forked from OSchip/llvm-project
356 lines
13 KiB
C++
356 lines
13 KiB
C++
//===- MachineSSAUpdater.cpp - Unstructured SSA Update Tool ---------------===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This file implements the MachineSSAUpdater class. It's based on SSAUpdater
|
|
// class in lib/Transforms/Utils.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "llvm/CodeGen/MachineSSAUpdater.h"
|
|
#include "llvm/ADT/DenseMap.h"
|
|
#include "llvm/ADT/SmallVector.h"
|
|
#include "llvm/CodeGen/MachineInstr.h"
|
|
#include "llvm/CodeGen/MachineInstrBuilder.h"
|
|
#include "llvm/CodeGen/MachineRegisterInfo.h"
|
|
#include "llvm/Support/AlignOf.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/TargetRegisterInfo.h"
|
|
#include "llvm/Target/TargetSubtargetInfo.h"
|
|
#include "llvm/Transforms/Utils/SSAUpdaterImpl.h"
|
|
using namespace llvm;
|
|
|
|
#define DEBUG_TYPE "machine-ssaupdater"
|
|
|
|
typedef DenseMap<MachineBasicBlock*, unsigned> AvailableValsTy;
|
|
static AvailableValsTy &getAvailableVals(void *AV) {
|
|
return *static_cast<AvailableValsTy*>(AV);
|
|
}
|
|
|
|
MachineSSAUpdater::MachineSSAUpdater(MachineFunction &MF,
|
|
SmallVectorImpl<MachineInstr*> *NewPHI)
|
|
: AV(nullptr), InsertedPHIs(NewPHI) {
|
|
TII = MF.getSubtarget().getInstrInfo();
|
|
MRI = &MF.getRegInfo();
|
|
}
|
|
|
|
MachineSSAUpdater::~MachineSSAUpdater() {
|
|
delete static_cast<AvailableValsTy*>(AV);
|
|
}
|
|
|
|
/// Initialize - Reset this object to get ready for a new set of SSA
|
|
/// updates. ProtoValue is the value used to name PHI nodes.
|
|
void MachineSSAUpdater::Initialize(unsigned V) {
|
|
if (!AV)
|
|
AV = new AvailableValsTy();
|
|
else
|
|
getAvailableVals(AV).clear();
|
|
|
|
VR = V;
|
|
VRC = MRI->getRegClass(VR);
|
|
}
|
|
|
|
/// HasValueForBlock - Return true if the MachineSSAUpdater already has a value for
|
|
/// the specified block.
|
|
bool MachineSSAUpdater::HasValueForBlock(MachineBasicBlock *BB) const {
|
|
return getAvailableVals(AV).count(BB);
|
|
}
|
|
|
|
/// AddAvailableValue - Indicate that a rewritten value is available in the
|
|
/// specified block with the specified value.
|
|
void MachineSSAUpdater::AddAvailableValue(MachineBasicBlock *BB, unsigned V) {
|
|
getAvailableVals(AV)[BB] = V;
|
|
}
|
|
|
|
/// GetValueAtEndOfBlock - Construct SSA form, materializing a value that is
|
|
/// live at the end of the specified block.
|
|
unsigned MachineSSAUpdater::GetValueAtEndOfBlock(MachineBasicBlock *BB) {
|
|
return GetValueAtEndOfBlockInternal(BB);
|
|
}
|
|
|
|
static
|
|
unsigned LookForIdenticalPHI(MachineBasicBlock *BB,
|
|
SmallVectorImpl<std::pair<MachineBasicBlock*, unsigned> > &PredValues) {
|
|
if (BB->empty())
|
|
return 0;
|
|
|
|
MachineBasicBlock::iterator I = BB->begin();
|
|
if (!I->isPHI())
|
|
return 0;
|
|
|
|
AvailableValsTy AVals;
|
|
for (unsigned i = 0, e = PredValues.size(); i != e; ++i)
|
|
AVals[PredValues[i].first] = PredValues[i].second;
|
|
while (I != BB->end() && I->isPHI()) {
|
|
bool Same = true;
|
|
for (unsigned i = 1, e = I->getNumOperands(); i != e; i += 2) {
|
|
unsigned SrcReg = I->getOperand(i).getReg();
|
|
MachineBasicBlock *SrcBB = I->getOperand(i+1).getMBB();
|
|
if (AVals[SrcBB] != SrcReg) {
|
|
Same = false;
|
|
break;
|
|
}
|
|
}
|
|
if (Same)
|
|
return I->getOperand(0).getReg();
|
|
++I;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/// InsertNewDef - Insert an empty PHI or IMPLICIT_DEF instruction which define
|
|
/// a value of the given register class at the start of the specified basic
|
|
/// block. It returns the virtual register defined by the instruction.
