[mirror_ubuntu-jammy-kernel.git] / arch / arm64 / lib / strcmp.S

/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * Copyright (C) 2013 ARM Ltd.
 * Copyright (C) 2013 Linaro.
 *
 * This code is based on glibc cortex strings work originally authored by Linaro
 * be found @
 *
 * http://bazaar.launchpad.net/~linaro-toolchain-dev/cortex-strings/trunk/
 * files/head:/src/aarch64/
 */

#include <linux/linkage.h>
#include <asm/assembler.h>

/*
 * compare two strings
 *
 * Parameters:
 *	x0 - const string 1 pointer
 *    x1 - const string 2 pointer
 * Returns:
 * x0 - an integer less than, equal to, or greater than zero
 * if  s1  is  found, respectively, to be less than, to match,
 * or be greater than s2.
 */

#define REP8_01 0x0101010101010101
#define REP8_7f 0x7f7f7f7f7f7f7f7f
#define REP8_80 0x8080808080808080

/* Parameters and result.  */
src1		.req	x0
src2		.req	x1
result		.req	x0

/* Internal variables.  */
data1		.req	x2
data1w		.req	w2
data2		.req	x3
data2w		.req	w3
has_nul		.req	x4
diff		.req	x5
syndrome	.req	x6
tmp1		.req	x7
tmp2		.req	x8
tmp3		.req	x9
zeroones	.req	x10
pos		.req	x11

WEAK(strcmp)
	eor	tmp1, src1, src2
	mov	zeroones, #REP8_01
	tst	tmp1, #7
	b.ne	.Lmisaligned8
	ands	tmp1, src1, #7
	b.ne	.Lmutual_align

	/*
	* NUL detection works on the principle that (X - 1) & (~X) & 0x80
	* (=> (X - 1) & ~(X | 0x7f)) is non-zero iff a byte is zero, and
	* can be done in parallel across the entire word.
	*/
.Lloop_aligned:
	ldr	data1, [src1], #8
	ldr	data2, [src2], #8
.Lstart_realigned:
	sub	tmp1, data1, zeroones
	orr	tmp2, data1, #REP8_7f
	eor	diff, data1, data2	/* Non-zero if differences found.  */
	bic	has_nul, tmp1, tmp2	/* Non-zero if NUL terminator.  */
	orr	syndrome, diff, has_nul
	cbz	syndrome, .Lloop_aligned
	b	.Lcal_cmpresult

.Lmutual_align:
	/*
	* Sources are mutually aligned, but are not currently at an
	* alignment boundary.  Round down the addresses and then mask off
	* the bytes that preceed the start point.
	*/
	bic	src1, src1, #7
	bic	src2, src2, #7
	lsl	tmp1, tmp1, #3		/* Bytes beyond alignment -> bits.  */
	ldr	data1, [src1], #8
	neg	tmp1, tmp1		/* Bits to alignment -64.  */
	ldr	data2, [src2], #8
	mov	tmp2, #~0
	/* Big-endian.  Early bytes are at MSB.  */
CPU_BE( lsl	tmp2, tmp2, tmp1 )	/* Shift (tmp1 & 63).  */
	/* Little-endian.  Early bytes are at LSB.  */
CPU_LE( lsr	tmp2, tmp2, tmp1 )	/* Shift (tmp1 & 63).  */

	orr	data1, data1, tmp2
	orr	data2, data2, tmp2
	b	.Lstart_realigned

.Lmisaligned8:
	/*
	* Get the align offset length to compare per byte first.
	* After this process, one string's address will be aligned.
	*/
	and	tmp1, src1, #7
	neg	tmp1, tmp1
	add	tmp1, tmp1, #8
	and	tmp2, src2, #7
	neg	tmp2, tmp2
	add	tmp2, tmp2, #8
	subs	tmp3, tmp1, tmp2
	csel	pos, tmp1, tmp2, hi /*Choose the maximum. */
.Ltinycmp:
	ldrb	data1w, [src1], #1
	ldrb	data2w, [src2], #1
	subs	pos, pos, #1
	ccmp	data1w, #1, #0, ne  /* NZCV = 0b0000.  */
	ccmp	data1w, data2w, #0, cs  /* NZCV = 0b0000.  */
	b.eq	.Ltinycmp
	cbnz	pos, 1f /*find the null or unequal...*/
	cmp	data1w, #1
	ccmp	data1w, data2w, #0, cs
	b.eq	.Lstart_align /*the last bytes are equal....*/
1:
	sub	result, data1, data2
	ret

