|
|	get_op.sa 3.6 5/19/92
|
|	get_op.sa 3.5 4/26/91
|
|  Description: This routine is called by the unsupported format/data
| type exception handler ('unsupp' - vector 55) and the unimplemented
| instruction exception handler ('unimp' - vector 11).  'get_op'
| determines the opclass (0, 2, or 3) and branches to the
| opclass handler routine.  See 68881/2 User's Manual table 4-11
| for a description of the opclasses.
|
| For UNSUPPORTED data/format (exception vector 55) and for
| UNIMPLEMENTED instructions (exception vector 11) the following
| applies:
|
| - For unnormormalized numbers (opclass 0, 2, or 3) the
| number(s) is normalized and the operand type tag is updated.
|		
| - For a packed number (opclass 2) the number is unpacked and the
| operand type tag is updated.
|
| - For denormalized numbers (opclass 0 or 2) the number(s) is not
| changed but passed to the next module.  The next module for
| unimp is do_func, the next module for unsupp is res_func.
|
| For UNSUPPORTED data/format (exception vector 55) only the
| following applies:
|
| - If there is a move out with a packed number (opclass 3) the
| number is packed and written to user memory.  For the other
| opclasses the number(s) are written back to the fsave stack
| and the instruction is then restored back into the '040.  The
| '040 is then able to complete the instruction.
|
| For example:
| fadd.x fpm,fpn where the fpm contains an unnormalized number.
| The '040 takes an unsupported data trap and gets to this
| routine.  The number is normalized, put back on the stack and
| then an frestore is done to restore the instruction back into
| the '040.  The '040 then re-executes the fadd.x fpm,fpn with
| a normalized number in the source and the instruction is
| successful.
|		
| Next consider if in the process of normalizing the un-
| normalized number it becomes a denormalized number.  The
| routine which converts the unnorm to a norm (called mk_norm)
| detects this and tags the number as a denorm.  The routine
| res_func sees the denorm tag and converts the denorm to a
| norm.  The instruction is then restored back into the '040
| which re_executess the instruction.
|
|
|		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|	THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA 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.

GET_OP:    |idnt    2,1 | Motorola 040 Floating Point Software Package

	|section	8

	.include "fpsp.h"

	.global	PIRN,PIRZRM,PIRP
	.global	SMALRN,SMALRZRM,SMALRP
	.global	BIGRN,BIGRZRM,BIGRP

PIRN:
	.long 0x40000000,0xc90fdaa2,0x2168c235    |pi
PIRZRM:
	.long 0x40000000,0xc90fdaa2,0x2168c234    |pi
PIRP:
	.long 0x40000000,0xc90fdaa2,0x2168c235    |pi

|round to nearest
SMALRN:
	.long 0x3ffd0000,0x9a209a84,0xfbcff798    |log10(2)
	.long 0x40000000,0xadf85458,0xa2bb4a9a    |e
	.long 0x3fff0000,0xb8aa3b29,0x5c17f0bc    |log2(e)
	.long 0x3ffd0000,0xde5bd8a9,0x37287195    |log10(e)
	.long 0x00000000,0x00000000,0x00000000    |0.0
| round to zero;round to negative infinity
SMALRZRM:
	.long 0x3ffd0000,0x9a209a84,0xfbcff798    |log10(2)
	.long 0x40000000,0xadf85458,0xa2bb4a9a    |e
	.long 0x3fff0000,0xb8aa3b29,0x5c17f0bb    |log2(e)
	.long 0x3ffd0000,0xde5bd8a9,0x37287195    |log10(e)
	.long 0x00000000,0x00000000,0x00000000    |0.0
| round to positive infinity
SMALRP:
	.long 0x3ffd0000,0x9a209a84,0xfbcff799    |log10(2)
	.long 0x40000000,0xadf85458,0xa2bb4a9b    |e
	.long 0x3fff0000,0xb8aa3b29,0x5c17f0bc    |log2(e)
	.long 0x3ffd0000,0xde5bd8a9,0x37287195    |log10(e)
	.long 0x00000000,0x00000000,0x00000000    |0.0

|round to nearest
BIGRN:
	.long 0x3ffe0000,0xb17217f7,0xd1cf79ac    |ln(2)
	.long 0x40000000,0x935d8ddd,0xaaa8ac17    |ln(10)
	.long 0x3fff0000,0x80000000,0x00000000    |10 ^ 0

