summaryrefslogtreecommitdiff
path: root/arch/cris/arch-v10/lib/checksum.S
diff options
context:
space:
mode:
Diffstat (limited to 'arch/cris/arch-v10/lib/checksum.S')
-rw-r--r--arch/cris/arch-v10/lib/checksum.S118
1 files changed, 118 insertions, 0 deletions
diff --git a/arch/cris/arch-v10/lib/checksum.S b/arch/cris/arch-v10/lib/checksum.S
new file mode 100644
index 000000000..7d552f4bd
--- /dev/null
+++ b/arch/cris/arch-v10/lib/checksum.S
@@ -0,0 +1,118 @@
+/*
+ * A fast checksum routine using movem
+ * Copyright (c) 1998-2001 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
+ movem $r8,[$sp]
+
+ ;; do a movem checksum
+
+ subq 10*4,$r11 ; update length for the first loop
+
+_mloop: movem [$r10+],$r9 ; read 10 longwords
+
+ ;; perform dword checksumming on the 10 longwords
+
+ add.d $r0,$r12
+ ax
+ add.d $r1,$r12
+ ax
+ add.d $r2,$r12
+ ax
+ add.d $r3,$r12
+ ax
+ add.d $r4,$r12
+ ax
+ add.d $r5,$r12
+ ax
+ add.d $r6,$r12
+ ax
+ add.d $r7,$r12
+ ax
+ add.d $r8,$r12
+ ax
+ add.d $r9,$r12
+
+ ;; fold the carry into the checksum, to avoid having to loop the carry
+ ;; back into the top
+
+ ax
+ addq 0,$r12
+
+ subq 10*4,$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
+
+_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
+