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

• Lines: 650
• Date: Sat Feb 24 22:58:43 1996
• Orig file: v1.3.93/linux/arch/m68k/fpsp040/round.S
• Orig date: Thu Jan 1 02:00:00 1970

diff -u --recursive --new-file v1.3.93/linux/arch/m68k/fpsp040/round.S linux/arch/m68k/fpsp040/round.S
@@ -0,0 +1,649 @@
+|
+|	round.sa 3.4 7/29/91
+|
+|	handle rounding and normalization tasks
+|
+|
+|
+|		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+|	THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA 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.
+
+|ROUND	idnt    2,1 | Motorola 040 Floating Point Software Package
+
+	|section	8
+
+	.include "fpsp.h"
+
+|
+|	round --- round result according to precision/mode
+|
+|	a0 points to the input operand in the internal extended format 
+|	d1(high word) contains rounding precision:
+|		ext = $0000xxxx
+|		sgl = $0001xxxx
+|		dbl = $0002xxxx
+|	d1(low word) contains rounding mode:
+|		RN  = $xxxx0000
+|		RZ  = $xxxx0001
+|		RM  = $xxxx0010
+|		RP  = $xxxx0011
+|	d0{31:29} contains the g,r,s bits (extended)
+|
+|	On return the value pointed to by a0 is correctly rounded,
+|	a0 is preserved and the g-r-s bits in d0 are cleared.
+|	The result is not typed - the tag field is invalid.  The
+|	result is still in the internal extended format.
+|
+|	The INEX bit of USER_FPSR will be set if the rounded result was
+|	inexact (i.e. if any of the g-r-s bits were set).
+|
+
+	.global	round
+round:
+| If g=r=s=0 then result is exact and round is done, else set 
+| the inex flag in status reg and continue.  
+|
+	bsrs	ext_grs			|this subroutine looks at the 
+|					:rounding precision and sets 
+|					;the appropriate g-r-s bits.
+	tstl	%d0			|if grs are zero, go force
+	bne	rnd_cont		|lower bits to zero for size
+	
+	swap	%d1			|set up d1.w for round prec.
+	bra	truncate
+
+rnd_cont:
+|
+| Use rounding mode as an index into a jump table for these modes.
+|
+	orl	#inx2a_mask,USER_FPSR(%a6) |set inex2/ainex
+	lea	mode_tab,%a1
+	movel	(%a1,%d1.w*4),%a1
+	jmp	(%a1)
+|
+| Jump table indexed by rounding mode in d1.w.  All following assumes
+| grs != 0.
+|
+mode_tab:
+	.long	rnd_near
+	.long	rnd_zero
+	.long	rnd_mnus
+	.long	rnd_plus
+|
+|	ROUND PLUS INFINITY
+|
+|	If sign of fp number = 0 (positive), then add 1 to l.
+|
+rnd_plus:
+	swap 	%d1			|set up d1 for round prec.
+	tstb	LOCAL_SGN(%a0)		|check for sign
+	bmi	truncate		|if positive then truncate
+	movel	#0xffffffff,%d0		|force g,r,s to be all f's
+	lea	add_to_l,%a1
+	movel	(%a1,%d1.w*4),%a1
+	jmp	(%a1)
+|
+|	ROUND MINUS INFINITY
+|
+|	If sign of fp number = 1 (negative), then add 1 to l.
+|
+rnd_mnus:
+	swap 	%d1			|set up d1 for round prec.
+	tstb	LOCAL_SGN(%a0)		|check for sign	
+	bpl	truncate		|if negative then truncate
+	movel	#0xffffffff,%d0		|force g,r,s to be all f's
+	lea	add_to_l,%a1
+	movel	(%a1,%d1.w*4),%a1
+	jmp	(%a1)
+|
+|	ROUND ZERO
+|
+|	Always truncate.
+rnd_zero:
+	swap 	%d1			|set up d1 for round prec.
