m68k/fpsp040/round.S

21 |	round --- round result according to precision/mode
23 |	a0 points to the input operand in the internal extended format
35 |	On return the value pointed to by a0 is correctly rounded,
53 	bne	rnd_cont		|lower bits to zero for size
78 |	If sign of fp number = 0 (positive), then add 1 to l.
84 	movel	#0xffffffff,%d0		|force g,r,s to be all f's
91 |	If sign of fp number = 1 (negative), then add 1 to l.
97 	movel	#0xffffffff,%d0		|force g,r,s to be all f's
112 |	If (g=1), then add 1 to l and if (r=s=0), then clear l
113 |	Note that this will round to even in case of a tie.
117 	asll	#1,%d0			|shift g-bit to c-bit
129 | The ext_grs extract the guard/round/sticky bits according to the
134 | Notes: the ext_grs uses the round PREC, and therefore has to swap d1
135 |	 prior to usage, and needs to restore d1 to original.
138 	swap	%d1			|have d1.w point to round precision
150 	lsll	%d2,%d3			|shift g-r bits to MSB of d3
153 	bnes	st_stky			|bits to the right of g-r
162 	lsll	%d2,%d3			|shift g-r bits to the MSB of d3
165 	bnes	st_stky			|other bits to the right of g-r
172 	movel	%d3,%d0			|return grs to d0
175 	swap	%d1			|restore d1 to original
179 	.set	ad_1_sgl,0x00000100	|  constant to add 1 to l-bit in sgl prec
180 	.set	ad_1_dbl,0x00000800	|  constant to add 1 to l-bit in dbl prec
183 |Jump table for adding 1 to the l-bit indexed by rnd prec
212 	addql  #1,LOCAL_LO(%a0)		|add 1 to l-bit
281 | exponent (d0) is set to 0 and the mantissa (d1 & d2) is not
285 | therefore do not have the easy to follow decrement/shift loop.
289 |	Distance to first 1 bit in mantissa = X
290 |	Distance to 0 from exponent = Y
315 	bfffo	%d1{#0:#32},%d3	|get the distance to the first 1
333 	movel	#0,%d0		|same as if decremented exp to 0
359 	bfffo	LOCAL_HI(%a0){#0:#32},%d7 |find first 1 in ms mant to d7)
368 	lsll	%d7,%d0		|shift first 1 to j bit position
389 	bfffo	%d1{#0:#32},%d7	|find first 1 in ls mant to d7)
391 	lsll	%d7,%d1		|shift first 1 to integer bit in ms mant
403 |	a0	 points to the operand to be denormalized
408 |	a0	 points to the denormalized result
485 |	dnrm_lp --- normalize exponent/mantissa to specified threshold
488 |	a0		points to the operand to be denormalized
492 |	a0		points to the denormalized operand
496 | The LOCAL_LO and LOCAL_GRS parts of the value are copied to FP_SCR2
497 | so that bfext can be used to extract the new low part of the mantissa.
498 | Dnrm_lp can be called with a0 pointing to ETEMP or WBTEMP and there
508 	lsll	%d0,%d2			|shift g,r,s to their positions
571 	bnes	c2_sstky		|bra if sticky bit to be set
573 	bnes	c2_sstky		|bra if sticky bit to be set
594 | d1 >= 64 Force the exponent to be the denorm threshold with the