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authorRoland McGrath <roland@gnu.org>1995-02-18 01:27:10 +0000
committerRoland McGrath <roland@gnu.org>1995-02-18 01:27:10 +0000
commit28f540f45bbacd939bfd07f213bcad2bf730b1bf (patch)
tree15f07c4c43d635959c6afee96bde71fb1b3614ee /sysdeps/i386/memset.c
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Diffstat (limited to 'sysdeps/i386/memset.c')
-rw-r--r--sysdeps/i386/memset.c83
1 files changed, 83 insertions, 0 deletions
diff --git a/sysdeps/i386/memset.c b/sysdeps/i386/memset.c
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+++ b/sysdeps/i386/memset.c
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+/* 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 <ansidecl.h>
+#include <string.h>
+#include <memcopy.h>
+
+#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 <sysdeps/generic/memset.c>
+#endif