	.global	PTENRN
PTENRN:
	.long 0x40020000,0xA0000000,0x00000000    |10 ^ 1
	.long 0x40050000,0xC8000000,0x00000000    |10 ^ 2
	.long 0x400C0000,0x9C400000,0x00000000    |10 ^ 4
	.long 0x40190000,0xBEBC2000,0x00000000    |10 ^ 8
	.long 0x40340000,0x8E1BC9BF,0x04000000    |10 ^ 16
	.long 0x40690000,0x9DC5ADA8,0x2B70B59E    |10 ^ 32
	.long 0x40D30000,0xC2781F49,0xFFCFA6D5    |10 ^ 64
	.long 0x41A80000,0x93BA47C9,0x80E98CE0    |10 ^ 128
	.long 0x43510000,0xAA7EEBFB,0x9DF9DE8E    |10 ^ 256
	.long 0x46A30000,0xE319A0AE,0xA60E91C7    |10 ^ 512
	.long 0x4D480000,0xC9767586,0x81750C17    |10 ^ 1024
	.long 0x5A920000,0x9E8B3B5D,0xC53D5DE5    |10 ^ 2048
	.long 0x75250000,0xC4605202,0x8A20979B    |10 ^ 4096
|round to minus infinity
BIGRZRM:
	.long 0x3ffe0000,0xb17217f7,0xd1cf79ab    |ln(2)
	.long 0x40000000,0x935d8ddd,0xaaa8ac16    |ln(10)
	.long 0x3fff0000,0x80000000,0x00000000    |10 ^ 0

	.global	PTENRM
PTENRM:
	.long 0x40020000,0xA0000000,0x00000000    |10 ^ 1
	.long 0x40050000,0xC8000000,0x00000000    |10 ^ 2
	.long 0x400C0000,0x9C400000,0x00000000    |10 ^ 4
	.long 0x40190000,0xBEBC2000,0x00000000    |10 ^ 8
	.long 0x40340000,0x8E1BC9BF,0x04000000    |10 ^ 16
	.long 0x40690000,0x9DC5ADA8,0x2B70B59D    |10 ^ 32
	.long 0x40D30000,0xC2781F49,0xFFCFA6D5    |10 ^ 64
	.long 0x41A80000,0x93BA47C9,0x80E98CDF    |10 ^ 128
	.long 0x43510000,0xAA7EEBFB,0x9DF9DE8D    |10 ^ 256
	.long 0x46A30000,0xE319A0AE,0xA60E91C6    |10 ^ 512
	.long 0x4D480000,0xC9767586,0x81750C17    |10 ^ 1024
	.long 0x5A920000,0x9E8B3B5D,0xC53D5DE5    |10 ^ 2048
	.long 0x75250000,0xC4605202,0x8A20979A    |10 ^ 4096
|round to positive infinity
BIGRP:
	.long 0x3ffe0000,0xb17217f7,0xd1cf79ac    |ln(2)
	.long 0x40000000,0x935d8ddd,0xaaa8ac17    |ln(10)
	.long 0x3fff0000,0x80000000,0x00000000    |10 ^ 0

	.global	PTENRP
PTENRP:
	.long 0x40020000,0xA0000000,0x00000000    |10 ^ 1
	.long 0x40050000,0xC8000000,0x00000000    |10 ^ 2
	.long 0x400C0000,0x9C400000,0x00000000    |10 ^ 4
	.long 0x40190000,0xBEBC2000,0x00000000    |10 ^ 8
	.long 0x40340000,0x8E1BC9BF,0x04000000    |10 ^ 16
	.long 0x40690000,0x9DC5ADA8,0x2B70B59E    |10 ^ 32
	.long 0x40D30000,0xC2781F49,0xFFCFA6D6    |10 ^ 64
	.long 0x41A80000,0x93BA47C9,0x80E98CE0    |10 ^ 128
	.long 0x43510000,0xAA7EEBFB,0x9DF9DE8E    |10 ^ 256
	.long 0x46A30000,0xE319A0AE,0xA60E91C7    |10 ^ 512
	.long 0x4D480000,0xC9767586,0x81750C18    |10 ^ 1024
	.long 0x5A920000,0x9E8B3B5D,0xC53D5DE6    |10 ^ 2048
	.long 0x75250000,0xC4605202,0x8A20979B    |10 ^ 4096

