patch-1.3.94 linux/arch/m68k/fpsp040/scale.S

• Lines: 372
• Date: Sat Feb 24 22:58:43 1996
• Orig file: v1.3.93/linux/arch/m68k/fpsp040/scale.S
• Orig date: Thu Jan 1 02:00:00 1970

diff -u --recursive --new-file v1.3.93/linux/arch/m68k/fpsp040/scale.S linux/arch/m68k/fpsp040/scale.S
@@ -0,0 +1,371 @@
+|
+|	scale.sa 3.3 7/30/91
+|
+|	The entry point sSCALE computes the destination operand
+|	scaled by the source operand.  If the absoulute value of
+|	the source operand is (>= 2^14) an overflow or underflow
+|	is returned.
+|
+|	The entry point sscale is called from do_func to emulate
+|	the fscale unimplemented instruction.
+|
+|	Input: Double-extended destination operand in FPTEMP, 
+|		double-extended source operand in ETEMP.
+|
+|	Output: The function returns scale(X,Y) to fp0.
+|
+|	Modifies: fp0.
+|
+|	Algorithm:
+|		
+|		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+|	THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA 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.
+
+|SCALE    idnt    2,1 | Motorola 040 Floating Point Software Package
+
+	|section	8
+
+	.include "fpsp.h"
+
+	|xref	t_ovfl2
+	|xref	t_unfl
+	|xref	round
+	|xref	t_resdnrm
+
+SRC_BNDS: .short	0x3fff,0x400c
+
+|
+| This entry point is used by the unimplemented instruction exception
+| handler.
+|
+|
+|
+|	FSCALE
+|
+	.global	sscale
+sscale:
+	fmovel		#0,%fpcr		|clr user enabled exc
+	clrl		%d1
+	movew		FPTEMP(%a6),%d1	|get dest exponent
+	smi		L_SCR1(%a6)	|use L_SCR1 to hold sign
+	andil		#0x7fff,%d1	|strip sign
+	movew		ETEMP(%a6),%d0	|check src bounds
+	andiw		#0x7fff,%d0	|clr sign bit
+	cmp2w		SRC_BNDS,%d0
+	bccs		src_in
+	cmpiw		#0x400c,%d0	|test for too large
+	bge		src_out
+|
+| The source input is below 1, so we check for denormalized numbers
+| and set unfl.
+|
+src_small:
+	moveb		DTAG(%a6),%d0
+	andib		#0xe0,%d0
+	tstb		%d0
+	beqs		no_denorm
+	st		STORE_FLG(%a6)	|dest already contains result
+	orl		#unfl_mask,USER_FPSR(%a6) |set UNFL
+den_done:
+	leal		FPTEMP(%a6),%a0
+	bra		t_resdnrm
+no_denorm:
+	fmovel		USER_FPCR(%a6),%FPCR
+	fmovex		FPTEMP(%a6),%fp0	|simply return dest
+	rts
+
+
+|
+| Source is within 2^14 range.  To perform the int operation,
+| move it to d0.
+|
+src_in:
+	fmovex		ETEMP(%a6),%fp0	|move in src for int
+	fmovel		#rz_mode,%fpcr	|force rz for src conversion
+	fmovel		%fp0,%d0		|int src to d0
+	fmovel		#0,%FPSR		|clr status from above
+	tstw		ETEMP(%a6)	|check src sign
+	blt		src_neg
+|
+| Source is positive.  Add the src to the dest exponent.
+| The result can be denormalized, if src = 0, or overflow,
+| if the result of the add sets a bit in the upper word.
+|
+src_pos:
+	tstw		%d1		|check for denorm
+	beq		dst_dnrm
+	addl		%d0,%d1		|add src to dest exp
+	beqs		denorm		|if zero, result is denorm
+	cmpil		#0x7fff,%d1	|test for overflow
+	bges		ovfl
+	tstb		L_SCR1(%a6)
+	beqs		spos_pos
+	orw		#0x8000,%d1
+spos_pos:
+	movew		%d1,FPTEMP(%a6)	|result in FPTEMP
+	fmovel		USER_FPCR(%a6),%FPCR
+	fmovex		FPTEMP(%a6),%fp0	|write result to fp0
+	rts
+ovfl:
+	tstb		L_SCR1(%a6)
+	beqs		sovl_pos
+	orw		#0x8000,%d1
+sovl_pos:
+	movew		FPTEMP(%a6),ETEMP(%a6)	|result in ETEMP
+	movel		FPTEMP_HI(%a6),ETEMP_HI(%a6)
+	movel		FPTEMP_LO(%a6),ETEMP_LO(%a6)
+	bra		t_ovfl2
+
+denorm:
+	tstb		L_SCR1(%a6)
+	beqs		den_pos
+	orw		#0x8000,%d1
+den_pos:
+	tstl		FPTEMP_HI(%a6)	|check j bit
+	blts		nden_exit	|if set, not denorm
+	movew		%d1,ETEMP(%a6)	|input expected in ETEMP
+	movel		FPTEMP_HI(%a6),ETEMP_HI(%a6)
+	movel		FPTEMP_LO(%a6),ETEMP_LO(%a6)
+	orl		#unfl_bit,USER_FPSR(%a6)	|set unfl
+	leal		ETEMP(%a6),%a0
+	bra		t_resdnrm
+nden_exit:
+	movew		%d1,FPTEMP(%a6)	|result in FPTEMP
+	fmovel		USER_FPCR(%a6),%FPCR
+	fmovex		FPTEMP(%a6),%fp0	|write result to fp0
+	rts
+
+|
+| Source is negative.  Add the src to the dest exponent.
