//
//===----------------------------------------------------------------------===//
//
-// This file implements the MachineSSAUpdater class.
+// This file implements the MachineSSAUpdater class. It's based on SSAUpdater
+// class in lib/Transforms/Utils.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/MachineSSAUpdater.h"
#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/Target/TargetInstrInfo.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/ADT/DenseMap.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/raw_ostream.h"
using namespace llvm;
-typedef DenseMap<MachineBasicBlock*, unsigned > AvailableValsTy;
+typedef DenseMap<MachineBasicBlock*, unsigned> AvailableValsTy;
typedef std::vector<std::pair<MachineBasicBlock*, unsigned> >
IncomingPredInfoTy;
}
-MachineSSAUpdater::MachineSSAUpdater(SmallVectorImpl<MachineInstr*> *NewPHI)
- : AV(0), IPI(0), InsertedPHIs(NewPHI) {}
+MachineSSAUpdater::MachineSSAUpdater(MachineFunction &MF,
+ SmallVectorImpl<MachineInstr*> *NewPHI)
+ : AV(0), IPI(0), InsertedPHIs(NewPHI) {
+ TII = MF.getTarget().getInstrInfo();
+ MRI = &MF.getRegInfo();
+}
MachineSSAUpdater::~MachineSSAUpdater() {
delete &getAvailableVals(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() {
+void MachineSSAUpdater::Initialize(unsigned V) {
if (AV == 0)
AV = new AvailableValsTy();
else
IPI = new IncomingPredInfoTy();
else
getIncomingPredInfo(IPI).clear();
+
+ VR = V;
+ VRC = MRI->getRegClass(VR);
}
/// HasValueForBlock - Return true if the MachineSSAUpdater already has a value for
return GetValueAtEndOfBlockInternal(BB);
}
+/// InsertNewPHI - Insert an empty PHI 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 PHI instruction.
+static
+MachineInstr *InsertNewPHI(MachineBasicBlock *BB, const TargetRegisterClass *RC,
+ MachineRegisterInfo *MRI, const TargetInstrInfo *TII) {
+ unsigned NewVR = MRI->createVirtualRegister(RC);
+ return BuildMI(*BB, BB->front(), BB->front().getDebugLoc(),
+ TII->get(TargetInstrInfo::PHI), NewVR);
+}
+
+
/// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that
/// is live in the middle of the specified block.
///
/// 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 (!getAvailableVals(AV).count(BB))
+ return GetValueAtEndOfBlock(BB);
+
+ if (BB->pred_empty())
+ llvm_unreachable("Unreachable block!");
+
+ // 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;
+
+ // Otherwise, we do need a PHI: insert one now.
+ MachineInstr *InsertedPHI = InsertNewPHI(BB, VRC, MRI, TII);
+
+ // Fill in all the predecessors of the PHI.
+ MachineInstrBuilder MIB(InsertedPHI);
+ for (unsigned i = 0, e = PredValues.size(); i != e; ++i)
+ MIB.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(errs() << " 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?");
return 0;
}
/// RewriteUse - Rewrite a use of the symbolic value. This handles PHI nodes,
/// which use their value in the corresponding predecessor.
-void MachineSSAUpdater::RewriteUse(unsigned &U) {
-}
+void MachineSSAUpdater::RewriteUse(MachineOperand &U) {
+ MachineInstr *UseMI = U.getParent();
+ unsigned NewVR = 0;
+ if (UseMI->getOpcode() == TargetInstrInfo::PHI) {
+ MachineBasicBlock *SourceBB = findCorrespondingPred(UseMI, &U);
+ NewVR = GetValueAtEndOfBlock(SourceBB);
+ } else {
+ NewVR = GetValueInMiddleOfBlock(UseMI->getParent());
+ }
+ U.setReg(NewVR);
+}
/// GetValueAtEndOfBlockInternal - Check to see if AvailableVals has an entry
/// for the specified BB and if so, return it. If not, construct SSA form by
/// where the value is available.
///
unsigned MachineSSAUpdater::GetValueAtEndOfBlockInternal(MachineBasicBlock *BB){
- return 0;
+ AvailableValsTy &AvailableVals = getAvailableVals(AV);
+
+ // Query AvailableVals by doing an insertion of null.
+ std::pair<AvailableValsTy::iterator, bool> InsertRes =
+ AvailableVals.insert(std::make_pair(BB, 0));
+
+ // Handle the case when the insertion fails because we have already seen BB.
+ if (!InsertRes.second) {
+ // If the insertion failed, there are two cases. The first case is that the
+ // value is already available for the specified block. If we get this, just
+ // return the value.
