patch-1.3.94 linux/arch/m68k/fpsp040/decbin.S

• Lines: 507
• Date: Sat Feb 24 22:58:42 1996
• Orig file: v1.3.93/linux/arch/m68k/fpsp040/decbin.S
• Orig date: Thu Jan 1 02:00:00 1970

diff -u --recursive --new-file v1.3.93/linux/arch/m68k/fpsp040/decbin.S linux/arch/m68k/fpsp040/decbin.S
@@ -0,0 +1,506 @@
+|
+|	decbin.sa 3.3 12/19/90
+|
+|	Description: Converts normalized packed bcd value pointed to by
+|	register A6 to extended-precision value in FP0.
+|
+|	Input: Normalized packed bcd value in ETEMP(a6).
+|
+|	Output:	Exact floating-point representation of the packed bcd value.
+|
+|	Saves and Modifies: D2-D5
+|
+|	Speed: The program decbin takes ??? cycles to execute.
+|
+|	Object Size:
+|
+|	External Reference(s): None.
+|
+|	Algorithm:
+|	Expected is a normal bcd (i.e. non-exceptional; all inf, zero,
+|	and NaN operands are dispatched without entering this routine)
+|	value in 68881/882 format at location ETEMP(A6).
+|
+|	A1.	Convert the bcd exponent to binary by successive adds and muls.
+|	Set the sign according to SE. Subtract 16 to compensate
+|	for the mantissa which is to be interpreted as 17 integer
+|	digits, rather than 1 integer and 16 fraction digits.
+|	Note: this operation can never overflow.
+|
+|	A2. Convert the bcd mantissa to binary by successive
+|	adds and muls in FP0. Set the sign according to SM.
+|	The mantissa digits will be converted with the decimal point
+|	assumed following the least-significant digit.
+|	Note: this operation can never overflow.
+|
+|	A3. Count the number of leading/trailing zeros in the
+|	bcd string.  If SE is positive, count the leading zeros;
+|	if negative, count the trailing zeros.  Set the adjusted
+|	exponent equal to the exponent from A1 and the zero count
+|	added if SM = 1 and subtracted if SM = 0.  Scale the
+|	mantissa the equivalent of forcing in the bcd value:
+|
+|	SM = 0	a non-zero digit in the integer position
+|	SM = 1	a non-zero digit in Mant0, lsd of the fraction
+|
+|	this will insure that any value, regardless of its
+|	representation (ex. 0.1E2, 1E1, 10E0, 100E-1), is converted
+|	consistently.
+|
+|	A4. Calculate the factor 10^exp in FP1 using a table of
+|	10^(2^n) values.  To reduce the error in forming factors
+|	greater than 10^27, a directed rounding scheme is used with
+|	tables rounded to RN, RM, and RP, according to the table
+|	in the comments of the pwrten section.
+|
+|	A5. Form the final binary number by scaling the mantissa by
+|	the exponent factor.  This is done by multiplying the
+|	mantissa in FP0 by the factor in FP1 if the adjusted
+|	exponent sign is positive, and dividing FP0 by FP1 if
+|	it is negative.
+|
+|	Clean up and return.  Check if the final mul or div resulted
+|	in an inex2 exception.  If so, set inex1 in the fpsr and 
+|	check if the inex1 exception is enabled.  If so, set d7 upper
+|	word to $0100.  This will signal unimp.sa that an enabled inex1
+|	exception occured.  Unimp will fix the stack.
+|	
+
+|		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.
+
+|DECBIN    idnt    2,1 | Motorola 040 Floating Point Software Package
+
+	|section	8
+
+	.include "fpsp.h"
+
+|
+|	PTENRN, PTENRM, and PTENRP are arrays of powers of 10 rounded
+|	to nearest, minus, and plus, respectively.  The tables include
+|	10**{1,2,4,8,16,32,64,128,256,512,1024,2048,4096}.  No rounding
+|	is required until the power is greater than 27, however, all
+|	tables include the first 5 for ease of indexing.