	|xref	nrm_zero
	|xref	decbin
	|xref	round

	.global    get_op
	.global    uns_getop
	.global    uni_getop
get_op:
	clrb	DY_MO_FLG(%a6)
	tstb	UFLG_TMP(%a6)	|test flag for unsupp/unimp state
	beqs	uni_getop

uns_getop:
	btstb	#direction_bit,CMDREG1B(%a6)
	bne	opclass3	|branch if a fmove out (any kind)
	btstb	#6,CMDREG1B(%a6)
	beqs	uns_notpacked

	bfextu	CMDREG1B(%a6){#3:#3},%d0
	cmpb	#3,%d0
	beq	pack_source	|check for a packed src op, branch if so
uns_notpacked:
	bsr	chk_dy_mo	|set the dyadic/monadic flag
	tstb	DY_MO_FLG(%a6)
	beqs	src_op_ck	|if monadic, go check src op
|				;else, check dst op (fall through)

	btstb	#7,DTAG(%a6)
	beqs	src_op_ck	|if dst op is norm, check src op
	bras	dst_ex_dnrm	|else, handle destination unnorm/dnrm

uni_getop:
	bfextu	CMDREG1B(%a6){#0:#6},%d0 |get opclass and src fields
	cmpil	#0x17,%d0		|if op class and size fields are $17, 
|				;it is FMOVECR; if not, continue
|
| If the instruction is fmovecr, exit get_op.  It is handled
| in do_func and smovecr.sa.
|
	bne	not_fmovecr	|handle fmovecr as an unimplemented inst
	rts

not_fmovecr:
	btstb	#E1,E_BYTE(%a6)	|if set, there is a packed operand
	bne	pack_source	|check for packed src op, branch if so

| The following lines of are coded to optimize on normalized operands
	moveb	STAG(%a6),%d0
	orb	DTAG(%a6),%d0	|check if either of STAG/DTAG msb set
	bmis	dest_op_ck	|if so, some op needs to be fixed
	rts

dest_op_ck:
	btstb	#7,DTAG(%a6)	|check for unsupported data types in
	beqs	src_op_ck	|the destination, if not, check src op
	bsr	chk_dy_mo	|set dyadic/monadic flag
	tstb	DY_MO_FLG(%a6)	|
	beqs	src_op_ck	|if monadic, check src op
|
| At this point, destination has an extended denorm or unnorm.
|
dst_ex_dnrm:
	movew	FPTEMP_EX(%a6),%d0 |get destination exponent
	andiw	#0x7fff,%d0	|mask sign, check if exp = 0000
	beqs	src_op_ck	|if denorm then check source op.
|				;denorms are taken care of in res_func 
|				;(unsupp) or do_func (unimp)
|				;else unnorm fall through
	leal	FPTEMP(%a6),%a0	|point a0 to dop - used in mk_norm
	bsr	mk_norm		|go normalize - mk_norm returns:
|				;L_SCR1{7:5} = operand tag 
|				;	(000 = norm, 100 = denorm)
|				;L_SCR1{4} = fpte15 or ete15 
|				;	0 = exp >  $3fff
|				;	1 = exp <= $3fff
|				;and puts the normalized num back 
|				;on the fsave stack
|
	moveb L_SCR1(%a6),DTAG(%a6) |write the new tag & fpte15 
|				;to the fsave stack and fall 
|				;through to check source operand
|
src_op_ck:
	btstb	#7,STAG(%a6)
	beq	end_getop	|check for unsupported data types on the
|				;source operand
	btstb	#5,STAG(%a6)
	bnes	src_sd_dnrm	|if bit 5 set, handle sgl/dbl denorms
|
| At this point only unnorms or extended denorms are possible.
|
src_ex_dnrm:
	movew	ETEMP_EX(%a6),%d0 |get source exponent
	andiw	#0x7fff,%d0	|mask sign, check if exp = 0000
	beq	end_getop	|if denorm then exit, denorms are 
|				;handled in do_func
	leal	ETEMP(%a6),%a0	|point a0 to sop - used in mk_norm
	bsr	mk_norm		|go normalize - mk_norm returns:
|				;L_SCR1{7:5} = operand tag 
|				;	(000 = norm, 100 = denorm)
|				;L_SCR1{4} = fpte15 or ete15 
|				;	0 = exp >  $3fff
|				;	1 = exp <= $3fff
|				;and puts the normalized num back 
|				;on the fsave stack
|
	moveb	L_SCR1(%a6),STAG(%a6) |write the new tag & ete15 
	rts			|end_getop

