aboutsummaryrefslogtreecommitdiff
path: root/arch/ia64/lib/memcpy_mck.S
blob: ab0f8763972954117b0ac6a7dc3ac120d6e042c5 (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
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
/*
 * Itanium 2-optimized version of memcpy and copy_user function
 *
 * Inputs:
 * 	in0:	destination address
 *	in1:	source address
 *	in2:	number of bytes to copy
 * Output:
 *	for memcpy:    return dest
 * 	for copy_user: return 0 if success,
 *		       or number of byte NOT copied if error occurred.
 *
 * Copyright (C) 2002 Intel Corp.
 * Copyright (C) 2002 Ken Chen <kenneth.w.chen@intel.com>
 */
#include <asm/asmmacro.h>
#include <asm/page.h>

#define EK(y...) EX(y)

/* McKinley specific optimization */

#define retval		r8
#define saved_pfs	r31
#define saved_lc	r10
#define saved_pr	r11
#define saved_in0	r14
#define saved_in1	r15
#define saved_in2	r16

#define src0		r2
#define src1		r3
#define dst0		r17
#define dst1		r18
#define cnt		r9

/* r19-r30 are temp for each code section */
#define PREFETCH_DIST	8
#define src_pre_mem	r19
#define dst_pre_mem	r20
#define src_pre_l2	r21
#define dst_pre_l2	r22
#define t1		r23
#define t2		r24
#define t3		r25
#define t4		r26
#define t5		t1	// alias!
#define t6		t2	// alias!
#define t7		t3	// alias!
#define n8		r27
#define t9		t5	// alias!
#define t10		t4	// alias!
#define t11		t7	// alias!
#define t12		t6	// alias!
#define t14		t10	// alias!
#define t13		r28
#define t15		r29
#define tmp		r30

/* defines for long_copy block */
#define	A	0
#define B	(PREFETCH_DIST)
#define C	(B + PREFETCH_DIST)
#define D	(C + 1)
#define N	(D + 1)
#define Nrot	((N + 7) & ~7)

/* alias */
#define in0		r32
#define in1		r33
#define in2		r34

GLOBAL_ENTRY(memcpy)
	and	r28=0x7,in0
	and	r29=0x7,in1
	mov	f6=f0
	mov	retval=in0
	br.cond.sptk .common_code
	;;
END(memcpy)
GLOBAL_ENTRY(__copy_user)
	.prologue
// check dest alignment
	and	r28=0x7,in0
	and	r29=0x7,in1
	mov	f6=f1
	mov	saved_in0=in0	// save dest pointer
	mov	saved_in1=in1	// save src pointer
	mov	retval=r0	// initialize return value
	;;
.common_code:
	cmp.gt	p15,p0=8,in2	// check for small size
	cmp.ne	p13,p0=0,r28	// check dest alignment
	cmp.ne	p14,p0=0,r29	// check src alignment
	add	src0=0,in1
	sub	r30=8,r28	// for .align_dest
	mov	saved_in2=in2	// save len
	;;
	add	dst0=0,in0
	add	dst1=1,in0	// dest odd index
	cmp.le	p6,p0 = 1,r30	// for .align_dest
(p15)	br.cond.dpnt .memcpy_short
(p13)	br.cond.dpnt .align_dest
(p14)	br.cond.dpnt .unaligned_src
	;;

// both dest and src are aligned on 8-byte boundary
.aligned_src:
	.save ar.pfs, saved_pfs
	alloc	saved_pfs=ar.pfs,3,Nrot-3,0,Nrot
	.save pr, saved_pr
	mov	saved_pr=pr

	shr.u	cnt=in2,7	// this much cache line
	;;
	cmp.lt	p6,p0=2*PREFETCH_DIST,cnt
	cmp.lt	p7,p8=1,cnt
	.save ar.lc, saved_lc
	mov	saved_lc=ar.lc
	.body
	add	cnt=-1,cnt
	add	src_pre_mem=0,in1	// prefetch src pointer
	add	dst_pre_mem=0,in0	// prefetch dest pointer
	;;
(p7)	mov	ar.lc=cnt	// prefetch count
(p8)	mov	ar.lc=r0
(p6)	br.cond.dpnt .long_copy
	;;

