1# Copyright (c) 1985, 1993 2# The Regents of the University of California. All rights reserved. 3# 4# %sccs.include.redist.sh% 5# 6# @(#)tan.s 8.1 (Berkeley) 06/04/93 7# 8 .data 9 .align 2 10_sccsid: 11.asciz "@(#)tan.s 1.1 (Berkeley) 8/21/85; 8.1 (ucb.elefunt) 06/04/93" 12 13# This is the implementation of Peter Tang's double precision 14# tangent for the VAX using Bob Corbett's argument reduction. 15# 16# Notes: 17# under 1,024,000 random arguments testing on [0,2*pi] 18# tan() observed maximum error = 2.15 ulps 19# 20# double tan(arg) 21# double arg; 22# method: true range reduction to [-pi/4,pi/4], P. Tang & B. Corbett 23# S. McDonald, April 4, 1985 24# 25 .globl _tan 26 .text 27 .align 1 28 29_tan: .word 0xffc # save r2-r11 30 movq 4(ap),r0 31 bicw3 $0x807f,r0,r2 32 beql 1f # if x is zero or reserved operand then return x 33# 34# Save the PSL's IV & FU bits on the stack. 35# 36 movpsl r2 37 bicw3 $0xff9f,r2,-(sp) 38# 39# Clear the IV & FU bits. 40# 41 bicpsw $0x0060 42 jsb libm$argred 43# 44# At this point, 45# r0 contains the quadrant number, 0, 1, 2, or 3; 46# r2/r1 contains the reduced argument as a D-format number; 47# r3 contains a F-format extension to the reduced argument; 48# 49# Save r3/r0 so that we can call cosine after calling sine. 50# 51 movq r2,-(sp) 52 movq r0,-(sp) 53# 54# Call sine. r4 = 0 implies sine. 55# 56 movl $0,r4 57 jsb libm$sincos 58# 59# Save sin(x) in r11/r10 . 60# 61 movd r0,r10 62# 63# Call cosine. r4 = 1 implies cosine. 64# 65 movq (sp)+,r0 66 movq (sp)+,r2 67 movl $1,r4 68 jsb libm$sincos 69 divd3 r0,r10,r0 70 bispsw (sp)+ 711: ret 72