[Vectorization] Actually return from error case in isStridedPtr

The early return seems to be missed. This causes a radical and wrong loop
optimization on powerpc. It isn't reproducible on x86_64, because
"UseInterleaved" is false.

Patch by Tim Shen.

llvm-svn: 257134
diff --git a/llvm/lib/Analysis/LoopAccessAnalysis.cpp b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
index d7896ad..8bcdcb8 100644
--- a/llvm/lib/Analysis/LoopAccessAnalysis.cpp
+++ b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
@@ -845,6 +845,7 @@
   if (Lp != AR->getLoop()) {
     DEBUG(dbgs() << "LAA: Bad stride - Not striding over innermost loop " <<
           *Ptr << " SCEV: " << *PtrScev << "\n");
+    return 0;
   }
 
   // The address calculation must not wrap. Otherwise, a dependence could be