[thirdparty/glibc.git] / sysdeps / powerpc / powerpc64 / power7 / strnlen.S

/* Optimized strnlen implementation for PowerPC64/POWER7 using cmpb insn.
   Copyright (C) 2010 Free Software Foundation, Inc.
   Contributed by Luis Machado <luisgpm@br.ibm.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, write to the Free
   Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA
   02110-1301 USA.  */

#include <sysdep.h>
#include <bp-sym.h>
#include <bp-asm.h>

/* int [r3] strnlen (char *s [r3], int size [r4])  */
	.machine  power7
ENTRY (BP_SYM (__strnlen))
	CALL_MCOUNT 2
	dcbt	0,r3
	clrrdi  r8,r3,3
	add	r7,r3,r4      /* Calculate the last acceptable address.  */
	cmpldi	r4,32
	li	r0,0	      /* Doubleword with null chars.  */
	/* If we have less than 33 bytes to search, skip to a faster code.  */
	ble	L(small_range)

	cmpld	cr7,r3,r7    /* Is the address equal or less than r3?  If
				it's equal or less, it means size is either 0
				or a negative number.  */
	ble	cr7,L(proceed)

	li	r7,-1	      /* Make r11 the biggest if r4 <= 0.  */
L(proceed):
	rlwinm	r6,r3,3,26,28 /* Calculate padding.  */
	ld	r12,0(r8)     /* Load doubleword from memory.  */
	cmpb	r10,r12,r0    /* Check for null bytes in DWORD1.  */
	sld	r10,r10,r6
	srd	r10,r10,r6
	cmpldi	cr7,r10,0     /* If r10 == 0, no null's have been found.  */
	bne	cr7,L(done)

	/* Are we done already?  */
	addi	r9,r8,8
	cmpld	cr6,r9,r7
	bge	cr6,L(end_max)

	mtcrf   0x01,r8
	/* Are we now aligned to a quadword boundary?  If so, skip to
	   the main loop.  Otherwise, go through the alignment code.  */

	bt	28,L(loop_setup)

	/* Handle DWORD2 of pair.  */
	ldu	r12,8(r8)
	cmpb	r10,r12,r0
	cmpldi	cr7,r10,0
	bne	cr7,L(done)

	/* Are we done already?  */
	addi	r9,r8,8
	cmpld	cr6,r9,r7
	bge	cr6,L(end_max)

L(loop_setup):
	sub	r5,r7,r9
	srdi	r6,r5,4	      /* Number of loop iterations.  */
	mtctr	r6	      /* Setup the counter.  */
	b	L(loop)
	/* Main loop to look for the null byte backwards in the string.  Since
	   it's a small loop (< 8 instructions), align it to 32-bytes.  */
	.p2align  5
L(loop):
	/* Load two doublewords, compare and merge in a
	   single register for speed.  This is an attempt
	   to speed up the null-checking process for bigger strings.  */

	ld	r12,8(r8)
	ldu	r11,16(r8)
	cmpb	r10,r12,r0
	cmpb	r9,r11,r0
	or	r5,r9,r10     /* Merge everything in one doubleword.  */
	cmpldi	cr7,r5,0
	bne	cr7,L(found)
	bdnz	L(loop)
	/* We're here because the counter reached 0, and that means we
	   didn't have any matches for null in the whole range.  Just return
	   the original size.  */
	addi	r9,r8,8
	cmpld	cr6,r9,r7
	blt	cr6,L(loop_small)

L(end_max):
	sub	r3,r7,r3
	blr

	/* OK, one (or both) of the doublewords contains a null byte.  Check
	   the first doubleword and decrement the address in case the first
	   doubleword really contains a null byte.  */
	.align	4
L(found):
	cmpldi	cr6,r10,0
	addi	r8,r8,-8
	bne	cr6,L(done)

