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/arch/sh64/lib/page_copy.S

https://bitbucket.org/evzijst/gittest
Assembly | 91 lines | 83 code | 8 blank | 0 comment | 6 complexity | aa12f25450fdd839d701f6a9a40ceceb MD5 | raw file
 1/*
 2   Copyright 2003 Richard Curnow, SuperH (UK) Ltd.
 3
 4   This file is subject to the terms and conditions of the GNU General Public
 5   License.  See the file "COPYING" in the main directory of this archive
 6   for more details.
 7
 8   Tight version of mempy for the case of just copying a page.
 9   Prefetch strategy empirically optimised against RTL simulations
10   of SH5-101 cut2 eval chip with Cayman board DDR memory.
11
12   Parameters:
13   r2 : source effective address (start of page)
14   r3 : destination effective address (start of page)
15
16   Always copies 4096 bytes.
17
18   Points to review.
19   * Currently the prefetch is 4 lines ahead and the alloco is 2 lines ahead.
20     It seems like the prefetch needs to be at at least 4 lines ahead to get
21     the data into the cache in time, and the allocos contend with outstanding
22     prefetches for the same cache set, so it's better to have the numbers
23     different.
24   */
25
26	.section .text..SHmedia32,"ax"
27	.little
28
29	.balign 8
30	.global sh64_page_copy
31sh64_page_copy:
32
33	/* Copy 4096 bytes worth of data from r2 to r3.
34	   Do prefetches 4 lines ahead.
35	   Do alloco 2 lines ahead */
36
37	pta 1f, tr1
38	pta 2f, tr2
39	pta 3f, tr3
40	ptabs r18, tr0
41
42#if 0
43	/* TAKum03020 */
44	ld.q r2, 0x00, r63
45	ld.q r2, 0x20, r63
46	ld.q r2, 0x40, r63
47	ld.q r2, 0x60, r63
48#endif
49	alloco r3, 0x00
50	synco		! TAKum03020
51	alloco r3, 0x20
52	synco		! TAKum03020
53
54	movi 3968, r6
55	add  r3, r6, r6
56	addi r6, 64, r7
57	addi r7, 64, r8
58	sub r2, r3, r60
59	addi r60, 8, r61
60	addi r61, 8, r62
61	addi r62, 8, r23
62	addi r60, 0x80, r22
63
64/* Minimal code size.  The extra branches inside the loop don't cost much
65   because they overlap with the time spent waiting for prefetches to
66   complete. */
671:
68#if 0
69	/* TAKum03020 */
70	bge/u r3, r6, tr2  ! skip prefetch for last 4 lines
71	ldx.q r3, r22, r63 ! prefetch 4 lines hence
72#endif
732:
74	bge/u r3, r7, tr3  ! skip alloco for last 2 lines
75	alloco r3, 0x40    ! alloc destination line 2 lines ahead
76	synco		! TAKum03020
773:
78	ldx.q r3, r60, r36
79	ldx.q r3, r61, r37
80	ldx.q r3, r62, r38
81	ldx.q r3, r23, r39
82	st.q  r3,   0, r36
83	st.q  r3,   8, r37
84	st.q  r3,  16, r38
85	st.q  r3,  24, r39
86	addi r3, 32, r3
87	bgt/l r8, r3, tr1
88
89	blink tr0, r63	   ! return
90
91