine &tm) {
return new Filler(tm);
}
template<typename IterTy>
bool Filler::searchRange(MachineBasicBlock &MBB, IterTy Begin, IterTy End,
RegDefsUses &RegDU, InspectMemInstr& IM, Iter Slot,
IterTy &Filler) const {
bool IsReverseIter = std::is_convertible<IterTy, ReverseIter>::value;
for (IterTy I = Begin; I != End;) {
IterTy CurrI = I;
++I;
// skip debug value
if (CurrI->isDebugValue())
continue;
if (terminateSearch(*CurrI))
break;
assert((!CurrI->isCall() && !CurrI->isReturn() && !CurrI->isBranch()) &&
"Cannot put calls, returns or branches in delay slot.");
if (CurrI->isKill()) {
CurrI->eraseFromParent();
// This special case is needed for reverse iterators, because when we
// erase an instruction, the iterators are updated to point to the next
// instruction.
if (IsReverseIter && I != End)
I = CurrI;
continue;
}
if (delayHasHazard(*CurrI, RegDU, IM))
continue;
const MipsSubtarget &STI = MBB.getParent()->getSubtarget<MipsSubtarget>();
if (STI.isTargetNaCl()) {
// In NaCl, instructions that must be masked are forbidden in delay slots.
// We only check for loads, stores and SP changes. Calls, returns and
// branches are not checked because non-NaCl targets never put them in
// delay slots.
unsigned AddrIdx;
if ((isBasePlusOffsetMemoryAccess(CurrI->getOpcode(), &AddrIdx) &&
baseRegNeedsLoadStoreMask(CurrI->getOperand(AddrIdx).getReg())) ||
CurrI->modifiesRegister(Mips::SP, STI.getRegisterInfo()))
continue;
}
bool InMicroMipsMode = STI.inMicroMipsMode();
const MipsInstrInfo *TII = STI.getInstrInfo();
unsigned Opcode = (*Slot).getOpcode();
if (InMicroMipsMode && TII->GetInstSizeInBytes(&(*CurrI)) == 2 &&
(Opcode == Mips::JR || Opcode == Mips::PseudoIndirectBranch ||
Opcode == Mips::PseudoReturn))
continue;
Filler = CurrI;
return true;
}
return false;
}
bool Filler::searchBackward(MachineBasicBlock &MBB, Iter Slot) const {
if (DisableBackwardSearch)
return false;
RegDefsUses RegDU(*MBB.getParent()->getSubtarget().getRegisterInfo());
MemDefsUses MemDU(*TM.getDataLayout(), MBB.getParent()->getFrameInfo());
ReverseIter Filler;
RegDU.init(*Slot);
if (!searchRange(MBB, ReverseIter(Slot), MBB.rend(), RegDU, MemDU, Slot,
Filler))
return false;
MBB.splice(std::next(Slot), &MBB, std::next(Filler).base());
MIBundleBuilder(MBB, Slot, std::next(Slot, 2));
++UsefulSlots;
return true;
}
bool Filler::searchForward(MachineBasicBlock &MBB, Iter Slot) const {
// Can handle only calls.
if (DisableForwardSearch || !Slot->isCall())
return false;
RegDefsUses RegDU(*MBB.getParent()->getSubtarget().getRegisterInfo());
NoMemInstr NM;
Iter Filler;
RegDU.setCallerSaved(*Slot);
if (!searchRange(MBB, std::next(Slot), MBB.end(), RegDU, NM, Slot, Filler))
return false;
MBB.splice(std::next(Slot), &MBB, Filler);
MIBundleBuilder(MBB, Slot, std::next(Slot, 2));
++UsefulSlots;
return true;
}
bool Filler::searchSuccBBs(MachineBasicBlock &MBB, Iter Slot) const {
if (DisableSuccBBSearch)
return false;
MachineBasicBlock *SuccBB = selectSuccBB(MBB);
if (!SuccBB)
return false;
RegDefsUses RegDU(*MBB.getParent()->getSubtarget().getRegisterInfo());
bool HasMultipleSuccs = false;
BB2BrMap BrMap;
std::unique_ptr<InspectMemInstr> IM;
Iter Filler;
// Iterate over SuccBB's predecessor list.
for (MachineBasicBlock::pred_iterator PI = SuccBB->pred_begin(),
PE = SuccBB->pred_end(); PI != PE; ++PI)
if (!examinePred(**PI, *SuccBB, RegDU, HasMultipleSuccs, BrMap))
return false;
// Do not allow moving instructions which have unallocatable register operands
// across basic block boundaries.