|
| At this point, only single or double denorms are possible.
| If the inst is not fmove, normalize the source.  If it is,
| do nothing to the input.
|
src_sd_dnrm:
	btstb	#4,CMDREG1B(%a6)	|differentiate between sgl/dbl denorm
	bnes	is_double
is_single:
	movew	#0x3f81,%d1	|write bias for sgl denorm
	bras	common		|goto the common code
is_double:
	movew	#0x3c01,%d1	|write the bias for a dbl denorm
common:
	btstb	#sign_bit,ETEMP_EX(%a6) |grab sign bit of mantissa
	beqs	pos	
	bset	#15,%d1		|set sign bit because it is negative
pos:
	movew	%d1,ETEMP_EX(%a6)
|				;put exponent on stack

	movew	CMDREG1B(%a6),%d1
	andw	#0xe3ff,%d1	|clear out source specifier
	orw	#0x0800,%d1	|set source specifier to extended prec
	movew	%d1,CMDREG1B(%a6)	|write back to the command word in stack
|				;this is needed to fix unsupp data stack
	leal	ETEMP(%a6),%a0	|point a0 to sop
	
	bsr	mk_norm		|convert sgl/dbl denorm to norm
	moveb	L_SCR1(%a6),STAG(%a6) |put tag into source tag reg - d0
	rts			|end_getop
|
| At this point, the source is definitely packed, whether
| instruction is dyadic or monadic is still unknown
|
pack_source:
	movel	FPTEMP_LO(%a6),ETEMP(%a6)	|write ms part of packed 
|				;number to etemp slot
	bsr	chk_dy_mo	|set dyadic/monadic flag
	bsr	unpack

	tstb	DY_MO_FLG(%a6)
	beqs	end_getop	|if monadic, exit
|				;else, fix FPTEMP
pack_dya:
	bfextu	CMDREG1B(%a6){#6:#3},%d0 |extract dest fp reg
	movel	#7,%d1
	subl	%d0,%d1
	clrl	%d0
	bsetl	%d1,%d0		|set up d0 as a dynamic register mask
	fmovemx %d0,FPTEMP(%a6)	|write to FPTEMP

	btstb	#7,DTAG(%a6)	|check dest tag for unnorm or denorm
	bne	dst_ex_dnrm	|else, handle the unnorm or ext denorm
|
| Dest is not denormalized.  Check for norm, and set fpte15 
| accordingly.
|
	moveb	DTAG(%a6),%d0
	andib	#0xf0,%d0		|strip to only dtag:fpte15
	tstb	%d0		|check for normalized value
	bnes	end_getop	|if inf/nan/zero leave get_op
	movew	FPTEMP_EX(%a6),%d0
	andiw	#0x7fff,%d0
	cmpiw	#0x3fff,%d0	|check if fpte15 needs setting
	bges	end_getop	|if >= $3fff, leave fpte15=0
	orb	#0x10,DTAG(%a6)
	bras	end_getop

|
| At this point, it is either an fmoveout packed, unnorm or denorm
|
opclass3:
	clrb	DY_MO_FLG(%a6)	|set dyadic/monadic flag to monadic
	bfextu	CMDREG1B(%a6){#4:#2},%d0
	cmpib	#3,%d0
	bne	src_ex_dnrm	|if not equal, must be unnorm or denorm
|				;else it is a packed move out
|				;exit
end_getop:
	rts

