[LoopVectorize] Don't crash on zero-sized types in isInductionPHI

isInductionPHI wants to calculate the stride based on the pointee size.
However, this is not possible when the pointee is zero sized.

This fixes PR23763.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@239143 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Utils/LoopUtils.cpp

@@ -491,6 +491,9 @@ bool llvm::isInductionPHI(PHINode *Phi, ScalarEvolution *SE,
 
   const DataLayout &DL = Phi->getModule()->getDataLayout();
   int64_t Size = static_cast<int64_t>(DL.getTypeAllocSize(PointerElementType));
+  if (!Size)
+    return false;
+
   int64_t CVSize = CV->getSExtValue();
   if (CVSize % Size)
     return false;