	/* The null byte must be in the second doubleword.  Adjust the address
	   again and move the result of cmpb to r10 so we can calculate the
	   length.  */

	mr	r10,r9
	addi	r8,r8,8

	/* r10 has the output of the cmpb instruction, that is, it contains
	   0xff in the same position as the null byte in the original
	   doubleword from the string.  Use that to calculate the length.
	   We need to make sure the null char is *before* the start of the
	   range (since we're going backwards).  */
L(done):
	cntlzd	r0,r10	      /* Count leading zeroes before the match.  */
	srdi	r0,r0,3	      /* Convert leading zeroes to bytes.  */
	add	r9,r8,r0
	sub	r6,r9,r3      /* Length until the match.  */
	cmpld	r9,r7
	bgt	L(end_max)
	mr	r3,r6
	blr

	.align	4
L(zero):
	li	r3,0
	blr

/* Deals with size <= 32.  */
	.align	4
L(small_range):
	cmpldi	r4,0
	beq	L(zero)

	rlwinm	r6,r3,3,26,28 /* Calculate padding.  */
	ld	r12,0(r8)     /* Load word from memory.  */
	cmpb	r10,r12,r0    /* Check for null bytes in DWORD1.  */
	sld	r10,r10,r6
	srd	r10,r10,r6
	cmpldi	cr7,r10,0
	bne	cr7,L(done)

	addi    r9,r8,8
	cmpld	r9,r7
	bge	L(end_max)
	b	L(loop_small)