|
| Sets the DY_MO_FLG correctly. This is used only on if it is an
| unuspported data type exception.  Set if dyadic.
|
chk_dy_mo:
	movew	CMDREG1B(%a6),%d0	
	btstl	#5,%d0		|testing extension command word
	beqs	set_mon		|if bit 5 = 0 then monadic
	btstl	#4,%d0		|know that bit 5 = 1
	beqs	set_dya		|if bit 4 = 0 then dyadic
	andiw	#0x007f,%d0	|get rid of all but extension bits {6:0}
	cmpiw 	#0x0038,%d0	|if extension = $38 then fcmp (dyadic)
	bnes	set_mon
set_dya:
	st	DY_MO_FLG(%a6)	|set the inst flag type to dyadic
	rts
set_mon:
	clrb	DY_MO_FLG(%a6)	|set the inst flag type to monadic
	rts
|
|	MK_NORM
|
| Normalizes unnormalized numbers, sets tag to norm or denorm, sets unfl
| exception if denorm.
|
| CASE opclass 0x0 unsupp
|	mk_norm till msb set
|	set tag = norm
|
| CASE opclass 0x0 unimp
|	mk_norm till msb set or exp = 0
|	if integer bit = 0
|	   tag = denorm
|	else
|	   tag = norm
|
| CASE opclass 011 unsupp
|	mk_norm till msb set or exp = 0
|	if integer bit = 0
|	   tag = denorm
|	   set unfl_nmcexe = 1
|	else
|	   tag = norm
|
| if exp <= $3fff
|   set ete15 or fpte15 = 1
| else set ete15 or fpte15 = 0

| input:
|	a0 = points to operand to be normalized
| output:
|	L_SCR1{7:5} = operand tag (000 = norm, 100 = denorm)
|	L_SCR1{4}   = fpte15 or ete15 (0 = exp > $3fff, 1 = exp <=$3fff)
|	the normalized operand is placed back on the fsave stack
mk_norm:	
	clrl	L_SCR1(%a6)
	bclrb	#sign_bit,LOCAL_EX(%a0)
	sne	LOCAL_SGN(%a0)	|transform into internal extended format

	cmpib	#0x2c,1+EXC_VEC(%a6) |check if unimp
	bnes	uns_data	|branch if unsupp
	bsr	uni_inst	|call if unimp (opclass 0x0)
	bras	reload
uns_data:
	btstb	#direction_bit,CMDREG1B(%a6) |check transfer direction
	bnes	bit_set		|branch if set (opclass 011)
	bsr	uns_opx		|call if opclass 0x0
	bras	reload
bit_set:
	bsr	uns_op3		|opclass 011
reload:
	cmpw	#0x3fff,LOCAL_EX(%a0) |if exp > $3fff
	bgts	end_mk		|   fpte15/ete15 already set to 0
	bsetb	#4,L_SCR1(%a6)	|else set fpte15/ete15 to 1
|				;calling routine actually sets the 
|				;value on the stack (along with the 
|				;tag), since this routine doesn't 
|				;know if it should set ete15 or fpte15
|				;ie, it doesn't know if this is the 
|				;src op or dest op.
end_mk:
	bfclr	LOCAL_SGN(%a0){#0:#8}
	beqs	end_mk_pos
	bsetb	#sign_bit,LOCAL_EX(%a0) |convert back to IEEE format
end_mk_pos:
	rts
|
|     CASE opclass 011 unsupp
|
uns_op3:
	bsr	nrm_zero	|normalize till msb = 1 or exp = zero
	btstb	#7,LOCAL_HI(%a0)	|if msb = 1
	bnes	no_unfl		|then branch
set_unfl:
	orw	#dnrm_tag,L_SCR1(%a6) |set denorm tag
	bsetb	#unfl_bit,FPSR_EXCEPT(%a6) |set unfl exception bit
no_unfl:
	rts
|
|     CASE opclass 0x0 unsupp
|
uns_opx:
	bsr	nrm_zero	|normalize the number
	btstb	#7,LOCAL_HI(%a0)	|check if integer bit (j-bit) is set 
	beqs	uns_den		|if clear then now have a denorm
uns_nrm:
	orb	#norm_tag,L_SCR1(%a6) |set tag to norm
	rts
uns_den:
	orb	#dnrm_tag,L_SCR1(%a6) |set tag to denorm
	rts
|
|     CASE opclass 0x0 unimp
|
uni_inst:
	bsr	nrm_zero
	btstb	#7,LOCAL_HI(%a0)	|check if integer bit (j-bit) is set 
	beqs	uni_den		|if clear then now have a denorm
uni_nrm:
	orb	#norm_tag,L_SCR1(%a6) |set tag to norm
	rts
uni_den:
	orb	#dnrm_tag,L_SCR1(%a6) |set tag to denorm
	rts

