diff --git a/include/swift/SILOptimizer/Analysis/Reachability.h b/include/swift/SILOptimizer/Analysis/Reachability.h
index e98f9d2901123..1eef74d1d83c3 100644
--- a/include/swift/SILOptimizer/Analysis/Reachability.h
+++ b/include/swift/SILOptimizer/Analysis/Reachability.h
@@ -149,7 +149,7 @@ class BackwardReachability {
 ///     Effect effectForPhi(SILBasicBlock *);
 ///
 ///     /// The uses from which reachability will begin.
-///     ArrayRef<SILInstruction *> gens();
+///     iterable gens();
 /// }
 template <typename Effects>
 class IterativeBackwardReachability final {
diff --git a/lib/SILOptimizer/Transforms/SSADestroyHoisting.cpp b/lib/SILOptimizer/Transforms/SSADestroyHoisting.cpp
index df81319a3d424..8e02d310f56c3 100644
--- a/lib/SILOptimizer/Transforms/SSADestroyHoisting.cpp
+++ b/lib/SILOptimizer/Transforms/SSADestroyHoisting.cpp
@@ -111,7 +111,7 @@ struct KnownStorageUses : UniqueStorageUseVisitor {
   bool preserveDebugInfo;
 
   SmallPtrSet<SILInstruction *, 16> storageUsers;
-  SmallVector<SILInstruction *, 4> originalDestroys;
+  SmallSetVector<SILInstruction *, 4> originalDestroys;
   SmallPtrSet<SILInstruction *, 4> debugInsts;
 
   KnownStorageUses(AccessStorage storage, SILFunction *function)
@@ -158,7 +158,7 @@ struct KnownStorageUses : UniqueStorageUseVisitor {
   bool visitStore(Operand *use) override { return recordUser(use->getUser()); }
 
   bool visitDestroy(Operand *use) override {
-    originalDestroys.push_back(use->getUser());
+    originalDestroys.insert(use->getUser());
     return true;
   }
 
@@ -283,9 +283,7 @@ class DeinitBarriers final {
     /// IterativeBackwardReachability::Effects
     /// VisitBarrierAccessScopes::Effects
 
-    ArrayRef<SILInstruction *> gens() {
-      return result.knownUses.originalDestroys;
-    }
+    auto gens() { return result.knownUses.originalDestroys; }
 
     Effect effectForInstruction(SILInstruction *instruction);
 
@@ -366,8 +364,7 @@ bool DeinitBarriers::classificationIsBarrier(Classification classification) {
 DeinitBarriers::DestroyReachability::Effect
 DeinitBarriers::DestroyReachability::effectForInstruction(
     SILInstruction *instruction) {
-  if (llvm::find(result.knownUses.originalDestroys, instruction) !=
-      result.knownUses.originalDestroys.end())
+  if (result.knownUses.originalDestroys.contains(instruction))
     return Effect::Gen();
   auto classification = result.classifyInstruction(instruction);
   if (recordDeadUsers && classification == Classification::DeadUser)
diff --git a/lib/SILOptimizer/Utils/LexicalDestroyHoisting.cpp b/lib/SILOptimizer/Utils/LexicalDestroyHoisting.cpp
index 254008483c0a5..91a1374b245a2 100644
--- a/lib/SILOptimizer/Utils/LexicalDestroyHoisting.cpp
+++ b/lib/SILOptimizer/Utils/LexicalDestroyHoisting.cpp
@@ -67,7 +67,7 @@ struct Usage final {
   /// Instructions which are users of the simple (i.e. not reborrowed) value.
   SmallPtrSet<SILInstruction *, 16> users;
   // The instructions from which the hoisting starts, the destroy_values.
-  llvm::SmallVector<SILInstruction *, 4> ends;
+  llvm::SmallSetVector<SILInstruction *, 4> ends;
 
   Usage(){};
   Usage(Usage const &) = delete;
@@ -89,7 +89,7 @@ bool findUsage(Context const &context, Usage &usage) {
     // flow and determine whether any were reused.  They aren't uses over which
     // we can't hoist though.
     if (isa<DestroyValueInst>(use->getUser())) {
-      usage.ends.push_back(use->getUser());
+      usage.ends.insert(use->getUser());
     } else {
       usage.users.insert(use->getUser());
     }
@@ -155,7 +155,7 @@ class Dataflow final {
   /// IterativeBackwardReachability::Effects
   /// VisitBarrierAccessScopes::Effects
 
-  ArrayRef<SILInstruction *> gens() { return uses.ends; }
+  auto gens() { return uses.ends; }
 
   Effect effectForInstruction(SILInstruction *);
   Effect effectForPhi(SILBasicBlock *);
@@ -211,7 +211,7 @@ bool Dataflow::classificationIsBarrier(Classification classification) {
 }
 
 Dataflow::Effect Dataflow::effectForInstruction(SILInstruction *instruction) {
-  if (llvm::find(uses.ends, instruction) != uses.ends.end())
+  if (uses.ends.contains(instruction))
     return Effect::Gen();
   auto classification = classifyInstruction(instruction);
   return classificationIsBarrier(classification) ? Effect::Kill()
diff --git a/lib/SILOptimizer/Utils/ShrinkBorrowScope.cpp b/lib/SILOptimizer/Utils/ShrinkBorrowScope.cpp
index 064eb410dab55..da994b085e4c0 100644
--- a/lib/SILOptimizer/Utils/ShrinkBorrowScope.cpp
+++ b/lib/SILOptimizer/Utils/ShrinkBorrowScope.cpp
@@ -79,7 +79,7 @@ struct Usage final {
   SmallPtrSet<SILInstruction *, 16> users;
   // The instructions from which the shrinking starts, the scope ending
   // instructions.
-  llvm::SmallVector<SILInstruction *, 4> ends;
+  llvm::SmallSetVector<SILInstruction *, 4> ends;
 
   Usage(){};
   Usage(Usage const &) = delete;
@@ -99,7 +99,7 @@ bool findUsage(Context const &context, Usage &usage) {
     // If a scope ending instruction is not an end_borrow, bail out.
     if (!isa<EndBorrowInst>(instruction))
       return false;
-    usage.ends.push_back(instruction);
+    usage.ends.insert(instruction);
   }
 
   SmallVector<Operand *, 16> uses;
@@ -181,7 +181,7 @@ class Dataflow final {
   /// IterativeBackwardReachability::Effects
   /// VisitBarrierAccessScopes::Effects
 
-  ArrayRef<SILInstruction *> gens() { return uses.ends; }
+  auto gens() { return uses.ends; }
 
   Effect effectForInstruction(SILInstruction *);
 
@@ -262,7 +262,7 @@ bool Dataflow::classificationIsBarrier(Classification classification) {
 }
 
 Dataflow::Effect Dataflow::effectForInstruction(SILInstruction *instruction) {
-  if (llvm::find(uses.ends, instruction) != uses.ends.end())
+  if (uses.ends.contains(instruction))
     return Effect::Gen();
   auto classification = classifyInstruction(instruction);
   if (recordCopies && classification == Classification::Copy)