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-rw-r--r--REORG.TODO/sysdeps/i386/memcmp.S73
1 files changed, 73 insertions, 0 deletions
diff --git a/REORG.TODO/sysdeps/i386/memcmp.S b/REORG.TODO/sysdeps/i386/memcmp.S
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+++ b/REORG.TODO/sysdeps/i386/memcmp.S
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+/* Compare two memory blocks for differences in the first COUNT bytes.
+   Copyright (C) 1995-2017 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <sysdep.h>
+#include "asm-syntax.h"
+
+#define PARMS	4+4	/* space for 1 saved reg */
+#define BLK1	PARMS
+#define BLK2	BLK1+4
+#define LEN	BLK2+4
+
+	.text
+ENTRY (memcmp)
+
+	pushl %esi		/* Save callee-safe registers.  */
+	cfi_adjust_cfa_offset (4)
+	movl %edi, %edx		/* Note that %edx is not used and can
+				   so be used to save %edi.  It's faster.  */
+	cfi_register (edi, edx)
+
+	movl BLK1(%esp), %esi
+	cfi_rel_offset (esi, 0)
+	movl BLK2(%esp), %edi
+	movl LEN(%esp), %ecx
+
+	cld			/* Set direction of comparison.  */
+
+	xorl %eax, %eax		/* Default result.  */
+
+	repe			/* Compare at most %ecx bytes.  */
+	cmpsb
+	jz L(1)			/* If even last byte was equal we return 0.  */
+
+	/* The memory blocks are not equal.  So result of the last
+	   subtraction is present in the carry flag.  It is set when
+	   the byte in block #2 is bigger.  In this case we have to
+	   return -1 (=0xffffffff), else 1.  */
+	sbbl %eax, %eax		/* This is tricky.  %eax == 0 and carry is set
+				   or not depending on last subtraction.  */
+
+	/* At this point %eax == 0, if the byte of block #1 was bigger, and
+	   0xffffffff if the last byte of block #2 was bigger.  The latter
+	   case is already correct but the former needs a little adjustment.
+	   Note that the following operation does not change 0xffffffff.  */
+	orb $1, %al		/* Change 0 to 1.  */
+
+L(1):	popl %esi		/* Restore registers.  */
+	cfi_adjust_cfa_offset (-4)
+	cfi_restore (esi)
+	movl %edx, %edi
+	cfi_restore (edi)
+
+	ret
+END (memcmp)
+
+#undef bcmp
+weak_alias (memcmp, bcmp)
+libc_hidden_builtin_def (memcmp)