1 files changed, 111 insertions, 0 deletions

diff --git a/arch/cris/arch-v32/lib/checksum.S b/arch/cris/arch-v32/lib/checksum.S
new file mode 100644
index 000000000000..32e66181b826
--- /dev/null
+++ b/arch/cris/arch-v32/lib/checksum.S
@@ -0,0 +1,111 @@
+/*
+ * A fast checksum routine using movem
+ * Copyright (c) 1998-2001, 2003 Axis Communications AB
+ *
+ * csum_partial(const unsigned char * buff, int len, unsigned int sum)
+ */
+
+        .globl  csum_partial
+csum_partial:
+
+        ;; r10 - src
+        ;; r11 - length
+        ;; r12 - checksum
+
+        ;; check for breakeven length between movem and normal word looping versions
+        ;; we also do _NOT_ want to compute a checksum over more than the
+        ;; actual length when length < 40
+
+        cmpu.w  80,$r11
+        blo     _word_loop
+        nop
+
+        ;; need to save the registers we use below in the movem loop
+        ;; this overhead is why we have a check above for breakeven length
+        ;; only r0 - r8 have to be saved, the other ones are clobber-able
+        ;; according to the ABI
+
+        subq    9*4,$sp
+        subq    10*4,$r11       ; update length for the first loop
+        movem   $r8,[$sp]
+
+        ;; do a movem checksum
+
+_mloop: movem   [$r10+],$r9     ; read 10 longwords
+
+        ;; perform dword checksumming on the 10 longwords
+
+        add.d   $r0,$r12
+        addc    $r1,$r12
+        addc    $r2,$r12
+        addc    $r3,$r12
+        addc    $r4,$r12
+        addc    $r5,$r12
+        addc    $r6,$r12
+        addc    $r7,$r12
+        addc    $r8,$r12
+        addc    $r9,$r12
+
+        ;; fold the carry into the checksum, to avoid having to loop the carry
+        ;; back into the top
+
+        addc    0,$r12
+        addc    0,$r12          ; do it again, since we might have generated a carry
+
+        subq    10*4,$r11
+        bge     _mloop
+        nop
+
+        addq    10*4,$r11       ; compensate for last loop underflowing length
+
+        movem   [$sp+],$r8      ; restore regs
+
+_word_loop:
+        ;; only fold if there is anything to fold.
+
+        cmpq    0,$r12
+        beq     _no_fold
+
+        ;; fold 32-bit checksum into a 16-bit checksum, to avoid carries below.
+        ;; r9 and r13 can be used as temporaries.
+
+        moveq   -1,$r9          ; put 0xffff in r9, faster than move.d 0xffff,r9
+        lsrq    16,$r9
+
+        move.d  $r12,$r13
+        lsrq    16,$r13         ; r13 = checksum >> 16
+        and.d   $r9,$r12                ; checksum = checksum & 0xffff
+        add.d   $r13,$r12               ; checksum += r13
+        move.d  $r12,$r13               ; do the same again, maybe we got a carry last add
+        lsrq    16,$r13
+        and.d   $r9,$r12
+        add.d   $r13,$r12
+
+_no_fold:
+        cmpq    2,$r11
+        blt     _no_words
+        nop
+
+        ;; checksum the rest of the words
+
+        subq    2,$r11
+
+_wloop: subq    2,$r11
+        bge     _wloop
+        addu.w  [$r10+],$r12
+
+        addq    2,$r11
+
+_no_words:
+        ;; see if we have one odd byte more
+        cmpq    1,$r11
+        beq     _do_byte
+        nop
+        ret
+        move.d  $r12,$r10
+
+_do_byte:
+        ;; copy and checksum the last byte
+        addu.b  [$r10],$r12
+        ret
+        move.d  $r12,$r10