+|
+	|xref	PTENRN
+	|xref	PTENRM
+	|xref	PTENRP
+
+RTABLE:	.byte	0,0,0,0
+	.byte	2,3,2,3
+	.byte	2,3,3,2
+	.byte	3,2,2,3
+
+	.global	decbin
+	.global	calc_e
+	.global	pwrten
+	.global	calc_m
+	.global	norm
+	.global	ap_st_z
+	.global	ap_st_n
+|
+	.set	FNIBS,7
+	.set	FSTRT,0
+|
+	.set	ESTRT,4
+	.set	EDIGITS,2	| 
+|
+| Constants in single precision
+FZERO: 	.long	0x00000000
+FONE: 	.long	0x3F800000
+FTEN: 	.long	0x41200000
+
+	.set	TEN,10
+
+|
+decbin:
+	| fmovel	#0,FPCR		;clr real fpcr
+	moveml	%d2-%d5,-(%a7)
+|
+| Calculate exponent:
+|  1. Copy bcd value in memory for use as a working copy.
+|  2. Calculate absolute value of exponent in d1 by mul and add.
+|  3. Correct for exponent sign.
+|  4. Subtract 16 to compensate for interpreting the mant as all integer digits.
+|     (i.e., all digits assumed left of the decimal point.)
+|
+| Register usage:
+|
+|  calc_e:
+|	(*)  d0: temp digit storage
+|	(*)  d1: accumulator for binary exponent
+|	(*)  d2: digit count
+|	(*)  d3: offset pointer
+|	( )  d4: first word of bcd
+|	( )  a0: pointer to working bcd value
+|	( )  a6: pointer to original bcd value
+|	(*)  FP_SCR1: working copy of original bcd value
+|	(*)  L_SCR1: copy of original exponent word
+|
+calc_e:
+	movel	#EDIGITS,%d2	|# of nibbles (digits) in fraction part
+	moveql	#ESTRT,%d3	|counter to pick up digits
+	leal	FP_SCR1(%a6),%a0	|load tmp bcd storage address
+	movel	ETEMP(%a6),(%a0)	|save input bcd value
+	movel	ETEMP_HI(%a6),4(%a0) |save words 2 and 3
+	movel	ETEMP_LO(%a6),8(%a0) |and work with these
+	movel	(%a0),%d4	|get first word of bcd
+	clrl	%d1		|zero d1 for accumulator
+e_gd:
+	mulul	#TEN,%d1	|mul partial product by one digit place
+	bfextu	%d4{%d3:#4},%d0	|get the digit and zero extend into d0
+	addl	%d0,%d1		|d1 = d1 + d0
+	addqb	#4,%d3		|advance d3 to the next digit
+	dbf	%d2,e_gd	|if we have used all 3 digits, exit loop
+	btst	#30,%d4		|get SE
+	beqs	e_pos		|don't negate if pos
+	negl	%d1		|negate before subtracting
+e_pos:
+	subl	#16,%d1		|sub to compensate for shift of mant
+	bges	e_save		|if still pos, do not neg
+	negl	%d1		|now negative, make pos and set SE
+	orl	#0x40000000,%d4	|set SE in d4,
+	orl	#0x40000000,(%a0)	|and in working bcd
+e_save:
+	movel	%d1,L_SCR1(%a6)	|save exp in memory
+|
+|
+| Calculate mantissa:
+|  1. Calculate absolute value of mantissa in fp0 by mul and add.
+|  2. Correct for mantissa sign.
+|     (i.e., all digits assumed left of the decimal point.)
+|
+| Register usage:
+|
+|  calc_m:
+|	(*)  d0: temp digit storage
+|	(*)  d1: lword counter
+|	(*)  d2: digit count
+|	(*)  d3: offset pointer
+|	( )  d4: words 2 and 3 of bcd
+|	( )  a0: pointer to working bcd value
+|	( )  a6: pointer to original bcd value
+|	(*) fp0: mantissa accumulator
+|	( )  FP_SCR1: working copy of original bcd value
+|	( )  L_SCR1: copy of original exponent word
+|
+calc_m:
+	moveql	#1,%d1		|word counter, init to 1
+	fmoves	FZERO,%fp0	|accumulator
+|
+|
+|  Since the packed number has a long word between the first & second parts,
+|  get the integer digit then skip down & get the rest of the
+|  mantissa.  We will unroll the loop once.
+|
+	bfextu	(%a0){#28:#4},%d0	|integer part is ls digit in long word
+	faddb	%d0,%fp0		|add digit to sum in fp0
+|
+|
+|  Get the rest of the mantissa.
+|
+loadlw:
+	movel	(%a0,%d1.L*4),%d4	|load mantissa lonqword into d4
+	moveql	#FSTRT,%d3	|counter to pick up digits
+	moveql	#FNIBS,%d2	|reset number of digits per a0 ptr
+md2b:
+	fmuls	FTEN,%fp0	|fp0 = fp0 * 10
+	bfextu	%d4{%d3:#4},%d0	|get the digit and zero extend
+	faddb	%d0,%fp0	|fp0 = fp0 + digit
+|
+|
+|  If all the digits (8) in that long word have been converted (d2=0),
+|  then inc d1 (=2) to point to the next long word and reset d3 to 0
+|  to initialize the digit offset, and set d2 to 7 for the digit count;
+|  else continue with this long word.
