[SCEV][NFC] Factor out common API for getting unique operands of a SCEV

This function is used at least in 2 places, to it makes sense to make it separate.

Differential Revision: https://reviews.llvm.org/D112516
Reviewed By: reames

llvm/lib/Analysis/ScalarEvolution.cpp

@@ -6589,6 +6589,26 @@ ScalarEvolution::getNonTrivialDefiningScopeBound(const SCEV *S) {
   return nullptr;
 }
 
+/// Fills \p Ops with unique operands of \p S, if it has operands. If not,
+/// \p Ops remains unmodified.
+static void collectUniqueOps(const SCEV *S,
+                             SmallVectorImpl<const SCEV *> &Ops) {
+  SmallPtrSet<const SCEV *, 4> Unique;
+  auto InsertUnique = [&](const SCEV *S) {
+    if (Unique.insert(S).second)
+      Ops.push_back(S);
+  };
+  if (auto *S2 = dyn_cast<SCEVCastExpr>(S))
+    for (auto *Op : S2->operands())
+      InsertUnique(Op);
+  else if (auto *S2 = dyn_cast<SCEVNAryExpr>(S))
+    for (auto *Op : S2->operands())
+      InsertUnique(Op);
+  else if (auto *S2 = dyn_cast<SCEVUDivExpr>(S))
+    for (auto *Op : S2->operands())
+      InsertUnique(Op);
+}
+
 const Instruction *
 ScalarEvolution::getDefiningScopeBound(ArrayRef<const SCEV *> Ops) {
   // Do a bounded search of the def relation of the requested SCEVs.
@@ -6612,15 +6632,12 @@ ScalarEvolution::getDefiningScopeBound(ArrayRef<const SCEV *> Ops) {
     if (auto *DefI = getNonTrivialDefiningScopeBound(S)) {
       if (!Bound || DT.dominates(Bound, DefI))
         Bound = DefI;
-    } else if (auto *S2 = dyn_cast<SCEVCastExpr>(S))
-      for (auto *Op : S2->operands())
-        pushOp(Op);
-    else if (auto *S2 = dyn_cast<SCEVNAryExpr>(S))
-      for (auto *Op : S2->operands())
-        pushOp(Op);
-    else if (auto *S2 = dyn_cast<SCEVUDivExpr>(S))
-      for (auto *Op : S2->operands())
+    } else {
+      SmallVector<const SCEV *, 4> Ops;
+      collectUniqueOps(S, Ops);
+      for (auto *Op : Ops)
         pushOp(Op);
+    }
   }
   return Bound ? Bound : &*F.getEntryBlock().begin();
 }
@@ -12908,15 +12925,8 @@ void ScalarEvolution::verify() const {
 
   // Verify intergity of SCEV users.
   for (const auto &S : UniqueSCEVs) {
-    SmallPtrSet<const SCEV *, 4> Ops;
-    if (const auto *NS = dyn_cast<SCEVNAryExpr>(&S))
-      Ops.insert(NS->op_begin(), NS->op_end());
-    else if (const auto *CS = dyn_cast<SCEVCastExpr>(&S))
-      Ops.insert(CS->getOperand());
-    else if (const auto *DS = dyn_cast<SCEVUDivExpr>(&S)) {
-      Ops.insert(DS->getLHS());
-      Ops.insert(DS->getRHS());
-    }
+    SmallVector<const SCEV *, 4> Ops;
+    collectUniqueOps(&S, Ops);
     for (const auto *Op : Ops) {
       // We do not store dependencies of constants.
       if (isa<SCEVConstant>(Op))