	.p2align  5
L(loop_small):
	ldu	r12,8(r8)
	cmpb	r10,r12,r0
	addi	r9,r8,8
	cmpldi	cr6,r10,0
	bne	cr6,L(done)
	cmpld	r9,r7
	bge	L(end_max)
	b	L(loop_small)
END (BP_SYM (__strnlen))
weak_alias (BP_SYM (__strnlen), BP_SYM(strnlen))
libc_hidden_builtin_def (strnlen)
Commit	Line	Data
fe2f79db LM	1	/* Optimized strnlen implementation for PowerPC64/POWER7 using cmpb insn.
	2	Copyright (C) 2010 Free Software Foundation, Inc.
	3	Contributed by Luis Machado <luisgpm@br.ibm.com>.
	4	This file is part of the GNU C Library.
	5
	6	The GNU C Library is free software; you can redistribute it and/or
	7	modify it under the terms of the GNU Lesser General Public
	8	License as published by the Free Software Foundation; either
	9	version 2.1 of the License, or (at your option) any later version.
	10
	11	The GNU C Library is distributed in the hope that it will be useful,
	12	but WITHOUT ANY WARRANTY; without even the implied warranty of
	13	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	14	Lesser General Public License for more details.
	15
	16	You should have received a copy of the GNU Lesser General Public
	17	License along with the GNU C Library; if not, write to the Free
	18	Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA
	19	02110-1301 USA. */
	20
	21	#include <sysdep.h>
	22	#include <bp-sym.h>
	23	#include <bp-asm.h>
	24
	25	/* int [r3] strnlen (char s [r3], int size [r4]) /
	26	.machine power7
	27	ENTRY (BP_SYM (__strnlen))
	28	CALL_MCOUNT 2
	29	dcbt 0,r3
	30	clrrdi r8,r3,3
	31	add r7,r3,r4 /* Calculate the last acceptable address. */
	32	cmpldi r4,32
	33	li r0,0 /* Doubleword with null chars. */
	34	/* If we have less than 33 bytes to search, skip to a faster code. */
	35	ble L(small_range)
	36
	37	cmpld cr7,r3,r7 /* Is the address equal or less than r3? If
	38	it's equal or less, it means size is either 0
	39	or a negative number. */
	40	ble cr7,L(proceed)
	41
	42	li r7,-1 /* Make r11 the biggest if r4 <= 0. */
	43	L(proceed):
	44	rlwinm r6,r3,3,26,28 /* Calculate padding. */
	45	ld r12,0(r8) /* Load doubleword from memory. */
	46	cmpb r10,r12,r0 /* Check for null bytes in DWORD1. */
	47	sld r10,r10,r6
	48	srd r10,r10,r6
	49	cmpldi cr7,r10,0 /* If r10 == 0, no null's have been found. */
	50	bne cr7,L(done)
	51
	52	/* Are we done already? */
	53	addi r9,r8,8
	54	cmpld cr6,r9,r7
	55	bge cr6,L(end_max)
	56
	57	mtcrf 0x01,r8
	58	/* Are we now aligned to a quadword boundary? If so, skip to
	59	the main loop. Otherwise, go through the alignment code. */
	60
	61	bt 28,L(loop_setup)
	62
	63	/* Handle DWORD2 of pair. */
	64	ldu r12,8(r8)
65	cmpb r10,r12,r0
66	cmpldi cr7,r10,0
67	bne cr7,L(done)
68
69	/* Are we done already? */
70	addi r9,r8,8
71	cmpld cr6,r9,r7
72	bge cr6,L(end_max)
73
74	L(loop_setup):
75	sub r5,r7,r9
76	srdi r6,r5,4 /* Number of loop iterations. */
77	mtctr r6 /* Setup the counter. */
78	b L(loop)
79	/* Main loop to look for the null byte backwards in the string. Since
80	it's a small loop (< 8 instructions), align it to 32-bytes. */
81	.p2align 5
82	L(loop):
83	/* Load two doublewords, compare and merge in a
84	single register for speed. This is an attempt
85	to speed up the null-checking process for bigger strings. */
86
87	ld r12,8(r8)
88	ldu r11,16(r8)
89	cmpb r10,r12,r0
90	cmpb r9,r11,r0
91	or r5,r9,r10 /* Merge everything in one doubleword. */
92	cmpldi cr7,r5,0
93	bne cr7,L(found)
94	bdnz L(loop)
95	/* We're here because the counter reached 0, and that means we
96	didn't have any matches for null in the whole range. Just return
97	the original size. */
98	addi r9,r8,8
99	cmpld cr6,r9,r7
100	blt cr6,L(loop_small)
101
102	L(end_max):
103	sub r3,r7,r3
104	blr
105
106	/* OK, one (or both) of the doublewords contains a null byte. Check
107	the first doubleword and decrement the address in case the first
108	doubleword really contains a null byte. */
109	.align 4
110	L(found):
111	cmpldi cr6,r10,0
112	addi r8,r8,-8
113	bne cr6,L(done)
114
115	/* The null byte must be in the second doubleword. Adjust the address
116	again and move the result of cmpb to r10 so we can calculate the
117	length. */
118
119	mr r10,r9
120	addi r8,r8,8
121
122	/* r10 has the output of the cmpb instruction, that is, it contains
123	0xff in the same position as the null byte in the original
124	doubleword from the string. Use that to calculate the length.
125	We need to make sure the null char is before the start of the
126	range (since we're going backwards). */
127	L(done):
128	cntlzd r0,r10 /* Count leading zeroes before the match. */
129	srdi r0,r0,3 /* Convert leading zeroes to bytes. */
130	add r9,r8,r0
131	sub r6,r9,r3 /* Length until the match. */
132	cmpld r9,r7
133	bgt L(end_max)
134	mr r3,r6
135	blr
136
137	.align 4
138	L(zero):
139	li r3,0
140	blr
141
142	/* Deals with size <= 32. */
143	.align 4
144	L(small_range):
145	cmpldi r4,0
146	beq L(zero)
147
148	rlwinm r6,r3,3,26,28 /* Calculate padding. */
149	ld r12,0(r8) /* Load word from memory. */
150	cmpb r10,r12,r0 /* Check for null bytes in DWORD1. */
151	sld r10,r10,r6
152	srd r10,r10,r6
153	cmpldi cr7,r10,0
154	bne cr7,L(done)
155
156	addi r9,r8,8
157	cmpld r9,r7
158	bge L(end_max)
159	b L(loop_small)
160
161	.p2align 5
162	L(loop_small):
163	ldu r12,8(r8)
164	cmpb r10,r12,r0
165	addi r9,r8,8
166	cmpldi cr6,r10,0
167	bne cr6,L(done)
168	cmpld r9,r7
169	bge L(end_max)
170	b L(loop_small)
171	END (BP_SYM (__strnlen))
172	weak_alias (BP_SYM (__strnlen), BP_SYM(strnlen))
173	libc_hidden_builtin_def (strnlen)