Greg Kroah-Hartman | b244131 | 2017-11-01 15:07:57 +0100 | [diff] [blame] | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2 | /* |
| 3 | * arch/alpha/lib/ev67-strlen.S |
| 4 | * 21264 version by Rick Gorton <rick.gorton@alpha-processor.com> |
| 5 | * |
| 6 | * Finds length of a 0-terminated string. Optimized for the |
| 7 | * Alpha architecture: |
| 8 | * |
| 9 | * - memory accessed as aligned quadwords only |
| 10 | * - uses bcmpge to compare 8 bytes in parallel |
| 11 | * |
| 12 | * Much of the information about 21264 scheduling/coding comes from: |
| 13 | * Compiler Writer's Guide for the Alpha 21264 |
| 14 | * abbreviated as 'CWG' in other comments here |
| 15 | * ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html |
| 16 | * Scheduling notation: |
| 17 | * E - either cluster |
| 18 | * U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1 |
| 19 | * L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1 |
| 20 | */ |
Al Viro | 00fc0e0 | 2016-01-11 09:51:29 -0500 | [diff] [blame] | 21 | #include <asm/export.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 22 | .set noreorder |
| 23 | .set noat |
| 24 | |
| 25 | .globl strlen |
| 26 | .ent strlen |
| 27 | .align 4 |
| 28 | strlen: |
| 29 | ldq_u $1, 0($16) # L : load first quadword ($16 may be misaligned) |
| 30 | lda $2, -1($31) # E : |
| 31 | insqh $2, $16, $2 # U : |
| 32 | andnot $16, 7, $0 # E : |
| 33 | |
| 34 | or $2, $1, $1 # E : |
| 35 | cmpbge $31, $1, $2 # E : $2 <- bitmask: bit i == 1 <==> i-th byte == 0 |
| 36 | nop # E : |
| 37 | bne $2, $found # U : |
| 38 | |
| 39 | $loop: ldq $1, 8($0) # L : |
| 40 | addq $0, 8, $0 # E : addr += 8 |
| 41 | cmpbge $31, $1, $2 # E : |
| 42 | beq $2, $loop # U : |
| 43 | |
| 44 | $found: |
| 45 | cttz $2, $3 # U0 : |
| 46 | addq $0, $3, $0 # E : |
| 47 | subq $0, $16, $0 # E : |
| 48 | ret $31, ($26) # L0 : |
| 49 | |
| 50 | .end strlen |
Al Viro | 00fc0e0 | 2016-01-11 09:51:29 -0500 | [diff] [blame] | 51 | EXPORT_SYMBOL(strlen) |