[MLIR] Guard DMA-specific logic with DMA option

[bondhugula]

Thanks for fixing this. If you prefer, you could even prefix stride with DMA.

stride -> dmaStride
strideInfos -> dmaStrideInfos
numEltPerStride -> numEltPerDmaStride

mlir/lib/Transforms/Utils/LoopUtils.cpp

if (!existingBuf) {
     // Reuse the one already created.
     fastMemRef = fastBufferMap[memref];
     *sizeInBytes = 0;
   }
 
   auto numElementsSSA =
       top.create<ConstantIndexOp>(loc, numElements.getValue());
 
+  Value stride = nullptr;
+  Value numEltPerStride = nullptr;
+  if (copyOptions.generateDma) {
     SmallVector<StrideInfo, 4> strideInfos;
     getMultiLevelStrides(region, fastBufferShape, &strideInfos);
 
     // TODO(bondhugula): use all stride levels once DmaStartOp is extended for
     // multi-level strides.
     if (strideInfos.size() > 1) {
       LLVM_DEBUG(llvm::dbgs() << "Only up to one level of stride supported\n");
       return failure();
     }
 
-  Value stride = nullptr;
-  Value numEltPerStride = nullptr;
     if (!strideInfos.empty()) {
       stride = top.create<ConstantIndexOp>(loc, strideInfos[0].stride);
       numEltPerStride =
           top.create<ConstantIndexOp>(loc, strideInfos[0].numEltPerStride);
     }
+  }
 
   // Record the last operation where we want the memref replacement to end. We
   // later do the memref replacement only in [begin, postDomFilter] so
   // that the original memref's used in the data movement code themselves don't
   // get replaced.
   auto postDomFilter = std::prev(end);
 
   // Create fully composed affine maps for each memref.