1|
  2|	sgetem.sa 3.1 12/10/90
  3|
  4|	The entry point sGETEXP returns the exponent portion
  5|	of the input argument.  The exponent bias is removed
  6|	and the exponent value is returned as an extended
  7|	precision number in fp0.  sGETEXPD handles denormalized
  8|	numbers.
  9|
 10|	The entry point sGETMAN extracts the mantissa of the
 11|	input argument.  The mantissa is converted to an
 12|	extended precision number and returned in fp0.  The
 13|	range of the result is [1.0 - 2.0).
 14|
 15|
 16|	Input:  Double-extended number X in the ETEMP space in
 17|		the floating-point save stack.
 18|
 19|	Output:	The functions return exp(X) or man(X) in fp0.
 20|
 21|	Modified: fp0.
 22|
 23|
 24|		Copyright (C) Motorola, Inc. 1990
 25|			All Rights Reserved
 26|
 27|       For details on the license for this file, please see the
 28|       file, README, in this same directory.
 29
 30|SGETEM	idnt	2,1 | Motorola 040 Floating Point Software Package
 31
 32	|section 8
 33
 34#include "fpsp.h"
 35
 36	|xref	nrm_set
 37
 38|
 39| This entry point is used by the unimplemented instruction exception
 40| handler.  It points a0 to the input operand.
 41|
 42|
 43|
 44|	SGETEXP
 45|
 46
 47	.global	sgetexp
 48sgetexp:
 49	movew	LOCAL_EX(%a0),%d0	|get the exponent
 50	bclrl	#15,%d0		|clear the sign bit
 51	subw	#0x3fff,%d0	|subtract off the bias
 52	fmovew  %d0,%fp0		|move the exp to fp0
 53	rts
 54
 55	.global	sgetexpd
 56sgetexpd:
 57	bclrb	#sign_bit,LOCAL_EX(%a0)
 58	bsr	nrm_set		|normalize (exp will go negative)
 59	movew	LOCAL_EX(%a0),%d0	|load resulting exponent into d0
 60	subw	#0x3fff,%d0	|subtract off the bias
 61	fmovew	%d0,%fp0		|move the exp to fp0
 62	rts
 63|
 64|
 65| This entry point is used by the unimplemented instruction exception
 66| handler.  It points a0 to the input operand.
 67|
 68|
 69|
 70|	SGETMAN
 71|
 72|
 73| For normalized numbers, leave the mantissa alone, simply load
 74| with an exponent of +/- $3fff.
 75|
 76	.global	sgetman
 77sgetman:
 78	movel	USER_FPCR(%a6),%d0
 79	andil	#0xffffff00,%d0	|clear rounding precision and mode
 80	fmovel	%d0,%fpcr		|this fpcr setting is used by the 882
 81	movew	LOCAL_EX(%a0),%d0	|get the exp (really just want sign bit)
 82	orw	#0x7fff,%d0	|clear old exp
 83	bclrl	#14,%d0		|make it the new exp +-3fff
 84	movew	%d0,LOCAL_EX(%a0)	|move the sign & exp back to fsave stack
 85	fmovex	(%a0),%fp0	|put new value back in fp0
 86	rts
 87
 88|
 89| For denormalized numbers, shift the mantissa until the j-bit = 1,
 90| then load the exponent with +/1 $3fff.
 91|
 92	.global	sgetmand
 93sgetmand:
 94	movel	LOCAL_HI(%a0),%d0	|load ms mant in d0
 95	movel	LOCAL_LO(%a0),%d1	|load ls mant in d1
 96	bsr	shft		|shift mantissa bits till msbit is set
 97	movel	%d0,LOCAL_HI(%a0)	|put ms mant back on stack
 98	movel	%d1,LOCAL_LO(%a0)	|put ls mant back on stack
 99	bras	sgetman
100
101|
102|	SHFT
103|
104|	Shifts the mantissa bits until msbit is set.
105|	input:
106|		ms mantissa part in d0
107|		ls mantissa part in d1
108|	output:
109|		shifted bits in d0 and d1
110shft:
111	tstl	%d0		|if any bits set in ms mant
112	bnes	upper		|then branch
113|				;else no bits set in ms mant
114	tstl	%d1		|test if any bits set in ls mant
115	bnes	cont		|if set then continue
116	bras	shft_end	|else return
117cont:
118	movel	%d3,-(%a7)	|save d3
119	exg	%d0,%d1		|shift ls mant to ms mant
120	bfffo	%d0{#0:#32},%d3	|find first 1 in ls mant to d0
121	lsll	%d3,%d0		|shift first 1 to integer bit in ms mant
122	movel	(%a7)+,%d3	|restore d3
123	bras	shft_end
124upper:
125
126	moveml	%d3/%d5/%d6,-(%a7)	|save registers
127	bfffo	%d0{#0:#32},%d3	|find first 1 in ls mant to d0
128	lsll	%d3,%d0		|shift ms mant until j-bit is set
129	movel	%d1,%d6		|save ls mant in d6
130	lsll	%d3,%d1		|shift ls mant by count
131	movel	#32,%d5
132	subl	%d3,%d5		|sub 32 from shift for ls mant
133	lsrl	%d5,%d6		|shift off all bits but those that will
134|				;be shifted into ms mant
135	orl	%d6,%d0		|shift the ls mant bits into the ms mant
136	moveml	(%a7)+,%d3/%d5/%d6	|restore registers
137shft_end:
138	rts
139
140	|end