/*
   * arch/alpha/lib/strchr.S
   * Contributed by Richard Henderson (rth@tamu.edu)
   *
   * Return the address of a given character within a null-terminated
   * string, or null if it is not found.
   */
  
  #include <asm/regdef.h>
  
  	.set noreorder
  	.set noat
  
  	.align 3
  	.globl strchr
  	.ent strchr
  strchr:
  	.frame sp, 0, ra
  	.prologue 0
  
  	zapnot	a1, 1, a1	# e0    : zero extend the search character
  	ldq_u   t0, 0(a0)	# .. e1 : load first quadword
  	sll	a1, 8, t5	# e0    : replicate the search character
  	andnot  a0, 7, v0	# .. e1 : align our loop pointer
  	or	t5, a1, a1	# e0    :
  	lda	t4, -1		# .. e1 : build garbage mask
  	sll	a1, 16, t5	# e0    :
  	cmpbge  zero, t0, t2	# .. e1 : bits set iff byte == zero
  	mskqh	t4, a0, t4	# e0    :
  	or	t5, a1, a1	# .. e1 :
  	sll	a1, 32, t5	# e0    :
  	cmpbge	zero, t4, t4	# .. e1 : bits set iff byte is garbage
  	or	t5, a1, a1	# e0    :
  	xor	t0, a1, t1	# .. e1 : make bytes == c zero
  	cmpbge  zero, t1, t3	# e0    : bits set iff byte == c
  	or	t2, t3, t0	# e1    : bits set iff char match or zero match
  	andnot	t0, t4, t0	# e0    : clear garbage bits
  	bne	t0, $found	# .. e1 (zdb)
  
  $loop:	ldq	t0, 8(v0)	# e0    :
  	addq	v0, 8, v0	# .. e1 :
  	nop			# e0    :
  	xor	t0, a1, t1	# .. e1 (ev5 data stall)
  	cmpbge	zero, t0, t2	# e0    : bits set iff byte == 0
  	cmpbge	zero, t1, t3	# .. e1 : bits set iff byte == c
  	or	t2, t3, t0	# e0    :
  	beq	t0, $loop	# .. e1 (zdb)
  
  $found:	negq    t0, t1		# e0    : clear all but least set bit
  	and     t0, t1, t0	# e1 (stall)
  
  	and	t0, t3, t1	# e0    : bit set iff byte was the char
  	beq	t1, $retnull	# .. e1 (zdb)
  
  	and     t0, 0xf0, t2	# e0    : binary search for that set bit
  	and	t0, 0xcc, t3	# .. e1 :
  	and	t0, 0xaa, t4	# e0    :
  	cmovne	t2, 4, t2	# .. e1 :
  	cmovne	t3, 2, t3	# e0    :
  	cmovne	t4, 1, t4	# .. e1 :
  	addq	t2, t3, t2	# e0    :
  	addq	v0, t4, v0	# .. e1 :
  	addq	v0, t2, v0	# e0    :
  	ret			# .. e1 :
  
  $retnull:
  	mov	zero, v0	# e0    :
  	ret			# .. e1 :
  
  	.end strchr