[mirror_ubuntu-bionic-kernel.git] / arch / alpha / lib / stxcpy.S

/* SPDX-License-Identifier: GPL-2.0 */
/*
 * arch/alpha/lib/stxcpy.S
 * Contributed by Richard Henderson (rth@tamu.edu)
 *
 * Copy a null-terminated string from SRC to DST.
 *
 * This is an internal routine used by strcpy, stpcpy, and strcat.
 * As such, it uses special linkage conventions to make implementation
 * of these public functions more efficient.
 *
 * On input:
 *	t9 = return address
 *	a0 = DST
 *	a1 = SRC
 *
 * On output:
 *	t12 = bitmask (with one bit set) indicating the last byte written
 *	a0  = unaligned address of the last *word* written
 *
 * Furthermore, v0, a3-a5, t11, and t12 are untouched.
 */

#include <asm/regdef.h>

	.set noat
	.set noreorder

	.text

/* There is a problem with either gdb (as of 4.16) or gas (as of 2.7) that
   doesn't like putting the entry point for a procedure somewhere in the
   middle of the procedure descriptor.  Work around this by putting the
   aligned copy in its own procedure descriptor */

	.ent stxcpy_aligned
	.align 3
stxcpy_aligned:
	.frame sp, 0, t9
	.prologue 0

	/* On entry to this basic block:
	   t0 == the first destination word for masking back in
	   t1 == the first source word.  */

	/* Create the 1st output word and detect 0's in the 1st input word.  */
	lda	t2, -1		# e1    : build a mask against false zero
	mskqh	t2, a1, t2	# e0    :   detection in the src word
	mskqh	t1, a1, t3	# e0    :
	ornot	t1, t2, t2	# .. e1 :
	mskql	t0, a1, t0	# e0    : assemble the first output word
	cmpbge	zero, t2, t8	# .. e1 : bits set iff null found
	or	t0, t3, t1	# e0    :
	bne	t8, $a_eos	# .. e1 :

	/* On entry to this basic block:
	   t0 == the first destination word for masking back in
	   t1 == a source word not containing a null.  */

$a_loop:
	stq_u	t1, 0(a0)	# e0    :
	addq	a0, 8, a0	# .. e1 :
	ldq_u	t1, 0(a1)	# e0    :
	addq	a1, 8, a1	# .. e1 :
	cmpbge	zero, t1, t8	# e0 (stall)
	beq	t8, $a_loop	# .. e1 (zdb)

	/* Take care of the final (partial) word store.
	   On entry to this basic block we have:
	   t1 == the source word containing the null
	   t8 == the cmpbge mask that found it.  */
$a_eos:
	negq	t8, t6		# e0    : find low bit set
	and	t8, t6, t12	# e1 (stall)

	/* For the sake of the cache, don't read a destination word
	   if we're not going to need it.  */
	and	t12, 0x80, t6	# e0    :
	bne	t6, 1f		# .. e1 (zdb)

	/* We're doing a partial word store and so need to combine
	   our source and original destination words.  */
	ldq_u	t0, 0(a0)	# e0    :
	subq	t12, 1, t6	# .. e1 :
	zapnot	t1, t6, t1	# e0    : clear src bytes >= null
	or	t12, t6, t8	# .. e1 :
	zap	t0, t8, t0	# e0    : clear dst bytes <= null
	or	t0, t1, t1	# e1    :

1:	stq_u	t1, 0(a0)	# e0    :
	ret	(t9)		# .. e1 :

	.end stxcpy_aligned

	.align 3
	.ent __stxcpy
	.globl __stxcpy
__stxcpy:
	.frame sp, 0, t9
	.prologue 0

	/* Are source and destination co-aligned?  */
	xor	a0, a1, t0	# e0    :
	unop			#       :
	and	t0, 7, t0	# e0    :
	bne	t0, $unaligned	# .. e1 :

