sint.s

Linux内核源代码 为压缩文件 是<<Linux内核>>一书中的源代码

|
|	sint.sa 3.1 12/10/90
|
|	The entry point sINT computes the rounded integer 
|	equivalent of the input argument, sINTRZ computes 
|	the integer rounded to zero of the input argument.
|
|	Entry points sint and sintrz are called from do_func
|	to emulate the fint and fintrz unimplemented instructions,
|	respectively.  Entry point sintdo is used by bindec.
|
|	Input: (Entry points sint and sintrz) Double-extended
|		number X in the ETEMP space in the floating-point
|		save stack.
|	       (Entry point sintdo) Double-extended number X in
|		location pointed to by the address register a0.
|	       (Entry point sintd) Double-extended denormalized
|		number X in the ETEMP space in the floating-point
|		save stack.
|
|	Output: The function returns int(X) or intrz(X) in fp0.
|
|	Modifies: fp0.
|
|	Algorithm: (sint and sintrz)
|
|	1. If exp(X) >= 63, return X. 
|	   If exp(X) < 0, return +/- 0 or +/- 1, according to
|	   the rounding mode.
|	
|	2. (X is in range) set rsc = 63 - exp(X). Unnormalize the
|	   result to the exponent $403e.
|
|	3. Round the result in the mode given in USER_FPCR. For
|	   sintrz, force round-to-zero mode.
|
|	4. Normalize the rounded result; store in fp0.
|
|	For the denormalized cases, force the correct result
|	for the given sign and rounding mode.
|
|		        Sign(X)
|		RMODE   +    -
|		-----  --------
|		 RN    +0   -0
|		 RZ    +0   -0
|		 RM    +0   -1
|		 RP    +1   -0
|
|
|		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|	THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA 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.

|SINT    idnt    2,1 | Motorola 040 Floating Point Software Package

	|section	8

	.include "fpsp.h"

	|xref	dnrm_lp
	|xref	nrm_set
	|xref	round
	|xref	t_inx2
	|xref	ld_pone
	|xref	ld_mone
	|xref	ld_pzero
	|xref	ld_mzero
	|xref	snzrinx

|
|	FINT
|
	.global	sint
sint:
	bfextu	FPCR_MODE(%a6){#2:#2},%d1	|use user's mode for rounding
|					;implicitly has extend precision
|					;in upper word. 
	movel	%d1,L_SCR1(%a6)		|save mode bits
	bras	sintexc			

|
|	FINT with extended denorm inputs.
|
	.global	sintd
sintd:
	btstb	#5,FPCR_MODE(%a6)
	beq	snzrinx		|if round nearest or round zero, +/- 0
	btstb	#4,FPCR_MODE(%a6)
	beqs	rnd_mns
rnd_pls:
	btstb	#sign_bit,LOCAL_EX(%a0)
	bnes	sintmz
	bsr	ld_pone		|if round plus inf and pos, answer is +1
	bra	t_inx2
rnd_mns:
	btstb	#sign_bit,LOCAL_EX(%a0)
	beqs	sintpz
	bsr	ld_mone		|if round mns inf and neg, answer is -1
	bra	t_inx2
sintpz:
	bsr	ld_pzero
	bra	t_inx2
sintmz:
	bsr	ld_mzero
	bra	t_inx2

