aboutsummaryrefslogtreecommitdiff
path: root/sysdeps/x86_64/multiarch/memcmp-avx2-movbe.S
blob: 2621ec907aedb781fcf0444e831c801f18fa68ba (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
/* memcmp/wmemcmp optimized with AVX2.
   Copyright (C) 2017-2021 Free Software Foundation, Inc.
   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/>.  */

#if IS_IN (libc)

/* memcmp/wmemcmp is implemented as:
   1. Use ymm vector compares when possible. The only case where
      vector compares is not possible for when size < VEC_SIZE
      and loading from either s1 or s2 would cause a page cross.
   2. For size from 2 to 7 bytes on page cross, load as big endian
      with movbe and bswap to avoid branches.
   3. Use xmm vector compare when size >= 4 bytes for memcmp or
      size >= 8 bytes for wmemcmp.
   4. Optimistically compare up to first 4 * VEC_SIZE one at a
      to check for early mismatches. Only do this if its guranteed the
      work is not wasted.
   5. If size is 8 * VEC_SIZE or less, unroll the loop.
   6. Compare 4 * VEC_SIZE at a time with the aligned first memory
      area.
   7. Use 2 vector compares when size is 2 * VEC_SIZE or less.
   8. Use 4 vector compares when size is 4 * VEC_SIZE or less.
   9. Use 8 vector compares when size is 8 * VEC_SIZE or less.  */


# include <sysdep.h>

# ifndef MEMCMP
#  define MEMCMP	__memcmp_avx2_movbe
# endif

# ifdef USE_AS_WMEMCMP
#  define CHAR_SIZE	4
#  define VPCMPEQ	vpcmpeqd
# else
#  define CHAR_SIZE	1
#  define VPCMPEQ	vpcmpeqb
# endif

# ifndef VZEROUPPER
#  define VZEROUPPER	vzeroupper
# endif

# ifndef SECTION
#  define SECTION(p)	p##.avx
# endif

# define VEC_SIZE 32
# define PAGE_SIZE	4096

/* Warning!
           wmemcmp has to use SIGNED comparison for elements.
           memcmp has to use UNSIGNED comparison for elemnts.
*/

	.section SECTION(.text),"ax",@progbits
ENTRY (MEMCMP)
# ifdef USE_AS_WMEMCMP
	shl	$2, %RDX_LP
# elif defined __ILP32__
	/* Clear the upper 32 bits.  */
	movl	%edx, %edx
# endif
	cmp	$VEC_SIZE, %RDX_LP
	jb	L(less_vec)

	/* From VEC to 2 * VEC.  No branch when size == VEC_SIZE.  */
	vmovdqu	(%rsi), %ymm1
	VPCMPEQ	(%rdi), %ymm1, %ymm1
	vpmovmskb %ymm1, %eax
	/* NB: eax must be destination register if going to
	   L(return_vec_[0,2]). For L(return_vec_3 destination register
	   must be ecx.  */
	incl	%eax
	jnz	L(return_vec_0)

	cmpq	$(VEC_SIZE * 2), %rdx
	jbe	L(last_1x_vec)

	/* Check second VEC no matter what.  */
	vmovdqu	VEC_SIZE(%rsi), %ymm2
	VPCMPEQ	VEC_SIZE(%rdi), %ymm2, %ymm2
	vpmovmskb %ymm2, %eax
	/* If all 4 VEC where equal eax will be all 1s so incl will
	   overflow and set zero flag.  */
	incl	%eax
	jnz	L(return_vec_1)

	/* Less than 4 * VEC.  */
	cmpq	$(VEC_SIZE * 4), %rdx
	jbe	L(last_2x_vec)

	/* Check third and fourth VEC no matter what.  */
	vmovdqu	(VEC_SIZE * 2)(%rsi), %ymm3
	VPCMPEQ	(VEC_SIZE * 2)(%rdi), %ymm3, %ymm3
	vpmovmskb %ymm3, %eax
	incl	%eax
	jnz	L(return_vec_2)
	vmovdqu	(VEC_SIZE * 3)(%rsi), %ymm4
	VPCMPEQ	(VEC_SIZE * 3)(%rdi), %ymm4, %ymm4
	vpmovmskb %ymm4, %ecx
	incl	%ecx
	jnz	L(return_vec_3)