	/* We are co-aligned; take care of a partial first word.  */
	ldq_u	t1, 0(a1)	# e0    : load first src word
	and	a0, 7, t0	# .. e1 : take care not to load a word ...
	addq	a1, 8, a1		# e0    :
	beq	t0, stxcpy_aligned	# .. e1 : ... if we wont need it
	ldq_u	t0, 0(a0)	# e0    :
	br	stxcpy_aligned	# .. e1 :


/* The source and destination are not co-aligned.  Align the destination
   and cope.  We have to be very careful about not reading too much and
   causing a SEGV.  */

	.align 3
$u_head:
	/* We know just enough now to be able to assemble the first
	   full source word.  We can still find a zero at the end of it
	   that prevents us from outputting the whole thing.

	   On entry to this basic block:
	   t0 == the first dest word, for masking back in, if needed else 0
	   t1 == the low bits of the first source word
	   t6 == bytemask that is -1 in dest word bytes */

	ldq_u	t2, 8(a1)	# e0    :
	addq	a1, 8, a1	# .. e1 :

	extql	t1, a1, t1	# e0    :
	extqh	t2, a1, t4	# e0    :
	mskql	t0, a0, t0	# e0    :
	or	t1, t4, t1	# .. e1 :
	mskqh	t1, a0, t1	# e0    :
	or	t0, t1, t1	# e1    :

	or	t1, t6, t6	# e0    :
	cmpbge	zero, t6, t8	# .. e1 :
	lda	t6, -1		# e0    : for masking just below
	bne	t8, $u_final	# .. e1 :

	mskql	t6, a1, t6		# e0    : mask out the bits we have
	or	t6, t2, t2		# e1    :   already extracted before
	cmpbge	zero, t2, t8		# e0    :   testing eos
	bne	t8, $u_late_head_exit	# .. e1 (zdb)

	/* Finally, we've got all the stupid leading edge cases taken care
	   of and we can set up to enter the main loop.  */

	stq_u	t1, 0(a0)	# e0    : store first output word
	addq	a0, 8, a0	# .. e1 :
	extql	t2, a1, t0	# e0    : position ho-bits of lo word
	ldq_u	t2, 8(a1)	# .. e1 : read next high-order source word
	addq	a1, 8, a1	# e0    :
	cmpbge	zero, t2, t8	# .. e1 :
	nop			# e0    :
	bne	t8, $u_eos	# .. e1 :

	/* Unaligned copy main loop.  In order to avoid reading too much,
	   the loop is structured to detect zeros in aligned source words.
	   This has, unfortunately, effectively pulled half of a loop
	   iteration out into the head and half into the tail, but it does
	   prevent nastiness from accumulating in the very thing we want
	   to run as fast as possible.

	   On entry to this basic block:
	   t0 == the shifted high-order bits from the previous source word
	   t2 == the unshifted current source word

	   We further know that t2 does not contain a null terminator.  */

	.align 3
$u_loop:
	extqh	t2, a1, t1	# e0    : extract high bits for current word
	addq	a1, 8, a1	# .. e1 :
	extql	t2, a1, t3	# e0    : extract low bits for next time
	addq	a0, 8, a0	# .. e1 :
	or	t0, t1, t1	# e0    : current dst word now complete
	ldq_u	t2, 0(a1)	# .. e1 : load high word for next time
	stq_u	t1, -8(a0)	# e0    : save the current word
	mov	t3, t0		# .. e1 :
	cmpbge	zero, t2, t8	# e0    : test new word for eos
	beq	t8, $u_loop	# .. e1 :

	/* We've found a zero somewhere in the source word we just read.
	   If it resides in the lower half, we have one (probably partial)
	   word to write out, and if it resides in the upper half, we
	   have one full and one partial word left to write out.

