91 lines
1.8 KiB
ArmAsm
91 lines
1.8 KiB
ArmAsm
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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 Intel Corp.
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* Copyright (C) 2002 Ken Chen <kenneth.w.chen@intel.com>
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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 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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;;
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andcm ret0=-1,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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