|
|
static
|
|
MachineInstrBuilder InsertNewDef(unsigned Opcode,
|
|
MachineBasicBlock *BB, MachineBasicBlock::iterator I,
|
|
const TargetRegisterClass *RC,
|
|
MachineRegisterInfo *MRI,
|
|
const TargetInstrInfo *TII) {
|
|
unsigned NewVR = MRI->createVirtualRegister(RC);
|
|
return BuildMI(*BB, I, DebugLoc(), TII->get(Opcode), NewVR);
|
|
}
|
|
|
|
/// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that
|
|
/// is live in the middle of the specified block.
|
|
///
|
|
/// GetValueInMiddleOfBlock is the same as GetValueAtEndOfBlock except in one
|
|
/// important case: if there is a definition of the rewritten value after the
|
|
/// 'use' in BB. Consider code like this:
|
|
///
|
|
/// X1 = ...
|
|
/// SomeBB:
|
|
/// use(X)
|
|
/// X2 = ...
|
|
/// br Cond, SomeBB, OutBB
|
|
///
|
|
/// In this case, there are two values (X1 and X2) added to the AvailableVals
|
|
/// set by the client of the rewriter, and those values are both live out of
|
|
/// their respective blocks. However, the use of X happens in the *middle* of
|
|
/// a block. Because of this, we need to insert a new PHI node in SomeBB to
|
|
/// merge the appropriate values, and this value isn't live out of the block.
|
|
///
|
|
unsigned MachineSSAUpdater::GetValueInMiddleOfBlock(MachineBasicBlock *BB) {
|
|
// If there is no definition of the renamed variable in this block, just use
|
|
// GetValueAtEndOfBlock to do our work.
|
|
if (!HasValueForBlock(BB))
|
|
return GetValueAtEndOfBlockInternal(BB);
|
|
|
|
// If there are no predecessors, just return undef.
|
|
if (BB->pred_empty()) {
|
|
// Insert an implicit_def to represent an undef value.
|
|
MachineInstr *NewDef = InsertNewDef(TargetOpcode::IMPLICIT_DEF,
|
|
BB, BB->getFirstTerminator(),
|
|
VRC, MRI, TII);
|
|
return NewDef->getOperand(0).getReg();
|
|
}
|
|
|
|
// Otherwise, we have the hard case. Get the live-in values for each
|
|
// predecessor.
|
|
SmallVector<std::pair<MachineBasicBlock*, unsigned>, 8> PredValues;
|
|
unsigned SingularValue = 0;
|
|
|
|
bool isFirstPred = true;
|
|
for (MachineBasicBlock::pred_iterator PI = BB->pred_begin(),
|
|
E = BB->pred_end(); PI != E; ++PI) {
|
|
MachineBasicBlock *PredBB = *PI;
|
|
unsigned PredVal = GetValueAtEndOfBlockInternal(PredBB);
|
|
PredValues.push_back(std::make_pair(PredBB, PredVal));
|
|
|
|
// Compute SingularValue.
|
|
if (isFirstPred) {
|
|
SingularValue = PredVal;
|
|
isFirstPred = false;
|
|
} else if (PredVal != SingularValue)
|
|
SingularValue = 0;
|
|
}
|
|
|
|
// Otherwise, if all the merged values are the same, just use it.
|
|
if (SingularValue != 0)
|
|
return SingularValue;
|
|
|
|
// If an identical PHI is already in BB, just reuse it.
|
|
unsigned DupPHI = LookForIdenticalPHI(BB, PredValues);
|
|
if (DupPHI)
|
|
return DupPHI;
|
|
|
|
// Otherwise, we do need a PHI: insert one now.
|
|
MachineBasicBlock::iterator Loc = BB->empty() ? BB->end() : BB->begin();
|
|
MachineInstrBuilder InsertedPHI = InsertNewDef(TargetOpcode::PHI, BB,
|
|
Loc, VRC, MRI, TII);
|
|
|
|
// Fill in all the predecessors of the PHI.