+ if (InsertRes.first->second != 0)
+ return InsertRes.first->second;
+
+ // Otherwise, if the value we find is null, then this is the value is not
+ // known but it is being computed elsewhere in our recursion. This means
+ // that we have a cycle. Handle this by inserting a PHI node and returning
+ // it. When we get back to the first instance of the recursion we will fill
+ // in the PHI node.
+ MachineInstr *NewPHI = InsertNewPHI(BB, VRC, MRI, TII);
+ unsigned NewVR = NewPHI->getOperand(0).getReg();
+ InsertRes.first->second = NewVR;
+ return NewVR;
+ }
+
+ if (BB->pred_empty())
+ llvm_unreachable("Unreachable block!");
+
+ // Okay, the value isn't in the map and we just inserted a null in the entry
+ // to indicate that we're processing the block. Since we have no idea what
+ // value is in this block, we have to recurse through our predecessors.
+ //
+ // While we're walking our predecessors, we keep track of them in a vector,
+ // then insert a PHI node in the end if we actually need one. We could use a
+ // smallvector here, but that would take a lot of stack space for every level
+ // of the recursion, just use IncomingPredInfo as an explicit stack.
+ IncomingPredInfoTy &IncomingPredInfo = getIncomingPredInfo(IPI);
+ unsigned FirstPredInfoEntry = IncomingPredInfo.size();
+
+ // As we're walking the predecessors, keep track of whether they are all
+ // producing the same value. If so, this value will capture it, if not, it
+ // will get reset to null. We distinguish the no-predecessor case explicitly
+ // below.
+ 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);
+ IncomingPredInfo.push_back(std::make_pair(PredBB, PredVal));
+
+ // Compute SingularValue.
+ if (isFirstPred) {
+ SingularValue = PredVal;
+ isFirstPred = false;
+ } else if (PredVal != SingularValue)
+ SingularValue = 0;
+ }
+
+ /// Look up BB's entry in AvailableVals. 'InsertRes' may be invalidated. If
+ /// this block is involved in a loop, a no-entry PHI node will have been
+ /// inserted as InsertedVal. Otherwise, we'll still have the null we inserted
+ /// above.
+ unsigned InsertedVal = AvailableVals[BB];
+
+ // If all the predecessor values are the same then we don't need to insert a
+ // PHI. This is the simple and common case.
+ if (SingularValue) {
+ // If a PHI node got inserted, replace it with the singlar value and delete
+ // it.
+ if (InsertedVal) {
+ MachineInstr *OldVal = MRI->getVRegDef(InsertedVal);
+ // Be careful about dead loops. These RAUW's also update InsertedVal.
+ assert(InsertedVal != SingularValue && "Dead loop?");
+ MRI->replaceRegWith(InsertedVal, SingularValue);
+ OldVal->eraseFromParent();
+ } else {
+ InsertedVal = SingularValue;
+ }
+
+ // Drop the entries we added in IncomingPredInfo to restore the stack.
+ IncomingPredInfo.erase(IncomingPredInfo.begin()+FirstPredInfoEntry,
+ IncomingPredInfo.end());
+ return InsertedVal;
+ }
+
+
+ // Otherwise, we do need a PHI: insert one now if we don't already have one.
+ MachineInstr *InsertedPHI;
+ if (InsertedVal == 0) {
+ InsertedPHI = InsertNewPHI(BB, VRC, MRI, TII);
+ InsertedVal = InsertedPHI->getOperand(0).getReg();
+ } else {
+ InsertedPHI = MRI->getVRegDef(InsertedVal);
+ }
+
+ // Fill in all the predecessors of the PHI.
+ MachineInstrBuilder MIB(InsertedPHI);
+ for (IncomingPredInfoTy::iterator I =
+ IncomingPredInfo.begin()+FirstPredInfoEntry,
+ E = IncomingPredInfo.end(); I != E; ++I)
+ MIB.addReg(I->second).addMBB(I->first);
+
+ // Drop the entries we added in IncomingPredInfo to restore the stack.
+ IncomingPredInfo.erase(IncomingPredInfo.begin()+FirstPredInfoEntry,
+ IncomingPredInfo.end());
+
+ // 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()) {
+ MRI->replaceRegWith(InsertedVal, ConstVal);
+ InsertedPHI->eraseFromParent();
+ InsertedVal = ConstVal;
+ } else {
+ DEBUG(errs() << " Inserted PHI: " << *InsertedPHI << "\n");
+
+ // If the client wants to know about all new instructions, tell it.
+ if (InsertedPHIs) InsertedPHIs->push_back(InsertedPHI);
+ }
+
+ return InsertedVal;
+
}
projects / oota-llvm.git / commitdiff