	/* Go to 4x VEC loop.  */
	cmpq	$(VEC_SIZE * 8), %rdx
	ja	L(more_8x_vec)

	/* Handle remainder of size = 4 * VEC + 1 to 8 * VEC without any
	   branches.  */

	/* Load first two VEC from s2 before adjusting addresses.  */
	vmovdqu	-(VEC_SIZE * 4)(%rsi, %rdx), %ymm1
	vmovdqu	-(VEC_SIZE * 3)(%rsi, %rdx), %ymm2
	leaq	-(4 * VEC_SIZE)(%rdi, %rdx), %rdi
	leaq	-(4 * VEC_SIZE)(%rsi, %rdx), %rsi

	/* Wait to load from s1 until addressed adjust due to
	   unlamination of microfusion with complex address mode.  */
	VPCMPEQ	(%rdi), %ymm1, %ymm1
	VPCMPEQ	(VEC_SIZE)(%rdi), %ymm2, %ymm2

	vmovdqu	(VEC_SIZE * 2)(%rsi), %ymm3
	VPCMPEQ	(VEC_SIZE * 2)(%rdi), %ymm3, %ymm3
	vmovdqu	(VEC_SIZE * 3)(%rsi), %ymm4
	VPCMPEQ	(VEC_SIZE * 3)(%rdi), %ymm4, %ymm4

	/* Reduce VEC0 - VEC4.  */
	vpand	%ymm1, %ymm2, %ymm5
	vpand	%ymm3, %ymm4, %ymm6
	vpand	%ymm5, %ymm6, %ymm7
	vpmovmskb %ymm7, %ecx
	incl	%ecx
	jnz	L(return_vec_0_1_2_3)
	/* NB: eax must be zero to reach here.  */
	VZEROUPPER_RETURN

	.p2align 4
L(return_vec_0):
	tzcntl	%eax, %eax
# ifdef USE_AS_WMEMCMP
	movl	(%rdi, %rax), %ecx
	xorl	%edx, %edx
	cmpl	(%rsi, %rax), %ecx
	/* NB: no partial register stall here because xorl zero idiom
	   above.  */
	setg	%dl
	leal	-1(%rdx, %rdx), %eax
# else
	movzbl	(%rsi, %rax), %ecx
	movzbl	(%rdi, %rax), %eax
	subl	%ecx, %eax
# endif
L(return_vzeroupper):
	ZERO_UPPER_VEC_REGISTERS_RETURN

	.p2align 4
L(return_vec_1):
	tzcntl	%eax, %eax
# ifdef USE_AS_WMEMCMP
	movl	VEC_SIZE(%rdi, %rax), %ecx
	xorl	%edx, %edx
	cmpl	VEC_SIZE(%rsi, %rax), %ecx
	setg	%dl
	leal	-1(%rdx, %rdx), %eax
# else
	movzbl	VEC_SIZE(%rsi, %rax), %ecx
	movzbl	VEC_SIZE(%rdi, %rax), %eax
	subl	%ecx, %eax
# endif
	VZEROUPPER_RETURN

	.p2align 4
L(return_vec_2):
	tzcntl	%eax, %eax
# ifdef USE_AS_WMEMCMP
	movl	(VEC_SIZE * 2)(%rdi, %rax), %ecx
	xorl	%edx, %edx
	cmpl	(VEC_SIZE * 2)(%rsi, %rax), %ecx
	setg	%dl
	leal	-1(%rdx, %rdx), %eax
# else
	movzbl	(VEC_SIZE * 2)(%rsi, %rax), %ecx
	movzbl	(VEC_SIZE * 2)(%rdi, %rax), %eax
	subl	%ecx, %eax
# endif
	VZEROUPPER_RETURN

	/* NB: p2align 5 here to ensure 4x loop is 32 byte aligned.  */
	.p2align 5
L(8x_return_vec_0_1_2_3):
	/* Returning from L(more_8x_vec) requires restoring rsi.  */
	addq	%rdi, %rsi
L(return_vec_0_1_2_3):
	vpmovmskb %ymm1, %eax
	incl	%eax
	jnz	L(return_vec_0)

	vpmovmskb %ymm2, %eax
	incl	%eax
	jnz	L(return_vec_1)

	vpmovmskb %ymm3, %eax
	incl	%eax
	jnz	L(return_vec_2)
L(return_vec_3):
	tzcntl	%ecx, %ecx
# ifdef USE_AS_WMEMCMP
	movl	(VEC_SIZE * 3)(%rdi, %rcx), %eax
	xorl	%edx, %edx
	cmpl	(VEC_SIZE * 3)(%rsi, %rcx), %eax
	setg	%dl
	leal	-1(%rdx, %rdx), %eax
# else
	movzbl	(VEC_SIZE * 3)(%rdi, %rcx), %eax
	movzbl	(VEC_SIZE * 3)(%rsi, %rcx), %ecx
	subl	%ecx, %eax
# endif
	VZEROUPPER_RETURN

