Index: llvm/lib/Transforms/Utils/Local.cpp
===================================================================
--- llvm/lib/Transforms/Utils/Local.cpp
+++ llvm/lib/Transforms/Utils/Local.cpp
@@ -182,6 +182,8 @@
       TheOnlyDest = SI->case_begin()->getCaseSuccessor();
     }
 
+    bool Changed = false;
+
     // Figure out which case it goes to.
     for (auto i = SI->case_begin(), e = SI->case_end(); i != e;) {
       // Found case matching a constant operand?
@@ -220,6 +222,7 @@
         DefaultDest->removePredecessor(ParentBB);
         i = SI->removeCase(i);
         e = SI->case_end();
+        Changed = true;
         if (DTU)
           DTU->applyUpdatesPermissive(
               {{DominatorTree::Delete, ParentBB, DefaultDest}});
@@ -308,7 +311,7 @@
       SI->eraseFromParent();
       return true;
     }
-    return false;
+    return Changed;
   }
 
   if (auto *IBI = dyn_cast<IndirectBrInst>(T)) {
Index: llvm/test/Transforms/SimplifyCFG/merge-default.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/SimplifyCFG/merge-default.ll
@@ -0,0 +1,45 @@
+; RUN: opt -simplifycfg -S < %s | FileCheck %s
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+declare void @g()
+declare void @f()
+
+define void @foo(i32 %Kind) {
+; CHECK-LABEL: @foo(
+; CHECK-NEXT:entry:
+; CHECK-NEXT:  switch i32 %Kind, label %sw.epilog [
+; CHECK-NEXT:    i32 15, label %sw.bb2
+; CHECK-NEXT:    i32 2, label %sw.bb
+; CHECK-NEXT:  ]
+; CHECK:     sw.bb:
+; CHECK-NEXT:  call void @g()
+; CHECK-NEXT:  call void @g()
+; CHECK-NEXT:  br label %sw.epilog
+; CHECK:     sw.bb2:
+; CHECK-NEXT:  call void @f()
+; CHECK-NEXT:  br label %sw.epilog
+; CHECK:     sw.epilog:
+; CHECK-NEXT:  ret void
+; CHECK-NEXT:}
+
+entry:
+  switch i32 %Kind, label %sw.epilog [
+    i32 1, label %sw.epilog
+    i32 2, label %sw.bb
+    i32 15, label %sw.bb2
+  ]
+
+sw.bb:
+  call void @g()
+  call void @g()
+  br label %sw.epilog
+
+sw.bb2:
+  call void @f()
+  br label %sw.epilog
+
+sw.epilog:
+  ret void
+}