.prefetch:
	lfetch.fault	  [src_pre_mem], 128
	lfetch.fault.excl [dst_pre_mem], 128
	br.cloop.dptk.few .prefetch
	;;

.medium_copy:
	and	tmp=31,in2	// copy length after iteration
	shr.u	r29=in2,5	// number of 32-byte iteration
	add	dst1=8,dst0	// 2nd dest pointer
	;;
	add	cnt=-1,r29	// ctop iteration adjustment
	cmp.eq	p10,p0=r29,r0	// do we really need to loop?
	add	src1=8,src0	// 2nd src pointer
	cmp.le	p6,p0=8,tmp
	;;
	cmp.le	p7,p0=16,tmp
	mov	ar.lc=cnt	// loop setup
	cmp.eq	p16,p17 = r0,r0
	mov	ar.ec=2
(p10)	br.dpnt.few .aligned_src_tail
	;;
	TEXT_ALIGN(32)
1:
EX(.ex_handler, (p16)	ld8	r34=[src0],16)
EK(.ex_handler, (p16)	ld8	r38=[src1],16)
EX(.ex_handler, (p17)	st8	[dst0]=r33,16)
EK(.ex_handler, (p17)	st8	[dst1]=r37,16)
	;;
EX(.ex_handler, (p16)	ld8	r32=[src0],16)
EK(.ex_handler, (p16)	ld8	r36=[src1],16)
EX(.ex_handler, (p16)	st8	[dst0]=r34,16)
EK(.ex_handler, (p16)	st8	[dst1]=r38,16)
	br.ctop.dptk.few 1b
	;;

.aligned_src_tail:
EX(.ex_handler, (p6)	ld8	t1=[src0])
	mov	ar.lc=saved_lc
	mov	ar.pfs=saved_pfs
EX(.ex_hndlr_s, (p7)	ld8	t2=[src1],8)
	cmp.le	p8,p0=24,tmp
	and	r21=-8,tmp
	;;
EX(.ex_hndlr_s, (p8)	ld8	t3=[src1])
EX(.ex_handler, (p6)	st8	[dst0]=t1)	// store byte 1
	and	in2=7,tmp	// remaining length
EX(.ex_hndlr_d, (p7)	st8	[dst1]=t2,8)	// store byte 2
	add	src0=src0,r21	// setting up src pointer
	add	dst0=dst0,r21	// setting up dest pointer
	;;
EX(.ex_handler, (p8)	st8	[dst1]=t3)	// store byte 3
	mov	pr=saved_pr,-1
	br.dptk.many .memcpy_short
	;;

/* code taken from copy_page_mck */
.long_copy:
	.rotr v[2*PREFETCH_DIST]
	.rotp p[N]

	mov src_pre_mem = src0
	mov pr.rot = 0x10000
	mov ar.ec = 1				// special unrolled loop