	   On entry to this basic block:
	   t0 == the shifted high-order bits from the previous source word
	   t2 == the unshifted current source word.  */
$u_eos:
	extqh	t2, a1, t1	# e0    :
	or	t0, t1, t1	# e1    : first (partial) source word complete

	cmpbge	zero, t1, t8	# e0    : is the null in this first bit?
	bne	t8, $u_final	# .. e1 (zdb)

$u_late_head_exit:
	stq_u	t1, 0(a0)	# e0    : the null was in the high-order bits
	addq	a0, 8, a0	# .. e1 :
	extql	t2, a1, t1	# e0    :
	cmpbge	zero, t1, t8	# .. e1 :

	/* Take care of a final (probably partial) result word.
	   On entry to this basic block:
	   t1 == assembled source word
	   t8 == cmpbge mask that found the null.  */
$u_final:
	negq	t8, t6		# e0    : isolate low bit set
	and	t6, t8, t12	# e1    :

	and	t12, 0x80, t6	# e0    : avoid dest word load if we can
	bne	t6, 1f		# .. e1 (zdb)

	ldq_u	t0, 0(a0)	# e0    :
	subq	t12, 1, t6	# .. e1 :
	or	t6, t12, t8	# e0    :
	zapnot	t1, t6, t1	# .. e1 : kill source bytes >= null
	zap	t0, t8, t0	# e0    : kill dest bytes <= null
	or	t0, t1, t1	# e1    :

1:	stq_u	t1, 0(a0)	# e0    :
	ret	(t9)		# .. e1 :

	/* Unaligned copy entry point.  */
	.align 3
$unaligned:

	ldq_u	t1, 0(a1)	# e0    : load first source word

	and	a0, 7, t4	# .. e1 : find dest misalignment
	and	a1, 7, t5	# e0    : find src misalignment

	/* Conditionally load the first destination word and a bytemask
	   with 0xff indicating that the destination byte is sacrosanct.  */

	mov	zero, t0	# .. e1 :
	mov	zero, t6	# e0    :
	beq	t4, 1f		# .. e1 :
	ldq_u	t0, 0(a0)	# e0    :
	lda	t6, -1		# .. e1 :
	mskql	t6, a0, t6	# e0    :
1:
	subq	a1, t4, a1	# .. e1 : sub dest misalignment from src addr

	/* If source misalignment is larger than dest misalignment, we need
	   extra startup checks to avoid SEGV.  */

	cmplt	t4, t5, t12	# e0    :
	beq	t12, $u_head	# .. e1 (zdb)

	lda	t2, -1		# e1    : mask out leading garbage in source
	mskqh	t2, t5, t2	# e0    :
	nop			# e0    :
	ornot	t1, t2, t3	# .. e1 :
	cmpbge	zero, t3, t8	# e0    : is there a zero?
	beq	t8, $u_head	# .. e1 (zdb)

	/* At this point we've found a zero in the first partial word of
	   the source.  We need to isolate the valid source data and mask
	   it into the original destination data.  (Incidentally, we know
	   that we'll need at least one byte of that original dest word.) */

	ldq_u	t0, 0(a0)	# e0    :

	negq	t8, t6		# .. e1 : build bitmask of bytes <= zero
	and	t6, t8, t12	# e0    :
	and	a1, 7, t5	# .. e1 :
	subq	t12, 1, t6	# e0    :
	or	t6, t12, t8	# e1    :
	srl	t12, t5, t12	# e0    : adjust final null return value

	zapnot	t2, t8, t2	# .. e1 : prepare source word; mirror changes
	and	t1, t2, t1	# e1    : to source validity mask
	extql	t2, a1, t2	# .. e0 :
	extql	t1, a1, t1	# e0    :

	andnot	t0, t2, t0	# .. e1 : zero place for source to reside
	or	t0, t1, t1	# e1    : and put it there
	stq_u	t1, 0(a0)	# .. e0 :
	ret	(t9)		# e1    :