.Lstart_align:
	ands	xzr, src1, #7
	b.eq	.Lrecal_offset
	/*process more leading bytes to make str1 aligned...*/
	add	src1, src1, tmp3
	add	src2, src2, tmp3
	/*load 8 bytes from aligned str1 and non-aligned str2..*/
	ldr	data1, [src1], #8
	ldr	data2, [src2], #8

	sub	tmp1, data1, zeroones
	orr	tmp2, data1, #REP8_7f
	bic	has_nul, tmp1, tmp2
	eor	diff, data1, data2 /* Non-zero if differences found.  */
	orr	syndrome, diff, has_nul
	cbnz	syndrome, .Lcal_cmpresult
	/*How far is the current str2 from the alignment boundary...*/
	and	tmp3, tmp3, #7
.Lrecal_offset:
	neg	pos, tmp3
.Lloopcmp_proc:
	/*
	* Divide the eight bytes into two parts. First,backwards the src2
	* to an alignment boundary,load eight bytes from the SRC2 alignment
	* boundary,then compare with the relative bytes from SRC1.
	* If all 8 bytes are equal,then start the second part's comparison.
	* Otherwise finish the comparison.
	* This special handle can garantee all the accesses are in the
	* thread/task space in avoid to overrange access.
	*/
	ldr	data1, [src1,pos]
	ldr	data2, [src2,pos]
	sub	tmp1, data1, zeroones
	orr	tmp2, data1, #REP8_7f
	bic	has_nul, tmp1, tmp2
	eor	diff, data1, data2  /* Non-zero if differences found.  */
	orr	syndrome, diff, has_nul
	cbnz	syndrome, .Lcal_cmpresult

	/*The second part process*/
	ldr	data1, [src1], #8
	ldr	data2, [src2], #8
	sub	tmp1, data1, zeroones
	orr	tmp2, data1, #REP8_7f
	bic	has_nul, tmp1, tmp2
	eor	diff, data1, data2  /* Non-zero if differences found.  */
	orr	syndrome, diff, has_nul
	cbz	syndrome, .Lloopcmp_proc

.Lcal_cmpresult:
	/*
	* reversed the byte-order as big-endian,then CLZ can find the most
	* significant zero bits.
	*/
CPU_LE( rev	syndrome, syndrome )
CPU_LE( rev	data1, data1 )
CPU_LE( rev	data2, data2 )

	/*
	* For big-endian we cannot use the trick with the syndrome value
	* as carry-propagation can corrupt the upper bits if the trailing
	* bytes in the string contain 0x01.
	* However, if there is no NUL byte in the dword, we can generate
	* the result directly.  We ca not just subtract the bytes as the
	* MSB might be significant.
	*/
CPU_BE( cbnz	has_nul, 1f )
CPU_BE( cmp	data1, data2 )
CPU_BE( cset	result, ne )
CPU_BE( cneg	result, result, lo )
CPU_BE( ret )
CPU_BE( 1: )
	/*Re-compute the NUL-byte detection, using a byte-reversed value. */
CPU_BE(	rev	tmp3, data1 )
CPU_BE(	sub	tmp1, tmp3, zeroones )
CPU_BE(	orr	tmp2, tmp3, #REP8_7f )
CPU_BE(	bic	has_nul, tmp1, tmp2 )
CPU_BE(	rev	has_nul, has_nul )
CPU_BE(	orr	syndrome, diff, has_nul )