+|
+	addqb	#4,%d3		|advance d3 to the next digit
+	dbf	%d2,md2b		|check for last digit in this lw
+nextlw:
+	addql	#1,%d1		|inc lw pointer in mantissa
+	cmpl	#2,%d1		|test for last lw
+	ble	loadlw		|if not, get last one
+	
+|
+|  Check the sign of the mant and make the value in fp0 the same sign.
+|
+m_sign:
+	btst	#31,(%a0)	|test sign of the mantissa
+	beqs	ap_st_z		|if clear, go to append/strip zeros
+	fnegx	%fp0		|if set, negate fp0
+	
+|
+| Append/strip zeros:
+|
+|  For adjusted exponents which have an absolute value greater than 27*,
+|  this routine calculates the amount needed to normalize the mantissa
+|  for the adjusted exponent.  That number is subtracted from the exp
+|  if the exp was positive, and added if it was negative.  The purpose
+|  of this is to reduce the value of the exponent and the possibility
+|  of error in calculation of pwrten.
+|
+|  1. Branch on the sign of the adjusted exponent.
+|  2p.(positive exp)
+|   2. Check M16 and the digits in lwords 2 and 3 in decending order.
+|   3. Add one for each zero encountered until a non-zero digit.
+|   4. Subtract the count from the exp.
+|   5. Check if the exp has crossed zero in #3 above; make the exp abs
+|	   and set SE.
+|	6. Multiply the mantissa by 10**count.
+|  2n.(negative exp)
+|   2. Check the digits in lwords 3 and 2 in decending order.
+|   3. Add one for each zero encountered until a non-zero digit.
+|   4. Add the count to the exp.
+|   5. Check if the exp has crossed zero in #3 above; clear SE.
+|   6. Divide the mantissa by 10**count.
+|
+|  *Why 27?  If the adjusted exponent is within -28 < expA < 28, than
+|   any adjustment due to append/strip zeros will drive the resultane
+|   exponent towards zero.  Since all pwrten constants with a power
+|   of 27 or less are exact, there is no need to use this routine to
+|   attempt to lessen the resultant exponent.
+|
+| Register usage:
+|
+|  ap_st_z:
+|	(*)  d0: temp digit storage
+|	(*)  d1: zero count
+|	(*)  d2: digit count
+|	(*)  d3: offset pointer
+|	( )  d4: first word of bcd
+|	(*)  d5: lword counter
+|	( )  a0: pointer to working bcd value
+|	( )  FP_SCR1: working copy of original bcd value
+|	( )  L_SCR1: copy of original exponent word
+|
+|
+| First check the absolute value of the exponent to see if this
+| routine is necessary.  If so, then check the sign of the exponent
+| and do append (+) or strip (-) zeros accordingly.
+| This section handles a positive adjusted exponent.
+|
+ap_st_z:
+	movel	L_SCR1(%a6),%d1	|load expA for range test
+	cmpl	#27,%d1		|test is with 27
+	ble	pwrten		|if abs(expA) <28, skip ap/st zeros
+	btst	#30,(%a0)	|check sign of exp
+	bnes	ap_st_n		|if neg, go to neg side
+	clrl	%d1		|zero count reg
+	movel	(%a0),%d4		|load lword 1 to d4
+	bfextu	%d4{#28:#4},%d0	|get M16 in d0
+	bnes	ap_p_fx		|if M16 is non-zero, go fix exp
+	addql	#1,%d1		|inc zero count
+	moveql	#1,%d5		|init lword counter
+	movel	(%a0,%d5.L*4),%d4	|get lword 2 to d4
+	bnes	ap_p_cl		|if lw 2 is zero, skip it
+	addql	#8,%d1		|and inc count by 8
+	addql	#1,%d5		|inc lword counter
+	movel	(%a0,%d5.L*4),%d4	|get lword 3 to d4
+ap_p_cl:
+	clrl	%d3		|init offset reg
+	moveql	#7,%d2		|init digit counter
+ap_p_gd:
+	bfextu	%d4{%d3:#4},%d0	|get digit
+	bnes	ap_p_fx		|if non-zero, go to fix exp
+	addql	#4,%d3		|point to next digit
+	addql	#1,%d1		|inc digit counter
+	dbf	%d2,ap_p_gd	|get next digit
+ap_p_fx:
+	movel	%d1,%d0		|copy counter to d2
+	movel	L_SCR1(%a6),%d1	|get adjusted exp from memory
+	subl	%d0,%d1		|subtract count from exp
+	bges	ap_p_fm		|if still pos, go to pwrten
+	negl	%d1		|now its neg; get abs
+	movel	(%a0),%d4		|load lword 1 to d4
+	orl	#0x40000000,%d4	| and set SE in d4
+	orl	#0x40000000,(%a0)	| and in memory
+|
+| Calculate the mantissa multiplier to compensate for the striping of
+| zeros from the mantissa.