RegDU.setUnallocatableRegs(*MBB.getParent());
// Only allow moving loads from stack or constants if any of the SuccBB's
// predecessors have multiple successors.
if (HasMultipleSuccs) {
IM.reset(new LoadFromStackOrConst());
} else {
const MachineFrameInfo *MFI = MBB.getParent()->getFrameInfo();
IM.reset(new MemDefsUses(*TM.getDataLayout(), MFI));
}
if (!searchRange(MBB, SuccBB->begin(), SuccBB->end(), RegDU, *IM, Slot,
Filler))
return false;
insertDelayFiller(Filler, BrMap);
addLiveInRegs(Filler, *SuccBB);
Filler->eraseFromParent();
return true;
}
MachineBasicBlock *Filler::selectSuccBB(MachineBasicBlock &B) const {
if (B.succ_empty())
return nullptr;
// Select the successor with the larget edge weight.
auto &Prob = getAnalysis<MachineBranchProbabilityInfo>();
MachineBasicBlock *S = *std::max_element(B.succ_begin(), B.succ_end(),
[&](const MachineBasicBlock *Dst0,
const MachineBasicBlock *Dst1) {
return Prob.getEdgeWeight(&B, Dst0) < Prob.getEdgeWeight(&B, Dst1);
});
return S->isLandingPad() ? nullptr : S;
}
std::pair<MipsInstrInfo::BranchType, MachineInstr *>
Filler::getBranch(MachineBasicBlock &MBB, const MachineBasicBlock &Dst) const {
const MipsInstrInfo *TII =
MBB.getParent()->getSubtarget<MipsSubtarget>().getInstrInfo();
MachineBasicBlock *TrueBB = nullptr, *FalseBB = nullptr;
SmallVector<MachineInstr*, 2> BranchInstrs;
SmallVector<MachineOperand, 2> Cond;
MipsInstrInfo::BranchType R =
TII->AnalyzeBranch(MBB, TrueBB, FalseBB, Cond, false, BranchInstrs);
if ((R == MipsInstrInfo::BT_None) || (R == MipsInstrInfo::BT_NoBranch))
return std::make_pair(R, nullptr);
if (R != MipsInstrInfo::BT_CondUncond) {
if (!hasUnoccupiedSlot(BranchInstrs[0]))
return std::make_pair(MipsInstrInfo::BT_None, nullptr);
assert(((R != MipsInstrInfo::BT_Uncond) || (TrueBB == &Dst)));
return std::make_pair(R, BranchInstrs[0]);
}
assert((TrueBB == &Dst) || (FalseBB == &Dst));
// Examine the conditional branch. See if its slot is occupied.
if (hasUnoccupiedSlot(BranchInstrs[0]))
return std::make_pair(MipsInstrInfo::BT_Cond, BranchInstrs[0]);
// If that fails, try the unconditional branch.
if (hasUnoccupiedSlot(BranchInstrs[1]) && (FalseBB == &Dst))
return std::make_pair(MipsInstrInfo::BT_Uncond, BranchInstrs[1]);
return std::make_pair(MipsInstrInfo::BT_None, nullptr);
}
bool Filler::examinePred(MachineBasicBlock &Pred, const MachineBasicBlock &Succ,
RegDefsUses &RegDU, bool &HasMultipleSuccs,
BB2BrMap &BrMap) const {
std::pair<MipsInstrInfo::BranchType, MachineInstr *> P =
getBranch(Pred, Succ);
// Return if either getBranch wasn't able to analyze the branches or there
// were no branches with unoccupied slots.
if (P.first == MipsInstrInfo::BT_None)
return false;
if ((P.first != MipsInstrInfo::BT_Uncond) &&
(P.first != MipsInstrInfo::BT_NoBranch)) {
HasMultipleSuccs = true;
RegDU.addLiveOut(Pred, Succ);
}
BrMap[&Pred] = P.second;
return true;
}
bool Filler::delayHasHazard(const MachineInstr &Candidate, RegDefsUses &RegDU,
InspectMemInstr &IM) const {
assert(!Candidate.isKill() &&
"KILL instructions should have been eliminated at this point.");
bool HasHazard = Candidate.isImplicitDef();
HasHazard |= IM.hasHazard(Candidate);
HasHazard |= RegDU.update(Candidate, 0, Candidate.getNumOperands());
return HasHazard;
}
bool Filler::terminateSearch(const MachineInstr &Candidate) const {
return (Candidate.isTerminator() || Candidate.isCall() ||
Candidate.isPosition() || Candidate.isInlineAsm() ||
Candidate.hasUnmodeledSideEffects());
}