Index: llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
+++ llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
@@ -418,7 +418,7 @@
       LI.removeBlock(BB);
     }
 
-    DetatchDeadBlocks(DeadLoopBlocks, &DTUpdates);
+    DetatchDeadBlocks(DeadLoopBlocks, &DTUpdates, /*KeepOneInputPHIs*/true);
     DTU.applyUpdates(DTUpdates);
     DTUpdates.clear();
     for (auto *BB : DeadLoopBlocks)
Index: llvm/trunk/test/Transforms/LoopSimplifyCFG/lcssa.ll
===================================================================
--- llvm/trunk/test/Transforms/LoopSimplifyCFG/lcssa.ll
+++ llvm/trunk/test/Transforms/LoopSimplifyCFG/lcssa.ll
@@ -1,6 +1,4 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; XFAIL: *
-; REQUIRES: asserts
 ; RUN: opt -S -enable-loop-simplifycfg-term-folding=true -loop-simplifycfg -verify-loop-info -verify-dom-info -verify-loop-lcssa < %s | FileCheck %s
 ; RUN: opt -S -enable-loop-simplifycfg-term-folding=true -passes='require<domtree>,loop(simplify-cfg)' -verify-loop-info -verify-dom-info -verify-loop-lcssa < %s | FileCheck %s
 ; RUN: opt -S -enable-loop-simplifycfg-term-folding=true -loop-simplifycfg -enable-mssa-loop-dependency=true -verify-memoryssa -verify-loop-info -verify-dom-info -verify-loop-lcssa < %s | FileCheck %s
@@ -93,8 +91,31 @@
 }
 
 define void @bar() {
-
-; CHECK-LABEL: @bar
+; CHECK-LABEL: @bar(
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    switch i32 0, label [[BB_SPLIT:%.*]] [
+; CHECK-NEXT:    i32 1, label [[BB10:%.*]]
+; CHECK-NEXT:    ]
+; CHECK:       bb-split:
+; CHECK-NEXT:    br label [[BB1:%.*]]
+; CHECK:       bb1:
+; CHECK-NEXT:    [[TMP:%.*]] = phi i32 [ [[TMP7:%.*]], [[BB6:%.*]] ], [ undef, [[BB_SPLIT]] ]
+; CHECK-NEXT:    switch i32 undef, label [[BB5:%.*]] [
+; CHECK-NEXT:    i32 0, label [[BB6]]
+; CHECK-NEXT:    i32 1, label [[BB8:%.*]]
+; CHECK-NEXT:    ]
+; CHECK:       bb5:
+; CHECK-NEXT:    ret void
+; CHECK:       bb6:
+; CHECK-NEXT:    [[TMP7]] = add i32 undef, 123
+; CHECK-NEXT:    br label [[BB1]]
+; CHECK:       bb8:
+; CHECK-NEXT:    [[TMP9:%.*]] = phi i32 [ [[TMP]], [[BB1]] ]
+; CHECK-NEXT:    [[USE:%.*]] = add i32 [[TMP9]], 1
+; CHECK-NEXT:    ret void
+; CHECK:       bb10:
+; CHECK-NEXT:    ret void
+;
 
 bb:
   br label %bb1
@@ -105,8 +126,8 @@
 
 bb2:                                              ; preds = %bb1
   switch i32 undef, label %bb10 [
-    i32 0, label %bb3
-    i32 1, label %bb8
+  i32 0, label %bb3
+  i32 1, label %bb8
   ]
 
 bb3:                                              ; preds = %bb2
@@ -114,8 +135,8 @@
 
 bb4:                                              ; preds = %bb1
   switch i32 undef, label %bb5 [
-    i32 0, label %bb6
-    i32 1, label %bb8
+  i32 0, label %bb6
+  i32 1, label %bb8
   ]
 
 bb5:                                              ; preds = %bb4