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cabs.s
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1993-09-23
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# Copyright (c) 1985 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. All advertising materials mentioning features or use of this software
# must display the following acknowledgement:
# This product includes software developed by the University of
# California, Berkeley and its contributors.
# 4. 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 5.4 (Berkeley) 10/9/90
#
.data
.align 2
_sccsid:
.asciz "@(#)cabs.s 1.2 (Berkeley) 8/21/85; 5.4 (ucb.elefunt) 10/9/90"
# 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)
.text
.align 1
.globl _cabs
.globl _hypot
.globl _z_abs
.globl libm$cdabs_r6
.globl libm$dsqrt_r5
# entry for c functions cabs and hypot
_cabs:
_hypot:
.word 0x807c # save r2-r6, enable floating overflow
movq 4(ap),r0 # r0:1 = x
movq 12(ap),r2 # r2:3 = y
jmp cabs2
# entry for Fortran use, call by: d = abs(z)
_z_abs:
.word 0x807c # save r2-r6, enable floating overflow
movl 4(ap),r2 # indirect addressing is necessary here
movq (r2)+,r0 # r0:1 = x
movq (r2),r2 # r2:3 = y
cabs2:
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 $0x80,r0 # halve r0 to get meaningful overflow
addd2 r0,r0 # overflow; r0 is half of true abs value
return:
ret
libm$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
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