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/* * Optmized version of the ip_fast_csum() function * Used for calculating IP header checksum * * Return: 16bit checksum, complemented * * Inputs: * in0: address of buffer to checksum (char *) * in1: length of the buffer (int) * * Copyright (C) 2002 Intel Corp. * Copyright (C) 2002 Ken Chen <kenneth.w.chen@intel.com> */ #include <asm/asmmacro.h> /* * Since we know that most likely this function is called with buf aligned * on 4-byte boundary and 20 bytes in length, we can execution rather quickly * versus calling generic version of do_csum, which has lots of overhead in * handling various alignments and sizes. However, due to lack of constrains * put on the function input argument, cases with alignment not on 4-byte or * size not equal to 20 bytes will be handled by the generic do_csum function. */ #define in0 r32 #define in1 r33 #define ret0 r8 GLOBAL_ENTRY(ip_fast_csum) .prologue .body cmp.ne p6,p7=5,in1 // size other than 20 byte? and r14=3,in0 // is it aligned on 4-byte? add r15=4,in0 // second source pointer ;; cmp.ne.or.andcm p6,p7=r14,r0 ;; (p7) ld4 r20=[in0],8 (p7) ld4 r21=[r15],8 (p6) br.spnt .generic ;; ld4 r22=[in0],8 ld4 r23=[r15],8 ;; ld4 r24=[in0] add r20=r20,r21 add r22=r22,r23 ;; add r20=r20,r22 ;; add r20=r20,r24 ;; shr.u ret0=r20,16 // now need to add the carry zxt2 r20=r20 ;; add r20=ret0,r20 ;; shr.u ret0=r20,16 // add carry again zxt2 r20=r20 ;; add r20=ret0,r20 ;; shr.u ret0=r20,16 zxt2 r20=r20 ;; add r20=ret0,r20 ;; andcm ret0=-1,r20 .restore sp // reset frame state br.ret.sptk.many b0 ;; .generic: .prologue .save ar.pfs, r35 alloc r35=ar.pfs,2,2,2,0 .save rp, r34 mov r34=b0 .body dep.z out1=in1,2,30 mov out0=in0 ;; br.call.sptk.many b0=do_csum ;; andcm ret0=-1,ret0 mov ar.pfs=r35 mov b0=r34 br.ret.sptk.many b0 END(ip_fast_csum) |