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+/* memchr (str, ch, n) -- Return pointer to first occurrence of CH in the
+   first N bytes of STR.
+   For Motorola 68000.
+   Copyright (C) 1999-2014 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Andreas Schwab <schwab@gnu.org>.
+
+   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"
+
+	TEXT
+ENTRY(__memchr)
+	/* Save the callee-saved registers we use.  */
+#ifdef __mcoldfire__
+	movel	R(d2),MEM_PREDEC(sp)
+	cfi_adjust_cfa_offset (4)
+	movel	R(d3),MEM_PREDEC(sp)
+	cfi_adjust_cfa_offset (4)
+	movel	R(d4),MEM_PREDEC(sp)
+	cfi_adjust_cfa_offset (4)
+	cfi_rel_offset (R(d2), 8)
+	cfi_rel_offset (R(d3), 4)
+	cfi_rel_offset (R(d4), 0)
+#else
+	moveml	R(d2)-R(d4),MEM_PREDEC(sp)
+	cfi_adjust_cfa_offset (3*4)
+	cfi_rel_offset (R(d2), 0)
+	cfi_rel_offset (R(d3), 4)
+	cfi_rel_offset (R(d4), 8)
+#endif
+
+	/* Get string pointer, character and length.  */
+	movel	MEM_DISP(sp,16),R(a0)
+	moveb	MEM_DISP(sp,23),R(d0)
+	movel	MEM_DISP(sp,24),R(d4)
+
+	/* Check if at least four bytes left to search.  */
+#ifdef __mcoldfire__
+	subql	#4,R(d4)
+	bcs	L(L6)
+	addql	#4,R(d4)
+#else
+	moveql	#4,R(d1)
+	cmpl	R(d1),R(d4)
+	bcs	L(L6)
+#endif
+
+	/* Distribute the character to all bytes of a longword.  */
+	movel	R(d0),R(d1)
+	lsll	#8,R(d1)
+	moveb	R(d0),R(d1)
+	movel	R(d1),R(d0)
+	swap	R(d0)
+	movew	R(d1),R(d0)
+
+	/* First search for the character one byte at a time until the
+	   pointer is aligned to a longword boundary.  */
+	movel	R(a0),R(d1)
+#ifdef __mcoldfire__
+	andl	#3,R(d1)
+#else
+	andw	#3,R(d1)
+#endif
+	beq	L(L1)
+	cmpb	MEM(a0),R(d0)
+	beq	L(L9)
+	addql	#1,R(a0)
+	subql	#1,R(d4)
+	beq	L(L7)
+
+#ifdef __mcoldfire__
+	subql	#3,R(d1)
+#else
+	subqw	#3,R(d1)
+#endif
+	beq	L(L1)
+	cmpb	MEM(a0),R(d0)
+	beq	L(L9)
+	addql	#1,R(a0)
+	subql	#1,R(d4)
+	beq	L(L7)
+
+#ifdef __mcoldfire__
+	addql	#1,R(d1)
+#else
+	addqw	#1,R(d1)
+#endif
+	beq	L(L1)
+	cmpb	MEM(a0),R(d0)
+	beq	L(L9)
+	addql	#1,R(a0)
+	subql	#1,R(d4)
+	beq	L(L7)
+
+L(L1:)
+	/* Load the magic bits.  Unlike the generic implementation we can
+	   use the carry bit as the fourth hole.  */
+	movel	#0xfefefeff,R(d3)
+
+      /* We exit the loop if adding MAGIC_BITS to LONGWORD fails to
+	 change any of the hole bits of LONGWORD.
+
+	 1) Is this safe?  Will it catch all the zero bytes?
+	 Suppose there is a byte with all zeros.  Any carry bits
+	 propagating from its left will fall into the hole at its
+	 least significant bit and stop.  Since there will be no
+	 carry from its most significant bit, the LSB of the
+	 byte to the left will be unchanged, and the zero will be
+	 detected.
+
+	 2) Is this worthwhile?  Will it ignore everything except
+	 zero bytes?  Suppose every byte of LONGWORD has a bit set
+	 somewhere.  There will be a carry into bit 8.	If bit 8
+	 is set, this will carry into bit 16.  If bit 8 is clear,
+	 one of bits 9-15 must be set, so there will be a carry
+	 into bit 16.  Similarly, there will be a carry into bit
+	 24.  If one of bits 24-31 is set, there will be a carry
+	 into bit 32 (=carry flag), so all of the hole bits will
+	 be changed.
+
+	 3) But wait!  Aren't we looking for C, not zero?
+	 Good point.  So what we do is XOR LONGWORD with a longword,
+	 each of whose bytes is C.  This turns each byte that is C
+	 into a zero.  */
+
+	/* Still at least 4 bytes to search?  */
+	subql	#4,R(d4)
+	bcs	L(L6)
+
+L(L2:)
+	/* Get the longword in question.  */
+	movel	MEM_POSTINC(a0),R(d1)
+	/* XOR with the byte we search for.  */
+	eorl	R(d0),R(d1)
+
+	/* Add the magic value.  We get carry bits reported for each byte
+	   which is not C.  */
+	movel	R(d3),R(d2)
+	addl	R(d1),R(d2)
+
+	/* Check the fourth carry bit before it is clobbered by the next
+	   XOR.  If it is not set we have a hit.  */
+	bcc	L(L8)
+
+	/* We are only interested in carry bits that change due to the
+	   previous add, so remove original bits.  */
+	eorl	R(d1),R(d2)
+
+	/* Now test for the other three overflow bits.
