glibc/sysdeps/alpha/alphaev67/strrchr.S

/* Copyright (C) 2000-2023 Free Software Foundation, Inc.
   EV67 optimized by Rick Gorton <rick.gorton@alpha-processor.com>.
   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
   <https://www.gnu.org/licenses/>.  */

/* Return the address of the last occurrence of a given character
   within a null-terminated string, or null if it is not found.  */

#include <sysdep.h>

	.arch ev6
	.set noreorder
	.set noat

ENTRY(strrchr)
#ifdef PROF
	ldgp	gp, 0(pv)
	lda	AT, _mcount
	jsr	AT, (AT), _mcount
	.prologue 1
#else
	.prologue 0
#endif

	and	a1, 0xff, t2	# E : 00000000000000ch
	insbl	a1, 1, t4	# U : 000000000000ch00
	insbl	a1, 2, t5	# U : 0000000000ch0000
	ldq_u   t0, 0(a0)	# L : load first quadword Latency=3

	mov	zero, t6	# E : t6 is last match aligned addr
	or	t2, t4, a1	# E : 000000000000chch
	sll	t5, 8, t3	# U : 00000000ch000000
	mov	zero, t8	# E : t8 is last match byte compare mask

	andnot  a0, 7, v0	# E : align source addr
	or	t5, t3, t3	# E : 00000000chch0000
	sll	a1, 32, t2	# U : 0000chch00000000
	sll	a1, 48, t4	# U : chch000000000000

	or	t4, a1, a1	# E : chch00000000chch
	or	t2, t3, t2	# E : 0000chchchch0000
	or	a1, t2, a1	# E : chchchchchchchch
	lda	t5, -1		# E : build garbage mask

	cmpbge  zero, t0, t1	# E : bits set iff byte == zero
	mskqh	t5, a0, t4	# E : Complete garbage mask
	xor	t0, a1, t2	# E : make bytes == c zero
	cmpbge	zero, t4, t4	# E : bits set iff byte is garbage

	cmpbge  zero, t2, t3	# E : bits set iff byte == c
	andnot	t1, t4, t1	# E : clear garbage from null test
	andnot	t3, t4, t3	# E : clear garbage from char test
	bne	t1, $eos	# U : did we already hit the terminator?

	/* Character search main loop */
$loop:
	ldq	t0, 8(v0)	# L : load next quadword
	cmovne	t3, v0, t6	# E : save previous comparisons match
	nop			#   : Latency=2, extra map slot (keep nop with cmov)
	nop

	cmovne	t3, t3, t8	# E : Latency=2, extra map slot
	nop			#   : keep with cmovne
	addq	v0, 8, v0	# E :
	xor	t0, a1, t2	# E :

	cmpbge	zero, t0, t1	# E : bits set iff byte == zero
	cmpbge	zero, t2, t3	# E : bits set iff byte == c
	beq	t1, $loop	# U : if we havnt seen a null, loop
	nop

	/* Mask out character matches after terminator */
$eos:
	negq	t1, t4		# E : isolate first null byte match
	and	t1, t4, t4	# E :
	subq	t4, 1, t5	# E : build a mask of the bytes upto...
	or	t4, t5, t4	# E : ... and including the null

	and	t3, t4, t3	# E : mask out char matches after null
	cmovne	t3, t3, t8	# E : save it, if match found Latency=2, extra map slot
	nop			#   : Keep with cmovne
	nop

	cmovne	t3, v0, t6	# E :
	nop			#   : Keep with cmovne
	/* Locate the address of the last matched character */
	ctlz	t8, t2		# U0 : Latency=3 (0x40 for t8=0)
	nop

	cmoveq	t8, 0x3f, t2	# E : Compensate for case when no match is seen
	nop			# E : hide the cmov latency (2) behind ctlz latency
	lda	t5, 0x3f($31)	# E :
	subq	t5, t2, t5	# E : Normalize leading zero count

	addq	t6, t5, v0	# E : and add to quadword address
	ret			# L0 : Latency=3
	nop
	nop

END(strrchr)

weak_alias (strrchr, rindex)
libc_hidden_builtin_def (strrchr)