| rjw | 1f88458 | 2022-01-06 17:20:42 +0800 | [diff] [blame^] | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
| 2 | /* |
| 3 | * arch/alpha/lib/strncat.S |
| 4 | * Contributed by Richard Henderson (rth@tamu.edu) |
| 5 | * |
| 6 | * Append no more than COUNT characters from the null-terminated string SRC |
| 7 | * to the null-terminated string DST. Always null-terminate the new DST. |
| 8 | * |
| 9 | * This differs slightly from the semantics in libc in that we never write |
| 10 | * past count, whereas libc may write to count+1. This follows the generic |
| 11 | * implementation in lib/string.c and is, IMHO, more sensible. |
| 12 | */ |
| 13 | #include <asm/export.h> |
| 14 | .text |
| 15 | |
| 16 | .align 3 |
| 17 | .globl strncat |
| 18 | .ent strncat |
| 19 | strncat: |
| 20 | .frame $30, 0, $26 |
| 21 | .prologue 0 |
| 22 | |
| 23 | mov $16, $0 # set up return value |
| 24 | beq $18, $zerocount |
| 25 | |
| 26 | /* Find the end of the string. */ |
| 27 | |
| 28 | ldq_u $1, 0($16) # load first quadword ($16 may be misaligned) |
| 29 | lda $2, -1($31) |
| 30 | insqh $2, $16, $2 |
| 31 | andnot $16, 7, $16 |
| 32 | or $2, $1, $1 |
| 33 | cmpbge $31, $1, $2 # bits set iff byte == 0 |
| 34 | bne $2, $found |
| 35 | |
| 36 | $loop: ldq $1, 8($16) |
| 37 | addq $16, 8, $16 |
| 38 | cmpbge $31, $1, $2 |
| 39 | beq $2, $loop |
| 40 | |
| 41 | $found: negq $2, $3 # clear all but least set bit |
| 42 | and $2, $3, $2 |
| 43 | |
| 44 | and $2, 0xf0, $3 # binary search for that set bit |
| 45 | and $2, 0xcc, $4 |
| 46 | and $2, 0xaa, $5 |
| 47 | cmovne $3, 4, $3 |
| 48 | cmovne $4, 2, $4 |
| 49 | cmovne $5, 1, $5 |
| 50 | addq $3, $4, $3 |
| 51 | addq $16, $5, $16 |
| 52 | addq $16, $3, $16 |
| 53 | |
| 54 | /* Now do the append. */ |
| 55 | |
| 56 | bsr $23, __stxncpy |
| 57 | |
| 58 | /* Worry about the null termination. */ |
| 59 | |
| 60 | zapnot $1, $27, $2 # was last byte a null? |
| 61 | bne $2, 0f |
| 62 | ret |
| 63 | |
| 64 | 0: cmplt $27, $24, $2 # did we fill the buffer completely? |
| 65 | or $2, $18, $2 |
| 66 | bne $2, 2f |
| 67 | |
| 68 | and $24, 0x80, $2 # no zero next byte |
| 69 | bne $2, 1f |
| 70 | |
| 71 | /* Here there are bytes left in the current word. Clear one. */ |
| 72 | addq $24, $24, $24 # end-of-count bit <<= 1 |
| 73 | 2: zap $1, $24, $1 |
| 74 | stq_u $1, 0($16) |
| 75 | ret |
| 76 | |
| 77 | 1: /* Here we must read the next DST word and clear the first byte. */ |
| 78 | ldq_u $1, 8($16) |
| 79 | zap $1, 1, $1 |
| 80 | stq_u $1, 8($16) |
| 81 | |
| 82 | $zerocount: |
| 83 | ret |
| 84 | |
| 85 | .end strncat |
| 86 | EXPORT_SYMBOL(strncat) |