	mov dst_pre_mem = dst0

	add src_pre_l2 = 8*8, src0
	add dst_pre_l2 = 8*8, dst0
	;;
	add src0 = 8, src_pre_mem		// first t1 src
	mov ar.lc = 2*PREFETCH_DIST - 1
	shr.u cnt=in2,7				// number of lines
	add src1 = 3*8, src_pre_mem		// first t3 src
	add dst0 = 8, dst_pre_mem		// first t1 dst
	add dst1 = 3*8, dst_pre_mem		// first t3 dst
	;;
	and tmp=127,in2				// remaining bytes after this block
	add cnt = -(2*PREFETCH_DIST) - 1, cnt
	// same as .line_copy loop, but with all predicated-off instructions removed:
.prefetch_loop:
EX(.ex_hndlr_lcpy_1, (p[A])	ld8 v[A] = [src_pre_mem], 128)		// M0
EK(.ex_hndlr_lcpy_1, (p[B])	st8 [dst_pre_mem] = v[B], 128)		// M2
	br.ctop.sptk .prefetch_loop
	;;
	cmp.eq p16, p0 = r0, r0			// reset p16 to 1
	mov ar.lc = cnt
	mov ar.ec = N				// # of stages in pipeline
	;;
.line_copy:
EX(.ex_handler,	(p[D])	ld8 t2 = [src0], 3*8)			// M0
EK(.ex_handler,	(p[D])	ld8 t4 = [src1], 3*8)			// M1
EX(.ex_handler_lcpy,	(p[B])	st8 [dst_pre_mem] = v[B], 128)		// M2 prefetch dst from memory
EK(.ex_handler_lcpy,	(p[D])	st8 [dst_pre_l2] = n8, 128)		// M3 prefetch dst from L2
	;;
EX(.ex_handler_lcpy,	(p[A])	ld8 v[A] = [src_pre_mem], 128)		// M0 prefetch src from memory
EK(.ex_handler_lcpy,	(p[C])	ld8 n8 = [src_pre_l2], 128)		// M1 prefetch src from L2
EX(.ex_handler,	(p[D])	st8 [dst0] =  t1, 8)			// M2
EK(.ex_handler,	(p[D])	st8 [dst1] =  t3, 8)			// M3
	;;
EX(.ex_handler,	(p[D])	ld8  t5 = [src0], 8)
EK(.ex_handler,	(p[D])	ld8  t7 = [src1], 3*8)
EX(.ex_handler,	(p[D])	st8 [dst0] =  t2, 3*8)
EK(.ex_handler,	(p[D])	st8 [dst1] =  t4, 3*8)
	;;
EX(.ex_handler,	(p[D])	ld8  t6 = [src0], 3*8)
EK(.ex_handler,	(p[D])	ld8 t10 = [src1], 8)
EX(.ex_handler,	(p[D])	st8 [dst0] =  t5, 8)
EK(.ex_handler,	(p[D])	st8 [dst1] =  t7, 3*8)
	;;
EX(.ex_handler,	(p[D])	ld8  t9 = [src0], 3*8)
EK(.ex_handler,	(p[D])	ld8 t11 = [src1], 3*8)
EX(.ex_handler,	(p[D])	st8 [dst0] =  t6, 3*8)
EK(.ex_handler,	(p[D])	st8 [dst1] = t10, 8)
	;;
EX(.ex_handler,	(p[D])	ld8 t12 = [src0], 8)
EK(.ex_handler,	(p[D])	ld8 t14 = [src1], 8)
EX(.ex_handler,	(p[D])	st8 [dst0] =  t9, 3*8)
EK(.ex_handler,	(p[D])	st8 [dst1] = t11, 3*8)
	;;
EX(.ex_handler,	(p[D])	ld8 t13 = [src0], 4*8)
EK(.ex_handler,	(p[D])	ld8 t15 = [src1], 4*8)
EX(.ex_handler,	(p[D])	st8 [dst0] = t12, 8)
EK(.ex_handler,	(p[D])	st8 [dst1] = t14, 8)
	;;
EX(.ex_handler,	(p[C])	ld8  t1 = [src0], 8)
EK(.ex_handler,	(p[C])	ld8  t3 = [src1], 8)
EX(.ex_handler,	(p[D])	st8 [dst0] = t13, 4*8)
EK(.ex_handler,	(p[D])	st8 [dst1] = t15, 4*8)
	br.ctop.sptk .line_copy
	;;

	add dst0=-8,dst0
	add src0=-8,src0
	mov in2=tmp
	.restore sp
	br.sptk.many .medium_copy
	;;

