slahqr(3) on Linux
The text e361226d0851, as Debian 4.0 (Etch), Debian 3.1 (Sarge) shipped it.
i an auxiliary routine called by SHSEQR to update the eigenvalues and Schur decomposition already computed by SHSEQR, by dealing with the Hessenberg submatrix in rows and columns ILO to IHI