+|
+ap_p_fm:
+	movel	#PTENRN,%a1	|get address of power-of-ten table
+	clrl	%d3		|init table index
+	fmoves	FONE,%fp1	|init fp1 to 1
+	moveql	#3,%d2		|init d2 to count bits in counter
+ap_p_el:
+	asrl	#1,%d0		|shift lsb into carry
+	bccs	ap_p_en		|if 1, mul fp1 by pwrten factor
+	fmulx	(%a1,%d3),%fp1	|mul by 10**(d3_bit_no)
+ap_p_en:
+	addl	#12,%d3		|inc d3 to next rtable entry
+	tstl	%d0		|check if d0 is zero
+	bnes	ap_p_el		|if not, get next bit
+	fmulx	%fp1,%fp0		|mul mantissa by 10**(no_bits_shifted)
+	bras	pwrten		|go calc pwrten
+|
+| This section handles a negative adjusted exponent.
+|
+ap_st_n:
+	clrl	%d1		|clr counter
+	moveql	#2,%d5		|set up d5 to point to lword 3
+	movel	(%a0,%d5.L*4),%d4	|get lword 3
+	bnes	ap_n_cl		|if not zero, check digits
+	subl	#1,%d5		|dec d5 to point to lword 2
+	addql	#8,%d1		|inc counter by 8
+	movel	(%a0,%d5.L*4),%d4	|get lword 2
+ap_n_cl:
+	movel	#28,%d3		|point to last digit
+	moveql	#7,%d2		|init digit counter
+ap_n_gd:
+	bfextu	%d4{%d3:#4},%d0	|get digit
+	bnes	ap_n_fx		|if non-zero, go to exp fix
+	subql	#4,%d3		|point to previous digit
+	addql	#1,%d1		|inc digit counter
+	dbf	%d2,ap_n_gd	|get next digit
+ap_n_fx:
+	movel	%d1,%d0		|copy counter to d0
+	movel	L_SCR1(%a6),%d1	|get adjusted exp from memory
+	subl	%d0,%d1		|subtract count from exp
+	bgts	ap_n_fm		|if still pos, go fix mantissa
+	negl	%d1		|take abs of exp and clr SE
+	movel	(%a0),%d4		|load lword 1 to d4
+	andl	#0xbfffffff,%d4	| and clr SE in d4
+	andl	#0xbfffffff,(%a0)	| and in memory
+|
+| Calculate the mantissa multiplier to compensate for the appending of
+| zeros to the mantissa.
+|
+ap_n_fm:
+	movel	#PTENRN,%a1	|get address of power-of-ten table
+	clrl	%d3		|init table index
+	fmoves	FONE,%fp1	|init fp1 to 1
+	moveql	#3,%d2		|init d2 to count bits in counter
+ap_n_el:
+	asrl	#1,%d0		|shift lsb into carry
+	bccs	ap_n_en		|if 1, mul fp1 by pwrten factor
+	fmulx	(%a1,%d3),%fp1	|mul by 10**(d3_bit_no)
+ap_n_en:
+	addl	#12,%d3		|inc d3 to next rtable entry
+	tstl	%d0		|check if d0 is zero
+	bnes	ap_n_el		|if not, get next bit
+	fdivx	%fp1,%fp0		|div mantissa by 10**(no_bits_shifted)
+|
+|
+| Calculate power-of-ten factor from adjusted and shifted exponent.
