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

Fixes PR16139.

llvm-svn: 182656

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -2428,7 +2428,10 @@ bool LoopVectorizationLegality::canVectorizeWithIfConvert() {
 }
 
 bool LoopVectorizationLegality::canVectorize() {
-  assert(TheLoop->getLoopPreheader() && "No preheader!!");
+  // We must have a loop in canonical form. Loops with indirectbr in them cannot
+  // be canonicalized.
+  if (!TheLoop->getLoopPreheader())
+    return false;
 
   // We can only vectorize innermost loops.
   if (TheLoop->getSubLoopsVector().size())

llvm/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
+}