diff options
Diffstat (limited to 'kernel/arch/alpha/lib/ev67-strncat.S')
| -rw-r--r-- | kernel/arch/alpha/lib/ev67-strncat.S | 94 |
1 files changed, 94 insertions, 0 deletions
diff --git a/kernel/arch/alpha/lib/ev67-strncat.S b/kernel/arch/alpha/lib/ev67-strncat.S new file mode 100644 index 000000000..4ae716cd2 --- /dev/null +++ b/kernel/arch/alpha/lib/ev67-strncat.S @@ -0,0 +1,94 @@ +/* + * arch/alpha/lib/ev67-strncat.S + * 21264 version contributed by Rick Gorton <rick.gorton@api-networks.com> + * + * 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 <<= 1 + 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 |