/*
   * strlen.S (c) 1995 David Mosberger (davidm@cs.arizona.edu)
   *
   * Finds length of a 0-terminated string.  Optimized for the
   * Alpha architecture:
   *
   *	- memory accessed as aligned quadwords only
   *	- uses bcmpge to compare 8 bytes in parallel
   *	- does binary search to find 0 byte in last
   *	  quadword (HAKMEM needed 12 instructions to
   *	  do this instead of the 9 instructions that
   *	  binary search needs).
   */
  
  	.set noreorder
  	.set noat
  
  	.align 3
  
  	.globl	strlen
  	.ent	strlen
  
  strlen:
  	ldq_u	$1, 0($16)	# load first quadword ($16  may be misaligned)
  	lda	$2, -1($31)
  	insqh	$2, $16, $2
  	andnot	$16, 7, $0
  	or	$2, $1, $1
  	cmpbge	$31, $1, $2	# $2  <- bitmask: bit i == 1 <==> i-th byte == 0
  	bne	$2, found
  
  loop:	ldq	$1, 8($0)
  	addq	$0, 8, $0	# addr += 8
  	nop			# helps dual issue last two insns
  	cmpbge	$31, $1, $2
  	beq	$2, loop
  
  found:	blbs	$2, done	# make aligned case fast
  	negq	$2, $3
  	and	$2, $3, $2
  
  	and	$2, 0x0f, $1
  	addq	$0, 4, $3
  	cmoveq	$1, $3, $0
  
  	and	$2, 0x33, $1
  	addq	$0, 2, $3
  	cmoveq	$1, $3, $0
  
  	and	$2, 0x55, $1
  	addq	$0, 1, $3
  	cmoveq	$1, $3, $0
  
  done:	subq	$0, $16, $0
  	ret	$31, ($26)
  
  	.end	strlen