[mlir][sparse] support sparse bufferization.alloc_tensor with copy argument.

Reviewed By: aartbik

Differential Revision: https://reviews.llvm.org/D147358

mlir/lib/Dialect/SparseTensor/Transforms/SparseTensorCodegen.cpp

@@ -749,11 +749,29 @@ public:
     const auto resType = getSparseTensorType(op);
     if (!resType.hasEncoding())
       return failure();
-    if (op.getCopy())
-      return rewriter.notifyMatchFailure(op, "tensor copy not implemented");
 
     // Construct allocation for each field.
     const Location loc = op.getLoc();
+    if (op.getCopy()) {
+      auto desc = getDescriptorFromTensorTuple(adaptor.getCopy());
+      SmallVector<Value> fields;
+      fields.reserve(desc.getNumFields());
+      // Memcpy on memref fields.
+      for (auto field : desc.getMemRefFields()) {
+        auto memrefTp = field.getType().cast<MemRefType>();
+        auto size = rewriter.create<memref::DimOp>(loc, field, 0);
+        auto copied =
+            rewriter.create<memref::AllocOp>(loc, memrefTp, ValueRange{size});
+        rewriter.create<memref::CopyOp>(loc, field, copied);
+        fields.push_back(copied);
+      }
+      // Reuses specifier.
+      fields.push_back(desc.getSpecifier());
+      assert(fields.size() == desc.getNumFields());
+      rewriter.replaceOp(op, genTuple(rewriter, loc, resType, fields));
+      return success();
+    }
+
     const Value sizeHint = op.getSizeHint();
     const ValueRange dynSizes = adaptor.getDynamicSizes();
     const size_t found = dynSizes.size();