+static bool isNoopBitcast(Type *T1, Type *T2,
+ const TargetLowering& TLI) {
+ return T1 == T2 || (T1->isPointerTy() && T2->isPointerTy()) ||
+ (isa<VectorType>(T1) && isa<VectorType>(T2) &&
+ TLI.isTypeLegal(EVT::getEVT(T1)) && TLI.isTypeLegal(EVT::getEVT(T2)));
+}
+
+/// sameNoopInput - Return true if V1 == V2, else if either V1 or V2 is a noop
+/// (i.e., lowers to no machine code), look through it (and any transitive noop
+/// operands to it) and check if it has the same noop input value. This is
+/// used to determine if a tail call can be formed.
+static bool sameNoopInput(const Value *V1, const Value *V2,
+ SmallVectorImpl<unsigned> &Els1,
+ SmallVectorImpl<unsigned> &Els2,
+ const TargetLowering &TLI) {
+ using std::swap;
+ bool swapParity = false;
+ bool equalEls = Els1 == Els2;
+ while (true) {
+ if ((equalEls && V1 == V2) || isa<UndefValue>(V1) || isa<UndefValue>(V2)) {
+ if (swapParity)
+ // Revert to original Els1 and Els2 to avoid confusing recursive calls
+ swap(Els1, Els2);
+ return true;
+ }
+
+ // Try to look through V1; if V1 is not an instruction, it can't be looked
+ // through.
+ const Instruction *I = dyn_cast<Instruction>(V1);
+ const Value *NoopInput = 0;
+ if (I != 0 && I->getNumOperands() > 0) {
+ Value *Op = I->getOperand(0);
+ if (isa<TruncInst>(I)) {
+ // Look through truly no-op truncates.
+ if (TLI.isTruncateFree(Op->getType(), I->getType()))
+ NoopInput = Op;
+ } else if (isa<BitCastInst>(I)) {
+ // Look through truly no-op bitcasts.
+ if (isNoopBitcast(Op->getType(), I->getType(), TLI))
+ NoopInput = Op;
+ } else if (isa<GetElementPtrInst>(I)) {
+ // Look through getelementptr
+ if (cast<GetElementPtrInst>(I)->hasAllZeroIndices())
+ NoopInput = Op;
+ } else if (isa<IntToPtrInst>(I)) {
+ // Look through inttoptr.
+ // Make sure this isn't a truncating or extending cast. We could
+ // support this eventually, but don't bother for now.
+ if (!isa<VectorType>(I->getType()) &&
+ TLI.getPointerTy().getSizeInBits() ==
+ cast<IntegerType>(Op->getType())->getBitWidth())
+ NoopInput = Op;
+ } else if (isa<PtrToIntInst>(I)) {
+ // Look through ptrtoint.
+ // Make sure this isn't a truncating or extending cast. We could
+ // support this eventually, but don't bother for now.
+ if (!isa<VectorType>(I->getType()) &&
+ TLI.getPointerTy().getSizeInBits() ==
+ cast<IntegerType>(I->getType())->getBitWidth())
+ NoopInput = Op;
+ } else if (isa<CallInst>(I)) {
+ // Look through call
+ for (User::const_op_iterator i = I->op_begin(),
+ // Skip Callee
+ e = I->op_end() - 1;
+ i != e; ++i) {
+ unsigned attrInd = i - I->op_begin() + 1;
+ if (cast<CallInst>(I)->paramHasAttr(attrInd, Attribute::Returned) &&
+ isNoopBitcast((*i)->getType(), I->getType(), TLI)) {
+ NoopInput = *i;
+ break;
+ }
+ }
+ } else if (isa<InvokeInst>(I)) {
+ // Look through invoke
+ for (User::const_op_iterator i = I->op_begin(),
+ // Skip BB, BB, Callee
+ e = I->op_end() - 3;
+ i != e; ++i) {
+ unsigned attrInd = i - I->op_begin() + 1;
+ if (cast<InvokeInst>(I)->paramHasAttr(attrInd, Attribute::Returned) &&
+ isNoopBitcast((*i)->getType(), I->getType(), TLI)) {
+ NoopInput = *i;
+ break;
+ }
+ }
+ }
+ }
+
+ if (NoopInput) {
+ V1 = NoopInput;
+ continue;
+ }
+
+ // If we already swapped, avoid infinite loop
+ if (swapParity)
+ break;
+
+ // Otherwise, swap V1<->V2, Els1<->Els2
+ swap(V1, V2);
+ swap(Els1, Els2);
+ swapParity = !swapParity;
+ }
+
+ for (unsigned n = 0; n < 2; ++n) {
+ if (isa<InsertValueInst>(V1)) {
+ if (isa<StructType>(V1->getType())) {
+ // Look through insertvalue
+ unsigned i, e;
+ for (i = 0, e = cast<StructType>(V1->getType())->getNumElements();
+ i != e; ++i) {
+ const Value *InScalar = FindInsertedValue(const_cast<Value*>(V1), i);
+ if (InScalar == 0)
+ break;
+ Els1.push_back(i);
+ if (!sameNoopInput(InScalar, V2, Els1, Els2, TLI)) {
+ Els1.pop_back();
+ break;
+ }
+ Els1.pop_back();
+ }
+ if (i == e) {
+ if (swapParity)
+ swap(Els1, Els2);
+ return true;
+ }
+ }
+ } else if (!Els1.empty() && isa<ExtractValueInst>(V1)) {
+ const ExtractValueInst *EVI = cast<ExtractValueInst>(V1);
+ unsigned i = Els1.back();
+ // If the scalar value being inserted is an extractvalue of the right
+ // index from the call, then everything is good.
+ if (isa<StructType>(EVI->getOperand(0)->getType()) &&
+ EVI->getNumIndices() == 1 && EVI->getIndices()[0] == i) {
+ // Look through extractvalue
+ Els1.pop_back();
+ if (sameNoopInput(EVI->getOperand(0), V2, Els1, Els2, TLI)) {
+ Els1.push_back(i);
+ if (swapParity)
+ swap(Els1, Els2);
+ return true;
+ }
+ Els1.push_back(i);
+ }
+ }
+
+ swap(V1, V2);
+ swap(Els1, Els2);
+ swapParity = !swapParity;
+ }
+
+ if (swapParity)
+ swap(Els1, Els2);
+ return false;
+}
+