diff --git a/llvm/lib/Passes/StandardInstrumentations.cpp b/llvm/lib/Passes/StandardInstrumentations.cpp
--- a/llvm/lib/Passes/StandardInstrumentations.cpp
+++ b/llvm/lib/Passes/StandardInstrumentations.cpp
@@ -540,7 +540,10 @@
     }
     // This section is in both; advance and print out any before-only
     // until we get to it.
-    while (*BI != *AI) {
+    // It's possible that this section has moved to be later than before. This
+    // will mess up printing most blocks side by side, but it's a rare case and
+    // it's better than crashing.
+    while (BI != BE && *BI != *AI) {
       HandlePotentiallyRemovedData(*BI);
       ++BI;
     }
@@ -550,7 +553,8 @@
     const T &AData = AFD.find(*AI)->getValue();
     const T &BData = BFD.find(*AI)->getValue();
     HandlePair(&BData, &AData);
-    ++BI;
+    if (BI != BE)
+      ++BI;
     ++AI;
   }
 
diff --git a/llvm/test/Other/ChangePrinters/print-changed-diff-block-ordering-changed.ll b/llvm/test/Other/ChangePrinters/print-changed-diff-block-ordering-changed.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Other/ChangePrinters/print-changed-diff-block-ordering-changed.ll
@@ -0,0 +1,20 @@
+; RUN: opt -passes=jump-threading %s -disable-output --print-changed=diff 2>&1 | FileCheck %s
+
+; CHECK: IR Dump After JumpThreadingPass
+
+define void @f(i1 %0) {
+  br i1 %0, label %5, label %2
+
+2:                                                ; preds = %1
+  br i1 false, label %b, label %3
+
+3:                                                ; preds = %2
+  %4 = call i64 null()
+  br label %b
+
+b:                                                ; preds = %3, %2
+  br label %5
+
+5:                                                ; preds = %b, %1
+  ret void
+}