	clz	pos, syndrome
	/*
	* The MS-non-zero bit of the syndrome marks either the first bit
	* that is different, or the top bit of the first zero byte.
	* Shifting left now will bring the critical information into the
	* top bits.
	*/
	lsl	data1, data1, pos
	lsl	data2, data2, pos
	/*
	* But we need to zero-extend (char is unsigned) the value and then
	* perform a signed 32-bit subtraction.
	*/
	lsr	data1, data1, #56
	sub	result, data1, data2, lsr #56
	ret
ENDPIPROC(strcmp)
EXPORT_SYMBOL_NOKASAN(strcmp)
Commit	Line	Data
caab277b	1	/* SPDX-License-Identifier: GPL-2.0-only */
192c4d90	2	/*
	3	* Copyright (C) 2013 ARM Ltd.
	4	* Copyright (C) 2013 Linaro.
	5	*
	6	* This code is based on glibc cortex strings work originally authored by Linaro
192c4d90	7	* be found @
	8	*
	9	* http://bazaar.launchpad.net/~linaro-toolchain-dev/cortex-strings/trunk/
	10	* files/head:/src/aarch64/
192c4d90	11	*/
	12
	13	#include <linux/linkage.h>
	14	#include <asm/assembler.h>
	15
	16	/*
	17	* compare two strings
	18	*
	19	* Parameters:
	20	* x0 - const string 1 pointer
	21	* x1 - const string 2 pointer
	22	* Returns:
	23	* x0 - an integer less than, equal to, or greater than zero
	24	* if s1 is found, respectively, to be less than, to match,
	25	* or be greater than s2.
	26	*/
	27
	28	#define REP8_01 0x0101010101010101
	29	#define REP8_7f 0x7f7f7f7f7f7f7f7f
	30	#define REP8_80 0x8080808080808080
	31
	32	/* Parameters and result. */
	33	src1 .req x0
	34	src2 .req x1
	35	result .req x0
	36
	37	/* Internal variables. */
	38	data1 .req x2
	39	data1w .req w2
	40	data2 .req x3
	41	data2w .req w3
	42	has_nul .req x4
	43	diff .req x5
	44	syndrome .req x6
	45	tmp1 .req x7
	46	tmp2 .req x8
	47	tmp3 .req x9
	48	zeroones .req x10
	49	pos .req x11
	50
19a2ca0f	51	WEAK(strcmp)
192c4d90	52	eor tmp1, src1, src2
	53	mov zeroones, #REP8_01
	54	tst tmp1, #7
	55	b.ne .Lmisaligned8
	56	ands tmp1, src1, #7
	57	b.ne .Lmutual_align
	58
	59	/*
	60	* NUL detection works on the principle that (X - 1) & (~X) & 0x80
	61	* (=> (X - 1) & ~(X \| 0x7f)) is non-zero iff a byte is zero, and
	62	* can be done in parallel across the entire word.
	63	*/
	64	.Lloop_aligned:
	65	ldr data1, [src1], #8
	66	ldr data2, [src2], #8
	67	.Lstart_realigned:
	68	sub tmp1, data1, zeroones
	69	orr tmp2, data1, #REP8_7f
	70	eor diff, data1, data2 /* Non-zero if differences found. */
	71	bic has_nul, tmp1, tmp2 /* Non-zero if NUL terminator. */
	72	orr syndrome, diff, has_nul
	73	cbz syndrome, .Lloop_aligned
	74	b .Lcal_cmpresult
	75
	76	.Lmutual_align:
	77	/*
	78	* Sources are mutually aligned, but are not currently at an
	79	* alignment boundary. Round down the addresses and then mask off
	80	* the bytes that preceed the start point.
	81	*/
	82	bic src1, src1, #7
	83	bic src2, src2, #7
	84	lsl tmp1, tmp1, #3 /* Bytes beyond alignment -> bits. */
	85	ldr data1, [src1], #8
	86	neg tmp1, tmp1 /* Bits to alignment -64. */
	87	ldr data2, [src2], #8
	88	mov tmp2, #~0
	89	/* Big-endian. Early bytes are at MSB. */
	90	CPU_BE( lsl tmp2, tmp2, tmp1 ) /* Shift (tmp1 & 63). */
	91	/* Little-endian. Early bytes are at LSB. */
	92	CPU_LE( lsr tmp2, tmp2, tmp1 ) /* Shift (tmp1 & 63). */
	93
	94	orr data1, data1, tmp2
	95	orr data2, data2, tmp2
	96	b .Lstart_realigned
	97
	98	.Lmisaligned8:
	99	/*
	100	* Get the align offset length to compare per byte first.
	101	* After this process, one string's address will be aligned.
	102	*/
	103	and tmp1, src1, #7
	104	neg tmp1, tmp1
	105	add tmp1, tmp1, #8
	106	and tmp2, src2, #7
	107	neg tmp2, tmp2
	108	add tmp2, tmp2, #8
	109	subs tmp3, tmp1, tmp2
	110	csel pos, tmp1, tmp2, hi /Choose the maximum. /
	111	.Ltinycmp:
	112	ldrb data1w, [src1], #1
	113	ldrb data2w, [src2], #1