+	bra	truncate
+|
+|
+|	ROUND NEAREST
+|
+|	If (g=1), then add 1 to l and if (r=s=0), then clear l
+|	Note that this will round to even in case of a tie.
+|
+rnd_near:
+	swap 	%d1			|set up d1 for round prec.
+	asll	#1,%d0			|shift g-bit to c-bit
+	bcc	truncate		|if (g=1) then
+	lea	add_to_l,%a1
+	movel	(%a1,%d1.w*4),%a1
+	jmp	(%a1)
+
+|
+|	ext_grs --- extract guard, round and sticky bits
+|
+| Input:	d1 =		PREC:ROUND
+| Output:  	d0{31:29}=	guard, round, sticky
+|
+| The ext_grs extract the guard/round/sticky bits according to the
+| selected rounding precision. It is called by the round subroutine
+| only.  All registers except d0 are kept intact. d0 becomes an 
+| updated guard,round,sticky in d0{31:29}
+|
+| Notes: the ext_grs uses the round PREC, and therefore has to swap d1
+|	 prior to usage, and needs to restore d1 to original.
+|
+ext_grs:
+	swap	%d1			|have d1.w point to round precision
+	cmpiw	#0,%d1
+	bnes	sgl_or_dbl
+	bras	end_ext_grs
+ 
+sgl_or_dbl:
+	moveml	%d2/%d3,-(%a7)		|make some temp registers
+	cmpiw	#1,%d1
+	bnes	grs_dbl
+grs_sgl:
+	bfextu	LOCAL_HI(%a0){#24:#2},%d3	|sgl prec. g-r are 2 bits right
+	movel	#30,%d2			|of the sgl prec. limits
+	lsll	%d2,%d3			|shift g-r bits to MSB of d3
+	movel	LOCAL_HI(%a0),%d2		|get word 2 for s-bit test
+	andil	#0x0000003f,%d2		|s bit is the or of all other 
+	bnes	st_stky			|bits to the right of g-r
+	tstl	LOCAL_LO(%a0)		|test lower mantissa
+	bnes	st_stky			|if any are set, set sticky
+	tstl	%d0			|test original g,r,s
+	bnes	st_stky			|if any are set, set sticky
+	bras	end_sd			|if words 3 and 4 are clr, exit
+grs_dbl:    
+	bfextu	LOCAL_LO(%a0){#21:#2},%d3	|dbl-prec. g-r are 2 bits right
+	movel	#30,%d2			|of the dbl prec. limits
+	lsll	%d2,%d3			|shift g-r bits to the MSB of d3
+	movel	LOCAL_LO(%a0),%d2		|get lower mantissa  for s-bit test
+	andil	#0x000001ff,%d2		|s bit is the or-ing of all 
+	bnes	st_stky			|other bits to the right of g-r
+	tstl	%d0			|test word original g,r,s
+	bnes	st_stky			|if any are set, set sticky
+	bras	end_sd			|if clear, exit
+st_stky:
+	bset	#rnd_stky_bit,%d3
+end_sd:
+	movel	%d3,%d0			|return grs to d0
+	moveml	(%a7)+,%d2/%d3		|restore scratch registers
+end_ext_grs:
+	swap	%d1			|restore d1 to original
+	rts
+
+|*******************  Local Equates
+	.set	ad_1_sgl,0x00000100	|  constant to add 1 to l-bit in sgl prec
+	.set	ad_1_dbl,0x00000800	|  constant to add 1 to l-bit in dbl prec
+
+
+|Jump table for adding 1 to the l-bit indexed by rnd prec
