[mlir][sparse] Use vector.step for index vector generation (#97692)

Author: c-rhodes

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

@@ -381,18 +381,7 @@ static bool vectorizeExpr(PatternRewriter &rewriter, scf::ForOp forOp, VL vl,
       if (codegen) {
         VectorType vtp = vectorType(vl, arg.getType());
         Value veci = rewriter.create<vector::BroadcastOp>(loc, vtp, arg);
-        Value incr;
-        if (vl.enableVLAVectorization) {
-          Type stepvty = vectorType(vl, rewriter.getI64Type());
-          Value stepv = rewriter.create<LLVM::StepVectorOp>(loc, stepvty);
-          incr = rewriter.create<arith::IndexCastOp>(loc, vtp, stepv);
-        } else {
-          SmallVector<APInt> integers;
-          for (unsigned i = 0, l = vl.vectorLength; i < l; i++)
-            integers.push_back(APInt(/*width=*/64, i));
-          auto values = DenseElementsAttr::get(vtp, integers);
-          incr = rewriter.create<arith::ConstantOp>(loc, vtp, values);
-        }
+        Value incr = rewriter.create<vector::StepOp>(loc, vtp);
         vexp = rewriter.create<arith::AddIOp>(loc, veci, incr);
       }
       return true;