	114	subs pos, pos, #1
	115	ccmp data1w, #1, #0, ne /* NZCV = 0b0000. */
116	ccmp data1w, data2w, #0, cs /* NZCV = 0b0000. */
117	b.eq .Ltinycmp
118	cbnz pos, 1f /find the null or unequal.../
119	cmp data1w, #1
120	ccmp data1w, data2w, #0, cs
121	b.eq .Lstart_align /the last bytes are equal..../
122	1:
123	sub result, data1, data2
124	ret
125
126	.Lstart_align:
127	ands xzr, src1, #7
128	b.eq .Lrecal_offset
129	/process more leading bytes to make str1 aligned.../
130	add src1, src1, tmp3
131	add src2, src2, tmp3
132	/load 8 bytes from aligned str1 and non-aligned str2../
133	ldr data1, [src1], #8
134	ldr data2, [src2], #8
135
136	sub tmp1, data1, zeroones
137	orr tmp2, data1, #REP8_7f
138	bic has_nul, tmp1, tmp2
139	eor diff, data1, data2 /* Non-zero if differences found. */
140	orr syndrome, diff, has_nul
141	cbnz syndrome, .Lcal_cmpresult
142	/How far is the current str2 from the alignment boundary.../
143	and tmp3, tmp3, #7
144	.Lrecal_offset:
145	neg pos, tmp3
146	.Lloopcmp_proc:
147	/*
148	* Divide the eight bytes into two parts. First,backwards the src2
149	* to an alignment boundary,load eight bytes from the SRC2 alignment
150	* boundary,then compare with the relative bytes from SRC1.
151	* If all 8 bytes are equal,then start the second part's comparison.
152	* Otherwise finish the comparison.
153	* This special handle can garantee all the accesses are in the
154	* thread/task space in avoid to overrange access.
155	*/
156	ldr data1, [src1,pos]
157	ldr data2, [src2,pos]
158	sub tmp1, data1, zeroones
159	orr tmp2, data1, #REP8_7f
160	bic has_nul, tmp1, tmp2
161	eor diff, data1, data2 /* Non-zero if differences found. */
162	orr syndrome, diff, has_nul
163	cbnz syndrome, .Lcal_cmpresult
164
165	/The second part process/
166	ldr data1, [src1], #8
167	ldr data2, [src2], #8
168	sub tmp1, data1, zeroones
169	orr tmp2, data1, #REP8_7f
170	bic has_nul, tmp1, tmp2
171	eor diff, data1, data2 /* Non-zero if differences found. */
172	orr syndrome, diff, has_nul
173	cbz syndrome, .Lloopcmp_proc
174
175	.Lcal_cmpresult:
176	/*
177	* reversed the byte-order as big-endian,then CLZ can find the most
178	* significant zero bits.
179	*/
180	CPU_LE( rev syndrome, syndrome )
181	CPU_LE( rev data1, data1 )
182	CPU_LE( rev data2, data2 )
183
184	/*
185	* For big-endian we cannot use the trick with the syndrome value
186	* as carry-propagation can corrupt the upper bits if the trailing
187	* bytes in the string contain 0x01.
188	* However, if there is no NUL byte in the dword, we can generate
189	* the result directly. We ca not just subtract the bytes as the
190	* MSB might be significant.
191	*/
192	CPU_BE( cbnz has_nul, 1f )
193	CPU_BE( cmp data1, data2 )
194	CPU_BE( cset result, ne )
195	CPU_BE( cneg result, result, lo )
196	CPU_BE( ret )
197	CPU_BE( 1: )
198	/Re-compute the NUL-byte detection, using a byte-reversed value. /
199	CPU_BE( rev tmp3, data1 )
200	CPU_BE( sub tmp1, tmp3, zeroones )
201	CPU_BE( orr tmp2, tmp3, #REP8_7f )
202	CPU_BE( bic has_nul, tmp1, tmp2 )
203	CPU_BE( rev has_nul, has_nul )
204	CPU_BE( orr syndrome, diff, has_nul )
205
206	clz pos, syndrome
207	/*
208	* The MS-non-zero bit of the syndrome marks either the first bit
209	* that is different, or the top bit of the first zero byte.
210	* Shifting left now will bring the critical information into the
211	* top bits.
212	*/
213	lsl data1, data1, pos
214	lsl data2, data2, pos
215	/*
216	* But we need to zero-extend (char is unsigned) the value and then
217	* perform a signed 32-bit subtraction.
218	*/
219	lsr data1, data1, #56
220	sub result, data1, data2, lsr #56
221	ret
20791846	222	ENDPIPROC(strcmp)
ac0e8c72	223	EXPORT_SYMBOL_NOKASAN(strcmp)