	.p2align 4
L(more_8x_vec):
	/* Set end of s1 in rdx.  */
	leaq	-(VEC_SIZE * 4)(%rdi, %rdx), %rdx
	/* rsi stores s2 - s1. This allows loop to only update one
	   pointer.  */
	subq	%rdi, %rsi
	/* Align s1 pointer.  */
	andq	$-VEC_SIZE, %rdi
	/* Adjust because first 4x vec where check already.  */
	subq	$-(VEC_SIZE * 4), %rdi
	.p2align 4
L(loop_4x_vec):
	/* rsi has s2 - s1 so get correct address by adding s1 (in rdi).
	 */
	vmovdqu	(%rsi, %rdi), %ymm1
	VPCMPEQ	(%rdi), %ymm1, %ymm1

	vmovdqu	VEC_SIZE(%rsi, %rdi), %ymm2
	VPCMPEQ	VEC_SIZE(%rdi), %ymm2, %ymm2

	vmovdqu	(VEC_SIZE * 2)(%rsi, %rdi), %ymm3
	VPCMPEQ	(VEC_SIZE * 2)(%rdi), %ymm3, %ymm3

	vmovdqu	(VEC_SIZE * 3)(%rsi, %rdi), %ymm4
	VPCMPEQ	(VEC_SIZE * 3)(%rdi), %ymm4, %ymm4

	vpand	%ymm1, %ymm2, %ymm5
	vpand	%ymm3, %ymm4, %ymm6
	vpand	%ymm5, %ymm6, %ymm7
	vpmovmskb %ymm7, %ecx
	incl	%ecx
	jnz	L(8x_return_vec_0_1_2_3)
	subq	$-(VEC_SIZE * 4), %rdi
	/* Check if s1 pointer at end.  */
	cmpq	%rdx, %rdi
	jb	L(loop_4x_vec)

	subq	%rdx, %rdi
	/* rdi has 4 * VEC_SIZE - remaining length.  */
	cmpl	$(VEC_SIZE * 3), %edi
	jae	L(8x_last_1x_vec)
	/* Load regardless of branch.  */
	vmovdqu	(VEC_SIZE * 2)(%rsi, %rdx), %ymm3
	cmpl	$(VEC_SIZE * 2), %edi
	jae	L(8x_last_2x_vec)

	/* Check last 4 VEC.  */
	vmovdqu	(%rsi, %rdx), %ymm1
	VPCMPEQ	(%rdx), %ymm1, %ymm1

	vmovdqu	VEC_SIZE(%rsi, %rdx), %ymm2
	VPCMPEQ	VEC_SIZE(%rdx), %ymm2, %ymm2

	VPCMPEQ	(VEC_SIZE * 2)(%rdx), %ymm3, %ymm3

	vmovdqu	(VEC_SIZE * 3)(%rsi, %rdx), %ymm4
	VPCMPEQ	(VEC_SIZE * 3)(%rdx), %ymm4, %ymm4

	vpand	%ymm1, %ymm2, %ymm5
	vpand	%ymm3, %ymm4, %ymm6
	vpand	%ymm5, %ymm6, %ymm7
	vpmovmskb %ymm7, %ecx
	/* Restore s1 pointer to rdi.  */
	movq	%rdx, %rdi
	incl	%ecx
	jnz	L(8x_return_vec_0_1_2_3)
	/* NB: eax must be zero to reach here.  */
	VZEROUPPER_RETURN

