Function lower_elementwise_to_cuda 

pub fn lower_elementwise_to_cuda(spec: &ElementwiseSpec) -> String

Lower a recognized elementwise op (C[p] = A[p] ⊕ B[p], from crate::tensor_recognize::recognize_elementwise) to a self-contained CUDA program — the elementwise analog of lower_matmul_to_cuda. One thread per element; the deterministic int8-range fill and the Σ C checksum match the matmul emitter’s convention, so it runs and prints on the GPU. A B of one row holds that row’s elements and is read at each element’s column.