+
+add_to_l:
+	.long	add_ext
+	.long	add_sgl
+	.long	add_dbl
+	.long	add_dbl
+|
+|	ADD SINGLE
+|
+add_sgl:
+	addl	#ad_1_sgl,LOCAL_HI(%a0)
+	bccs	scc_clr			|no mantissa overflow
+	roxrw  LOCAL_HI(%a0)		|shift v-bit back in
+	roxrw  LOCAL_HI+2(%a0)		|shift v-bit back in
+	addw	#0x1,LOCAL_EX(%a0)	|and incr exponent
+scc_clr:
+	tstl	%d0			|test for rs = 0
+	bnes	sgl_done
+	andiw  #0xfe00,LOCAL_HI+2(%a0)	|clear the l-bit
+sgl_done:
+	andil	#0xffffff00,LOCAL_HI(%a0) |truncate bits beyond sgl limit
+	clrl	LOCAL_LO(%a0)		|clear d2
+	rts
+
+|
+|	ADD EXTENDED
+|
+add_ext:
+	addql  #1,LOCAL_LO(%a0)		|add 1 to l-bit
+	bccs	xcc_clr			|test for carry out
+	addql  #1,LOCAL_HI(%a0)		|propogate carry
+	bccs	xcc_clr
+	roxrw  LOCAL_HI(%a0)		|mant is 0 so restore v-bit
+	roxrw  LOCAL_HI+2(%a0)		|mant is 0 so restore v-bit
+	roxrw	LOCAL_LO(%a0)
+	roxrw	LOCAL_LO+2(%a0)
+	addw	#0x1,LOCAL_EX(%a0)	|and inc exp
+xcc_clr:
+	tstl	%d0			|test rs = 0
+	bnes	add_ext_done
+	andib	#0xfe,LOCAL_LO+3(%a0)	|clear the l bit
+add_ext_done:
+	rts
+|
+|	ADD DOUBLE
+|
+add_dbl:
+	addl	#ad_1_dbl,LOCAL_LO(%a0)
+	bccs	dcc_clr
+	addql	#1,LOCAL_HI(%a0)		|propogate carry
+	bccs	dcc_clr
+	roxrw	LOCAL_HI(%a0)		|mant is 0 so restore v-bit
+	roxrw	LOCAL_HI+2(%a0)		|mant is 0 so restore v-bit
+	roxrw	LOCAL_LO(%a0)
+	roxrw	LOCAL_LO+2(%a0)
+	addw	#0x1,LOCAL_EX(%a0)	|incr exponent
+dcc_clr:
+	tstl	%d0			|test for rs = 0
+	bnes	dbl_done
+	andiw	#0xf000,LOCAL_LO+2(%a0)	|clear the l-bit
+
+dbl_done:
+	andil	#0xfffff800,LOCAL_LO(%a0) |truncate bits beyond dbl limit
+	rts
+
+error:
+	rts
+|
+| Truncate all other bits
+|
+trunct:
+	.long	end_rnd
+	.long	sgl_done
+	.long	dbl_done
+	.long	dbl_done
+
+truncate:
+	lea	trunct,%a1
+	movel	(%a1,%d1.w*4),%a1
+	jmp	(%a1)
+
+end_rnd:
+	rts
+
+|
+|	NORMALIZE
+|
+| These routines (nrm_zero & nrm_set) normalize the unnorm.  This 
+| is done by shifting the mantissa left while decrementing the 
+| exponent.
+|
+| NRM_SET shifts and decrements until there is a 1 set in the integer 
+| bit of the mantissa (msb in d1).
+|
+| NRM_ZERO shifts and decrements until there is a 1 set in the integer 
+| bit of the mantissa (msb in d1) unless this would mean the exponent 
+| would go less than 0.  In that case the number becomes a denorm - the 
+| exponent (d0) is set to 0 and the mantissa (d1 & d2) is not 
+| normalized.
+|
+| Note that both routines have been optimized (for the worst case) and 
+| therefore do not have the easy to follow decrement/shift loop.