	/* Only entry is from L(more_8x_vec).  */
	.p2align 4
L(8x_last_2x_vec):
	/* Check second to last VEC. rdx store end pointer of s1 and
	   ymm3 has already been loaded with second to last VEC from s2.
	 */
	VPCMPEQ	(VEC_SIZE * 2)(%rdx), %ymm3, %ymm3
	vpmovmskb %ymm3, %eax
	incl	%eax
	jnz	L(8x_return_vec_2)
	/* Check last VEC.  */
	.p2align 4
L(8x_last_1x_vec):
	vmovdqu	(VEC_SIZE * 3)(%rsi, %rdx), %ymm4
	VPCMPEQ	(VEC_SIZE * 3)(%rdx), %ymm4, %ymm4
	vpmovmskb %ymm4, %eax
	incl	%eax
	jnz	L(8x_return_vec_3)
	VZEROUPPER_RETURN

	.p2align 4
L(last_2x_vec):
	/* Check second to last VEC.  */
	vmovdqu	-(VEC_SIZE * 2)(%rsi, %rdx), %ymm1
	VPCMPEQ	-(VEC_SIZE * 2)(%rdi, %rdx), %ymm1, %ymm1
	vpmovmskb %ymm1, %eax
	incl	%eax
	jnz	L(return_vec_1_end)
	/* Check last VEC.  */
L(last_1x_vec):
	vmovdqu	-(VEC_SIZE * 1)(%rsi, %rdx), %ymm1
	VPCMPEQ	-(VEC_SIZE * 1)(%rdi, %rdx), %ymm1, %ymm1
	vpmovmskb %ymm1, %eax
	incl	%eax
	jnz	L(return_vec_0_end)
	VZEROUPPER_RETURN

	.p2align 4
L(8x_return_vec_2):
	subq	$VEC_SIZE, %rdx
L(8x_return_vec_3):
	tzcntl	%eax, %eax
	addq	%rdx, %rax
# ifdef USE_AS_WMEMCMP
	movl	(VEC_SIZE * 3)(%rax), %ecx
	xorl	%edx, %edx
	cmpl	(VEC_SIZE * 3)(%rsi, %rax), %ecx
	setg	%dl
	leal	-1(%rdx, %rdx), %eax
# else
	movzbl	(VEC_SIZE * 3)(%rsi, %rax), %ecx
	movzbl	(VEC_SIZE * 3)(%rax), %eax
	subl	%ecx, %eax
# endif
	VZEROUPPER_RETURN

	.p2align 4
L(return_vec_1_end):
	tzcntl	%eax, %eax
	addl	%edx, %eax
# ifdef USE_AS_WMEMCMP
	movl	-(VEC_SIZE * 2)(%rdi, %rax), %ecx
	xorl	%edx, %edx
	cmpl	-(VEC_SIZE * 2)(%rsi, %rax), %ecx
	setg	%dl
	leal	-1(%rdx, %rdx), %eax
# else
	movzbl	-(VEC_SIZE * 2)(%rsi, %rax), %ecx
	movzbl	-(VEC_SIZE * 2)(%rdi, %rax), %eax
	subl	%ecx, %eax
# endif
	VZEROUPPER_RETURN

	.p2align 4
L(return_vec_0_end):
	tzcntl	%eax, %eax
	addl	%edx, %eax
# ifdef USE_AS_WMEMCMP
	movl	-VEC_SIZE(%rdi, %rax), %ecx
	xorl	%edx, %edx
	cmpl	-VEC_SIZE(%rsi, %rax), %ecx
	setg	%dl
	leal	-1(%rdx, %rdx), %eax
# else
	movzbl	-VEC_SIZE(%rsi, %rax), %ecx
	movzbl	-VEC_SIZE(%rdi, %rax), %eax
	subl	%ecx, %eax
# endif
	VZEROUPPER_RETURN

	.p2align 4
L(less_vec):
	/* Check if one or less CHAR. This is necessary for size = 0 but
	   is also faster for size = CHAR_SIZE.  */
	cmpl	$CHAR_SIZE, %edx
	jbe	L(one_or_less)

	/* Check if loading one VEC from either s1 or s2 could cause a
	   page cross. This can have false positives but is by far the
	   fastest method.  */
	movl	%edi, %eax
	orl	%esi, %eax
	andl	$(PAGE_SIZE - 1), %eax
	cmpl	$(PAGE_SIZE - VEC_SIZE), %eax
	jg	L(page_cross_less_vec)

