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diff --git a/arch/mn10300/lib/do_csum.S b/arch/mn10300/lib/do_csum.S
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+/* Optimised simple memory checksum
+ *
+ * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+#include <asm/cache.h>
+
+ .section .text
+ .balign L1_CACHE_BYTES
+
+###############################################################################
+#
+# unsigned int do_csum(const unsigned char *buff, size_t len)
+#
+###############################################################################
+ .globl do_csum
+ .type do_csum,@function
+do_csum:
+ movm [d2,d3],(sp)
+ mov d0,(12,sp)
+ mov d1,(16,sp)
+ mov d1,d2 # count
+ mov d0,a0 # buff
+ clr d1 # accumulator
+
+ cmp +0,d2
+ beq do_csum_done # return if zero-length buffer
+
+ # 4-byte align the buffer pointer
+ btst +3,a0
+ beq do_csum_now_4b_aligned
+
+ btst +1,a0
+ beq do_csum_addr_not_odd
+ movbu (a0),d0
+ inc a0
+ asl +8,d0
+ add d0,d1
+ addc +0,d1
+ add -1,d2
+do_csum_addr_not_odd:
+
+ cmp +2,d2
+ bcs do_csum_fewer_than_4
+ btst +2,a0
+ beq do_csum_now_4b_aligned
+ movhu (a0+),d0
+ add d0,d1
+ addc +0,d1
+ add -2,d2
+ cmp +4,d2
+ bcs do_csum_fewer_than_4
+
+do_csum_now_4b_aligned:
+ # we want to checksum as much as we can in chunks of 32 bytes
+ cmp +31,d2
+ bls do_csum_remainder # 4-byte aligned remainder
+
+ add -32,d2
+ mov +32,d3
+
+do_csum_loop:
+ mov (a0+),d0
+ add d0,d1
+ mov (a0+),e0
+ addc e0,d1
+ mov (a0+),e1
+ addc e1,d1
+ mov (a0+),e3
+ addc e3,d1
+ mov (a0+),d0
+ addc d0,d1
+ mov (a0+),e0
+ addc e0,d1
+ mov (a0+),e1
+ addc e1,d1
+ mov (a0+),e3
+ addc e3,d1
+ addc +0,d1
+
+ sub d3,d2
+ bcc do_csum_loop
+
+ add d3,d2
+ beq do_csum_done
+
+do_csum_remainder:
+ # cut 16-31 bytes down to 0-15
+ cmp +16,d2
+ bcs do_csum_fewer_than_16
+ mov (a0+),d0
+ add d0,d1
+ mov (a0+),e0
+ addc e0,d1
+ mov (a0+),e1
+ addc e1,d1
+ mov (a0+),e3
+ addc e3,d1
+ addc +0,d1
+ add -16,d2
+ beq do_csum_done
+
+do_csum_fewer_than_16:
+ # copy the remaining whole words
+ cmp +4,d2
+ bcs do_csum_fewer_than_4
+ cmp +8,d2
+ bcs do_csum_one_word
+ cmp +12,d2
+ bcs do_csum_two_words
+ mov (a0+),d0
+ add d0,d1
+ addc +0,d1
+do_csum_two_words:
+ mov (a0+),d0
+ add d0,d1
+ addc +0,d1
+do_csum_one_word:
+ mov (a0+),d0
+ add d0,d1
+ addc +0,d1
+
+do_csum_fewer_than_4:
+ and +3,d2
+ beq do_csum_done
+ xor_cmp d0,d0,+2,d2
+ bcs do_csum_fewer_than_2
+ movhu (a0+),d0
+do_csum_fewer_than_2:
+ and +1,d2
+ beq do_csum_add_last_bit
+ movbu (a0),d3
+ add d3,d0
+do_csum_add_last_bit:
+ add d0,d1
+ addc +0,d1
+
+do_csum_done:
+ # compress the checksum down to 16 bits
+ mov +0xffff0000,d2
+ and d1,d2
+ asl +16,d1
+ add d2,d1,d0
+ addc +0xffff,d0
+ lsr +16,d0
+
+ # flip the halves of the word result if the buffer was oddly aligned
+ mov (12,sp),d1
+ and +1,d1
+ beq do_csum_not_oddly_aligned
+ swaph d0,d0 # exchange bits 15:8 with 7:0
+
+do_csum_not_oddly_aligned:
+ ret [d2,d3],8
+
+do_csum_end:
+ .size do_csum, do_csum_end-do_csum