|
|	Decimal to binary conversion
|
| Special cases of inf and NaNs are completed outside of decbin.  
| If the input is an snan, the snan bit is not set.
| 
| input:
|	ETEMP(a6)	- points to packed decimal string in memory
| output:
|	fp0	- contains packed string converted to extended precision
|	ETEMP	- same as fp0
unpack:
	movew	CMDREG1B(%a6),%d0	|examine command word, looking for fmove's
	andw	#0x3b,%d0
	beq	move_unpack	|special handling for fmove: must set FPSR_CC

	movew	ETEMP(%a6),%d0	|get word with inf information
	bfextu	%d0{#20:#12},%d1	|get exponent into d1
	cmpiw	#0x0fff,%d1	|test for inf or NaN
	bnes	try_zero	|if not equal, it is not special
	bfextu	%d0{#17:#3},%d1	|get SE and y bits into d1
	cmpiw	#7,%d1		|SE and y bits must be on for special
	bnes	try_zero	|if not on, it is not special
|input is of the special cases of inf and NaN
	tstl	ETEMP_HI(%a6)	|check ms mantissa
	bnes	fix_nan		|if non-zero, it is a NaN
	tstl	ETEMP_LO(%a6)	|check ls mantissa
	bnes	fix_nan		|if non-zero, it is a NaN
	bra	finish		|special already on stack
fix_nan:
	btstb	#signan_bit,ETEMP_HI(%a6) |test for snan
	bne	finish
	orl	#snaniop_mask,USER_FPSR(%a6) |always set snan if it is so
	bra	finish
try_zero:
	movew	ETEMP_EX+2(%a6),%d0 |get word 4
	andiw	#0x000f,%d0	|clear all but last ni(y)bble
	tstw	%d0		|check for zero.
	bne	not_spec
	tstl	ETEMP_HI(%a6)	|check words 3 and 2
	bne	not_spec
	tstl	ETEMP_LO(%a6)	|check words 1 and 0
	bne	not_spec
	tstl	ETEMP(%a6)	|test sign of the zero
	bges	pos_zero
	movel	#0x80000000,ETEMP(%a6) |write neg zero to etemp
	clrl	ETEMP_HI(%a6)
	clrl	ETEMP_LO(%a6)
	bra	finish
pos_zero:
	clrl	ETEMP(%a6)
	clrl	ETEMP_HI(%a6)
	clrl	ETEMP_LO(%a6)
	bra	finish

not_spec:
	fmovemx %fp0-%fp1,-(%a7)	|save fp0 - decbin returns in it
	bsr	decbin
	fmovex %fp0,ETEMP(%a6)	|put the unpacked sop in the fsave stack
	fmovemx (%a7)+,%fp0-%fp1
	fmovel	#0,%FPSR		|clr fpsr from decbin
	bra	finish

|
| Special handling for packed move in:  Same results as all other
| packed cases, but we must set the FPSR condition codes properly.
|
move_unpack:
	movew	ETEMP(%a6),%d0	|get word with inf information
	bfextu	%d0{#20:#12},%d1	|get exponent into d1
	cmpiw	#0x0fff,%d1	|test for inf or NaN
	bnes	mtry_zero	|if not equal, it is not special
	bfextu	%d0{#17:#3},%d1	|get SE and y bits into d1
	cmpiw	#7,%d1		|SE and y bits must be on for special
	bnes	mtry_zero	|if not on, it is not special
|input is of the special cases of inf and NaN
	tstl	ETEMP_HI(%a6)	|check ms mantissa
	bnes	mfix_nan		|if non-zero, it is a NaN
	tstl	ETEMP_LO(%a6)	|check ls mantissa
	bnes	mfix_nan		|if non-zero, it is a NaN
|input is inf
	orl	#inf_mask,USER_FPSR(%a6) |set I bit
	tstl	ETEMP(%a6)	|check sign
	bge	finish
	orl	#neg_mask,USER_FPSR(%a6) |set N bit
	bra	finish		|special already on stack
mfix_nan:
	orl	#nan_mask,USER_FPSR(%a6) |set NaN bit
	moveb	#nan_tag,STAG(%a6)	|set stag to NaN
	btstb	#signan_bit,ETEMP_HI(%a6) |test for snan
	bnes	mn_snan
	orl	#snaniop_mask,USER_FPSR(%a6) |set snan bit
	btstb	#snan_bit,FPCR_ENABLE(%a6) |test for snan enabled
	bnes	mn_snan
	bsetb	#signan_bit,ETEMP_HI(%a6) |force snans to qnans
mn_snan:
	tstl	ETEMP(%a6)	|check for sign
	bge	finish		|if clr, go on
	orl	#neg_mask,USER_FPSR(%a6) |set N bit
	bra	finish

