diff --git a/llvm/lib/IR/LLVMContextImpl.cpp b/llvm/lib/IR/LLVMContextImpl.cpp
--- a/llvm/lib/IR/LLVMContextImpl.cpp
+++ b/llvm/lib/IR/LLVMContextImpl.cpp
@@ -129,18 +129,24 @@
 }
 
 void LLVMContextImpl::dropTriviallyDeadConstantArrays() {
-  SmallSetVector<ConstantArray *, 4> WorkList(ArrayConstants.begin(),
-                                              ArrayConstants.end());
+  SmallSetVector<ConstantArray *, 4> WorkList;
+
+  // When ArrayConstants are of substantial size and only a few in them are
+  // dead, starting WorkList with all elements of ArrayConstants can be
+  // wasteful. Instead, starting WorkList with only elements that have empty
+  // uses.
+  for (ConstantArray *C : ArrayConstants)
+    if (C->use_empty())
+      WorkList.insert(C);
 
   while (!WorkList.empty()) {
     ConstantArray *C = WorkList.pop_back_val();
-    if (C->use_empty()) {
-      for (const Use &Op : C->operands()) {
-        if (auto *COp = dyn_cast<ConstantArray>(Op))
-          WorkList.insert(COp);
-      }
-      C->destroyConstant();
-    }
+    if (!C->use_empty())
+      continue;
+    for (const Use &Op : C->operands())
+      if (auto *COp = dyn_cast<ConstantArray>(Op))
+        WorkList.insert(COp);
+    C->destroyConstant();
   }
 }