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22723828 AB |
1 | /* |
2 | * Copyright (C) 2004, 2007-2010, 2011-2014 Synopsys, Inc. All rights reserved. | |
3 | * | |
4 | * SPDX-License-Identifier: GPL-2.0+ | |
5 | */ | |
6 | ||
7 | /* | |
8 | * This is optimized primarily for the ARC700. | |
9 | * It would be possible to speed up the loops by one cycle / word | |
10 | * respective one cycle / byte by forcing double source 1 alignment, unrolling | |
11 | * by a factor of two, and speculatively loading the second word / byte of | |
12 | * source 1; however, that would increase the overhead for loop setup / finish, | |
13 | * and strcmp might often terminate early. | |
14 | */ | |
15 | ||
16 | .global strcmp | |
17 | .align 4 | |
18 | strcmp: | |
19 | or %r2, %r0, %r1 | |
20 | bmsk_s %r2, %r2, 1 | |
21 | brne %r2, 0, .Lcharloop | |
22 | mov_s %r12, 0x01010101 | |
23 | ror %r5, %r12 | |
24 | .Lwordloop: | |
25 | ld.ab %r2, [%r0, 4] | |
26 | ld.ab %r3, [%r1, 4] | |
27 | nop_s | |
28 | sub %r4, %r2, %r12 | |
29 | bic %r4, %r4, %r2 | |
30 | and %r4, %r4, %r5 | |
31 | brne %r4, 0, .Lfound0 | |
32 | breq %r2 ,%r3, .Lwordloop | |
33 | #ifdef __LITTLE_ENDIAN__ | |
34 | xor %r0, %r2, %r3 /* mask for difference */ | |
35 | sub_s %r1, %r0, 1 | |
36 | bic_s %r0, %r0, %r1 /* mask for least significant difference bit */ | |
37 | sub %r1, %r5, %r0 | |
38 | xor %r0, %r5, %r1 /* mask for least significant difference byte */ | |
39 | and_s %r2, %r2, %r0 | |
40 | and_s %r3, %r3, %r0 | |
41 | #endif /* _ENDIAN__ */ | |
42 | cmp_s %r2, %r3 | |
43 | mov_s %r0, 1 | |
44 | j_s.d [%blink] | |
45 | bset.lo %r0, %r0, 31 | |
46 | ||
47 | .balign 4 | |
48 | #ifdef __LITTLE_ENDIAN__ | |
49 | .Lfound0: | |
50 | xor %r0, %r2, %r3 /* mask for difference */ | |
51 | or %r0, %r0, %r4 /* or in zero indicator */ | |
52 | sub_s %r1, %r0, 1 | |
53 | bic_s %r0, %r0, %r1 /* mask for least significant difference bit */ | |
54 | sub %r1, %r5, %r0 | |
55 | xor %r0, %r5, %r1 /* mask for least significant difference byte */ | |
56 | and_s %r2, %r2, %r0 | |
57 | and_s %r3, %r3, %r0 | |
58 | sub.f %r0, %r2, %r3 | |
59 | mov.hi %r0, 1 | |
60 | j_s.d [%blink] | |
61 | bset.lo %r0, %r0, 31 | |
62 | #else /* __BIG_ENDIAN__ */ | |
63 | /* | |
64 | * The zero-detection above can mis-detect 0x01 bytes as zeroes | |
65 | * because of carry-propagateion from a lower significant zero byte. | |
66 | * We can compensate for this by checking that bit0 is zero. | |
67 | * This compensation is not necessary in the step where we | |
68 | * get a low estimate for r2, because in any affected bytes | |
69 | * we already have 0x00 or 0x01, which will remain unchanged | |
70 | * when bit 7 is cleared. | |
71 | */ | |
72 | .balign 4 | |
73 | .Lfound0: | |
74 | lsr %r0, %r4, 8 | |
75 | lsr_s %r1, %r2 | |
76 | bic_s %r2, %r2, %r0 /* get low estimate for r2 and get ... */ | |
77 | bic_s %r0, %r0, %r1 /* <this is the adjusted mask for zeros> */ | |
78 | or_s %r3, %r3, %r0 /* ... high estimate r3 so that r2 > r3 will */ | |
79 | cmp_s %r3, %r2 /* ... be independent of trailing garbage */ | |
80 | or_s %r2, %r2, %r0 /* likewise for r3 > r2 */ | |
81 | bic_s %r3, %r3, %r0 | |
82 | rlc %r0, 0 /* r0 := r2 > r3 ? 1 : 0 */ | |
83 | cmp_s %r2, %r3 | |
84 | j_s.d [%blink] | |
85 | bset.lo %r0, %r0, 31 | |
86 | #endif /* _ENDIAN__ */ | |
87 | ||
88 | .balign 4 | |
89 | .Lcharloop: | |
90 | ldb.ab %r2,[%r0,1] | |
91 | ldb.ab %r3,[%r1,1] | |
92 | nop_s | |
93 | breq %r2, 0, .Lcmpend | |
94 | breq %r2, %r3, .Lcharloop | |
95 | .Lcmpend: | |
96 | j_s.d [%blink] | |
97 | sub %r0, %r2, %r3 |