#define BLOCK_SIZE	128*32
#define blocksize	r23
#define curlen		r24

// dest is on 8-byte boundary, src is not. We need to do
// ld8-ld8, shrp, then st8.  Max 8 byte copy per cycle.
.unaligned_src:
	.prologue
	.save ar.pfs, saved_pfs
	alloc	saved_pfs=ar.pfs,3,5,0,8
	.save ar.lc, saved_lc
	mov	saved_lc=ar.lc
	.save pr, saved_pr
	mov	saved_pr=pr
	.body
.4k_block:
	mov	saved_in0=dst0	// need to save all input arguments
	mov	saved_in2=in2
	mov	blocksize=BLOCK_SIZE
	;;
	cmp.lt	p6,p7=blocksize,in2
	mov	saved_in1=src0
	;;
(p6)	mov	in2=blocksize
	;;
	shr.u	r21=in2,7	// this much cache line
	shr.u	r22=in2,4	// number of 16-byte iteration
	and	curlen=15,in2	// copy length after iteration
	and	r30=7,src0	// source alignment
	;;
	cmp.lt	p7,p8=1,r21
	add	cnt=-1,r21
	;;

	add	src_pre_mem=0,src0	// prefetch src pointer
	add	dst_pre_mem=0,dst0	// prefetch dest pointer
	and	src0=-8,src0		// 1st src pointer
(p7)	mov	ar.lc = cnt
(p8)	mov	ar.lc = r0
	;;
	TEXT_ALIGN(32)
1:	lfetch.fault	  [src_pre_mem], 128
	lfetch.fault.excl [dst_pre_mem], 128
	br.cloop.dptk.few 1b
	;;

	shladd	dst1=r22,3,dst0	// 2nd dest pointer
	shladd	src1=r22,3,src0	// 2nd src pointer
	cmp.eq	p8,p9=r22,r0	// do we really need to loop?
	cmp.le	p6,p7=8,curlen;	// have at least 8 byte remaining?
	add	cnt=-1,r22	// ctop iteration adjustment
	;;
EX(.ex_handler, (p9)	ld8	r33=[src0],8)	// loop primer
EK(.ex_handler, (p9)	ld8	r37=[src1],8)
(p8)	br.dpnt.few .noloop
	;;

// The jump address is calculated based on src alignment. The COPYU
// macro below need to confine its size to power of two, so an entry
// can be caulated using shl instead of an expensive multiply. The
// size is then hard coded by the following #define to match the
// actual size.  This make it somewhat tedious when COPYU macro gets
// changed and this need to be adjusted to match.
#define LOOP_SIZE 6
1:
	mov	r29=ip		// jmp_table thread
	mov	ar.lc=cnt
	;;
	add	r29=.jump_table - 1b - (.jmp1-.jump_table), r29
	shl	r28=r30, LOOP_SIZE	// jmp_table thread
	mov	ar.ec=2		// loop setup
	;;
	add	r29=r29,r28		// jmp_table thread
	cmp.eq	p16,p17=r0,r0
	;;
	mov	b6=r29			// jmp_table thread
	;;
	br.cond.sptk.few b6

// for 8-15 byte case
// We will skip the loop, but need to replicate the side effect
// that the loop produces.
.noloop:
EX(.ex_handler, (p6)	ld8	r37=[src1],8)
	add	src0=8,src0
(p6)	shl	r25=r30,3
	;;
EX(.ex_handler, (p6)	ld8	r27=[src1])
(p6)	shr.u	r28=r37,r25
(p6)	sub	r26=64,r25
	;;
(p6)	shl	r27=r27,r26
	;;
(p6)	or	r21=r28,r27

.unaligned_src_tail:
/* check if we have more than blocksize to copy, if so go back */
	cmp.gt	p8,p0=saved_in2,blocksize
	;;
(p8)	add	dst0=saved_in0,blocksize
(p8)	add	src0=saved_in1,blocksize
(p8)	sub	in2=saved_in2,blocksize
(p8)	br.dpnt	.4k_block
	;;