+| (The result exponent will be reduced).  The result can be
+| denormalized.
+|
+src_neg:
+	addl		%d0,%d1		|add src to dest
+	beqs		denorm		|if zero, result is denorm
+	blts		fix_dnrm	|if negative, result is 
+|					;needing denormalization
+	tstb		L_SCR1(%a6)
+	beqs		sneg_pos
+	orw		#0x8000,%d1
+sneg_pos:
+	movew		%d1,FPTEMP(%a6)	|result in FPTEMP
+	fmovel		USER_FPCR(%a6),%FPCR
+	fmovex		FPTEMP(%a6),%fp0	|write result to fp0
+	rts
+
+
+|
+| The result exponent is below denorm value.  Test for catastrophic
+| underflow and force zero if true.  If not, try to shift the 
+| mantissa right until a zero exponent exists.
+|
+fix_dnrm:
+	cmpiw		#0xffc0,%d1	|lower bound for normalization
+	blt		fix_unfl	|if lower, catastrophic unfl
+	movew		%d1,%d0		|use d0 for exp
+	movel		%d2,-(%a7)	|free d2 for norm
+	movel		FPTEMP_HI(%a6),%d1
+	movel		FPTEMP_LO(%a6),%d2
+	clrl		L_SCR2(%a6)
+fix_loop:
+	addw		#1,%d0		|drive d0 to 0
+	lsrl		#1,%d1		|while shifting the
+	roxrl		#1,%d2		|mantissa to the right
+	bccs		no_carry
+	st		L_SCR2(%a6)	|use L_SCR2 to capture inex
+no_carry:
+	tstw		%d0		|it is finished when
+	blts		fix_loop	|d0 is zero or the mantissa
+	tstb		L_SCR2(%a6)
+	beqs		tst_zero
+	orl		#unfl_inx_mask,USER_FPSR(%a6)
+|					;set unfl, aunfl, ainex
+|
+| Test for zero. If zero, simply use fmove to return +/- zero
+| to the fpu.
+|
+tst_zero:
+	clrw		FPTEMP_EX(%a6)
+	tstb		L_SCR1(%a6)	|test for sign
+	beqs		tst_con
+	orw		#0x8000,FPTEMP_EX(%a6) |set sign bit
+tst_con:
+	movel		%d1,FPTEMP_HI(%a6)
+	movel		%d2,FPTEMP_LO(%a6)
+	movel		(%a7)+,%d2
+	tstl		%d1
+	bnes		not_zero
+	tstl		FPTEMP_LO(%a6)
+	bnes		not_zero
+|
+| Result is zero.  Check for rounding mode to set lsb.  If the
+| mode is rp, and the zero is positive, return smallest denorm.
+| If the mode is rm, and the zero is negative, return smallest
+| negative denorm.
+|
+	btstb		#5,FPCR_MODE(%a6) |test if rm or rp
+	beqs		no_dir
+	btstb		#4,FPCR_MODE(%a6) |check which one
+	beqs		zer_rm
+zer_rp:
+	tstb		L_SCR1(%a6)	|check sign
+	bnes		no_dir		|if set, neg op, no inc
+	movel		#1,FPTEMP_LO(%a6) |set lsb
+	bras		sm_dnrm
+zer_rm:
+	tstb		L_SCR1(%a6)	|check sign
+	beqs		no_dir		|if clr, neg op, no inc
+	movel		#1,FPTEMP_LO(%a6) |set lsb
+	orl		#neg_mask,USER_FPSR(%a6) |set N
+	bras		sm_dnrm
+no_dir:
+	fmovel		USER_FPCR(%a6),%FPCR
+	fmovex		FPTEMP(%a6),%fp0	|use fmove to set cc's
+	rts
+
+|
+| The rounding mode changed the zero to a smallest denorm. Call 
+| t_resdnrm with exceptional operand in ETEMP.
