| /* |
| * Copyright (C) 2024 Michael Brown <mbrown@fensystems.co.uk>. |
| * |
| * This program is free software; you can redistribute it and/or |
| * modify it under the terms of the GNU General Public License as |
| * published by the Free Software Foundation; either version 2 of the |
| * License, or any later version. |
| * |
| * This program is distributed in the hope that it will be useful, but |
| * WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| * General Public License for more details. |
| * |
| * You should have received a copy of the GNU General Public License |
| * along with this program; if not, write to the Free Software |
| * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
| * 02110-1301, USA. |
| * |
| * You can also choose to distribute this program under the terms of |
| * the Unmodified Binary Distribution Licence (as given in the file |
| * COPYING.UBDL), provided that you have satisfied its requirements. |
| */ |
| |
| FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL ) |
| |
| /** @file |
| * |
| * Byte swapping |
| * |
| */ |
| |
| .section ".note.GNU-stack", "", @progbits |
| .text |
| |
| .section ".text.riscv_swap", "ax", @progbits |
| riscv_swap: |
| .globl riscv_swap_word |
| .globl riscv_swap_half |
| .globl riscv_swap_byte |
| riscv_swap_word: |
| /* Swap all bytes in a0 */ |
| mv t0, ra |
| jal riscv_swap_half |
| mv ra, t0 |
| /* Swap words a0 and a1 */ |
| mv t1, a0 |
| mv a0, a1 |
| mv a1, t1 |
| riscv_swap_half: |
| /* Swap half-words within a0 */ |
| slli t2, a0, 16 |
| srli a0, a0, 16 |
| or a0, a0, t2 |
| riscv_swap_byte: |
| /* Swap bytes within each half-word of a0 */ |
| li t3, 0xff00ff00 |
| slli t4, a0, 8 |
| and a0, a0, t3 |
| and t4, t4, t3 |
| srli a0, a0, 8 |
| or a0, a0, t4 |
| ret |
| .size riscv_swap, . - riscv_swap |