/* we have up to 15 byte to copy in the tail.
 * part of work is already done in the jump table code
 * we are at the following state.
 * src side:
 * 
 *   xxxxxx xx                   <----- r21 has xxxxxxxx already
 * -------- -------- --------
 * 0        8        16
 *          ^
 *          |
 *          src1
 * 
 * dst
 * -------- -------- --------
 * ^
 * |
 * dst1
 */
EX(.ex_handler, (p6)	st8	[dst1]=r21,8)	// more than 8 byte to copy
(p6)	add	curlen=-8,curlen	// update length
	mov	ar.pfs=saved_pfs
	;;
	mov	ar.lc=saved_lc
	mov	pr=saved_pr,-1
	mov	in2=curlen	// remaining length
	mov	dst0=dst1	// dest pointer
	add	src0=src1,r30	// forward by src alignment
	;;

// 7 byte or smaller.
.memcpy_short:
	cmp.le	p8,p9   = 1,in2
	cmp.le	p10,p11 = 2,in2
	cmp.le	p12,p13 = 3,in2
	cmp.le	p14,p15 = 4,in2
	add	src1=1,src0	// second src pointer
	add	dst1=1,dst0	// second dest pointer
	;;

EX(.ex_handler_short, (p8)	ld1	t1=[src0],2)
EK(.ex_handler_short, (p10)	ld1	t2=[src1],2)
(p9)	br.ret.dpnt rp		// 0 byte copy
	;;

EX(.ex_handler_short, (p8)	st1	[dst0]=t1,2)
EK(.ex_handler_short, (p10)	st1	[dst1]=t2,2)
(p11)	br.ret.dpnt rp		// 1 byte copy

EX(.ex_handler_short, (p12)	ld1	t3=[src0],2)
EK(.ex_handler_short, (p14)	ld1	t4=[src1],2)
(p13)	br.ret.dpnt rp		// 2 byte copy
	;;

	cmp.le	p6,p7   = 5,in2
	cmp.le	p8,p9   = 6,in2
	cmp.le	p10,p11 = 7,in2

EX(.ex_handler_short, (p12)	st1	[dst0]=t3,2)
EK(.ex_handler_short, (p14)	st1	[dst1]=t4,2)
(p15)	br.ret.dpnt rp		// 3 byte copy
	;;

EX(.ex_handler_short, (p6)	ld1	t5=[src0],2)
EK(.ex_handler_short, (p8)	ld1	t6=[src1],2)
(p7)	br.ret.dpnt rp		// 4 byte copy
	;;

EX(.ex_handler_short, (p6)	st1	[dst0]=t5,2)
EK(.ex_handler_short, (p8)	st1	[dst1]=t6,2)
(p9)	br.ret.dptk rp		// 5 byte copy

EX(.ex_handler_short, (p10)	ld1	t7=[src0],2)
(p11)	br.ret.dptk rp		// 6 byte copy
	;;

EX(.ex_handler_short, (p10)	st1	[dst0]=t7,2)
	br.ret.dptk rp		// done all cases


/* Align dest to nearest 8-byte boundary. We know we have at
 * least 7 bytes to copy, enough to crawl to 8-byte boundary.
 * Actual number of byte to crawl depend on the dest alignment.
 * 7 byte or less is taken care at .memcpy_short

 * src0 - source even index
 * src1 - source  odd index
 * dst0 - dest even index
 * dst1 - dest  odd index
 * r30  - distance to 8-byte boundary
 */

