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