PageRenderTime 23ms CodeModel.GetById 2ms app.highlight 14ms RepoModel.GetById 1ms app.codeStats 1ms

/arch/m68k/fpsp040/sacos.S

https://bitbucket.org/evzijst/gittest
Assembly | 115 lines | 109 code | 6 blank | 0 comment | 1 complexity | f7ba707af3b0ffdeeb1da29d9d56f4e0 MD5 | raw file
  1|
  2|	sacos.sa 3.3 12/19/90
  3|
  4|	Description: The entry point sAcos computes the inverse cosine of
  5|		an input argument; sAcosd does the same except for denormalized
  6|		input.
  7|
  8|	Input: Double-extended number X in location pointed to
  9|		by address register a0.
 10|
 11|	Output: The value arccos(X) returned in floating-point register Fp0.
 12|
 13|	Accuracy and Monotonicity: The returned result is within 3 ulps in
 14|		64 significant bit, i.e. within 0.5001 ulp to 53 bits if the
 15|		result is subsequently rounded to double precision. The
 16|		result is provably monotonic in double precision.
 17|
 18|	Speed: The program sCOS takes approximately 310 cycles.
 19|
 20|	Algorithm:
 21|
 22|	ACOS
 23|	1. If |X| >= 1, go to 3.
 24|
 25|	2. (|X| < 1) Calculate acos(X) by
 26|		z := (1-X) / (1+X)
 27|		acos(X) = 2 * atan( sqrt(z) ).
 28|		Exit.
 29|
 30|	3. If |X| > 1, go to 5.
 31|
 32|	4. (|X| = 1) If X > 0, return 0. Otherwise, return Pi. Exit.
 33|
 34|	5. (|X| > 1) Generate an invalid operation by 0 * infinity.
 35|		Exit.
 36|
 37
 38|		Copyright (C) Motorola, Inc. 1990
 39|			All Rights Reserved
 40|
 41|	THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA
 42|	The copyright notice above does not evidence any
 43|	actual or intended publication of such source code.
 44
 45|SACOS	idnt	2,1 | Motorola 040 Floating Point Software Package
 46
 47	|section	8
 48
 49PI:	.long 0x40000000,0xC90FDAA2,0x2168C235,0x00000000
 50PIBY2:	.long 0x3FFF0000,0xC90FDAA2,0x2168C235,0x00000000
 51
 52	|xref	t_operr
 53	|xref	t_frcinx
 54	|xref	satan
 55
 56	.global	sacosd
 57sacosd:
 58|--ACOS(X) = PI/2 FOR DENORMALIZED X
 59	fmovel		%d1,%fpcr		| ...load user's rounding mode/precision
 60	fmovex		PIBY2,%fp0
 61	bra		t_frcinx
 62
 63	.global	sacos
 64sacos:
 65	fmovex		(%a0),%fp0	| ...LOAD INPUT
 66
 67	movel		(%a0),%d0		| ...pack exponent with upper 16 fraction
 68	movew		4(%a0),%d0
 69	andil		#0x7FFFFFFF,%d0
 70	cmpil		#0x3FFF8000,%d0
 71	bges		ACOSBIG
 72
 73|--THIS IS THE USUAL CASE, |X| < 1
 74|--ACOS(X) = 2 * ATAN(	SQRT( (1-X)/(1+X) )	)
 75
 76	fmoves		#0x3F800000,%fp1
 77	faddx		%fp0,%fp1		| ...1+X
 78	fnegx		%fp0		| ... -X
 79	fadds		#0x3F800000,%fp0	| ...1-X
 80	fdivx		%fp1,%fp0		| ...(1-X)/(1+X)
 81	fsqrtx		%fp0		| ...SQRT((1-X)/(1+X))
 82	fmovemx	%fp0-%fp0,(%a0)	| ...overwrite input
 83	movel		%d1,-(%sp)	|save original users fpcr
 84	clrl		%d1
 85	bsr		satan		| ...ATAN(SQRT([1-X]/[1+X]))
 86	fmovel		(%sp)+,%fpcr	|restore users exceptions
 87	faddx		%fp0,%fp0		| ...2 * ATAN( STUFF )
 88	bra		t_frcinx
 89
 90ACOSBIG:
 91	fabsx		%fp0
 92	fcmps		#0x3F800000,%fp0
 93	fbgt		t_operr		|cause an operr exception
 94
 95|--|X| = 1, ACOS(X) = 0 OR PI
 96	movel		(%a0),%d0		| ...pack exponent with upper 16 fraction
 97	movew		4(%a0),%d0
 98	cmpl		#0,%d0		|D0 has original exponent+fraction
 99	bgts		ACOSP1
100
101|--X = -1
102|Returns PI and inexact exception
103	fmovex		PI,%fp0
104	fmovel		%d1,%FPCR
105	fadds		#0x00800000,%fp0	|cause an inexact exception to be put
106|					;into the 040 - will not trap until next
107|					;fp inst.
108	bra		t_frcinx
109
110ACOSP1:
111	fmovel		%d1,%FPCR
112	fmoves		#0x00000000,%fp0
113	rts				|Facos ; of +1 is exact
114
115	|end