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awilliam
GitHub Repository: awilliam/linux-vfio
 Path: blob/master/arch/ia64/lib/ip_fast_csum.S
10817 views
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/*

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 * Optmized version of the ip_fast_csum() function

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 * Used for calculating IP header checksum

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 *

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 * Return: 16bit checksum, complemented

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 *

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 * Inputs:

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 *      in0: address of buffer to checksum (char *)

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 *      in1: length of the buffer (int)

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 *

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 * Copyright (C) 2002, 2006 Intel Corp.

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 * Copyright (C) 2002, 2006 Ken Chen <[email protected]>

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 */

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#include <asm/asmmacro.h>

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/*

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 * Since we know that most likely this function is called with buf aligned

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 * on 4-byte boundary and 20 bytes in length, we can execution rather quickly

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 * versus calling generic version of do_csum, which has lots of overhead in

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 * handling various alignments and sizes.  However, due to lack of constrains

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 * put on the function input argument, cases with alignment not on 4-byte or

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 * size not equal to 20 bytes will be handled by the generic do_csum function.

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 */

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#define in0	r32

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#define in1	r33

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#define in2	r34

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#define in3	r35

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#define in4	r36

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#define ret0	r8

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GLOBAL_ENTRY(ip_fast_csum)

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	.prologue

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	.body

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	cmp.ne	p6,p7=5,in1	// size other than 20 byte?

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	and	r14=3,in0	// is it aligned on 4-byte?

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	add	r15=4,in0	// second source pointer

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	;;

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	cmp.ne.or.andcm p6,p7=r14,r0

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	;;

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(p7)	ld4	r20=[in0],8

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(p7)	ld4	r21=[r15],8

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(p6)	br.spnt	.generic

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	;;

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	ld4	r22=[in0],8

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	ld4	r23=[r15],8

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	;;

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	ld4	r24=[in0]

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	add	r20=r20,r21

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	add	r22=r22,r23

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	;;

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	add	r20=r20,r22

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	;;

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	add	r20=r20,r24

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	;;

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	shr.u	ret0=r20,16	// now need to add the carry

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	zxt2	r20=r20

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	;;

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	add	r20=ret0,r20

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	;;

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	shr.u	ret0=r20,16	// add carry again

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	zxt2	r20=r20

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	;;

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	add	r20=ret0,r20

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	;;

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	shr.u	ret0=r20,16

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	zxt2	r20=r20

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	;;

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	add	r20=ret0,r20

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	mov	r9=0xffff

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	;;

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	andcm	ret0=r9,r20

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	.restore sp		// reset frame state

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	br.ret.sptk.many b0

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	;;

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.generic:

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	.prologue

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	.save ar.pfs, r35

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	alloc	r35=ar.pfs,2,2,2,0

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	.save rp, r34

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	mov	r34=b0

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	.body

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	dep.z	out1=in1,2,30

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	mov	out0=in0

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	;;

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	br.call.sptk.many b0=do_csum

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	;;

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	andcm	ret0=-1,ret0

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	mov	ar.pfs=r35

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	mov	b0=r34

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	br.ret.sptk.many b0

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END(ip_fast_csum)

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GLOBAL_ENTRY(csum_ipv6_magic)

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	ld4	r20=[in0],4

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	ld4	r21=[in1],4

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	zxt4	in2=in2

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	;;

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	ld4	r22=[in0],4

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	ld4	r23=[in1],4

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	dep	r15=in3,in2,32,16

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	;;

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	ld4	r24=[in0],4

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	ld4	r25=[in1],4

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	mux1	r15=r15,@rev

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	add	r16=r20,r21

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	add	r17=r22,r23

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	zxt4	in4=in4

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	;;

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	ld4	r26=[in0],4

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	ld4	r27=[in1],4

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	shr.u	r15=r15,16

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	add	r18=r24,r25

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	add	r8=r16,r17

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	;;

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	add	r19=r26,r27

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	add	r8=r8,r18

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	;;

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	add	r8=r8,r19

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	add	r15=r15,in4

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	;;

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	add	r8=r8,r15

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	;;

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	shr.u	r10=r8,32	// now fold sum into short

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	zxt4	r11=r8

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	;;

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	add	r8=r10,r11

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	;;

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	shr.u	r10=r8,16	// yeah, keep it rolling

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	zxt2	r11=r8

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	;;

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	add	r8=r10,r11

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	;;

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	shr.u	r10=r8,16	// three times lucky

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	zxt2	r11=r8

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	;;

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	add	r8=r10,r11

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	mov	r9=0xffff

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	;;

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	andcm	r8=r9,r8

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	br.ret.sptk.many b0

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END(csum_ipv6_magic)

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