From 28f540f45bbacd939bfd07f213bcad2bf730b1bf Mon Sep 17 00:00:00 2001 From: Roland McGrath Date: Sat, 18 Feb 1995 01:27:10 +0000 Subject: initial import --- sysdeps/i386/memset.c | 83 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 83 insertions(+) create mode 100644 sysdeps/i386/memset.c (limited to 'sysdeps/i386/memset.c') diff --git a/sysdeps/i386/memset.c b/sysdeps/i386/memset.c new file mode 100644 index 0000000000..2987445d4f --- /dev/null +++ b/sysdeps/i386/memset.c @@ -0,0 +1,83 @@ +/* memset -- set a block of memory to some byte value. + For Intel 80x86, x>=3. + Copyright (C) 1991, 1992, 1993 Free Software Foundation, Inc. + Contributed by Torbjorn Granlund (tege@sics.se). + +The GNU C Library is free software; you can redistribute it and/or +modify it under the terms of the GNU Library General Public License as +published by the Free Software Foundation; either version 2 of the +License, or (at your option) any later version. + +The GNU C Library is distributed in the hope that it will be useful, +but WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +Library General Public License for more details. + +You should have received a copy of the GNU Library General Public +License along with the GNU C Library; see the file COPYING.LIB. If +not, write to the Free Software Foundation, Inc., 675 Mass Ave, +Cambridge, MA 02139, USA. */ + +#include +#include +#include + +#ifdef __GNUC__ + +PTR +DEFUN(memset, (dstpp, c, len), + PTR dstpp AND int c AND size_t len) +{ + unsigned long int dstp = (unsigned long int) dstpp; + + /* This explicit register allocation + improves code very much indeed. */ + register op_t x asm("ax"); + + x = (unsigned char) c; + + /* Clear the direction flag, so filling will move forward. */ + asm volatile("cld"); + + /* This threshold value is optimal. */ + if (len >= 12) + { + /* Fill X with four copies of the char we want to fill with. */ + x |= (x << 8); + x |= (x << 16); + + /* Adjust LEN for the bytes handled in the first loop. */ + len -= (-dstp) % OPSIZ; + + /* There are at least some bytes to set. + No need to test for LEN == 0 in this alignment loop. */ + + /* Fill bytes until DSTP is aligned on a longword boundary. */ + asm volatile("rep\n" + "stosb" /* %0, %2, %3 */ : + "=D" (dstp) : + "0" (dstp), "c" ((-dstp) % OPSIZ), "a" (x) : + "cx"); + + /* Fill longwords. */ + asm volatile("rep\n" + "stosl" /* %0, %2, %3 */ : + "=D" (dstp) : + "0" (dstp), "c" (len / OPSIZ), "a" (x) : + "cx"); + len %= OPSIZ; + } + + /* Write the last few bytes. */ + asm volatile("rep\n" + "stosb" /* %0, %2, %3 */ : + "=D" (dstp) : + "0" (dstp), "c" (len), "a" (x) : + "cx"); + + return dstpp; +} + +#else +#include +#endif -- cgit v1.2.1