/*      $NetBSD: byte_swap_8.S,v 1.2 2009/12/14 00:39:00 matt Exp $     */

/*-
 * Copyright (c) 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Ralph Campbell.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <mips/asm.h>

#if defined(LIBC_SCCS) && !defined(lint)
        RCSID("$NetBSD: byte_swap_8.S,v 1.2 2009/12/14 00:39:00 matt Exp $")
#endif /* LIBC_SCCS and not lint */

#undef _LOCORE
#define _LOCORE         /* XXX not really, just assembly-code source */
#include <machine/endian.h>

NLEAF(bswap64)  # a0 = 0xffeeddccbbaa9988 return 0x8899aabbccddeeff
#if (__mips == 32 || __mips == 64) && __mips_isa_rev == 2
#if !defined(__mips_o32)
        /*
         * If we are on MIPS32r2 or MIPS64r2 use the new instructions.
         */
        dsbh    v0, a0                  # dwords swap bytes within halfwords
        dshd    v0, v0                  # dwords swap halwords within dwords
        j       ra
#else /* defined(__mips_o32) */
        /*
         * If we are on MIPS32r2 or MIPS64r2 use the new instructions.
         * (except we must use the 32bit versions) 
         */
        wsbh    v1, a0                  # word swap bytes within halfwords
        wsbh    v0, a1                  # word swap bytes within halfwords
        rotr    v1, v1, 16              # rotate word 16bits and swap word
        rotr    v0, v0, 16              # rotate word 16bits and swap word
        j       ra
#endif /* defined(__mips_o32) */
#elif !defined(__mips_o32)
                                        # a0  = 0xffeeddccbbaa9988
        li      t0, 0xffff              # t0  = 0x000000000000ffff
        dsll    t1, t0, 32              # t1  = 0x0000ffff00000000
        or      t0, t1                  # t0  = 0x0000ffff0000ffff
        dsll    t2, t0, 8               # t2  = 0x00ffff0000ffff00
        xor     t2, t0                  # t2  = 0x00ff00ff00ff00ff
        /*
         * We could swap by halfword, but that would be one instruction longer.
         */
        dsrl    ta0, a0, 32             # ta0 = 0x00000000ffeeddcc
        dsll    ta1, a0, 32             # ta1 = 0xbbaa998800000000
        or      a1, ta0, ta1            # a1  = 0xbbaa9988ffeeddcc
                                        # words swapped
        and     ta0, a1, t0             # ta0 = 0x000099880000ddcc
        dsrl    ta1, a1, 16             # ta1 = 0x0000bbaa9988ffee
        and     ta1, t0                 # ta1 = 0x0000bbaa0000ffee
        dsll    a2, ta0, 16             # a2  = 0x99880000ddcc0000
        or      a2, ta1                 # a2  = 0x9988bbaaddccffee
                                        # halfwords swapped
        and     ta0, a2, t2             # ta0 = 0x008800aa00cc00ee
        dsrl    ta1, a2, 8              # ta1 = 0x009988bbaaddccff
        and     ta1, t2                 # ta1 = 0x009900bb00dd00ff
        dsll    v0, ta0, 8              # v0  = 0x8800aa00cc00ee00
        or      v0, ta1                 # v0  = 0x8899aabbccddeeff
                                        # bytes swapped
        j       ra
#else /* defined(__mips_o32) */
        /*
         * 32bit ABI.
         */
                                        # a0  = 0xccddeeff
                                        # a1  = 0x8899aabb
        srl     t0, a0, 24              # t0  = 0x000000cc
        srl     t1, a1, 24              # t1  = 0x00000088
        sll     ta0, a0, 24             # ta0 = 0xff000000
        sll     ta1, a1, 24             # ta1 = 0xbb000000
        or      ta0, ta0, t0            # ta0 = 0xff0000cc
        or      ta1, ta1, t1            # ta1 = 0xbb000088
        and     t0, a0, 0xff00          # t0  = 0x0000ee00
        and     t1, a1, 0xff00          # t1  = 0x0000aa00
        sll     t0, t0, 8               # t0  = 0x00ee0000
        sll     t1, t1, 8               # t1  = 0x00aa0000
        or      ta0, ta0, t0            # ta0 = 0xffee00cc
        or      ta1, ta1, t1            # ta1 = 0xbbaa0088
        srl     t0, a0, 8               # t0  = 0x00ccddee
        srl     t1, a1, 8               # t1  = 0x008899aa
        and     t0, t0, 0xff00          # t0  = 0x0000dd00
        and     t1, t1, 0xff00          # t1  = 0x00009900
        or      v1, ta0, t0             # v1  = 0xffeeddcc
        or      v0, ta1, t1             # v0  = 0xbbaa9988
        j       ra
#endif /* defined(__mips_o32) */
END(bswap64)