/*-
 * Copyright (c) 2018 The FreeBSD Foundation
 *
 * This software was developed by Mateusz Guzik <mjg@FreeBSD.org>
 * under sponsorship from the FreeBSD Foundation.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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 <machine/asm.h>
/*
 * Note: this routine was written with kernel use in mind (read: no simd),
 * it is only present in userspace as a temporary measure until something
 * better gets imported.
 */

#define ALIGN_TEXT      .p2align 4,0x90 /* 16-byte alignment, nop filled */

/*
 * memmove(dst, src, cnt)
 *         rdi, rsi, rdx
 */

/*
 * Register state at entry is supposed to be as follows:
 * rdi - destination
 * rsi - source
 * rdx - count
 *
 * The macro possibly clobbers the above and: rcx, r8, r9, 10
 * It does not clobber rax nor r11.
 */
.macro MEMMOVE erms overlap begin end
        \begin

        /*
         * For sizes 0..32 all data is read before it is written, so there
         * is no correctness issue with direction of copying.
         */
        cmpq    $32,%rcx
        jbe     101632f

.if \overlap == 1
        movq    %rdi,%r8
        subq    %rsi,%r8
        cmpq    %rcx,%r8        /* overlapping && src < dst? */
        jb      2f
.endif

        cmpq    $256,%rcx
        ja      1256f

        ALIGN_TEXT
103200:
        movq    (%rsi),%rdx
        movq    %rdx,(%rdi)
        movq    8(%rsi),%rdx
        movq    %rdx,8(%rdi)
        movq    16(%rsi),%rdx
        movq    %rdx,16(%rdi)
        movq    24(%rsi),%rdx
        movq    %rdx,24(%rdi)
        leaq    32(%rsi),%rsi
        leaq    32(%rdi),%rdi
        subq    $32,%rcx
        cmpq    $32,%rcx
        jae     103200b
        cmpb    $0,%cl
        jne     101632f
        \end
        ret
        ALIGN_TEXT
101632:
        cmpb    $16,%cl
        jl      100816f
        movq    (%rsi),%rdx
        movq    8(%rsi),%r8
        movq    -16(%rsi,%rcx),%r9
        movq    -8(%rsi,%rcx),%r10
        movq    %rdx,(%rdi)
        movq    %r8,8(%rdi)
        movq    %r9,-16(%rdi,%rcx)
        movq    %r10,-8(%rdi,%rcx)
        \end
        ret
        ALIGN_TEXT
100816:
        cmpb    $8,%cl
        jl      100408f
        movq    (%rsi),%rdx
        movq    -8(%rsi,%rcx),%r8
        movq    %rdx,(%rdi)
        movq    %r8,-8(%rdi,%rcx,)
        \end
        ret
        ALIGN_TEXT
100408:
        cmpb    $4,%cl
        jl      100204f
        movl    (%rsi),%edx
        movl    -4(%rsi,%rcx),%r8d
        movl    %edx,(%rdi)
        movl    %r8d,-4(%rdi,%rcx)
        \end
        ret
        ALIGN_TEXT
100204:
        cmpb    $2,%cl
        jl      100001f
        movzwl  (%rsi),%edx
        movzwl  -2(%rsi,%rcx),%r8d
        movw    %dx,(%rdi)
        movw    %r8w,-2(%rdi,%rcx)
        \end
        ret
        ALIGN_TEXT
100001:
        cmpb    $1,%cl
        jl      100000f
        movb    (%rsi),%dl
        movb    %dl,(%rdi)
100000:
        \end
        ret

