Bug fix for alternative 80386 math library

[Glenn Geers]

There is a bug in atan2. The fp stack was filling up when atan2(x,0) was called
repeatedly (Thanks Ross!). The affected files are inserted below (sorry, not
shar'd) and are available for ftp from suphys.physics.su.oz.au.

********************atan2.s**********************************

/*
** This file is part of the alternative 80386 math library and is
** covered by the GNU General Public license with my modification
** as noted in the README file that accompanied this file.
**
** Copyright 1990 G. Geers
**
*/

	.align 4
.Lpi:
	.double 3.14159265358979323846

	.align 4
.Lmpi:
	.double -3.14159265358979323846

	.align 4
.Lhalfpi: 
	.double 1.57079632679489661923

	.align 4
.Lmhalfpi:
	.double -1.57079632679489661923

	.align 4
	.globl atan2
atan2:
	pushl %ebp
	movl %esp,%ebp

	fldl 16(%ebp)
	ftst
	fnstsw %ax
	sahf 
	fldl 8(%ebp)
	jz .Lgotzero
	jc .Lgotneg

	fdivp
	fld1
	fpatan

	leave
	ret

.Lgotneg:
	ftst
	fnstsw %ax
	sahf 
	jc .Lneg1

	fdivp
	fld1
	fpatan
	fldl .Lmpi
	fsubrp

	leave
	ret

.Lneg1:
	fdivp
	fld1
	fpatan
	fldl .Lpi
	fsubrp

	leave
	ret

.Lgotzero:
	ftst
	fnstsw %ax
	sahf
	ffree %st(0)
	ffree %st(1)
	jz .Lzero
	jc .Lneg

	fldl .Lhalfpi

	leave
	ret

.Lzero:
	fldz

	leave
	ret

.Lneg:
	fldl .Lmhalfpi

	leave
	ret

***************atan2f.s************************************

/*
** This file is part of the alternative 80386 math library and is
** covered by the GNU General Public license with my modification
** as noted in the README file that accompanied this file.
**
** Copyright 1990 G. Geers
**
*/

	.align 4
.Lpi:
	.double 3.14159265358979323846

	.align 4
.Lmpi:
	.double -3.14159265358979323846

	.align 4
.Lhalfpi: 
	.double 1.57079632679489661923

	.align 4
.Lmhalfpi:
	.double -1.57079632679489661923

	.align 4
	.globl atan2f
atan2f:
	pushl %ebp
	movl %esp,%ebp

	flds 12(%ebp)
	ftst
	fnstsw %ax
	sahf 
	flds 8(%ebp)
	jz .Lgotzero
	jc .Lgotneg

	fdivp
	fld1
	fpatan

	leave
	ret

.Lgotneg:
	ftst
	fnstsw %ax
	sahf 
	jc .Lneg1

	fdivp
	fld1
	fpatan
	flds .Lmpi
	fsubrp

	leave
	ret

.Lneg1:
	fdivp
	fld1
	fpatan
	flds .Lpi
	fsubrp

	leave
	ret

.Lgotzero:
	ftst
	fnstsw %ax
	sahf
	ffree %st(0)
	ffree %st(1)
	jz .Lzero
	jc .Lneg

	flds .Lhalfpi

	leave
	ret

.Lzero:
	fldz

	leave
	ret

.Lneg:
	flds .Lmhalfpi

	leave
	ret


********************************************************************************

Enjoy,
	Glenn
--
Glenn Geers                       | "So when it's over, we're back to people.
Department of Theoretical Physics |  Just to prove that human touch can have
The University of Sydney          |  no equal."
Sydney NSW 2006 Australia         |  - Basia Trzetrzelewska, 'Prime Time TV'