x_store.s

RTEMS (Real-Time Executive for Multiprocessor Systems) is a free open source real-time operating sys

//
//      $Id: x_store.S,v 1.2 1999/07/26 22:11:02 joel Exp $
//
//	x_store.sa 3.2 1/24/91
//
//	store --- store operand to memory or register
//
//	Used by underflow and overflow handlers.
//
//	a6 = points to fp value to be stored.
//

//		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//	THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA 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.

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

	|section	8

fpreg_mask:
	.byte	0x80,0x40,0x20,0x10,0x08,0x04,0x02,0x01

#include "fpsp.defs"

	|xref	mem_write
	|xref	get_fline
	|xref	g_opcls
	|xref	g_dfmtou
	|xref	reg_dest

	.global	dest_ext
	.global	dest_dbl
	.global	dest_sgl

	.global	store
store:
	btstb	#E3,E_BYTE(%a6)
	beqs	E1_sto
E3_sto:
	movel	CMDREG3B(%a6),%d0
	bfextu	%d0{#6:#3},%d0		//isolate dest. reg from cmdreg3b
sto_fp:
	lea	fpreg_mask,%a1
	moveb	(%a1,%d0.w),%d0		//convert reg# to dynamic register mask
	tstb	LOCAL_SGN(%a0)
	beqs	is_pos
	bsetb	#sign_bit,LOCAL_EX(%a0)
is_pos:
	fmovemx (%a0),%d0		//move to correct register
//
//	if fp0-fp3 is being modified, we must put a copy
//	in the USER_FPn variable on the stack because all exception
//	handlers restore fp0-fp3 from there.
//
	cmpb	#0x80,%d0		
	bnes	not_fp0
	fmovemx %fp0-%fp0,USER_FP0(%a6)
	rts
not_fp0:
	cmpb	#0x40,%d0
	bnes	not_fp1
	fmovemx %fp1-%fp1,USER_FP1(%a6)
	rts
not_fp1:
	cmpb	#0x20,%d0
	bnes	not_fp2
	fmovemx %fp2-%fp2,USER_FP2(%a6)
	rts
not_fp2:
	cmpb	#0x10,%d0
	bnes	not_fp3
	fmovemx %fp3-%fp3,USER_FP3(%a6)
	rts
not_fp3:
	rts

E1_sto:
	bsrl	g_opcls		//returns opclass in d0
	cmpib	#3,%d0
	beq	opc011		//branch if opclass 3
	movel	CMDREG1B(%a6),%d0
	bfextu	%d0{#6:#3},%d0	//extract destination register
	bras	sto_fp

opc011:
	bsrl	g_dfmtou	//returns dest format in d0
//				;ext=00, sgl=01, dbl=10
	movel	%a0,%a1		//save source addr in a1
	movel	EXC_EA(%a6),%a0	//get the address
	cmpil	#0,%d0		//if dest format is extended
	beq	dest_ext	//then branch
	cmpil	#1,%d0		//if dest format is single
	beq	dest_sgl	//then branch
//
//	fall through to dest_dbl
//

