+static bool addNoRecurseAttrs(const CallGraphSCC &SCC,
+ SmallVectorImpl<WeakVH> &Revisit) {
+ // Try and identify functions that do not recurse.
+
+ // If the SCC contains multiple nodes we know for sure there is recursion.
+ if (!SCC.isSingular())
+ return false;
+
+ const CallGraphNode *CGN = *SCC.begin();
+ Function *F = CGN->getFunction();
+ if (!F || F->isDeclaration() || F->doesNotRecurse())
+ return false;
+
+ // If all of the calls in F are identifiable and are to norecurse functions, F
+ // is norecurse. This check also detects self-recursion as F is not currently
+ // marked norecurse, so any called from F to F will not be marked norecurse.
+ if (std::all_of(CGN->begin(), CGN->end(),
+ [](const CallGraphNode::CallRecord &CR) {
+ Function *F = CR.second->getFunction();
+ return F && F->doesNotRecurse();
+ }))
+ // Function calls a potentially recursive function.
+ return setDoesNotRecurse(*F);
+
+ // We know that F is not obviously recursive, but we haven't been able to
+ // prove that it doesn't actually recurse. Add it to the Revisit list to try
+ // again top-down later.
+ Revisit.push_back(F);
+ return false;
+}
+
+static bool addNoRecurseAttrsTopDownOnly(Function *F) {
+ // If F is internal and all uses are in norecurse functions, then F is also
+ // norecurse.
+ if (F->doesNotRecurse())
+ return false;
+ if (F->hasInternalLinkage()) {
+ for (auto *U : F->users())
+ if (auto *I = dyn_cast<Instruction>(U)) {
+ if (!I->getParent()->getParent()->doesNotRecurse())
+ return false;
+ } else {
+ return false;
+ }
+ return setDoesNotRecurse(*F);
+ }
+ return false;
+}
+