        ALIGN_TEXT
1256:
        testb   $15,%dil
        jnz     100f
.if \erms == 1
        rep
        movsb
.else
        shrq    $3,%rcx                         /* copy by 64-bit words */
        rep
        movsq
        movq    %rdx,%rcx
        andl    $7,%ecx                         /* any bytes left? */
        jne     100408b
.endif
        \end
        ret
100:
        movq    (%rsi),%r8
        movq    8(%rsi),%r9
        movq    %rdi,%r10
        movq    %rdi,%rcx
        andq    $15,%rcx
        leaq    -16(%rdx,%rcx),%rdx
        neg     %rcx
        leaq    16(%rdi,%rcx),%rdi
        leaq    16(%rsi,%rcx),%rsi
        movq    %rdx,%rcx
.if \erms == 1
        rep
        movsb
        movq    %r8,(%r10)
        movq    %r9,8(%r10)
.else
        shrq    $3,%rcx                         /* copy by 64-bit words */
        rep
        movsq
        movq    %r8,(%r10)
        movq    %r9,8(%r10)
        movq    %rdx,%rcx
        andl    $7,%ecx                         /* any bytes left? */
        jne     100408b
.endif
        \end
        ret

.if \overlap == 1
        /*
         * Copy backwards.
         */
        ALIGN_TEXT
2:
        cmpq    $256,%rcx
        ja      2256f

        leaq    -8(%rdi,%rcx),%rdi
        leaq    -8(%rsi,%rcx),%rsi

        cmpq    $32,%rcx
        jb      2016f

        ALIGN_TEXT
2032:
        movq    (%rsi),%rdx
        movq    %rdx,(%rdi)
        movq    -8(%rsi),%rdx
        movq    %rdx,-8(%rdi)
        movq    -16(%rsi),%rdx
        movq    %rdx,-16(%rdi)
        movq    -24(%rsi),%rdx
        movq    %rdx,-24(%rdi)
        leaq    -32(%rsi),%rsi
        leaq    -32(%rdi),%rdi
        subq    $32,%rcx
        cmpq    $32,%rcx
        jae     2032b
        cmpb    $0,%cl
        jne     2016f
        \end
        ret
        ALIGN_TEXT
2016:
        cmpb    $16,%cl
        jl      2008f
        movq    (%rsi),%rdx
        movq    %rdx,(%rdi)
        movq    -8(%rsi),%rdx
        movq    %rdx,-8(%rdi)
        subb    $16,%cl
        jz      2000f
        leaq    -16(%rsi),%rsi
        leaq    -16(%rdi),%rdi
2008:
        cmpb    $8,%cl
        jl      2004f
        movq    (%rsi),%rdx
        movq    %rdx,(%rdi)
        subb    $8,%cl
        jz      2000f
        leaq    -8(%rsi),%rsi
        leaq    -8(%rdi),%rdi
2004:
        cmpb    $4,%cl
        jl      2002f
        movl    4(%rsi),%edx
        movl    %edx,4(%rdi)
        subb    $4,%cl
        jz      2000f
        leaq    -4(%rsi),%rsi
        leaq    -4(%rdi),%rdi
2002:
        cmpb    $2,%cl
        jl      2001f
        movw    6(%rsi),%dx
        movw    %dx,6(%rdi)
        subb    $2,%cl
        jz      2000f
        leaq    -2(%rsi),%rsi
        leaq    -2(%rdi),%rdi
2001:
        cmpb    $1,%cl
        jl      2000f
        movb    7(%rsi),%dl
        movb    %dl,7(%rdi)
2000:
        \end
        ret
        ALIGN_TEXT
2256:
        std
        leaq    -8(%rdi,%rcx),%rdi
        leaq    -8(%rsi,%rcx),%rsi
        shrq    $3,%rcx
        rep
        movsq
        cld
        movq    %rdx,%rcx
        andb    $7,%cl
        jne     2004b
        \end
        ret
.endif
.endm


.macro MEMMOVE_BEGIN
        movq    %rdi,%rax
        movq    %rdx,%rcx
.endm

.macro MEMMOVE_END
.endm

#ifndef MEMCPY
ENTRY(memmove)
        MEMMOVE erms=0 overlap=1 begin=MEMMOVE_BEGIN end=MEMMOVE_END
END(memmove)
#else
ENTRY(memcpy)
        MEMMOVE erms=0 overlap=1 begin=MEMMOVE_BEGIN end=MEMMOVE_END
END(memcpy)
#endif

        .section .note.GNU-stack,"",%progbits