mtry_zero:
	movew	ETEMP_EX+2(%a6),%d0 |get word 4
	andiw	#0x000f,%d0	|clear all but last ni(y)bble
	tstw	%d0		|check for zero.
	bnes	mnot_spec
	tstl	ETEMP_HI(%a6)	|check words 3 and 2
	bnes	mnot_spec
	tstl	ETEMP_LO(%a6)	|check words 1 and 0
	bnes	mnot_spec
	tstl	ETEMP(%a6)	|test sign of the zero
	bges	mpos_zero
	orl	#neg_mask+z_mask,USER_FPSR(%a6) |set N and Z
	movel	#0x80000000,ETEMP(%a6) |write neg zero to etemp
	clrl	ETEMP_HI(%a6)
	clrl	ETEMP_LO(%a6)
	bras	finish
mpos_zero:
	orl	#z_mask,USER_FPSR(%a6) |set Z
	clrl	ETEMP(%a6)
	clrl	ETEMP_HI(%a6)
	clrl	ETEMP_LO(%a6)
	bras	finish

mnot_spec:
	fmovemx %fp0-%fp1,-(%a7)	|save fp0 ,fp1 - decbin returns in fp0
	bsr	decbin
	fmovex %fp0,ETEMP(%a6)
|				;put the unpacked sop in the fsave stack
	fmovemx (%a7)+,%fp0-%fp1

finish:
	movew	CMDREG1B(%a6),%d0	|get the command word
	andw	#0xfbff,%d0	|change the source specifier field to 
|				;extended (was packed).
	movew	%d0,CMDREG1B(%a6)	|write command word back to fsave stack
|				;we need to do this so the 040 will 
|				;re-execute the inst. without taking 
|				;another packed trap.

fix_stag:
|Converted result is now in etemp on fsave stack, now set the source 
|tag (stag) 
|	if (ete =$7fff) then INF or NAN
|		if (etemp = $x.0----0) then
|			stag = INF
|		else
|			stag = NAN
|	else
|		if (ete = $0000) then
|			stag = ZERO
|		else
|			stag = NORM
|
| Note also that the etemp_15 bit (just right of the stag) must
| be set accordingly.  
|
	movew		ETEMP_EX(%a6),%d1
	andiw		#0x7fff,%d1   |strip sign
	cmpw  		#0x7fff,%d1
	bnes  		z_or_nrm
	movel		ETEMP_HI(%a6),%d1
	bnes		is_nan
	movel		ETEMP_LO(%a6),%d1
	bnes		is_nan
is_inf:
	moveb		#0x40,STAG(%a6)
	movel		#0x40,%d0
	rts
is_nan:
	moveb		#0x60,STAG(%a6)
	movel		#0x60,%d0
	rts
z_or_nrm:
	tstw		%d1  
	bnes		is_nrm
is_zro:
| For a zero, set etemp_15
	moveb		#0x30,STAG(%a6)
	movel		#0x20,%d0
	rts
is_nrm:
| For a norm, check if the exp <= $3fff; if so, set etemp_15
	cmpiw		#0x3fff,%d1
	bles		set_bit15
	moveb		#0,STAG(%a6)
	bras		end_is_nrm
set_bit15:
	moveb		#0x10,STAG(%a6)
end_is_nrm:
	movel		#0,%d0
end_fix:
	rts
 
end_get:
	rts
	|end