	.end __stxcpy
Commit	Line	Data
b2441318	1	/* SPDX-License-Identifier: GPL-2.0 */
1da177e4 LT	2	/*
	3	* arch/alpha/lib/stxcpy.S
	4	* Contributed by Richard Henderson (rth@tamu.edu)
	5	*
	6	* Copy a null-terminated string from SRC to DST.
	7	*
	8	* This is an internal routine used by strcpy, stpcpy, and strcat.
	9	* As such, it uses special linkage conventions to make implementation
	10	* of these public functions more efficient.
	11	*
	12	* On input:
	13	* t9 = return address
	14	* a0 = DST
	15	* a1 = SRC
	16	*
	17	* On output:
	18	* t12 = bitmask (with one bit set) indicating the last byte written
	19	* a0 = unaligned address of the last word written
	20	*
	21	* Furthermore, v0, a3-a5, t11, and t12 are untouched.
	22	*/
	23
	24	#include <asm/regdef.h>
	25
	26	.set noat
	27	.set noreorder
	28
	29	.text
	30
	31	/* There is a problem with either gdb (as of 4.16) or gas (as of 2.7) that
	32	doesn't like putting the entry point for a procedure somewhere in the
	33	middle of the procedure descriptor. Work around this by putting the
	34	aligned copy in its own procedure descriptor */
	35
	36	.ent stxcpy_aligned
	37	.align 3
	38	stxcpy_aligned:
	39	.frame sp, 0, t9
	40	.prologue 0
	41
	42	/* On entry to this basic block:
	43	t0 == the first destination word for masking back in
	44	t1 == the first source word. */
	45
	46	/* Create the 1st output word and detect 0's in the 1st input word. */
	47	lda t2, -1 # e1 : build a mask against false zero
	48	mskqh t2, a1, t2 # e0 : detection in the src word
	49	mskqh t1, a1, t3 # e0 :
	50	ornot t1, t2, t2 # .. e1 :
	51	mskql t0, a1, t0 # e0 : assemble the first output word
	52	cmpbge zero, t2, t8 # .. e1 : bits set iff null found
	53	or t0, t3, t1 # e0 :
	54	bne t8, $a_eos # .. e1 :
	55
	56	/* On entry to this basic block:
	57	t0 == the first destination word for masking back in
	58	t1 == a source word not containing a null. */
	59
	60	$a_loop:
	61	stq_u t1, 0(a0) # e0 :
	62	addq a0, 8, a0 # .. e1 :
	63	ldq_u t1, 0(a1) # e0 :
	64	addq a1, 8, a1 # .. e1 :
	65	cmpbge zero, t1, t8 # e0 (stall)
66	beq t8, $a_loop # .. e1 (zdb)
67
68	/* Take care of the final (partial) word store.
69	On entry to this basic block we have:
70	t1 == the source word containing the null
71	t8 == the cmpbge mask that found it. */
72	$a_eos:
73	negq t8, t6 # e0 : find low bit set
74	and t8, t6, t12 # e1 (stall)
75
76	/* For the sake of the cache, don't read a destination word
77	if we're not going to need it. */
78	and t12, 0x80, t6 # e0 :
79	bne t6, 1f # .. e1 (zdb)
80
81	/* We're doing a partial word store and so need to combine
82	our source and original destination words. */
83	ldq_u t0, 0(a0) # e0 :
84	subq t12, 1, t6 # .. e1 :
85	zapnot t1, t6, t1 # e0 : clear src bytes >= null
86	or t12, t6, t8 # .. e1 :
87	zap t0, t8, t0 # e0 : clear dst bytes <= null
88	or t0, t1, t1 # e1 :
89
90	1: stq_u t1, 0(a0) # e0 :
91	ret (t9) # .. e1 :
92
93	.end stxcpy_aligned
94
95	.align 3
96	.ent __stxcpy
97	.globl __stxcpy
98	__stxcpy:
99	.frame sp, 0, t9
100	.prologue 0
101
102	/* Are source and destination co-aligned? */
103	xor a0, a1, t0 # e0 :
104	unop # :
105	and t0, 7, t0 # e0 :
106	bne t0, $unaligned # .. e1 :
