return GetValueAtEndOfBlockInternal(BB);
}
+static
+unsigned LookForIdenticalPHI(MachineBasicBlock *BB,
+ SmallVector<std::pair<MachineBasicBlock*, unsigned>, 8> &PredValues) {
+ if (BB->empty())
+ return 0;
+
+ MachineBasicBlock::iterator I = BB->front();
+ if (I->getOpcode() != TargetInstrInfo::PHI)
+ 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->getOpcode() == TargetInstrInfo::PHI) {
+ 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.
return BuildMI(*BB, I, DebugLoc::getUnknownLoc(), TII->get(Opcode), NewVR);
}
-
/// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that
/// is live in the middle of the specified block.
///
// 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);
+ return GetValueAtEndOfBlockInternal(BB);
// If there are no predecessors, just return undef.
if (BB->pred_empty()) {
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->front();
MachineInstr *InsertedPHI = InsertNewDef(TargetInstrInfo::PHI, BB,
unsigned NewVR = 0;
if (UseMI->getOpcode() == TargetInstrInfo::PHI) {
MachineBasicBlock *SourceBB = findCorrespondingPred(UseMI, &U);
- NewVR = GetValueAtEndOfBlock(SourceBB);
+ NewVR = GetValueAtEndOfBlockInternal(SourceBB);
} else {
NewVR = GetValueInMiddleOfBlock(UseMI->getParent());
}
U.setReg(NewVR);
}
+void MachineSSAUpdater::ReplaceRegWith(unsigned OldReg, unsigned NewReg) {
+ MRI->replaceRegWith(OldReg, NewReg);
+
+ AvailableValsTy &AvailableVals = getAvailableVals(AV);
+ for (DenseMap<MachineBasicBlock*, unsigned>::iterator
+ I = AvailableVals.begin(), E = AvailableVals.end(); I != E; ++I)
+ if (I->second == OldReg)
+ I->second = NewReg;
+}
+
/// GetValueAtEndOfBlockInternal - Check to see if AvailableVals has an entry
/// for the specified BB and if so, return it. If not, construct SSA form by
/// walking predecessors inserting PHI nodes as needed until we get to a block
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);
+ ReplaceRegWith(InsertedVal, SingularValue);
OldVal->eraseFromParent();
}