.align_dest:
	add	src1=1,in1	// source odd index
	cmp.le	p7,p0 = 2,r30	// for .align_dest
	cmp.le	p8,p0 = 3,r30	// for .align_dest
EX(.ex_handler_short, (p6)	ld1	t1=[src0],2)
	cmp.le	p9,p0 = 4,r30	// for .align_dest
	cmp.le	p10,p0 = 5,r30
	;;
EX(.ex_handler_short, (p7)	ld1	t2=[src1],2)
EK(.ex_handler_short, (p8)	ld1	t3=[src0],2)
	cmp.le	p11,p0 = 6,r30
EX(.ex_handler_short, (p6)	st1	[dst0] = t1,2)
	cmp.le	p12,p0 = 7,r30
	;;
EX(.ex_handler_short, (p9)	ld1	t4=[src1],2)
EK(.ex_handler_short, (p10)	ld1	t5=[src0],2)
EX(.ex_handler_short, (p7)	st1	[dst1] = t2,2)
EK(.ex_handler_short, (p8)	st1	[dst0] = t3,2)
	;;
EX(.ex_handler_short, (p11)	ld1	t6=[src1],2)
EK(.ex_handler_short, (p12)	ld1	t7=[src0],2)
	cmp.eq	p6,p7=r28,r29
EX(.ex_handler_short, (p9)	st1	[dst1] = t4,2)
EK(.ex_handler_short, (p10)	st1	[dst0] = t5,2)
	sub	in2=in2,r30
	;;
EX(.ex_handler_short, (p11)	st1	[dst1] = t6,2)
EK(.ex_handler_short, (p12)	st1	[dst0] = t7)
	add	dst0=in0,r30	// setup arguments
	add	src0=in1,r30
(p6)	br.cond.dptk .aligned_src
(p7)	br.cond.dpnt .unaligned_src
	;;

/* main loop body in jump table format */
#define COPYU(shift)									\
1:											\
EX(.ex_handler,  (p16)	ld8	r32=[src0],8);		/* 1 */				\
EK(.ex_handler,  (p16)	ld8	r36=[src1],8);						\
		 (p17)	shrp	r35=r33,r34,shift;;	/* 1 */				\
EX(.ex_handler,  (p6)	ld8	r22=[src1]);	/* common, prime for tail section */	\
		 nop.m	0;								\
		 (p16)	shrp	r38=r36,r37,shift;					\
EX(.ex_handler,  (p17)	st8	[dst0]=r35,8);		/* 1 */				\
EK(.ex_handler,  (p17)	st8	[dst1]=r39,8);						\
		 br.ctop.dptk.few 1b;;							\
		 (p7)	add	src1=-8,src1;	/* back out for <8 byte case */		\
		 shrp	r21=r22,r38,shift;	/* speculative work */			\
		 br.sptk.few .unaligned_src_tail /* branch out of jump table */		\
		 ;;
	TEXT_ALIGN(32)
.jump_table:
	COPYU(8)	// unaligned cases
.jmp1:
	COPYU(16)
	COPYU(24)
	COPYU(32)
	COPYU(40)
	COPYU(48)
	COPYU(56)

#undef A
#undef B
#undef C
#undef D

/*
 * Due to lack of local tag support in gcc 2.x assembler, it is not clear which
 * instruction failed in the bundle.  The exception algorithm is that we
 * first figure out the faulting address, then detect if there is any
 * progress made on the copy, if so, redo the copy from last known copied
 * location up to the faulting address (exclusive). In the copy_from_user
 * case, remaining byte in kernel buffer will be zeroed.
 *
 * Take copy_from_user as an example, in the code there are multiple loads
 * in a bundle and those multiple loads could span over two pages, the
 * faulting address is calculated as page_round_down(max(src0, src1)).
 * This is based on knowledge that if we can access one byte in a page, we
 * can access any byte in that page.
 *
 * predicate used in the exception handler:
 * p6-p7: direction
 * p10-p11: src faulting addr calculation
 * p12-p13: dst faulting addr calculation
 */

