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Diffstat (limited to 'newlib/libc/machine/i960/strlen.S')
| -rw-r--r-- | newlib/libc/machine/i960/strlen.S | 117 |
1 files changed, 117 insertions, 0 deletions
diff --git a/newlib/libc/machine/i960/strlen.S b/newlib/libc/machine/i960/strlen.S new file mode 100644 index 0000000..dfbeec2 --- /dev/null +++ b/newlib/libc/machine/i960/strlen.S @@ -0,0 +1,117 @@ +/******************************************************************************* + * + * Copyright (c) 1993 Intel Corporation + * + * Intel hereby grants you permission to copy, modify, and distribute this + * software and its documentation. Intel grants this permission provided + * that the above copyright notice appears in all copies and that both the + * copyright notice and this permission notice appear in supporting + * documentation. In addition, Intel grants this permission provided that + * you prominently mark as "not part of the original" any modifications + * made to this software or documentation, and that the name of Intel + * Corporation not be used in advertising or publicity pertaining to + * distribution of the software or the documentation without specific, + * written prior permission. + * + * Intel Corporation provides this AS IS, WITHOUT ANY WARRANTY, EXPRESS OR + * IMPLIED, INCLUDING, WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY + * OR FITNESS FOR A PARTICULAR PURPOSE. Intel makes no guarantee or + * representations regarding the use of, or the results of the use of, + * the software and documentation in terms of correctness, accuracy, + * reliability, currentness, or otherwise; and you rely on the software, + * documentation and results solely at your own risk. + * + * IN NO EVENT SHALL INTEL BE LIABLE FOR ANY LOSS OF USE, LOSS OF BUSINESS, + * LOSS OF PROFITS, INDIRECT, INCIDENTAL, SPECIAL OR CONSEQUENTIAL DAMAGES + * OF ANY KIND. IN NO EVENT SHALL INTEL'S TOTAL LIABILITY EXCEED THE SUM + * PAID TO INTEL FOR THE PRODUCT LICENSED HEREUNDER. + * + ******************************************************************************/ + + .file "strlen.s" +#ifdef __PIC + .pic +#endif +#ifdef __PID + .pid +#endif + +/* + * (c) copyright 1988,1993 Intel Corp., all rights reserved + */ + +/* + procedure strlen (optimized assembler version for the 80960K series) + + src_addr = strlen (src_addr) + + return the number of bytes that precede the null byte in the + string pointed to by src_addr. + + Undefined behavior will occur if the end of the source string (i.e. + the terminating null byte) is in the last four words of the program's + allocated memory space. This is so because strlen fetches ahead + several words. Disallowing the fetch ahead would impose a severe + performance penalty. + + Strategy: + + Fetch the source array by long-words and scanbyte the words for the + null byte until found. Examine the word in which the null byte is + found, to determine its actual position, and return the length. + + Tactics: + + 1) Do NOT try to fetch the words in a word aligned manner because, + in my judgement, the performance degradation experienced due to + non-aligned accesses does NOT outweigh the time and complexity added + by the preamble that would be necessary to assure alignment. This + is supported by the intuition that many source strings will be word + aligned to begin with. +*/ + + .globl _strlen + .globl __strlen + .leafproc _strlen, __strlen + .align 2 +_strlen: +#ifndef __PIC + lda Lrett,g14 +#else + lda Lrett-(.+8)(ip),g14 +#endif +__strlen: + + mov g14,g13 # preserve return address + ldl (g0),g4 # fetch first two words + addo 8,g0,g2 # post-increment src word pointer + lda 0xff,g3 # byte extraction mask + + +Lsearch_for_word_with_null_byte: + scanbyte 0,g4 # check for null byte + mov g5,g7 # copy second word + bo.f Lsearch_for_null # branch if null found + scanbyte 0,g7 # check for null byte + ldl (g2),g4 # fetch next pair of word of src + addo 8,g2,g2 # post-increment src word pointer + bno Lsearch_for_word_with_null_byte # branch if null not found yet + + subo 4,g2,g2 # back up the byte pointer + mov g7,g4 # move word with null to search word +Lsearch_for_null: + subo 9,g2,g2 # back up the byte pointer +Lsearch_for_null.a: + and g4,g3,g14 # extract byte + cmpo 0,g14 # is it null? + addo 1,g2,g2 # bump src byte ptr + shro 8,g4,g4 # shift word to position next byte + bne Lsearch_for_null.a + +Lexit_code: + subo g0,g2,g0 # calculate string length + bx (g13) # g0 = addr of src; g14 = 0 +Lrett: + ret + +/* end of strlen */ |