+	   Set all non-carry bits.  */
+	orl	R(d3),R(d2)
+	/* Add 1 to get zero if all carry bits were set.  */
+	addql	#1,R(d2)
+
+	/* If we don't get zero then at least one byte of the word equals
+	   C.  */
+	bne	L(L8)
+
+	/* Still at least 4 bytes to search?  */
+	subql	#4,R(d4)
+	bcs	L(L6)
+
+	/* Get the longword in question.  */
+	movel	MEM_POSTINC(a0),R(d1)
+	/* XOR with the byte we search for.  */
+	eorl	R(d0),R(d1)
+
+	/* Add the magic value.  We get carry bits reported for each byte
+	   which is not C.  */
+	movel	R(d3),R(d2)
+	addl	R(d1),R(d2)
+
+	/* Check the fourth carry bit before it is clobbered by the next
+	   XOR.  If it is not set we have a hit.  */
+	bcc	L(L8)
+
+	/* We are only interested in carry bits that change due to the
+	   previous add, so remove original bits */
+	eorl	R(d1),R(d2)
+
+	/* Now test for the other three overflow bits.
+	   Set all non-carry bits.  */
+	orl	R(d3),R(d2)
+	/* Add 1 to get zero if all carry bits were set.  */
+	addql	#1,R(d2)
+
+	/* If we don't get zero then at least one byte of the word equals
+	   C.  */
+	bne	L(L8)
+
+	/* Still at least 4 bytes to search?  */
+	subql	#4,R(d4)
+	bcc	L(L2)
+
+L(L6:)
+	/* Search one byte at a time in the remaining less than 4 bytes.  */
+#ifdef __mcoldfire__
+	addql	#4,R(d4)
+#else
+	andw	#3,R(d4)
+#endif
+	beq	L(L7)
+	cmpb	MEM(a0),R(d0)
+	beq	L(L9)
+	addql	#1,R(a0)
+
+#ifdef __mcoldfire__
+	subql	#1,R(d4)
+#else
+	subqw	#1,R(d4)
+#endif
+	beq	L(L7)
+	cmpb	MEM(a0),R(d0)
+	beq	L(L9)
+	addql	#1,R(a0)
+
+#ifdef __mcoldfire__
+	subql	#1,R(d4)
+#else
+	subqw	#1,R(d4)
+#endif
+	beq	L(L7)
+	cmpb	MEM(a0),R(d0)
+	beq	L(L9)
+
+L(L7:)
+	/* Return NULL.  */
+	clrl	R(d0)
+	movel	R(d0),R(a0)
+#ifdef __mcoldfire__
+	movel	MEM_POSTINC(sp),R(d4)
+	cfi_remember_state
+	cfi_adjust_cfa_offset (-4)
+	cfi_restore (R(d4))
+	movel	MEM_POSTINC(sp),R(d3)
+	cfi_adjust_cfa_offset (-4)
+	cfi_restore (R(d3))
+	movel	MEM_POSTINC(sp),R(d2)
+	cfi_adjust_cfa_offset (-4)
+	cfi_restore (R(d2))
+#else
+	moveml	MEM_POSTINC(sp),R(d2)-R(d4)
+	cfi_remember_state
+	cfi_adjust_cfa_offset (-3*4)
+	cfi_restore (R(d2))
+	cfi_restore (R(d3))
+	cfi_restore (R(d4))
+#endif
+	rts
+
+	cfi_restore_state
+L(L8:)
+	/* We have a hit.  Check to see which byte it was.  First
+	   compensate for the autoincrement in the loop.  */
+	subql	#4,R(a0)
+
+	cmpb	MEM(a0),R(d0)
+	beq	L(L9)
+	addql	#1,R(a0)
+
+	cmpb	MEM(a0),R(d0)
+	beq	L(L9)
+	addql	#1,R(a0)
+
+	cmpb	MEM(a0),R(d0)
+	beq	L(L9)
+	addql	#1,R(a0)
+
+	/* Otherwise the fourth byte must equal C.  */
+L(L9:)
+	movel	R(a0),R(d0)
+#ifdef __mcoldfire__
+	movel	MEM_POSTINC(sp),R(d4)
+	cfi_adjust_cfa_offset (-4)
+	cfi_restore (R(d4))
+	movel	MEM_POSTINC(sp),R(d3)
+	cfi_adjust_cfa_offset (-4)
+	cfi_restore (R(d3))
+	movel	MEM_POSTINC(sp),R(d2)
+	cfi_adjust_cfa_offset (-4)
+	cfi_restore (R(d2))
+#else
+	moveml	MEM_POSTINC(sp),R(d2)-R(d4)
+	cfi_adjust_cfa_offset (-3*4)
+	cfi_restore (R(d2))
+	cfi_restore (R(d3))
+	cfi_restore (R(d4))
+#endif
+	rts
+END(__memchr)
+
+weak_alias (__memchr, memchr)
+libc_hidden_builtin_def (memchr)
generated by cgit-pink 1.4.1 (git 2.36.1) at 2024-12-15 22:39:10 +0000