107
108	/* We are co-aligned; take care of a partial first word. */
109	ldq_u t1, 0(a1) # e0 : load first src word
110	and a0, 7, t0 # .. e1 : take care not to load a word ...
111	addq a1, 8, a1 # e0 :
112	beq t0, stxcpy_aligned # .. e1 : ... if we wont need it
113	ldq_u t0, 0(a0) # e0 :
114	br stxcpy_aligned # .. e1 :
115
116
117	/* The source and destination are not co-aligned. Align the destination
118	and cope. We have to be very careful about not reading too much and
119	causing a SEGV. */
120
121	.align 3
122	$u_head:
123	/* We know just enough now to be able to assemble the first
124	full source word. We can still find a zero at the end of it
125	that prevents us from outputting the whole thing.
126
127	On entry to this basic block:
128	t0 == the first dest word, for masking back in, if needed else 0
129	t1 == the low bits of the first source word
130	t6 == bytemask that is -1 in dest word bytes */
131
132	ldq_u t2, 8(a1) # e0 :
133	addq a1, 8, a1 # .. e1 :
134
135	extql t1, a1, t1 # e0 :
136	extqh t2, a1, t4 # e0 :
137	mskql t0, a0, t0 # e0 :
138	or t1, t4, t1 # .. e1 :
139	mskqh t1, a0, t1 # e0 :
140	or t0, t1, t1 # e1 :
141
142	or t1, t6, t6 # e0 :
143	cmpbge zero, t6, t8 # .. e1 :
144	lda t6, -1 # e0 : for masking just below
145	bne t8, $u_final # .. e1 :
146
147	mskql t6, a1, t6 # e0 : mask out the bits we have
148	or t6, t2, t2 # e1 : already extracted before
149	cmpbge zero, t2, t8 # e0 : testing eos
150	bne t8, $u_late_head_exit # .. e1 (zdb)
151
152	/* Finally, we've got all the stupid leading edge cases taken care
153	of and we can set up to enter the main loop. */
154
155	stq_u t1, 0(a0) # e0 : store first output word
156	addq a0, 8, a0 # .. e1 :
157	extql t2, a1, t0 # e0 : position ho-bits of lo word
158	ldq_u t2, 8(a1) # .. e1 : read next high-order source word
159	addq a1, 8, a1 # e0 :
160	cmpbge zero, t2, t8 # .. e1 :
161	nop # e0 :
162	bne t8, $u_eos # .. e1 :
163
164	/* Unaligned copy main loop. In order to avoid reading too much,
165	the loop is structured to detect zeros in aligned source words.
166	This has, unfortunately, effectively pulled half of a loop
167	iteration out into the head and half into the tail, but it does
168	prevent nastiness from accumulating in the very thing we want
169	to run as fast as possible.
170
171	On entry to this basic block:
172	t0 == the shifted high-order bits from the previous source word
173	t2 == the unshifted current source word
174
175	We further know that t2 does not contain a null terminator. */
176
177	.align 3
178	$u_loop:
179	extqh t2, a1, t1 # e0 : extract high bits for current word
180	addq a1, 8, a1 # .. e1 :
181	extql t2, a1, t3 # e0 : extract low bits for next time
182	addq a0, 8, a0 # .. e1 :
183	or t0, t1, t1 # e0 : current dst word now complete
184	ldq_u t2, 0(a1) # .. e1 : load high word for next time
185	stq_u t1, -8(a0) # e0 : save the current word
186	mov t3, t0 # .. e1 :
187	cmpbge zero, t2, t8 # e0 : test new word for eos
188	beq t8, $u_loop # .. e1 :
189
190	/* We've found a zero somewhere in the source word we just read.
191	If it resides in the lower half, we have one (probably partial)
