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/* $OpenBSD: n_cabs.S,v 1.4 2008/09/13 21:25:40 martynas Exp $ */
/* $NetBSD: n_cabs.S,v 1.1 1995/10/10 23:40:26 ragge Exp $ */
/*
* Copyright (c) 1985, 1993
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)cabs.s 8.1 (Berkeley) 6/4/93
*/
#include <machine/asm.h>
/*
* double precision complex absolute value
* CABS by W. Kahan, 9/7/80.
* Revised for reserved operands by E. LeBlanc, 8/18/82
* argument for complex absolute value by reference, *4(ap)
* argument for cabs and hypot (C fcns) by value, 4(ap)
* output is in r0:r1 (error less than 0.86 ulps)
*/
/* entry for c functions cabs and hypot */
.text
_ALIGN_TEXT
ALTENTRY(hypot)
ENTRY(cabs, 0x8000|R2|R3|R4|R5|R6) # enable floating overflow
movq 4(ap),r0 # r0:1 = x
movq 12(ap),r2 # r2:3 = y
bicw3 $0x7f,r0,r4 # r4 has signed biased exp of x
cmpw $0x8000,r4
jeql return # x is a reserved operand, so return it
bicw3 $0x7f,r2,r5 # r5 has signed biased exp of y
cmpw $0x8000,r5
jneq cont /* y isn't a reserved operand */
movq r2,r0 /* return y if it's reserved */
ret
cont:
bsbb regs_set # r0:1 = dsqrt(x^2+y^2)/2^r6
addw2 r6,r0 # unscaled cdabs in r0:1
jvc return # unless it overflows
subw2 $0x80,r0 # halve r0 to get meaningful overflow
addd2 r0,r0 # overflow; r0 is half of true abs value
return:
ret
#if 0 /* apparently not used */
_ALTENTRY(__libm_cdabs_r6) # ENTRY POINT for cdsqrt
# calculates a scaled (factor in r6)
# complex absolute value
movq (r4)+,r0 # r0:r1 = x via indirect addressing
movq (r4),r2 # r2:r3 = y via indirect addressing
bicw3 $0x7f,r0,r5 # r5 has signed biased exp of x
cmpw $0x8000,r5
jeql cdreserved # x is a reserved operand
bicw3 $0x7f,r2,r5 # r5 has signed biased exp of y
cmpw $0x8000,r5
jneq regs_set /* y isn't a reserved operand either? */
cdreserved:
movl *4(ap),r4 # r4 -> (u,v), if x or y is reserved
movq r0,(r4)+ # copy u and v as is and return
movq r2,(r4) # (again addressing is indirect)
ret
#endif
regs_set:
bicw2 $0x8000,r0 # r0:r1 = dabs(x)
bicw2 $0x8000,r2 # r2:r3 = dabs(y)
cmpw r0,r2
jgeq ordered
movq r0,r4
movq r2,r0
movq r4,r2 # force y's exp <= x's exp
ordered:
bicw3 $0x7f,r0,r6 # r6 = exponent(x) + bias(129)
jeql retsb # if x = y = 0 then cdabs(x,y) = 0
subw2 $0x4780,r6 # r6 = exponent(x) - 14
subw2 r6,r0 # 2^14 <= scaled x < 2^15
bitw $0xff80,r2
jeql retsb # if y = 0 return dabs(x)
subw2 r6,r2
cmpw $0x3780,r2 # if scaled y < 2^-18
jgtr retsb # return dabs(x)
emodd r0,$0,r0,r4,r0 # r4 + r0:1 = scaled x^2
emodd r2,$0,r2,r5,r2 # r5 + r2:3 = scaled y^2
addd2 r2,r0
addl2 r5,r4
cvtld r4,r2
addd2 r2,r0 # r0:1 = scaled x^2 + y^2
jmp __libm_dsqrt_r5 # r0:1 = dsqrt(x^2+y^2)/2^r6
retsb:
rsb # error < 0.86 ulp
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