Index: lib/CodeGen/MachineBlockPlacement.cpp
===================================================================
--- lib/CodeGen/MachineBlockPlacement.cpp
+++ lib/CodeGen/MachineBlockPlacement.cpp
@@ -453,8 +453,11 @@
     // If we outline optional branches, look whether Succ is unavoidable, i.e.
     // dominates all terminators of the MachineFunction. If it does, other
     // successors must be optional. Don't do this for cold branches.
+    // Also, return branches seem to behave perversely as well. Don't outline in
+    // favor of them either, unless the exit branch is hot.
     if (OutlineOptionalBranches && SuccProb > HotProb.getCompl() &&
-        UnavoidableBlocks.count(Succ) > 0) {
+        UnavoidableBlocks.count(Succ) > 0 &&
+        (!Succ->isReturnBlock() || SuccProb > HotProb)) {
       auto HasShortOptionalBranch = [&]() {
         for (MachineBasicBlock *Pred : Succ->predecessors()) {
           // Check whether there is an unplaced optional branch.
@@ -672,7 +675,7 @@
     // after this block.
     MachineBasicBlock *BestSucc = selectBestSuccessor(BB, Chain, BlockFilter);
 
-    // If an immediate successor isn't available, look for the best viable
+   // If an immediate successor isn't available, look for the best viable
     // block among those we've identified as not violating the loop's CFG at
     // this point. This won't be a fallthrough, but it will increase locality.
     if (!BestSucc)