192	word to write out, and if it resides in the upper half, we
193	have one full and one partial word left to write out.
194
195	On entry to this basic block:
196	t0 == the shifted high-order bits from the previous source word
197	t2 == the unshifted current source word. */
198	$u_eos:
199	extqh t2, a1, t1 # e0 :
200	or t0, t1, t1 # e1 : first (partial) source word complete
201
202	cmpbge zero, t1, t8 # e0 : is the null in this first bit?
203	bne t8, $u_final # .. e1 (zdb)
204
205	$u_late_head_exit:
206	stq_u t1, 0(a0) # e0 : the null was in the high-order bits
207	addq a0, 8, a0 # .. e1 :
208	extql t2, a1, t1 # e0 :
209	cmpbge zero, t1, t8 # .. e1 :
210
211	/* Take care of a final (probably partial) result word.
212	On entry to this basic block:
213	t1 == assembled source word
214	t8 == cmpbge mask that found the null. */
215	$u_final:
216	negq t8, t6 # e0 : isolate low bit set
217	and t6, t8, t12 # e1 :
218
219	and t12, 0x80, t6 # e0 : avoid dest word load if we can
220	bne t6, 1f # .. e1 (zdb)
221
222	ldq_u t0, 0(a0) # e0 :
223	subq t12, 1, t6 # .. e1 :
224	or t6, t12, t8 # e0 :
225	zapnot t1, t6, t1 # .. e1 : kill source bytes >= null
226	zap t0, t8, t0 # e0 : kill dest bytes <= null
227	or t0, t1, t1 # e1 :
228
229	1: stq_u t1, 0(a0) # e0 :
230	ret (t9) # .. e1 :
231
232	/* Unaligned copy entry point. */
233	.align 3
234	$unaligned:
235
236	ldq_u t1, 0(a1) # e0 : load first source word
237
238	and a0, 7, t4 # .. e1 : find dest misalignment
239	and a1, 7, t5 # e0 : find src misalignment
240
241	/* Conditionally load the first destination word and a bytemask
242	with 0xff indicating that the destination byte is sacrosanct. */
243
244	mov zero, t0 # .. e1 :
245	mov zero, t6 # e0 :
246	beq t4, 1f # .. e1 :
247	ldq_u t0, 0(a0) # e0 :
248	lda t6, -1 # .. e1 :
249	mskql t6, a0, t6 # e0 :
250	1:
251	subq a1, t4, a1 # .. e1 : sub dest misalignment from src addr
252
253	/* If source misalignment is larger than dest misalignment, we need
254	extra startup checks to avoid SEGV. */
255
256	cmplt t4, t5, t12 # e0 :
257	beq t12, $u_head # .. e1 (zdb)
258
259	lda t2, -1 # e1 : mask out leading garbage in source
260	mskqh t2, t5, t2 # e0 :
261	nop # e0 :
262	ornot t1, t2, t3 # .. e1 :
263	cmpbge zero, t3, t8 # e0 : is there a zero?
264	beq t8, $u_head # .. e1 (zdb)
265
266	/* At this point we've found a zero in the first partial word of
267	the source. We need to isolate the valid source data and mask
268	it into the original destination data. (Incidentally, we know
269	that we'll need at least one byte of that original dest word.) */
270
271	ldq_u t0, 0(a0) # e0 :
272
273	negq t8, t6 # .. e1 : build bitmask of bytes <= zero
274	and t6, t8, t12 # e0 :
275	and a1, 7, t5 # .. e1 :
276	subq t12, 1, t6 # e0 :
277	or t6, t12, t8 # e1 :
278	srl t12, t5, t12 # e0 : adjust final null return value
279
280	zapnot t2, t8, t2 # .. e1 : prepare source word; mirror changes
281	and t1, t2, t1 # e1 : to source validity mask
282	extql t2, a1, t2 # .. e0 :
283	extql t1, a1, t1 # e0 :
284
285	andnot t0, t2, t0 # .. e1 : zero place for source to reside
286	or t0, t1, t1 # e1 : and put it there
287	stq_u t1, 0(a0) # .. e0 :
288	ret (t9) # e1 :
289
290	.end __stxcpy