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lampret |
/*******************************************************************************
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*
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* Copyright (c) 1993 Intel Corporation
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*
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* Intel hereby grants you permission to copy, modify, and distribute this
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* software and its documentation. Intel grants this permission provided
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* that the above copyright notice appears in all copies and that both the
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* copyright notice and this permission notice appear in supporting
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* documentation. In addition, Intel grants this permission provided that
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* you prominently mark as "not part of the original" any modifications
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* made to this software or documentation, and that the name of Intel
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* Corporation not be used in advertising or publicity pertaining to
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* distribution of the software or the documentation without specific,
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* written prior permission.
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*
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* Intel Corporation provides this AS IS, WITHOUT ANY WARRANTY, EXPRESS OR
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* IMPLIED, INCLUDING, WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY
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* OR FITNESS FOR A PARTICULAR PURPOSE. Intel makes no guarantee or
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* representations regarding the use of, or the results of the use of,
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* the software and documentation in terms of correctness, accuracy,
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* reliability, currentness, or otherwise; and you rely on the software,
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* documentation and results solely at your own risk.
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*
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* IN NO EVENT SHALL INTEL BE LIABLE FOR ANY LOSS OF USE, LOSS OF BUSINESS,
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* LOSS OF PROFITS, INDIRECT, INCIDENTAL, SPECIAL OR CONSEQUENTIAL DAMAGES
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* OF ANY KIND. IN NO EVENT SHALL INTEL'S TOTAL LIABILITY EXCEED THE SUM
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* PAID TO INTEL FOR THE PRODUCT LICENSED HEREUNDER.
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*
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******************************************************************************/
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.file "memcmp.s"
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#ifdef __PIC
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.pic
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#endif
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#ifdef __PID
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.pid
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#endif
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/*
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* (c) copyright 1988,1993 Intel Corp., all rights reserved
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*/
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/*
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procedure memcmp (optimized assembler version for the 80960K series)
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result = memcmp (src1_addr, src2_addr, max_bytes)
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compare the byte array pointed to by src1_addr to the byte array
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pointed to by src2_addr. Return 0 iff the arrays are equal, -1 iff
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src1_addr is lexicographically less than src2_addr, and 1 iff it is
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lexicographically greater. Do not compare more than max_bytes bytes.
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Undefined behavior will occur if the end of either source array
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is in the last two words of the program's allocated memory space.
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This is so because memcmp fetches ahead. Disallowing the fetch ahead
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would impose a severe performance penalty.
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Strategy:
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Fetch the source strings by words and compare the words until either
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a differing word is found or max_bytes is exhausted. In the former
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case, move through the words to find the differing byte and return
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plus or minus one, appropriately. In the latter case, return zero
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(equality).
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Tactics:
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1) Do NOT try to fetch the words in a word aligned manner because,
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in my judgement, the performance degradation experienced due to
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non-aligned accesses does NOT outweigh the time and complexity added
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by the preamble that would be necessary to assure alignment. This
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is supported by the intuition that most source arrays (even more
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true of most big source arrays) will be word aligned to begin with.
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2) Rather than decrementing max_bytes to zero, I calculate the
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address of the byte after the last byte of the source_1 array, and
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quit when the source byte pointer passes that.
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*/
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.globl _memcmp
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.globl __memcmp
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.leafproc _memcmp,__memcmp
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.align 2
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_memcmp:
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#ifndef __PIC
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lda .Lrett,g14
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#else
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lda .Lrett-(.+8)(ip),g14
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#endif
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__memcmp:
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mov g14,g13 # preserve return address
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ldconst 0,g14 # conform to register conventions
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cmpibge 0,g2,Lequal_exit # quit if max_bytes <= 0
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addo g0,g2,g2 # calculate byte addr of byte after last in src1
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.Lwloop:
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cmpo g0,g2
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ld (g0), g5 # fetch word of source_1
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bge Lequal_exit # quit (equal) if max_bytes exhausted
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ld (g1), g3 # fetch word of source_2
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addo 4,g0,g0 # post-increment source_1 byte ptr
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addo 4,g1,g1 # post-increment source_2 byte ptr
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cmpobe g5,g3,.Lwloop # branch if source words are equal
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ldconst 0xff,g4 # byte extraction mask
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subo 4,g0,g0 # back up src1 pointer
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.Lcloop: and g4,g5,g7 # extract and compare individual bytes
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and g4,g3,g6
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cmpobne g7,g6,.diff # branch if they are different
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shlo 8,g4,g4 # position mask for next extraction
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addo 1,g0,g0
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cmpobl g0,g2,.Lcloop # quit if max_bytes is exhausted
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Lequal_exit:
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mov 0,g0
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bx (g13)
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.Lrett:
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ret
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.diff: bl .neg # arrays differ at current byte.
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/* return 1 or -1 appropriately */
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mov 1,g0
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bx (g13)
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.neg: subi 1,0,g0
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.Lexit:
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bx (g13)
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/* end or memcmp */
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