#define A	r19
#define B	r20
#define C	r21
#define D	r22
#define F	r28

#define memset_arg0	r32
#define memset_arg2	r33

#define saved_retval	loc0
#define saved_rtlink	loc1
#define saved_pfs_stack	loc2

.ex_hndlr_s:
	add	src0=8,src0
	br.sptk .ex_handler
	;;
.ex_hndlr_d:
	add	dst0=8,dst0
	br.sptk .ex_handler
	;;
.ex_hndlr_lcpy_1:
	mov	src1=src_pre_mem
	mov	dst1=dst_pre_mem
	cmp.gtu	p10,p11=src_pre_mem,saved_in1
	cmp.gtu	p12,p13=dst_pre_mem,saved_in0
	;;
(p10)	add	src0=8,saved_in1
(p11)	mov	src0=saved_in1
(p12)	add	dst0=8,saved_in0
(p13)	mov	dst0=saved_in0
	br.sptk	.ex_handler
.ex_handler_lcpy:
	// in line_copy block, the preload addresses should always ahead
	// of the other two src/dst pointers.  Furthermore, src1/dst1 should
	// always ahead of src0/dst0.
	mov	src1=src_pre_mem
	mov	dst1=dst_pre_mem
.ex_handler:
	mov	pr=saved_pr,-1		// first restore pr, lc, and pfs
	mov	ar.lc=saved_lc
	mov	ar.pfs=saved_pfs
	;;
.ex_handler_short: // fault occurred in these sections didn't change pr, lc, pfs
	cmp.ltu	p6,p7=saved_in0, saved_in1	// get the copy direction
	cmp.ltu	p10,p11=src0,src1
	cmp.ltu	p12,p13=dst0,dst1
	fcmp.eq	p8,p0=f6,f0		// is it memcpy?
	mov	tmp = dst0
	;;
(p11)	mov	src1 = src0		// pick the larger of the two
(p13)	mov	dst0 = dst1		// make dst0 the smaller one
(p13)	mov	dst1 = tmp		// and dst1 the larger one
	;;
(p6)	dep	F = r0,dst1,0,PAGE_SHIFT // usr dst round down to page boundary
(p7)	dep	F = r0,src1,0,PAGE_SHIFT // usr src round down to page boundary
	;;
(p6)	cmp.le	p14,p0=dst0,saved_in0	// no progress has been made on store
(p7)	cmp.le	p14,p0=src0,saved_in1	// no progress has been made on load
	mov	retval=saved_in2
(p8)	ld1	tmp=[src1]		// force an oops for memcpy call
(p8)	st1	[dst1]=r0		// force an oops for memcpy call
(p14)	br.ret.sptk.many rp

/*
 * The remaining byte to copy is calculated as:
 *
 * A =	(faulting_addr - orig_src)	-> len to faulting ld address
 *	or 
 * 	(faulting_addr - orig_dst)	-> len to faulting st address
 * B =	(cur_dst - orig_dst)		-> len copied so far
 * C =	A - B				-> len need to be copied
 * D =	orig_len - A			-> len need to be zeroed
 */
(p6)	sub	A = F, saved_in0
(p7)	sub	A = F, saved_in1
	clrrrb
	;;
	alloc	saved_pfs_stack=ar.pfs,3,3,3,0
	cmp.lt	p8,p0=A,r0
	sub	B = dst0, saved_in0	// how many byte copied so far
	;;
(p8)	mov	A = 0;			// A shouldn't be negative, cap it
	;;
	sub	C = A, B
	sub	D = saved_in2, A
	;;
	cmp.gt	p8,p0=C,r0		// more than 1 byte?
	add	memset_arg0=saved_in0, A
(p6)	mov	memset_arg2=0		// copy_to_user should not call memset
(p7)	mov	memset_arg2=D		// copy_from_user need to have kbuf zeroed
	mov	r8=0
	mov	saved_retval = D
	mov	saved_rtlink = b0

	add	out0=saved_in0, B
	add	out1=saved_in1, B
	mov	out2=C
(p8)	br.call.sptk.few b0=__copy_user	// recursive call
	;;

	add	saved_retval=saved_retval,r8	// above might return non-zero value
	cmp.gt	p8,p0=memset_arg2,r0	// more than 1 byte?
	mov	out0=memset_arg0	// *s
	mov	out1=r0			// c
	mov	out2=memset_arg2	// n
(p8)	br.call.sptk.few b0=memset
	;;

	mov	retval=saved_retval
	mov	ar.pfs=saved_pfs_stack
	mov	b0=saved_rtlink
	br.ret.sptk.many rp

/* end of McKinley specific optimization */
END(__copy_user)