|
|
for (unsigned i = 0, e = PredValues.size(); i != e; ++i)
|
|
InsertedPHI.addReg(PredValues[i].second).addMBB(PredValues[i].first);
|
|
|
|
// See if the PHI node can be merged to a single value. This can happen in
|
|
// loop cases when we get a PHI of itself and one other value.
|
|
if (unsigned ConstVal = InsertedPHI->isConstantValuePHI()) {
|
|
InsertedPHI->eraseFromParent();
|
|
return ConstVal;
|
|
}
|
|
|
|
// If the client wants to know about all new instructions, tell it.
|
|
if (InsertedPHIs) InsertedPHIs->push_back(InsertedPHI);
|
|
|
|
DEBUG(dbgs() << " Inserted PHI: " << *InsertedPHI << "\n");
|
|
return InsertedPHI->getOperand(0).getReg();
|
|
}
|
|
|
|
static
|
|
MachineBasicBlock *findCorrespondingPred(const MachineInstr *MI,
|
|
MachineOperand *U) {
|
|
for (unsigned i = 1, e = MI->getNumOperands(); i != e; i += 2) {
|
|
if (&MI->getOperand(i) == U)
|
|
return MI->getOperand(i+1).getMBB();
|
|
}
|
|
|
|
llvm_unreachable("MachineOperand::getParent() failure?");
|
|
}
|
|
|
|
/// RewriteUse - Rewrite a use of the symbolic value. This handles PHI nodes,
|
|
/// which use their value in the corresponding predecessor.
|
|
void MachineSSAUpdater::RewriteUse(MachineOperand &U) {
|
|
MachineInstr *UseMI = U.getParent();
|
|
unsigned NewVR = 0;
|
|
if (UseMI->isPHI()) {
|
|
MachineBasicBlock *SourceBB = findCorrespondingPred(UseMI, &U);
|
|
NewVR = GetValueAtEndOfBlockInternal(SourceBB);
|
|
} else {
|
|
NewVR = GetValueInMiddleOfBlock(UseMI->getParent());
|
|
}
|
|
|
|
U.setReg(NewVR);
|
|
}
|
|
|
|
/// SSAUpdaterTraits<MachineSSAUpdater> - Traits for the SSAUpdaterImpl
|
|
/// template, specialized for MachineSSAUpdater.
|
|
namespace llvm {
|
|
template<>
|
|
class SSAUpdaterTraits<MachineSSAUpdater> {
|
|
public:
|
|
typedef MachineBasicBlock BlkT;
|
|
typedef unsigned ValT;
|
|
typedef MachineInstr PhiT;
|
|
|
|
typedef MachineBasicBlock::succ_iterator BlkSucc_iterator;
|
|
static BlkSucc_iterator BlkSucc_begin(BlkT *BB) { return BB->succ_begin(); }
|
|
static BlkSucc_iterator BlkSucc_end(BlkT *BB) { return BB->succ_end(); }
|
|
|
|
/// Iterator for PHI operands.
|
|
class PHI_iterator {
|
|
private:
|
|
MachineInstr *PHI;
|
|
unsigned idx;
|
|
|
|
public:
|
|
explicit PHI_iterator(MachineInstr *P) // begin iterator
|
|
: PHI(P), idx(1) {}
|
|
PHI_iterator(MachineInstr *P, bool) // end iterator
|
|
: PHI(P), idx(PHI->getNumOperands()) {}
|
|
|
|
PHI_iterator &operator++() { idx += 2; return *this; }
|
|
bool operator==(const PHI_iterator& x) const { return idx == x.idx; }
|
|
bool operator!=(const PHI_iterator& x) const { return !operator==(x); }
|
|
unsigned getIncomingValue() { return PHI->getOperand(idx).getReg(); }
|
|
MachineBasicBlock *getIncomingBlock() {
|
|
return PHI->getOperand(idx+1).getMBB();
|
|
}
|
|
};
|
|
static inline PHI_iterator PHI_begin(PhiT *PHI) { return PHI_iterator(PHI); }
|
|
static inline PHI_iterator PHI_end(PhiT *PHI) {
|
|
return PHI_iterator(PHI, true);
|
|
}
|
|
|
|
/// FindPredecessorBlocks - Put the predecessors of BB into the Preds
|
|
/// vector.
