Index: lib/Transforms/Utils/CloneFunction.cpp
===================================================================
--- lib/Transforms/Utils/CloneFunction.cpp
+++ lib/Transforms/Utils/CloneFunction.cpp
@@ -636,6 +636,22 @@
   Function::iterator Begin = cast<BasicBlock>(VMap[StartingBB])->getIterator();
   Function::iterator I = Begin;
   while (I != NewFunc->end()) {
+    // We need to simplify conditional branches and switches with a constant
+    // operand. We try to prune these out when cloning, but if the
+    // simplification required looking through PHI nodes, those are only
+    // available after forming the full basic block. That may leave some here,
+    // and we still want to prune the dead code as early as possible.
+    //
+    // Do the folding before we check if the block is dead since we want code
+    // like
+    //  bb:
+    //    br i1 undef, label %bb, label %bb
+    // to be simplified to
+    //  bb:
+    //    br label %bb
+    // before we call I->getSinglePredecessor().
+    ConstantFoldTerminator(&*I);
+
     // Check if this block has become dead during inlining or other
     // simplifications. Note that the first block will appear dead, as it has
     // not yet been wired up properly.
@@ -646,13 +662,6 @@
       continue;
     }
 
-    // We need to simplify conditional branches and switches with a constant
-    // operand. We try to prune these out when cloning, but if the
-    // simplification required looking through PHI nodes, those are only
-    // available after forming the full basic block. That may leave some here,
-    // and we still want to prune the dead code as early as possible.
-    ConstantFoldTerminator(&*I);
-
     BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
     if (!BI || BI->isConditional()) { ++I; continue; }
 
Index: test/Transforms/Inline/infinite-loop-two-predecessors.ll
===================================================================
--- /dev/null
+++ test/Transforms/Inline/infinite-loop-two-predecessors.ll
@@ -0,0 +1,39 @@
+; RUN: opt -S -o - %s -inline | FileCheck %s
+
+define void @f1() {
+bb.0:
+  br i1 false, label %bb.2, label %bb.1
+
+bb.1:                                             ; preds = %bb.0
+  br label %bb.2
+
+bb.2:                                             ; preds = %bb.0, %bb.1
+  %tmp0 = phi i16 [ 1, %bb.1 ], [ 0, %bb.0 ]
+  %tmp1 = icmp eq i16 %tmp0, 0
+  br i1 %tmp1, label %bb.3, label %bb.6
+
+bb.3:                                             ; preds = %bb.2
+  br label %bb.5
+
+bb.4:                                             ; preds = %bb.5, %bb.5
+  br label %bb.5
+
+bb.5:                                             ; preds = %bb.4, %bb.3
+  br i1 undef, label %bb.4, label %bb.4
+
+bb.6:                                             ; preds = %bb.2
+  ret void
+}
+
+define void @f2() {
+bb.0:
+  call void @f1()
+  ret void
+}
+
+; f1 should be inlined into f2 and simplified/collapsed to nothing.
+
+; CHECK:      define void @f2() {
+; CHECK-NEXT: bb.0:
+; CHECK-NEXT:   ret void
+; CHECK-NEXT: }