+|
+|	NRM_ZERO
+|
+|	Distance to first 1 bit in mantissa = X
+|	Distance to 0 from exponent = Y
+|	If X < Y
+|	Then
+|	  nrm_set
+|	Else
+|	  shift mantissa by Y
+|	  set exponent = 0
+|
+|input:
+|	FP_SCR1 = exponent, ms mantissa part, ls mantissa part
+|output:
+|	L_SCR1{4} = fpte15 or ete15 bit
+|
+	.global	nrm_zero
+nrm_zero:
+	movew	LOCAL_EX(%a0),%d0
+	cmpw   #64,%d0          |see if exp > 64 
+	bmis	d0_less
+	bsr	nrm_set		|exp > 64 so exp won't exceed 0 
+	rts
+d0_less:
+	moveml	%d2/%d3/%d5/%d6,-(%a7)
+	movel	LOCAL_HI(%a0),%d1
+	movel	LOCAL_LO(%a0),%d2
+
+	bfffo	%d1{#0:#32},%d3	|get the distance to the first 1 
+|				;in ms mant
+	beqs	ms_clr		|branch if no bits were set
+	cmpw	%d3,%d0		|of X>Y
+	bmis	greater		|then exp will go past 0 (neg) if 
+|				;it is just shifted
+	bsr	nrm_set		|else exp won't go past 0
+	moveml	(%a7)+,%d2/%d3/%d5/%d6
+	rts	
+greater:
+	movel	%d2,%d6		|save ls mant in d6
+	lsll	%d0,%d2		|shift ls mant by count
+	lsll	%d0,%d1		|shift ms mant by count
+	movel	#32,%d5
+	subl	%d0,%d5		|make op a denorm by shifting bits 
+	lsrl	%d5,%d6		|by the number in the exp, then 
+|				;set exp = 0.
+	orl	%d6,%d1		|shift the ls mant bits into the ms mant
+	movel	#0,%d0		|same as if decremented exp to 0 
+|				;while shifting
+	movew	%d0,LOCAL_EX(%a0)
+	movel	%d1,LOCAL_HI(%a0)
+	movel	%d2,LOCAL_LO(%a0)
+	moveml	(%a7)+,%d2/%d3/%d5/%d6
+	rts
+ms_clr:
+	bfffo	%d2{#0:#32},%d3	|check if any bits set in ls mant
+	beqs	all_clr		|branch if none set
+	addw	#32,%d3
+	cmpw	%d3,%d0		|if X>Y
+	bmis	greater		|then branch
+	bsr	nrm_set		|else exp won't go past 0
+	moveml	(%a7)+,%d2/%d3/%d5/%d6
+	rts
+all_clr:
+	movew	#0,LOCAL_EX(%a0)	|no mantissa bits set. Set exp = 0.
+	moveml	(%a7)+,%d2/%d3/%d5/%d6
+	rts
+|
+|	NRM_SET
+|
+	.global	nrm_set
+nrm_set:
+	movel	%d7,-(%a7)
+	bfffo	LOCAL_HI(%a0){#0:#32},%d7 |find first 1 in ms mant to d7)
+	beqs	lower		|branch if ms mant is all 0's
+
+	movel	%d6,-(%a7)
+
+	subw	%d7,LOCAL_EX(%a0)	|sub exponent by count
+	movel	LOCAL_HI(%a0),%d0	|d0 has ms mant
+	movel	LOCAL_LO(%a0),%d1 |d1 has ls mant
+
+	lsll	%d7,%d0		|shift first 1 to j bit position
+	movel	%d1,%d6		|copy ls mant into d6
+	lsll	%d7,%d6		|shift ls mant by count
+	movel	%d6,LOCAL_LO(%a0)	|store ls mant into memory
+	moveql	#32,%d6
+	subl	%d7,%d6		|continue shift
+	lsrl	%d6,%d1		|shift off all bits but those that will
+|				;be shifted into ms mant
+	orl	%d1,%d0		|shift the ls mant bits into the ms mant
+	movel	%d0,LOCAL_HI(%a0)	|store ms mant into memory
+	moveml	(%a7)+,%d7/%d6	|restore registers
+	rts
+
+|
+| We get here if ms mant was = 0, and we assume ls mant has bits 
+| set (otherwise this would have been tagged a zero not a denorm).
