/* sacos.s - Motorola 68040 FP arc-cosine routines (EXC) *//* Copyright 1991-1993 Wind River Systems, Inc. */	.data	.globl	_copyright_wind_river	.long	_copyright_wind_river/*modification history--------------------01f,14jun95,tpr  changed fbxx to fbxxl.01e,21jul93,kdl  added .text (SPR #2372).01d,23aug92,jcf  changed bxxx to jxx.01c,26may92,rrr  the tree shuffle01b,10jan92,kdl  added modification history; general cleanup.01a,15aug91,kdl  original version, from Motorola FPSP v2.0.*//*DESCRIPTION	sacossa 3.3 12/19/90	Description: The entry point sAcos computes the inverse cosine of		an input argument|  sAcosd does the same except for denormalized		input.	Input: Double-extended number X in location pointed to		by address register a0.	Output: The value arccos(X) returned in floating-point register Fp0.	Accuracy and Monotonicity: The returned result is within 3 ulps in		64 significant bit, i.e. within 0.5001 ulp to 53 bits if the		result is subsequently rounded to double precision. The		result is provably monotonic in double precision.	Speed: The program sCOS takes approximately 310 cycles.	Algorithm:	ACOS	1. If |X| >= 1, go to 3.	2. (|X| < 1) Calculate acos(X) by		z := (1-X) / (1+X)		acos(X) = 2 * atan( sqrt(z) ).		Exit.	3. If |X| > 1, go to 5.	4. (|X| = 1) If X > 0, return 0. Otherwise, return Pi. Exit.	5. (|X| > 1) Generate an invalid operation by 0 * infinity.		Exit.		Copyright (C) Motorola, Inc. 1990			All Rights Reserved	THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA	The copyright notice above does not evidence any	actual or intended publication of such source code.SACOS	idnt	2,1 Motorola 040 Floating Point Software Package	section	8NOMANUAL*/PI:	.long 0x40000000,0xC90FDAA2,0x2168C235,0x00000000PIBY2:	.long 0x3FFF0000,0xC90FDAA2,0x2168C235,0x00000000|	xref	__x_t_operr|	xref	__x_t_frcinx|	xref	__x_satan	.globl	__x_sacosd	.text__x_sacosd:|--ACOS(X) = PI/2 FOR DENORMALIZED X	fmovel		d1,fpcr		/* load user's round mode/precision */	fmovex		PIBY2,fp0	jra 		__x_t_frcinx	.globl	__x_sacos__x_sacos:	fmovex		a0@,fp0		|...lOAD INPUT	movel		a0@,d0		|...pack exponent with upper 16 fraction	movew		a0@(4),d0	andil		#0x7FFFFFFF,d0	cmpil		#0x3FFF8000,d0	jge 		ACOSBIG|--THIS IS THE USUAL CASE, |X| < 1|--ACOS(X) = 2 * ATAN(	SQRT( (1-X)/(1+X) )	)	.long 0xf23c4480,0x3f800000	/*  fmoves  &0x3F800000,fp1 */	faddx		fp0,fp1	 	|...1+X	fnegx		fp0	 	|... -X	.long 0xf23c4422,0x3f800000	/*  fadds  &0x3F800000,fp0 */	fdivx		fp1,fp0	 	|...(1-X)/(1+X)	fsqrtx		fp0		|...SQRT((1-X)/(1+X))	fmovemx	fp0-fp0,a0@		|...overwrite input	movel		d1,a7@-		| save original users fpcr	clrl		d1	bsrl		__x_satan		|...ATAN(SQRT([1-X]/[1+X]))	fmovel		a7@+,fpcr	| restore users exceptions	faddx		fp0,fp0	 	|...2 * ATAN( STUFF )	jra 		__x_t_frcinxACOSBIG:	fabsx		fp0,fp0	.long 0xf23c4438,0x3f800000	/*  fcmps  &0x3F800000,fp0 */	fbgtl		__x_t_operr		| cause an operr exception|--|X| = 1, ACOS(X) = 0 OR PI	movel		a0@,d0		|...pack exponent with upper 16 fraction	movew		a0@(4),d0	cmpl		#0,d0		| D0 has original exponent+fraction	jgt 		ACOSP1|--X = -1|Returns PI and inexact exception	fmovex		PI,fp0	fmovel		d1,fpcr	.long 0xf23c4422,0x00800000	/*  fadds  &0x00800000,fp0 */					| cause an inexact exception to be put|					| into the 040 - will not trap until next|					| fp inst.	jra 		__x_t_frcinxACOSP1:	fmovel		d1,fpcr	.long 0xf23c4400,0x00000000	/*  fmoves  &0x00000000,fp0 */	rts				| Facos of +1 is exact|	end