LoopVectorize: LoopSimplify can't canonicalize loops with an indirectbr in it, don't assert on those cases.

Fixes PR16139.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182656 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/LoopVectorize/lcssa-crash.ll

@@ -27,3 +27,14 @@ for.end.i.i.i:
   unreachable
 }
 
+; PR16139
+define void @test2(i8* %x) {
+entry:
+  indirectbr i8* %x, [ label %L0, label %L1 ]
+
+L0:
+  br label %L0
+
+L1:
+  ret void
+}