+|
+| Register usage:
+|
+|  pwrten:
+|	(*)  d0: temp
+|	( )  d1: exponent
+|	(*)  d2: {FPCR[6:5],SM,SE} as index in RTABLE; temp
+|	(*)  d3: FPCR work copy
+|	( )  d4: first word of bcd
+|	(*)  a1: RTABLE pointer
+|  calc_p:
+|	(*)  d0: temp
+|	( )  d1: exponent
+|	(*)  d3: PWRTxx table index
+|	( )  a0: pointer to working copy of bcd
+|	(*)  a1: PWRTxx pointer
+|	(*) fp1: power-of-ten accumulator
+|
+| Pwrten calculates the exponent factor in the selected rounding mode
+| according to the following table:
+|	
+|	Sign of Mant  Sign of Exp  Rounding Mode  PWRTEN Rounding Mode
+|
+|	ANY	  ANY	RN	RN
+|
+|	 +	   +	RP	RP
+|	 -	   +	RP	RM
+|	 +	   -	RP	RM
+|	 -	   -	RP	RP
+|
+|	 +	   +	RM	RM
+|	 -	   +	RM	RP
+|	 +	   -	RM	RP
+|	 -	   -	RM	RM
+|
+|	 +	   +	RZ	RM
+|	 -	   +	RZ	RM
+|	 +	   -	RZ	RP
+|	 -	   -	RZ	RP
+|
+|
+pwrten:
+	movel	USER_FPCR(%a6),%d3 |get user's FPCR
+	bfextu	%d3{#26:#2},%d2	|isolate rounding mode bits
+	movel	(%a0),%d4		|reload 1st bcd word to d4
+	asll	#2,%d2		|format d2 to be
+	bfextu	%d4{#0:#2},%d0	| {FPCR[6],FPCR[5],SM,SE}
+	addl	%d0,%d2		|in d2 as index into RTABLE
+	leal	RTABLE,%a1	|load rtable base
+	moveb	(%a1,%d2),%d0	|load new rounding bits from table
+	clrl	%d3			|clear d3 to force no exc and extended
+	bfins	%d0,%d3{#26:#2}	|stuff new rounding bits in FPCR
+	fmovel	%d3,%FPCR		|write new FPCR
+	asrl	#1,%d0		|write correct PTENxx table
+	bccs	not_rp		|to a1
+	leal	PTENRP,%a1	|it is RP
+	bras	calc_p		|go to init section
+not_rp:
+	asrl	#1,%d0		|keep checking
+	bccs	not_rm
+	leal	PTENRM,%a1	|it is RM
+	bras	calc_p		|go to init section
+not_rm:
+	leal	PTENRN,%a1	|it is RN
+calc_p:
+	movel	%d1,%d0		|copy exp to d0;use d0
+	bpls	no_neg		|if exp is negative,
+	negl	%d0		|invert it
+	orl	#0x40000000,(%a0)	|and set SE bit
+no_neg:
+	clrl	%d3		|table index
+	fmoves	FONE,%fp1	|init fp1 to 1
+e_loop:
+	asrl	#1,%d0		|shift next bit into carry
+	bccs	e_next		|if zero, skip the mul
+	fmulx	(%a1,%d3),%fp1	|mul by 10**(d3_bit_no)
+e_next:
+	addl	#12,%d3		|inc d3 to next rtable entry
+	tstl	%d0		|check if d0 is zero
+	bnes	e_loop		|not zero, continue shifting
+|
+|
+|  Check the sign of the adjusted exp and make the value in fp0 the
+|  same sign. If the exp was pos then multiply fp1*fp0;
+|  else divide fp0/fp1.
+|
+| Register Usage:
+|  norm:
+|	( )  a0: pointer to working bcd value
+|	(*) fp0: mantissa accumulator
+|	( ) fp1: scaling factor - 10**(abs(exp))
+|
+norm:
+	btst	#30,(%a0)	|test the sign of the exponent
+	beqs	mul		|if clear, go to multiply
+div:
+	fdivx	%fp1,%fp0		|exp is negative, so divide mant by exp
+	bras	end_dec
+mul:
+	fmulx	%fp1,%fp0		|exp is positive, so multiply by exp
+|
+|
+| Clean up and return with result in fp0.
+|
+| If the final mul/div in decbin incurred an inex exception,
+| it will be inex2, but will be reported as inex1 by get_op.
+|
+end_dec:
+	fmovel	%FPSR,%d0		|get status register	
+	bclrl	#inex2_bit+8,%d0	|test for inex2 and clear it
+	fmovel	%d0,%FPSR		|return status reg w/o inex2
+	beqs	no_exc		|skip this if no exc
+	orl	#inx1a_mask,USER_FPSR(%a6) |set inex1/ainex
+no_exc:
+	moveml	(%a7)+,%d2-%d5
+	rts
+	|end