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/arch/m68k/fpsp040/sasin.S

https://bitbucket.org/evzijst/gittest
Assembly | 104 lines | 89 code | 15 blank | 0 comment | 1 complexity | 512783df7e22336de229dc0206ebb25b MD5 | raw file
  1|
  2|	sasin.sa 3.3 12/19/90
  3|
  4|	Description: The entry point sAsin computes the inverse sine of
  5|		an input argument; sAsind 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 arcsin(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 sASIN takes approximately 310 cycles.
 19|
 20|	Algorithm:
 21|
 22|	ASIN
 23|	1. If |X| >= 1, go to 3.
 24|
 25|	2. (|X| < 1) Calculate asin(X) by
 26|		z := sqrt( [1-X][1+X] )
 27|		asin(X) = atan( x / z ).
 28|		Exit.
 29|
 30|	3. If |X| > 1, go to 5.
 31|
 32|	4. (|X| = 1) sgn := sign(X), return asin(X) := sgn * Pi/2. 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 41|	THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA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|SASIN	idnt	2,1 | Motorola 040 Floating Point Software Package
 46
 47	|section	8
 48
 49PIBY2:	.long 0x3FFF0000,0xC90FDAA2,0x2168C235,0x00000000
 50
 51	|xref	t_operr
 52	|xref	t_frcinx
 53	|xref	t_extdnrm
 54	|xref	satan
 55
 56	.global	sasind
 57sasind:
 58|--ASIN(X) = X FOR DENORMALIZED X
 59
 60	bra		t_extdnrm
 61
 62	.global	sasin
 63sasin:
 64	fmovex		(%a0),%fp0	| ...LOAD INPUT
 65
 66	movel		(%a0),%d0
 67	movew		4(%a0),%d0
 68	andil		#0x7FFFFFFF,%d0
 69	cmpil		#0x3FFF8000,%d0
 70	bges		asinbig
 71
 72|--THIS IS THE USUAL CASE, |X| < 1
 73|--ASIN(X) = ATAN( X / SQRT( (1-X)(1+X) ) )
 74
 75	fmoves		#0x3F800000,%fp1
 76	fsubx		%fp0,%fp1		| ...1-X
 77	fmovemx	%fp2-%fp2,-(%a7)
 78	fmoves		#0x3F800000,%fp2
 79	faddx		%fp0,%fp2		| ...1+X
 80	fmulx		%fp2,%fp1		| ...(1+X)(1-X)
 81	fmovemx	(%a7)+,%fp2-%fp2
 82	fsqrtx		%fp1		| ...SQRT([1-X][1+X])
 83	fdivx		%fp1,%fp0		| ...X/SQRT([1-X][1+X])
 84	fmovemx	%fp0-%fp0,(%a0)
 85	bsr		satan
 86	bra		t_frcinx
 87
 88asinbig:
 89	fabsx		%fp0	 | ...|X|
 90	fcmps		#0x3F800000,%fp0
 91	fbgt		t_operr		|cause an operr exception
 92
 93|--|X| = 1, ASIN(X) = +- PI/2.
 94
 95	fmovex		PIBY2,%fp0
 96	movel		(%a0),%d0
 97	andil		#0x80000000,%d0	| ...SIGN BIT OF X
 98	oril		#0x3F800000,%d0	| ...+-1 IN SGL FORMAT
 99	movel		%d0,-(%sp)	| ...push SIGN(X) IN SGL-FMT
100	fmovel		%d1,%FPCR
101	fmuls		(%sp)+,%fp0
102	bra		t_frcinx
103
104	|end