1 /* SPDX-License-Identifier: GPL-2.0 */ 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 */ 21 #include <linux/export.h> 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 51 EXPORT_SYMBOL(strlen) 52