Fix how we get alignment for memrefs

Author: Lily Orth-Smith

mlir/lib/Conversion/VectorToLLVM/ConvertVectorToLLVM.cpp

@@ -70,15 +70,19 @@ static Value extractOne(ConversionPatternRewriter &rewriter,
 // Helper that returns data layout alignment of a memref.
 LogicalResult getMemRefAlignment(const LLVMTypeConverter &typeConverter,
                                  MemRefType memrefType, unsigned &align) {
-  Type elementTy = typeConverter.convertType(memrefType.getElementType());
-  if (!elementTy)
+  // Align MemRefTypes to the alignment of a VectorType with the same
+  // size and dtype.
+  Type convertedVecType = typeConverter.convertType(
+      VectorType::get(memrefType.getNumElements(), memrefType.getElementType()));
+  if (!convertedVecType)
     return failure();
 
   // TODO: this should use the MLIR data layout when it becomes available and
   // stop depending on translation.
   llvm::LLVMContext llvmContext;
   align = LLVM::TypeToLLVMIRTranslator(llvmContext)
-              .getPreferredAlignment(elementTy, typeConverter.getDataLayout());
+              .getPreferredAlignment(convertedVecType,
+                                     typeConverter.getDataLayout());
   return success();
 }