+/// IsChainDependent - Test if Outer is reachable from Inner through
+/// chain dependencies.
+static bool IsChainDependent(SDNode *Outer, SDNode *Inner,
+ unsigned NestLevel,
+ const TargetInstrInfo *TII) {
+ SDNode *N = Outer;
+ for (;;) {
+ if (N == Inner)
+ return true;
+ // For a TokenFactor, examine each operand. There may be multiple ways
+ // to get to the CALLSEQ_BEGIN, but we need to find the path with the
+ // most nesting in order to ensure that we find the corresponding match.
+ if (N->getOpcode() == ISD::TokenFactor) {
+ for (const SDValue &Op : N->op_values())
+ if (IsChainDependent(Op.getNode(), Inner, NestLevel, TII))
+ return true;
+ return false;
+ }
+ // Check for a lowered CALLSEQ_BEGIN or CALLSEQ_END.
+ if (N->isMachineOpcode()) {
+ if (N->getMachineOpcode() ==
+ (unsigned)TII->getCallFrameDestroyOpcode()) {
+ ++NestLevel;
+ } else if (N->getMachineOpcode() ==
+ (unsigned)TII->getCallFrameSetupOpcode()) {
+ if (NestLevel == 0)
+ return false;
+ --NestLevel;
+ }
+ }
+ // Otherwise, find the chain and continue climbing.
+ for (const SDValue &Op : N->op_values())
+ if (Op.getValueType() == MVT::Other) {
+ N = Op.getNode();
+ goto found_chain_operand;
+ }
+ return false;
+ found_chain_operand:;
+ if (N->getOpcode() == ISD::EntryToken)
+ return false;
+ }
+}
+
+/// FindCallSeqStart - Starting from the (lowered) CALLSEQ_END node, locate
+/// the corresponding (lowered) CALLSEQ_BEGIN node.
+///
+/// NestLevel and MaxNested are used in recursion to indcate the current level
+/// of nesting of CALLSEQ_BEGIN and CALLSEQ_END pairs, as well as the maximum
+/// level seen so far.
+///
+/// TODO: It would be better to give CALLSEQ_END an explicit operand to point
+/// to the corresponding CALLSEQ_BEGIN to avoid needing to search for it.
+static SDNode *
+FindCallSeqStart(SDNode *N, unsigned &NestLevel, unsigned &MaxNest,
+ const TargetInstrInfo *TII) {
+ for (;;) {
+ // For a TokenFactor, examine each operand. There may be multiple ways
+ // to get to the CALLSEQ_BEGIN, but we need to find the path with the
+ // most nesting in order to ensure that we find the corresponding match.
+ if (N->getOpcode() == ISD::TokenFactor) {
+ SDNode *Best = nullptr;
+ unsigned BestMaxNest = MaxNest;
+ for (const SDValue &Op : N->op_values()) {
+ unsigned MyNestLevel = NestLevel;
+ unsigned MyMaxNest = MaxNest;
+ if (SDNode *New = FindCallSeqStart(Op.getNode(),
+ MyNestLevel, MyMaxNest, TII))
+ if (!Best || (MyMaxNest > BestMaxNest)) {
+ Best = New;
+ BestMaxNest = MyMaxNest;
+ }
+ }
+ assert(Best);
+ MaxNest = BestMaxNest;
+ return Best;
+ }
+ // Check for a lowered CALLSEQ_BEGIN or CALLSEQ_END.
+ if (N->isMachineOpcode()) {
+ if (N->getMachineOpcode() ==
+ (unsigned)TII->getCallFrameDestroyOpcode()) {
+ ++NestLevel;
+ MaxNest = std::max(MaxNest, NestLevel);
+ } else if (N->getMachineOpcode() ==
+ (unsigned)TII->getCallFrameSetupOpcode()) {
+ assert(NestLevel != 0);
+ --NestLevel;
+ if (NestLevel == 0)
+ return N;
+ }
+ }
+ // Otherwise, find the chain and continue climbing.
+ for (const SDValue &Op : N->op_values())
+ if (Op.getValueType() == MVT::Other) {
+ N = Op.getNode();
+ goto found_chain_operand;
+ }
+ return nullptr;
+ found_chain_operand:;
+ if (N->getOpcode() == ISD::EntryToken)
+ return nullptr;
+ }
+}
+