| 1 | /* SPDX-License-Identifier: GPL-2.0-only */
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| 2 | /*
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| 3 | * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
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| 4 | */
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| 5 |
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| 6 | /* This is optimized primarily for the ARC700.
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| 7 | It would be possible to speed up the loops by one cycle / word
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| 8 | respective one cycle / byte by forcing double source 1 alignment, unrolling
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| 9 | by a factor of two, and speculatively loading the second word / byte of
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| 10 | source 1; however, that would increase the overhead for loop setup / finish,
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| 11 | and strcmp might often terminate early. */
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| 12 |
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| 13 | |
| 14 |
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| 15 | ENTRY_CFI(strcmp)
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| 16 | or r2,r0,r1
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| 17 | bmsk_s r2,r2,1
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| 18 | brne r2,0,.Lcharloop
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| 19 | mov_s r12,0x01010101
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| 20 | ror r5,r12
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| 21 | .Lwordloop:
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| 22 | ld.ab r2,[r0,4]
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| 23 | ld.ab r3,[r1,4]
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| 24 | nop_s
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| 25 | sub r4,r2,r12
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| 26 | bic r4,r4,r2
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| 27 | and r4,r4,r5
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| 28 | brne r4,0,.Lfound0
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| 29 | breq r2,r3,.Lwordloop
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| 30 | |
| 31 | xor r0,r2,r3 ; mask for difference
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| 32 | sub_s r1,r0,1
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| 33 | bic_s r0,r0,r1 ; mask for least significant difference bit
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| 34 | sub r1,r5,r0
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| 35 | xor r0,r5,r1 ; mask for least significant difference byte
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| 36 | and_s r2,r2,r0
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| 37 | and_s r3,r3,r0
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| 38 | |
| 39 | cmp_s r2,r3
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| 40 | mov_s r0,1
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| 41 | j_s.d [blink]
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| 42 | bset.lo r0,r0,31
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| 43 |
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| 44 | .balign 4
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| 45 | |
| 46 | .Lfound0:
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| 47 | xor r0,r2,r3 ; mask for difference
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| 48 | or r0,r0,r4 ; or in zero indicator
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| 49 | sub_s r1,r0,1
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| 50 | bic_s r0,r0,r1 ; mask for least significant difference bit
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| 51 | sub r1,r5,r0
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| 52 | xor r0,r5,r1 ; mask for least significant difference byte
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| 53 | and_s r2,r2,r0
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| 54 | and_s r3,r3,r0
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| 55 | sub.f r0,r2,r3
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| 56 | mov.hi r0,1
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| 57 | j_s.d [blink]
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| 58 | bset.lo r0,r0,31
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| 59 | |
| 60 | /* The zero-detection above can mis-detect 0x01 bytes as zeroes
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| 61 | because of carry-propagateion from a lower significant zero byte.
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| 62 | We can compensate for this by checking that bit0 is zero.
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| 63 | This compensation is not necessary in the step where we
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| 64 | get a low estimate for r2, because in any affected bytes
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| 65 | we already have 0x00 or 0x01, which will remain unchanged
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| 66 | when bit 7 is cleared. */
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| 67 | .balign 4
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| 68 | .Lfound0:
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| 69 | lsr r0,r4,8
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| 70 | lsr_s r1,r2
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| 71 | bic_s r2,r2,r0 ; get low estimate for r2 and get ...
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| 72 | bic_s r0,r0,r1 ; <this is the adjusted mask for zeros>
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| 73 | or_s r3,r3,r0 ; ... high estimate r3 so that r2 > r3 will ...
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| 74 | cmp_s r3,r2 ; ... be independent of trailing garbage
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| 75 | or_s r2,r2,r0 ; likewise for r3 > r2
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| 76 | bic_s r3,r3,r0
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| 77 | rlc r0,0 ; r0 := r2 > r3 ? 1 : 0
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| 78 | cmp_s r2,r3
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| 79 | j_s.d [blink]
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| 80 | bset.lo r0,r0,31
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| 81 | |
| 82 |
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| 83 | .balign 4
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| 84 | .Lcharloop:
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| 85 | ldb.ab r2,[r0,1]
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| 86 | ldb.ab r3,[r1,1]
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| 87 | nop_s
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| 88 | breq r2,0,.Lcmpend
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| 89 | breq r2,r3,.Lcharloop
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| 90 | .Lcmpend:
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| 91 | j_s.d [blink]
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| 92 | sub r0,r2,r3
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| 93 | END_CFI(strcmp)
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