|
  |	sgetem.sa 3.1 12/10/90
  |
  |	The entry point sGETEXP returns the exponent portion
  |	of the input argument.  The exponent bias is removed
  |	and the exponent value is returned as an extended
  |	precision number in fp0.  sGETEXPD handles denormalized
  |	numbers.
  |
  |	The entry point sGETMAN extracts the mantissa of the
  |	input argument.  The mantissa is converted to an
  |	extended precision number and returned in fp0.  The
  |	range of the result is [1.0 - 2.0).
  |
  |
  |	Input:  Double-extended number X in the ETEMP space in
  |		the floating-point save stack.
  |
  |	Output:	The functions return exp(X) or man(X) in fp0.
  |
  |	Modified: fp0.
  |
  |
  |		Copyright (C) Motorola, Inc. 1990
  |			All Rights Reserved
  |

  |       For details on the license for this file, please see the
  |       file, README, in this same directory.

  
  |SGETEM	idnt	2,1 | Motorola 040 Floating Point Software Package
  
  	|section 8
  
  #include "fpsp.h"
  
  	|xref	nrm_set
  
  |
  | This entry point is used by the unimplemented instruction exception
  | handler.  It points a0 to the input operand.
  |
  |
  |
  |	SGETEXP
  |
  
  	.global	sgetexp
  sgetexp:
  	movew	LOCAL_EX(%a0),%d0	|get the exponent
  	bclrl	#15,%d0		|clear the sign bit
  	subw	#0x3fff,%d0	|subtract off the bias
  	fmovew  %d0,%fp0		|move the exp to fp0
  	rts
  
  	.global	sgetexpd
  sgetexpd:
  	bclrb	#sign_bit,LOCAL_EX(%a0)
  	bsr	nrm_set		|normalize (exp will go negative)
  	movew	LOCAL_EX(%a0),%d0	|load resulting exponent into d0
  	subw	#0x3fff,%d0	|subtract off the bias
  	fmovew	%d0,%fp0		|move the exp to fp0
  	rts
  |
  |
  | This entry point is used by the unimplemented instruction exception
  | handler.  It points a0 to the input operand.
  |
  |
  |
  |	SGETMAN
  |
  |
  | For normalized numbers, leave the mantissa alone, simply load
  | with an exponent of +/- $3fff.
  |
  	.global	sgetman
  sgetman:
  	movel	USER_FPCR(%a6),%d0
  	andil	#0xffffff00,%d0	|clear rounding precision and mode
  	fmovel	%d0,%fpcr		|this fpcr setting is used by the 882
  	movew	LOCAL_EX(%a0),%d0	|get the exp (really just want sign bit)
  	orw	#0x7fff,%d0	|clear old exp
  	bclrl	#14,%d0		|make it the new exp +-3fff
  	movew	%d0,LOCAL_EX(%a0)	|move the sign & exp back to fsave stack
  	fmovex	(%a0),%fp0	|put new value back in fp0
  	rts
  
  |
  | For denormalized numbers, shift the mantissa until the j-bit = 1,
  | then load the exponent with +/1 $3fff.
  |
  	.global	sgetmand
  sgetmand:
  	movel	LOCAL_HI(%a0),%d0	|load ms mant in d0
  	movel	LOCAL_LO(%a0),%d1	|load ls mant in d1
  	bsr	shft		|shift mantissa bits till msbit is set
  	movel	%d0,LOCAL_HI(%a0)	|put ms mant back on stack
  	movel	%d1,LOCAL_LO(%a0)	|put ls mant back on stack
  	bras	sgetman
  
  |
  |	SHFT
  |
  |	Shifts the mantissa bits until msbit is set.
  |	input:
  |		ms mantissa part in d0
  |		ls mantissa part in d1
  |	output:
  |		shifted bits in d0 and d1
  shft:
  	tstl	%d0		|if any bits set in ms mant
  	bnes	upper		|then branch
  |				;else no bits set in ms mant
  	tstl	%d1		|test if any bits set in ls mant
  	bnes	cont		|if set then continue
  	bras	shft_end	|else return
  cont:
  	movel	%d3,-(%a7)	|save d3
  	exg	%d0,%d1		|shift ls mant to ms mant
  	bfffo	%d0{#0:#32},%d3	|find first 1 in ls mant to d0
  	lsll	%d3,%d0		|shift first 1 to integer bit in ms mant
  	movel	(%a7)+,%d3	|restore d3
  	bras	shft_end
  upper:
  
  	moveml	%d3/%d5/%d6,-(%a7)	|save registers
  	bfffo	%d0{#0:#32},%d3	|find first 1 in ls mant to d0
  	lsll	%d3,%d0		|shift ms mant until j-bit is set
  	movel	%d1,%d6		|save ls mant in d6
  	lsll	%d3,%d1		|shift ls mant by count
  	movel	#32,%d5
  	subl	%d3,%d5		|sub 32 from shift for ls mant
  	lsrl	%d5,%d6		|shift off all bits but those that will
  |				;be shifted into ms mant
  	orl	%d6,%d0		|shift the ls mant bits into the ms mant
  	moveml	(%a7)+,%d3/%d5/%d6	|restore registers
  shft_end:
  	rts
  
  	|end