+|
+lower:
+	movew	LOCAL_EX(%a0),%d0	|d0 has exponent
+	movel	LOCAL_LO(%a0),%d1	|d1 has ls mant
+	subw	#32,%d0		|account for ms mant being all zeros
+	bfffo	%d1{#0:#32},%d7	|find first 1 in ls mant to d7)
+	subw	%d7,%d0		|subtract shift count from exp
+	lsll	%d7,%d1		|shift first 1 to integer bit in ms mant
+	movew	%d0,LOCAL_EX(%a0)	|store ms mant
+	movel	%d1,LOCAL_HI(%a0)	|store exp
+	clrl	LOCAL_LO(%a0)	|clear ls mant
+	movel	(%a7)+,%d7
+	rts
+|
+|	denorm --- denormalize an intermediate result
+|
+|	Used by underflow.
+|
+| Input: 
+|	a0	 points to the operand to be denormalized
+|		 (in the internal extended format)
+|		 
+|	d0: 	 rounding precision
+| Output:
+|	a0	 points to the denormalized result
+|		 (in the internal extended format)
+|
+|	d0 	is guard,round,sticky
+|
+| d0 comes into this routine with the rounding precision. It 
+| is then loaded with the denormalized exponent threshold for the 
+| rounding precision.
+|
+
+	.global	denorm
+denorm:
+	btstb	#6,LOCAL_EX(%a0)	|check for exponents between $7fff-$4000
+	beqs	no_sgn_ext	
+	bsetb	#7,LOCAL_EX(%a0)	|sign extend if it is so
+no_sgn_ext:
+
+	cmpib	#0,%d0		|if 0 then extended precision
+	bnes	not_ext		|else branch
+
+	clrl	%d1		|load d1 with ext threshold
+	clrl	%d0		|clear the sticky flag
+	bsr	dnrm_lp		|denormalize the number
+	tstb	%d1		|check for inex
+	beq	no_inex		|if clr, no inex
+	bras	dnrm_inex	|if set, set inex
+
+not_ext:
+	cmpil	#1,%d0		|if 1 then single precision
+	beqs	load_sgl	|else must be 2, double prec
+
+load_dbl:
+	movew	#dbl_thresh,%d1	|put copy of threshold in d1
+	movel	%d1,%d0		|copy d1 into d0
+	subw	LOCAL_EX(%a0),%d0	|diff = threshold - exp
+	cmpw	#67,%d0		|if diff > 67 (mant + grs bits)
+	bpls	chk_stky	|then branch (all bits would be 
+|				; shifted off in denorm routine)
+	clrl	%d0		|else clear the sticky flag
+	bsr	dnrm_lp		|denormalize the number
+	tstb	%d1		|check flag
+	beqs	no_inex		|if clr, no inex
+	bras	dnrm_inex	|if set, set inex
+
+load_sgl:
+	movew	#sgl_thresh,%d1	|put copy of threshold in d1
+	movel	%d1,%d0		|copy d1 into d0
+	subw	LOCAL_EX(%a0),%d0	|diff = threshold - exp
+	cmpw	#67,%d0		|if diff > 67 (mant + grs bits)
+	bpls	chk_stky	|then branch (all bits would be 
+|				; shifted off in denorm routine)
+	clrl	%d0		|else clear the sticky flag
+	bsr	dnrm_lp		|denormalize the number
+	tstb	%d1		|check flag
+	beqs	no_inex		|if clr, no inex
+	bras	dnrm_inex	|if set, set inex
+
+chk_stky:
+	tstl	LOCAL_HI(%a0)	|check for any bits set
+	bnes	set_stky
+	tstl	LOCAL_LO(%a0)	|check for any bits set
+	bnes	set_stky
+	bras	clr_mant
+set_stky:
+	orl	#inx2a_mask,USER_FPSR(%a6) |set inex2/ainex
+	movel	#0x20000000,%d0	|set sticky bit in return value
+clr_mant:
+	movew	%d1,LOCAL_EX(%a0)		|load exp with threshold
+	movel	#0,LOCAL_HI(%a0) 	|set d1 = 0 (ms mantissa)
+	movel	#0,LOCAL_LO(%a0)		|set d2 = 0 (ms mantissa)
+	rts
+dnrm_inex:
+	orl	#inx2a_mask,USER_FPSR(%a6) |set inex2/ainex
+no_inex:
+	rts
+
+|
+|	dnrm_lp --- normalize exponent/mantissa to specified threshhold
+|
+| Input:
+|	a0		points to the operand to be denormalized
+|	d0{31:29} 	initial guard,round,sticky
+|	d1{15:0}	denormalization threshold
+| Output:
+|	a0		points to the denormalized operand
+|	d0{31:29}	final guard,round,sticky
+|	d1.b		inexact flag:  all ones means inexact result
+|
+| The LOCAL_LO and LOCAL_GRS parts of the value are copied to FP_SCR2
+| so that bfext can be used to extract the new low part of the mantissa.
