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/*
 *  linux/arch/arm/lib/csumpartialcopygeneric.S
 *
 *  Copyright (C) 1995-2001 Russell King
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

/*
 * unsigned int
 * csum_partial_copy_xxx(const char *src, char *dst, int len, int sum, )
 *  r0 = src, r1 = dst, r2 = len, r3 = sum
 *  Returns : r0 = checksum
 *
 * Note that 'tst' and 'teq' preserve the carry flag.
 */

src     .req    r0
dst     .req    r1
len     .req    r2
sum     .req    r3

.zero:          mov     r0, sum
                load_regs       ea

                /*
                 * Align an unaligned destination pointer.  We know that
                 * we have >= 8 bytes here, so we don't need to check
                 * the length.  Note that the source pointer hasn't been
                 * aligned yet.
                 */
.dst_unaligned: tst     dst, #1
                beq     .dst_16bit

                load1b  ip
                sub     len, len, #1
                adcs    sum, sum, ip, lsl #8    @ update checksum
                strb    ip, [dst], #1
                tst     dst, #2
                moveq   pc, lr                  @ dst is now 32bit aligned

.dst_16bit:     load2b  r8, ip
                sub     len, len, #2
                adcs    sum, sum, r8
                strb    r8, [dst], #1
                adcs    sum, sum, ip, lsl #8
                strb    ip, [dst], #1
                mov     pc, lr                  @ dst is now 32bit aligned

                /*
                 * Handle 0 to 7 bytes, with any alignment of source and
                 * destination pointers.  Note that when we get here, C = 0
                 */
.less8:         teq     len, #0                 @ check for zero count
                beq     .zero

                /* we must have at least one byte. */
                tst     dst, #1                 @ dst 16-bit aligned
                beq     .less8_aligned

                /* Align dst */
                load1b  ip
                sub     len, len, #1
                adcs    sum, sum, ip, lsl #8    @ update checksum
                strb    ip, [dst], #1
                tst     len, #6
                beq     .less8_byteonly

1:              load2b  r8, ip
                sub     len, len, #2
                adcs    sum, sum, r8
                strb    r8, [dst], #1
                adcs    sum, sum, ip, lsl #8
                strb    ip, [dst], #1
.less8_aligned: tst     len, #6
                bne     1b
.less8_byteonly:
                tst     len, #1
                beq     .done
                load1b  r8
                adcs    sum, sum, r8            @ update checksum
                strb    r8, [dst], #1
                b       .done

FN_ENTRY
                mov     ip, sp
                save_regs
                sub     fp, ip, #4

                cmp     len, #8                 @ Ensure that we have at least
                blo     .less8                  @ 8 bytes to copy.

                adds    sum, sum, #0            @ C = 0
                tst     dst, #3                 @ Test destination alignment
                blne    .dst_unaligned          @ align destination, return here

                /*
                 * Ok, the dst pointer is now 32bit aligned, and we know
                 * that we must have more than 4 bytes to copy.  Note
                 * that C contains the carry from the dst alignment above.
                 */

                tst     src, #3                 @ Test source alignment
                bne     .src_not_aligned

                /* Routine for src & dst aligned */

                bics    ip, len, #15
                beq     2f

1:              load4l  r4, r5, r6, r7
                stmia   dst!, {r4, r5, r6, r7}
                adcs    sum, sum, r4
                adcs    sum, sum, r5
                adcs    sum, sum, r6
                adcs    sum, sum, r7
                sub     ip, ip, #16
                teq     ip, #0
                bne     1b

2:              ands    ip, len, #12
                beq     4f
                tst     ip, #8
                beq     3f
                load2l  r4, r5
                stmia   dst!, {r4, r5}
                adcs    sum, sum, r4
                adcs    sum, sum, r5
                tst     ip, #4
                beq     4f

3:              load1l  r4
                str     r4, [dst], #4
                adcs    sum, sum, r4

4:              ands    len, len, #3
                beq     .done
                load1l  r4
                tst     len, #2
                beq     .exit
                adcs    sum, sum, r4, lsl #16
                strb    r4, [dst], #1
                mov     r4, r4, lsr #8
                strb    r4, [dst], #1
                mov     r4, r4, lsr #8
.exit:          tst     len, #1
                strneb  r4, [dst], #1
                andne   r4, r4, #255
                adcnes  sum, sum, r4

                /*
                 * If the dst pointer was not 16-bit aligned, we
                 * need to rotate the checksum here to get around
                 * the inefficient byte manipulations in the
                 * architecture independent code.
                 */
.done:          adc     r0, sum, #0
                ldr     sum, [sp, #0]           @ dst
                tst     sum, #1
                movne   sum, r0, lsl #8
                orrne   r0, sum, r0, lsr #24
                load_regs       ea