	/* No page cross possible.  */
	vmovdqu	(%rsi), %ymm2
	VPCMPEQ	(%rdi), %ymm2, %ymm2
	vpmovmskb %ymm2, %eax
	incl	%eax
	/* Result will be zero if s1 and s2 match. Otherwise first set
	   bit will be first mismatch.  */
	bzhil	%edx, %eax, %edx
	jnz	L(return_vec_0)
	xorl	%eax, %eax
	VZEROUPPER_RETURN

	.p2align 4
L(page_cross_less_vec):
	/* if USE_AS_WMEMCMP it can only be 0, 4, 8, 12, 16, 20, 24, 28
	   bytes.  */
	cmpl	$16, %edx
	jae	L(between_16_31)
# ifndef USE_AS_WMEMCMP
	cmpl	$8, %edx
	jae	L(between_8_15)
	cmpl	$4, %edx
	jae	L(between_4_7)

	/* Load as big endian to avoid branches.  */
	movzwl	(%rdi), %eax
	movzwl	(%rsi), %ecx
	shll	$8, %eax
	shll	$8, %ecx
	bswap	%eax
	bswap	%ecx
	movzbl	-1(%rdi, %rdx), %edi
	movzbl	-1(%rsi, %rdx), %esi
	orl	%edi, %eax
	orl	%esi, %ecx
	/* Subtraction is okay because the upper 8 bits are zero.  */
	subl	%ecx, %eax
	/* No ymm register was touched.  */
	ret

	.p2align 4
L(one_or_less):
	jb	L(zero)
	movzbl	(%rsi), %ecx
	movzbl	(%rdi), %eax
	subl	%ecx, %eax
	/* No ymm register was touched.  */
	ret

	.p2align 4
L(between_8_15):
# endif
	/* If USE_AS_WMEMCMP fall through into 8-15 byte case.  */
	vmovq	(%rdi), %xmm1
	vmovq	(%rsi), %xmm2
	VPCMPEQ	%xmm1, %xmm2, %xmm2
	vpmovmskb %xmm2, %eax
	subl	$0xffff, %eax
	jnz	L(return_vec_0)
	/* Use overlapping loads to avoid branches.  */
	leaq	-8(%rdi, %rdx), %rdi
	leaq	-8(%rsi, %rdx), %rsi
	vmovq	(%rdi), %xmm1
	vmovq	(%rsi), %xmm2
	VPCMPEQ	%xmm1, %xmm2, %xmm2
	vpmovmskb %xmm2, %eax
	subl	$0xffff, %eax
	jnz	L(return_vec_0)
	/* No ymm register was touched.  */
	ret

	.p2align 4
L(zero):
	xorl	%eax, %eax
	ret

	.p2align 4
L(between_16_31):
	/* From 16 to 31 bytes.  No branch when size == 16.  */
	vmovdqu	(%rsi), %xmm2
	VPCMPEQ	(%rdi), %xmm2, %xmm2
	vpmovmskb %xmm2, %eax
	subl	$0xffff, %eax
	jnz	L(return_vec_0)

	/* Use overlapping loads to avoid branches.  */

	vmovdqu	-16(%rsi, %rdx), %xmm2
	leaq	-16(%rdi, %rdx), %rdi
	leaq	-16(%rsi, %rdx), %rsi
	VPCMPEQ	(%rdi), %xmm2, %xmm2
	vpmovmskb %xmm2, %eax
	subl	$0xffff, %eax
	jnz	L(return_vec_0)
	/* No ymm register was touched.  */
	ret

# ifdef USE_AS_WMEMCMP
	.p2align 4
L(one_or_less):
	jb	L(zero)
	movl	(%rdi), %ecx
	xorl	%edx, %edx
	cmpl	(%rsi), %ecx
	je	L(zero)
	setg	%dl
	leal	-1(%rdx, %rdx), %eax
	/* No ymm register was touched.  */
	ret
# else

	.p2align 4
L(between_4_7):
	/* Load as big endian with overlapping movbe to avoid branches.
	 */
	movbe	(%rdi), %eax
	movbe	(%rsi), %ecx
	shlq	$32, %rax
	shlq	$32, %rcx
	movbe	-4(%rdi, %rdx), %edi
	movbe	-4(%rsi, %rdx), %esi
	orq	%rdi, %rax
	orq	%rsi, %rcx
	subq	%rcx, %rax
	jz	L(zero_4_7)
	sbbl	%eax, %eax
	orl	$1, %eax
L(zero_4_7):
	/* No ymm register was touched.  */
	ret
# endif

END (MEMCMP)
#endif