/* * arch/alpha/lib/ev67-strncat.S * 21264 version contributed by Rick Gorton * * Append no more than COUNT characters from the null-terminated string SRC * to the null-terminated string DST. Always null-terminate the new DST. * * This differs slightly from the semantics in libc in that we never write * past count, whereas libc may write to count+1. This follows the generic * implementation in lib/string.c and is, IMHO, more sensible. * * Much of the information about 21264 scheduling/coding comes from: * Compiler Writer's Guide for the Alpha 21264 * abbreviated as 'CWG' in other comments here * ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html * Scheduling notation: * E - either cluster * U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1 * L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1 * Try not to change the actual algorithm if possible for consistency. */ .text .align 4 .globl strncat .ent strncat strncat: .frame $30, 0, $26 .prologue 0 mov $16, $0 # set up return value beq $18, $zerocount # U : /* Find the end of the string. */ ldq_u $1, 0($16) # L : load first quadword ($16 may be misaligned) lda $2, -1($31) # E : insqh $2, $0, $2 # U : andnot $16, 7, $16 # E : nop # E : or $2, $1, $1 # E : nop # E : nop # E : cmpbge $31, $1, $2 # E : bits set iff byte == 0 bne $2, $found # U : $loop: ldq $1, 8($16) # L : addq $16, 8, $16 # E : cmpbge $31, $1, $2 # E : beq $2, $loop # U : $found: cttz $2, $3 # U0 : addq $16, $3, $16 # E : nop # E : bsr $23, __stxncpy # L0 :/* Now do the append. */ /* Worry about the null termination. */ zapnot $1, $27, $2 # U : was last byte a null? cmplt $27, $24, $5 # E : did we fill the buffer completely? bne $2, 0f # U : ret # L0 : 0: or $5, $18, $2 # E : nop bne $2, 2f # U : and $24, 0x80, $3 # E : no zero next byte nop # E : bne $3, 1f # U : /* Here there are bytes left in the current word. Clear one. */ addq $24, $24, $24 # E : end-of-count bit nop # E : 2: zap $1, $24, $1 # U : nop # E : stq_u $1, 0($16) # L : ret # L0 : 1: /* Here we must clear the first byte of the next DST word */ stb $31, 8($16) # L : nop # E : nop # E : ret # L0 : $zerocount: nop # E : nop # E : nop # E : ret # L0 : .end strncat
