Method getRelatedIndV

lib/propanalysis/ArrayAnalyzer.cpp:220–266

This API returns an induction variable or A variable dependent on the induction variable

// This API returns an induction variable or
// A variable dependent on the induction variable
Value *ArrayAnalyzer::getRelatedIndV(Loop &L, ScalarEvolution &SEA) {
  if (!L.isLoopSimplifyForm())
    return nullptr;

  auto *Header = L.getHeader();
  assert(Header && "Unexpected Program State");

  ICmpInst *CmpInst = getLoopExitCond(L);
  if (!CmpInst)
    return nullptr;
  assert(CmpInst->getNumOperands() > 1 && "Unexpected Program State");

  auto *LatchCmpOp0 = dyn_cast<Instruction>(CmpInst->getOperand(0));
  auto *LatchCmpOp1 = dyn_cast<Instruction>(CmpInst->getOperand(1));

  for (auto &IndVar : Header->phis()) {
    InductionDescriptor IndDesc;
    if (!InductionDescriptor::isInductionPHI(&IndVar, &L, &SEA, IndDesc))
      continue;

    // case 1: Induction Variable
    if (&IndVar == LatchCmpOp0 || &IndVar == LatchCmpOp1)
      return &IndVar;

    // case 2: If IndVar is related to the operands of ICMP inst,
    // it also depend on the count of loop
    // ex) for (i = 0; i+1 < len; i++) : "i+1" dependent on IndVar
    if (LatchCmpOp0) {
      for (unsigned Opnum = 0; Opnum < LatchCmpOp0->getNumOperands(); Opnum++) {
        if (LatchCmpOp0->getOperand(Opnum) != &IndVar)
          continue;
        return LatchCmpOp0;
      }
    }

    // ex) for (i = 0; len > i+1; i++)
    if (LatchCmpOp1) {
      for (unsigned Opnum = 0; Opnum < LatchCmpOp1->getNumOperands(); Opnum++) {
        if (LatchCmpOp1->getOperand(Opnum) != &IndVar)
          continue;
        return LatchCmpOp1;
      }
    }
  }

  return nullptr;
}

void ArrayAnalyzer::handleStackFrame(StackFrame &Frame,
                                     std::stack<StackFrame> &DefUseChains,