+| Dnrm_lp can be called with a0 pointing to ETEMP or WBTEMP and there 
+| is no LOCAL_GRS scratch word following it on the fsave frame.
+|
+	.global	dnrm_lp
+dnrm_lp:
+	movel	%d2,-(%sp)		|save d2 for temp use
+	btstb	#E3,E_BYTE(%a6)		|test for type E3 exception
+	beqs	not_E3			|not type E3 exception
+	bfextu	WBTEMP_GRS(%a6){#6:#3},%d2	|extract guard,round, sticky  bit
+	movel	#29,%d0
+	lsll	%d0,%d2			|shift g,r,s to their postions
+	movel	%d2,%d0
+not_E3:
+	movel	(%sp)+,%d2		|restore d2
+	movel	LOCAL_LO(%a0),FP_SCR2+LOCAL_LO(%a6)
+	movel	%d0,FP_SCR2+LOCAL_GRS(%a6)
+	movel	%d1,%d0			|copy the denorm threshold
+	subw	LOCAL_EX(%a0),%d1		|d1 = threshold - uns exponent
+	bles	no_lp			|d1 <= 0
+	cmpw	#32,%d1			
+	blts	case_1			|0 = d1 < 32 
+	cmpw	#64,%d1
+	blts	case_2			|32 <= d1 < 64
+	bra	case_3			|d1 >= 64
+|
+| No normalization necessary
+|
+no_lp:
+	clrb	%d1			|set no inex2 reported
+	movel	FP_SCR2+LOCAL_GRS(%a6),%d0	|restore original g,r,s
+	rts
+|
+| case (0<d1<32)
+|
+case_1:
+	movel	%d2,-(%sp)
+	movew	%d0,LOCAL_EX(%a0)		|exponent = denorm threshold
+	movel	#32,%d0
+	subw	%d1,%d0			|d0 = 32 - d1
+	bfextu	LOCAL_EX(%a0){%d0:#32},%d2
+	bfextu	%d2{%d1:%d0},%d2		|d2 = new LOCAL_HI
+	bfextu	LOCAL_HI(%a0){%d0:#32},%d1	|d1 = new LOCAL_LO
+	bfextu	FP_SCR2+LOCAL_LO(%a6){%d0:#32},%d0	|d0 = new G,R,S
+	movel	%d2,LOCAL_HI(%a0)		|store new LOCAL_HI
+	movel	%d1,LOCAL_LO(%a0)		|store new LOCAL_LO
+	clrb	%d1
+	bftst	%d0{#2:#30}	
+	beqs	c1nstky
+	bsetl	#rnd_stky_bit,%d0
+	st	%d1
+c1nstky:
+	movel	FP_SCR2+LOCAL_GRS(%a6),%d2	|restore original g,r,s
+	andil	#0xe0000000,%d2		|clear all but G,R,S
+	tstl	%d2			|test if original G,R,S are clear
+	beqs	grs_clear
+	orl	#0x20000000,%d0		|set sticky bit in d0
+grs_clear:
+	andil	#0xe0000000,%d0		|clear all but G,R,S
+	movel	(%sp)+,%d2
+	rts
+|
+| case (32<=d1<64)
+|
+case_2:
+	movel	%d2,-(%sp)