|
|	FINTRZ
|
	.global	sintrz
sintrz:
	movel	#1,L_SCR1(%a6)		|use rz mode for rounding
|					;implicitly has extend precision
|					;in upper word. 
	bras	sintexc			
|
|	SINTDO
|
|	Input:	a0 points to an IEEE extended format operand
| 	Output:	fp0 has the result 
|
| Exceptions:
|
| If the subroutine results in an inexact operation, the inx2 and
| ainx bits in the USER_FPSR are set.
|
|
	.global	sintdo
sintdo:
	bfextu	FPCR_MODE(%a6){#2:#2},%d1	|use user's mode for rounding
|					;implicitly has ext precision
|					;in upper word. 
	movel	%d1,L_SCR1(%a6)		|save mode bits
|
| Real work of sint is in sintexc
|
sintexc:
	bclrb	#sign_bit,LOCAL_EX(%a0)	|convert to internal extended
|					;format
	sne	LOCAL_SGN(%a0)		
	cmpw	#0x403e,LOCAL_EX(%a0)	|check if (unbiased) exp > 63
	bgts	out_rnge			|branch if exp < 63
	cmpw	#0x3ffd,LOCAL_EX(%a0)	|check if (unbiased) exp < 0
	bgt	in_rnge			|if 63 >= exp > 0, do calc
|
| Input is less than zero.  Restore sign, and check for directed
| rounding modes.  L_SCR1 contains the rmode in the lower byte.
|
un_rnge:
	btstb	#1,L_SCR1+3(%a6)		|check for rn and rz
	beqs	un_rnrz
	tstb	LOCAL_SGN(%a0)		|check for sign
	bnes	un_rmrp_neg
|
| Sign is +.  If rp, load +1.0, if rm, load +0.0
|
	cmpib	#3,L_SCR1+3(%a6)		|check for rp
	beqs	un_ldpone		|if rp, load +1.0
	bsr	ld_pzero		|if rm, load +0.0
	bra	t_inx2
un_ldpone:
	bsr	ld_pone
	bra	t_inx2
|
| Sign is -.  If rm, load -1.0, if rp, load -0.0
|
un_rmrp_neg:
	cmpib	#2,L_SCR1+3(%a6)		|check for rm
	beqs	un_ldmone		|if rm, load -1.0
	bsr	ld_mzero		|if rp, load -0.0
	bra	t_inx2
un_ldmone:
	bsr	ld_mone
	bra	t_inx2
|
| Rmode is rn or rz; return signed zero
|
un_rnrz:
	tstb	LOCAL_SGN(%a0)		|check for sign
	bnes	un_rnrz_neg
	bsr	ld_pzero
	bra	t_inx2
un_rnrz_neg:
	bsr	ld_mzero
	bra	t_inx2
	
|
| Input is greater than 2^63.  All bits are significant.  Return
| the input.
|
out_rnge:
	bfclr	LOCAL_SGN(%a0){#0:#8}	|change back to IEEE ext format
	beqs	intps
	bsetb	#sign_bit,LOCAL_EX(%a0)
intps:
	fmovel	%fpcr,-(%sp)
	fmovel	#0,%fpcr
	fmovex LOCAL_EX(%a0),%fp0	|if exp > 63
|					;then return X to the user
|					;there are no fraction bits
	fmovel	(%sp)+,%fpcr
	rts

in_rnge:
| 					;shift off fraction bits
	clrl	%d0			|clear d0 - initial g,r,s for
|					;dnrm_lp
	movel	#0x403e,%d1		|set threshold for dnrm_lp
|					;assumes a0 points to operand
	bsr	dnrm_lp
|					;returns unnormalized number
|					;pointed by a0
|					;output d0 supplies g,r,s
|					;used by round
	movel	L_SCR1(%a6),%d1		|use selected rounding mode
|
|
	bsr	round			|round the unnorm based on users
|					;input	a0 ptr to ext X
|					;	d0 g,r,s bits
|					;	d1 PREC/MODE info
|					;output a0 ptr to rounded result
|					;inexact flag set in USER_FPSR
|					;if initial grs set
|
| normalize the rounded result and store value in fp0
|
	bsr	nrm_set			|normalize the unnorm
|					;Input: a0 points to operand to
|					;be normalized
|					;Output: a0 points to normalized
|					;result
	bfclr	LOCAL_SGN(%a0){#0:#8}
	beqs	nrmrndp
	bsetb	#sign_bit,LOCAL_EX(%a0)	|return to IEEE extended format
nrmrndp:
	fmovel	%fpcr,-(%sp)
	fmovel	#0,%fpcr
	fmovex LOCAL_EX(%a0),%fp0	|move result to fp0
	fmovel	(%sp)+,%fpcr
	rts

	|end