.src_not_aligned:
                adc     sum, sum, #0            @ include C from dst alignment
                and     ip, src, #3
                bic     src, src, #3
                load1l  r4
                cmp     ip, #2
                beq     .src2_aligned
                bhi     .src3_aligned
                mov     r4, r4, lsr #8          @ C = 0
                bics    ip, len, #15
                beq     2f
1:              load4l  r5, r6, r7, r8
                orr     r4, r4, r5, lsl #24
                mov     r5, r5, lsr #8
                orr     r5, r5, r6, lsl #24
                mov     r6, r6, lsr #8
                orr     r6, r6, r7, lsl #24
                mov     r7, r7, lsr #8
                orr     r7, r7, r8, lsl #24
                stmia   dst!, {r4, r5, r6, r7}
                adcs    sum, sum, r4
                adcs    sum, sum, r5
                adcs    sum, sum, r6
                adcs    sum, sum, r7
                mov     r4, r8, lsr #8
                sub     ip, ip, #16
                teq     ip, #0
                bne     1b
2:              ands    ip, len, #12
                beq     4f
                tst     ip, #8
                beq     3f
                load2l  r5, r6
                orr     r4, r4, r5, lsl #24
                mov     r5, r5, lsr #8
                orr     r5, r5, r6, lsl #24
                stmia   dst!, {r4, r5}
                adcs    sum, sum, r4
                adcs    sum, sum, r5
                mov     r4, r6, lsr #8
                tst     ip, #4
                beq     4f
3:              load1l  r5
                orr     r4, r4, r5, lsl #24
                str     r4, [dst], #4
                adcs    sum, sum, r4
                mov     r4, r5, lsr #8
4:              ands    len, len, #3
                beq     .done
                tst     len, #2
                beq     .exit
                adcs    sum, sum, r4, lsl #16
                strb    r4, [dst], #1
                mov     r4, r4, lsr #8
                strb    r4, [dst], #1
                mov     r4, r4, lsr #8
                b       .exit

.src2_aligned:  mov     r4, r4, lsr #16
                adds    sum, sum, #0
                bics    ip, len, #15
                beq     2f
1:              load4l  r5, r6, r7, r8
                orr     r4, r4, r5, lsl #16
                mov     r5, r5, lsr #16
                orr     r5, r5, r6, lsl #16
                mov     r6, r6, lsr #16
                orr     r6, r6, r7, lsl #16
                mov     r7, r7, lsr #16
                orr     r7, r7, r8, lsl #16
                stmia   dst!, {r4, r5, r6, r7}
                adcs    sum, sum, r4
                adcs    sum, sum, r5
                adcs    sum, sum, r6
                adcs    sum, sum, r7
                mov     r4, r8, lsr #16
                sub     ip, ip, #16
                teq     ip, #0
                bne     1b
2:              ands    ip, len, #12
                beq     4f
                tst     ip, #8
                beq     3f
                load2l  r5, r6
                orr     r4, r4, r5, lsl #16
                mov     r5, r5, lsr #16
                orr     r5, r5, r6, lsl #16
                stmia   dst!, {r4, r5}
                adcs    sum, sum, r4
                adcs    sum, sum, r5
                mov     r4, r6, lsr #16
                tst     ip, #4
                beq     4f
3:              load1l  r5
                orr     r4, r4, r5, lsl #16
                str     r4, [dst], #4
                adcs    sum, sum, r4
                mov     r4, r5, lsr #16
4:              ands    len, len, #3
                beq     .done
                tst     len, #2
                beq     .exit
                adcs    sum, sum, r4, lsl #16
                strb    r4, [dst], #1
                mov     r4, r4, lsr #8
                strb    r4, [dst], #1
                tst     len, #1
                beq     .done
                load1b  r4
                b       .exit

.src3_aligned:  mov     r4, r4, lsr #24
                adds    sum, sum, #0
                bics    ip, len, #15
                beq     2f
1:              load4l  r5, r6, r7, r8
                orr     r4, r4, r5, lsl #8
                mov     r5, r5, lsr #24
                orr     r5, r5, r6, lsl #8
                mov     r6, r6, lsr #24
                orr     r6, r6, r7, lsl #8
                mov     r7, r7, lsr #24
                orr     r7, r7, r8, lsl #8
                stmia   dst!, {r4, r5, r6, r7}
                adcs    sum, sum, r4
                adcs    sum, sum, r5
                adcs    sum, sum, r6
                adcs    sum, sum, r7
                mov     r4, r8, lsr #24
                sub     ip, ip, #16
                teq     ip, #0
                bne     1b
2:              ands    ip, len, #12
                beq     4f
                tst     ip, #8
                beq     3f
                load2l  r5, r6
                orr     r4, r4, r5, lsl #8
                mov     r5, r5, lsr #24
                orr     r5, r5, r6, lsl #8
                stmia   dst!, {r4, r5}
                adcs    sum, sum, r4
                adcs    sum, sum, r5
                mov     r4, r6, lsr #24
                tst     ip, #4
                beq     4f
3:              load1l  r5
                orr     r4, r4, r5, lsl #8
                str     r4, [dst], #4
                adcs    sum, sum, r4
                mov     r4, r5, lsr #24
4:              ands    len, len, #3
                beq     .done
                tst     len, #2
                beq     .exit
                adcs    sum, sum, r4, lsl #16
                strb    r4, [dst], #1
                load1l  r4
                strb    r4, [dst], #1
                adcs    sum, sum, r4, lsl #24
                mov     r4, r4, lsr #8
                b       .exit