+	movew	%d0,LOCAL_EX(%a0)		|unsigned exponent = threshold
+	subw	#32,%d1			|d1 now between 0 and 32
+	movel	#32,%d0
+	subw	%d1,%d0			|d0 = 32 - d1
+	bfextu	LOCAL_EX(%a0){%d0:#32},%d2
+	bfextu	%d2{%d1:%d0},%d2		|d2 = new LOCAL_LO
+	bfextu	LOCAL_HI(%a0){%d0:#32},%d1	|d1 = new G,R,S
+	bftst	%d1{#2:#30}
+	bnes	c2_sstky		|bra if sticky bit to be set
+	bftst	FP_SCR2+LOCAL_LO(%a6){%d0:#32}
+	bnes	c2_sstky		|bra if sticky bit to be set
+	movel	%d1,%d0
+	clrb	%d1
+	bras	end_c2
+c2_sstky:
+	movel	%d1,%d0
+	bsetl	#rnd_stky_bit,%d0
+	st	%d1
+end_c2:
+	clrl	LOCAL_HI(%a0)		|store LOCAL_HI = 0
+	movel	%d2,LOCAL_LO(%a0)		|store LOCAL_LO
+	movel	FP_SCR2+LOCAL_GRS(%a6),%d2	|restore original g,r,s
+	andil	#0xe0000000,%d2		|clear all but G,R,S
+	tstl	%d2			|test if original G,R,S are clear
+	beqs	clear_grs		
+	orl	#0x20000000,%d0		|set sticky bit in d0
+clear_grs:
+	andil	#0xe0000000,%d0		|get rid of all but G,R,S
+	movel	(%sp)+,%d2
+	rts
+|
+| d1 >= 64 Force the exponent to be the denorm threshold with the
+| correct sign.
+|
+case_3:
+	movew	%d0,LOCAL_EX(%a0)
+	tstw	LOCAL_SGN(%a0)
+	bges	c3con
+c3neg:
+	orl	#0x80000000,LOCAL_EX(%a0)
+c3con:
+	cmpw	#64,%d1
+	beqs	sixty_four
+	cmpw	#65,%d1
+	beqs	sixty_five
+|
+| Shift value is out of range.  Set d1 for inex2 flag and
+| return a zero with the given threshold.
+|
+	clrl	LOCAL_HI(%a0)
+	clrl	LOCAL_LO(%a0)
+	movel	#0x20000000,%d0
+	st	%d1
+	rts
+
+sixty_four:
+	movel	LOCAL_HI(%a0),%d0
+	bfextu	%d0{#2:#30},%d1
+	andil	#0xc0000000,%d0
+	bras	c3com
+	
+sixty_five:
+	movel	LOCAL_HI(%a0),%d0
+	bfextu	%d0{#1:#31},%d1
+	andil	#0x80000000,%d0
+	lsrl	#1,%d0			|shift high bit into R bit
+
+c3com:
+	tstl	%d1
+	bnes	c3ssticky
+	tstl	LOCAL_LO(%a0)
+	bnes	c3ssticky
+	tstb	FP_SCR2+LOCAL_GRS(%a6)
+	bnes	c3ssticky
+	clrb	%d1
+	bras	c3end
+
+c3ssticky:
+	bsetl	#rnd_stky_bit,%d0
+	st	%d1
+c3end:
+	clrl	LOCAL_HI(%a0)
+	clrl	LOCAL_LO(%a0)
+	rts
+
+	|end