1*4882a593Smuzhiyun/* SPDX-License-Identifier: GPL-2.0 */ 2*4882a593Smuzhiyun/* 3*4882a593Smuzhiyun * strlen.S (c) 1995 David Mosberger (davidm@cs.arizona.edu) 4*4882a593Smuzhiyun * 5*4882a593Smuzhiyun * Finds length of a 0-terminated string. Optimized for the 6*4882a593Smuzhiyun * Alpha architecture: 7*4882a593Smuzhiyun * 8*4882a593Smuzhiyun * - memory accessed as aligned quadwords only 9*4882a593Smuzhiyun * - uses bcmpge to compare 8 bytes in parallel 10*4882a593Smuzhiyun * - does binary search to find 0 byte in last 11*4882a593Smuzhiyun * quadword (HAKMEM needed 12 instructions to 12*4882a593Smuzhiyun * do this instead of the 9 instructions that 13*4882a593Smuzhiyun * binary search needs). 14*4882a593Smuzhiyun */ 15*4882a593Smuzhiyun#include <asm/export.h> 16*4882a593Smuzhiyun .set noreorder 17*4882a593Smuzhiyun .set noat 18*4882a593Smuzhiyun 19*4882a593Smuzhiyun .align 3 20*4882a593Smuzhiyun 21*4882a593Smuzhiyun .globl strlen 22*4882a593Smuzhiyun .ent strlen 23*4882a593Smuzhiyun 24*4882a593Smuzhiyunstrlen: 25*4882a593Smuzhiyun ldq_u $1, 0($16) # load first quadword ($16 may be misaligned) 26*4882a593Smuzhiyun lda $2, -1($31) 27*4882a593Smuzhiyun insqh $2, $16, $2 28*4882a593Smuzhiyun andnot $16, 7, $0 29*4882a593Smuzhiyun or $2, $1, $1 30*4882a593Smuzhiyun cmpbge $31, $1, $2 # $2 <- bitmask: bit i == 1 <==> i-th byte == 0 31*4882a593Smuzhiyun bne $2, found 32*4882a593Smuzhiyun 33*4882a593Smuzhiyunloop: ldq $1, 8($0) 34*4882a593Smuzhiyun addq $0, 8, $0 # addr += 8 35*4882a593Smuzhiyun nop # helps dual issue last two insns 36*4882a593Smuzhiyun cmpbge $31, $1, $2 37*4882a593Smuzhiyun beq $2, loop 38*4882a593Smuzhiyun 39*4882a593Smuzhiyunfound: blbs $2, done # make aligned case fast 40*4882a593Smuzhiyun negq $2, $3 41*4882a593Smuzhiyun and $2, $3, $2 42*4882a593Smuzhiyun 43*4882a593Smuzhiyun and $2, 0x0f, $1 44*4882a593Smuzhiyun addq $0, 4, $3 45*4882a593Smuzhiyun cmoveq $1, $3, $0 46*4882a593Smuzhiyun 47*4882a593Smuzhiyun and $2, 0x33, $1 48*4882a593Smuzhiyun addq $0, 2, $3 49*4882a593Smuzhiyun cmoveq $1, $3, $0 50*4882a593Smuzhiyun 51*4882a593Smuzhiyun and $2, 0x55, $1 52*4882a593Smuzhiyun addq $0, 1, $3 53*4882a593Smuzhiyun cmoveq $1, $3, $0 54*4882a593Smuzhiyun 55*4882a593Smuzhiyundone: subq $0, $16, $0 56*4882a593Smuzhiyun ret $31, ($26) 57*4882a593Smuzhiyun 58*4882a593Smuzhiyun .end strlen 59*4882a593Smuzhiyun EXPORT_SYMBOL(strlen) 60