//
//	dest_dbl --- write double precision value to user space
//
//Input
//	a0 -> destination address
//	a1 -> source in extended precision
//Output
//	a0 -> destroyed
//	a1 -> destroyed
//	d0 -> 0
//
//Changes extended precision to double precision.
// Note: no attempt is made to round the extended value to double.
//	dbl_sign = ext_sign
//	dbl_exp = ext_exp - $3fff(ext bias) + $7ff(dbl bias)
//	get rid of ext integer bit
//	dbl_mant = ext_mant{62:12}
//
//	    	---------------   ---------------    ---------------
//  extended ->  |s|    exp    |   |1| ms mant   |    | ls mant     |
//	    	---------------   ---------------    ---------------
//	   	 95	    64    63 62	      32      31     11	  0
//				     |			     |
//				     |			     |
//				     |			     |
//		 	             v   		     v
//	    		      ---------------   ---------------
//  double   ->  	      |s|exp| mant  |   |  mant       |
//	    		      ---------------   ---------------
//	   	 	      63     51   32   31	       0
//
dest_dbl:
	clrl	%d0		//clear d0
	movew	LOCAL_EX(%a1),%d0	//get exponent
	subw	#0x3fff,%d0	//subtract extended precision bias
	cmpw	#0x4000,%d0	//check if inf
	beqs	inf		//if so, special case
	addw	#0x3ff,%d0	//add double precision bias
	swap	%d0		//d0 now in upper word
	lsll	#4,%d0		//d0 now in proper place for dbl prec exp
	tstb	LOCAL_SGN(%a1)	
	beqs	get_mant	//if positive, go process mantissa
	bsetl	#31,%d0		//if negative, put in sign information
//				; before continuing
	bras	get_mant	//go process mantissa
inf:
	movel	#0x7ff00000,%d0	//load dbl inf exponent
	clrl	LOCAL_HI(%a1)	//clear msb
	tstb	LOCAL_SGN(%a1)
	beqs	dbl_inf		//if positive, go ahead and write it
	bsetl	#31,%d0		//if negative put in sign information
dbl_inf:
	movel	%d0,LOCAL_EX(%a1)	//put the new exp back on the stack
	bras	dbl_wrt
get_mant:
	movel	LOCAL_HI(%a1),%d1	//get ms mantissa
	bfextu	%d1{#1:#20},%d1	//get upper 20 bits of ms
	orl	%d1,%d0		//put these bits in ms word of double
	movel	%d0,LOCAL_EX(%a1)	//put the new exp back on the stack
	movel	LOCAL_HI(%a1),%d1	//get ms mantissa
	movel	#21,%d0		//load shift count
	lsll	%d0,%d1		//put lower 11 bits in upper bits
	movel	%d1,LOCAL_HI(%a1)	//build lower lword in memory
	movel	LOCAL_LO(%a1),%d1	//get ls mantissa
	bfextu	%d1{#0:#21},%d0	//get ls 21 bits of double
	orl	%d0,LOCAL_HI(%a1)	//put them in double result
dbl_wrt:
	movel	#0x8,%d0		//byte count for double precision number
	exg	%a0,%a1		//a0=supervisor source, a1=user dest
	bsrl	mem_write	//move the number to the user's memory
	rts
//
//	dest_sgl --- write single precision value to user space
//
//Input
//	a0 -> destination address
//	a1 -> source in extended precision
//
//Output
//	a0 -> destroyed
//	a1 -> destroyed
//	d0 -> 0
//
//Changes extended precision to single precision.
//	sgl_sign = ext_sign
//	sgl_exp = ext_exp - $3fff(ext bias) + $7f(sgl bias)
//	get rid of ext integer bit
//	sgl_mant = ext_mant{62:12}
//
//	    	---------------   ---------------    ---------------
//  extended ->  |s|    exp    |   |1| ms mant   |    | ls mant     |
//	    	---------------   ---------------    ---------------
//	   	 95	    64    63 62	   40 32      31     12	  0
//				     |	   |
//				     |	   |
//				     |	   |
//		 	             v     v
//	    		      ---------------
//  single   ->  	      |s|exp| mant  |
//	    		      ---------------
//	   	 	      31     22     0
//
dest_sgl:
	clrl	%d0
	movew	LOCAL_EX(%a1),%d0	//get exponent
	subw	#0x3fff,%d0	//subtract extended precision bias
	cmpw	#0x4000,%d0	//check if inf
	beqs	sinf		//if so, special case
	addw	#0x7f,%d0		//add single precision bias
	swap	%d0		//put exp in upper word of d0
	lsll	#7,%d0		//shift it into single exp bits
	tstb	LOCAL_SGN(%a1)	
	beqs	get_sman	//if positive, continue
	bsetl	#31,%d0		//if negative, put in sign first
	bras	get_sman	//get mantissa
sinf:
	movel	#0x7f800000,%d0	//load single inf exp to d0
	tstb	LOCAL_SGN(%a1)
	beqs	sgl_wrt		//if positive, continue
	bsetl	#31,%d0		//if negative, put in sign info
	bras	sgl_wrt

get_sman:
	movel	LOCAL_HI(%a1),%d1	//get ms mantissa
	bfextu	%d1{#1:#23},%d1	//get upper 23 bits of ms
	orl	%d1,%d0		//put these bits in ms word of single

sgl_wrt:
	movel	%d0,L_SCR1(%a6)	//put the new exp back on the stack
	movel	#0x4,%d0		//byte count for single precision number
	tstl	%a0		//users destination address
	beqs	sgl_Dn		//destination is a data register
	exg	%a0,%a1		//a0=supervisor source, a1=user dest
	leal	L_SCR1(%a6),%a0	//point a0 to data
	bsrl	mem_write	//move the number to the user's memory
	rts
sgl_Dn:
	bsrl	get_fline	//returns fline word in d0
	andw	#0x7,%d0		//isolate register number
	movel	%d0,%d1		//d1 has size:reg formatted for reg_dest
	orl	#0x10,%d1		//reg_dest wants size added to reg#
	bral	reg_dest	//size is X, rts in reg_dest will
//				;return to caller of dest_sgl
	
dest_ext:
	tstb	LOCAL_SGN(%a1)	//put back sign into exponent word
	beqs	dstx_cont
	bsetb	#sign_bit,LOCAL_EX(%a1)
dstx_cont:
	clrb	LOCAL_SGN(%a1)	//clear out the sign byte

	movel	#0x0c,%d0		//byte count for extended number
	exg	%a0,%a1		//a0=supervisor source, a1=user dest
	bsrl	mem_write	//move the number to the user's memory
	rts

	|end