|
|
static void FindPredecessorBlocks(MachineBasicBlock *BB,
|
|
SmallVectorImpl<MachineBasicBlock*> *Preds){
|
|
for (MachineBasicBlock::pred_iterator PI = BB->pred_begin(),
|
|
E = BB->pred_end(); PI != E; ++PI)
|
|
Preds->push_back(*PI);
|
|
}
|
|
|
|
/// GetUndefVal - Create an IMPLICIT_DEF instruction with a new register.
|
|
/// Add it into the specified block and return the register.
|
|
static unsigned GetUndefVal(MachineBasicBlock *BB,
|
|
MachineSSAUpdater *Updater) {
|
|
// Insert an implicit_def to represent an undef value.
|
|
MachineInstr *NewDef = InsertNewDef(TargetOpcode::IMPLICIT_DEF,
|
|
BB, BB->getFirstTerminator(),
|
|
Updater->VRC, Updater->MRI,
|
|
Updater->TII);
|
|
return NewDef->getOperand(0).getReg();
|
|
}
|
|
|
|
/// CreateEmptyPHI - Create a PHI instruction that defines a new register.
|
|
/// Add it into the specified block and return the register.
|
|
static unsigned CreateEmptyPHI(MachineBasicBlock *BB, unsigned NumPreds,
|
|
MachineSSAUpdater *Updater) {
|
|
MachineBasicBlock::iterator Loc = BB->empty() ? BB->end() : BB->begin();
|
|
MachineInstr *PHI = InsertNewDef(TargetOpcode::PHI, BB, Loc,
|
|
Updater->VRC, Updater->MRI,
|
|
Updater->TII);
|
|
return PHI->getOperand(0).getReg();
|
|
}
|
|
|
|
/// AddPHIOperand - Add the specified value as an operand of the PHI for
|
|
/// the specified predecessor block.
|
|
static void AddPHIOperand(MachineInstr *PHI, unsigned Val,
|
|
MachineBasicBlock *Pred) {
|
|
MachineInstrBuilder(*Pred->getParent(), PHI).addReg(Val).addMBB(Pred);
|
|
}
|
|
|
|
/// InstrIsPHI - Check if an instruction is a PHI.
|
|
///
|
|
static MachineInstr *InstrIsPHI(MachineInstr *I) {
|
|
if (I && I->isPHI())
|
|
return I;
|
|
return nullptr;
|
|
}
|
|
|
|
/// ValueIsPHI - Check if the instruction that defines the specified register
|
|
/// is a PHI instruction.
|
|
static MachineInstr *ValueIsPHI(unsigned Val, MachineSSAUpdater *Updater) {
|
|
return InstrIsPHI(Updater->MRI->getVRegDef(Val));
|
|
}
|
|
|
|
/// ValueIsNewPHI - Like ValueIsPHI but also check if the PHI has no source
|
|
/// operands, i.e., it was just added.
|
|
static MachineInstr *ValueIsNewPHI(unsigned Val, MachineSSAUpdater *Updater) {
|
|
MachineInstr *PHI = ValueIsPHI(Val, Updater);
|
|
if (PHI && PHI->getNumOperands() <= 1)
|
|
return PHI;
|
|
return nullptr;
|
|
}
|
|
|
|
/// GetPHIValue - For the specified PHI instruction, return the register
|
|
/// that it defines.
|
|
static unsigned GetPHIValue(MachineInstr *PHI) {
|
|
return PHI->getOperand(0).getReg();
|
|
}
|
|
};
|
|
|
|
} // End llvm namespace
|
|
|
|
/// GetValueAtEndOfBlockInternal - Check to see if AvailableVals has an entry
|
|
/// for the specified BB and if so, return it. If not, construct SSA form by
|
|
/// first calculating the required placement of PHIs and then inserting new
|
|
/// PHIs where needed.
|
|
unsigned MachineSSAUpdater::GetValueAtEndOfBlockInternal(MachineBasicBlock *BB){
|
|
AvailableValsTy &AvailableVals = getAvailableVals(AV);
|
|
if (unsigned V = AvailableVals[BB])
|
|
return V;
|
|
|
|
SSAUpdaterImpl<MachineSSAUpdater> Impl(this, &AvailableVals, InsertedPHIs);
|
|
return Impl.GetValue(BB);
|
|
}
|