+|
+sm_dnrm:
+	movel		FPTEMP_EX(%a6),ETEMP_EX(%a6)
+	movel		FPTEMP_HI(%a6),ETEMP_HI(%a6)
+	movel		FPTEMP_LO(%a6),ETEMP_LO(%a6)
+	leal		ETEMP(%a6),%a0
+	bra		t_resdnrm
+
+|
+| Result is still denormalized.
+|
+not_zero:
+	orl		#unfl_mask,USER_FPSR(%a6) |set unfl
+	tstb		L_SCR1(%a6)	|check for sign
+	beqs		fix_exit
+	orl		#neg_mask,USER_FPSR(%a6) |set N
+fix_exit:
+	bras		sm_dnrm
+
+	
+|
+| The result has underflowed to zero. Return zero and set
+| unfl, aunfl, and ainex.
+|
+fix_unfl:
+	orl		#unfl_inx_mask,USER_FPSR(%a6)
+	btstb		#5,FPCR_MODE(%a6) |test if rm or rp
+	beqs		no_dir2
+	btstb		#4,FPCR_MODE(%a6) |check which one
+	beqs		zer_rm2
+zer_rp2:
+	tstb		L_SCR1(%a6)	|check sign
+	bnes		no_dir2		|if set, neg op, no inc
+	clrl		FPTEMP_EX(%a6)
+	clrl		FPTEMP_HI(%a6)
+	movel		#1,FPTEMP_LO(%a6) |set lsb
+	bras		sm_dnrm		|return smallest denorm
+zer_rm2:
+	tstb		L_SCR1(%a6)	|check sign
+	beqs		no_dir2		|if clr, neg op, no inc
+	movew		#0x8000,FPTEMP_EX(%a6)
+	clrl		FPTEMP_HI(%a6)
+	movel		#1,FPTEMP_LO(%a6) |set lsb
+	orl		#neg_mask,USER_FPSR(%a6) |set N
+	bra		sm_dnrm		|return smallest denorm
+
+no_dir2:
+	tstb		L_SCR1(%a6)
+	bges		pos_zero
+neg_zero:
+	clrl		FP_SCR1(%a6)	|clear the exceptional operand
+	clrl		FP_SCR1+4(%a6)	|for gen_except.
+	clrl		FP_SCR1+8(%a6)
+	fmoves		#0x80000000,%fp0	
+	rts
+pos_zero:
+	clrl		FP_SCR1(%a6)	|clear the exceptional operand
+	clrl		FP_SCR1+4(%a6)	|for gen_except.
+	clrl		FP_SCR1+8(%a6)
+	fmoves		#0x00000000,%fp0
+	rts
+
+|
+| The destination is a denormalized number.  It must be handled
+| by first shifting the bits in the mantissa until it is normalized,
+| then adding the remainder of the source to the exponent.
+|
+dst_dnrm:
+	moveml		%d2/%d3,-(%a7)	
+	movew		FPTEMP_EX(%a6),%d1
+	movel		FPTEMP_HI(%a6),%d2
+	movel		FPTEMP_LO(%a6),%d3
+dst_loop:
+	tstl		%d2		|test for normalized result
+	blts		dst_norm	|exit loop if so
+	tstl		%d0		|otherwise, test shift count
+	beqs		dst_fin		|if zero, shifting is done
+	subil		#1,%d0		|dec src
+	lsll		#1,%d3
+	roxll		#1,%d2
+	bras		dst_loop
+|
+| Destination became normalized.  Simply add the remaining 
+| portion of the src to the exponent.
+|
+dst_norm:
+	addw		%d0,%d1		|dst is normalized; add src
+	tstb		L_SCR1(%a6)
+	beqs		dnrm_pos
+	orl		#0x8000,%d1
+dnrm_pos:
+	movemw		%d1,FPTEMP_EX(%a6)
+	moveml		%d2,FPTEMP_HI(%a6)
+	moveml		%d3,FPTEMP_LO(%a6)
+	fmovel		USER_FPCR(%a6),%FPCR
+	fmovex		FPTEMP(%a6),%fp0
+	moveml		(%a7)+,%d2/%d3
+	rts
+
+|
+| Destination remained denormalized.  Call t_excdnrm with
+| exceptional operand in ETEMP.
+|
+dst_fin:
+	tstb		L_SCR1(%a6)	|check for sign
+	beqs		dst_exit
+	orl		#neg_mask,USER_FPSR(%a6) |set N
+	orl		#0x8000,%d1
+dst_exit:
+	movemw		%d1,ETEMP_EX(%a6)
+	moveml		%d2,ETEMP_HI(%a6)
+	moveml		%d3,ETEMP_LO(%a6)
+	orl		#unfl_mask,USER_FPSR(%a6) |set unfl
+	moveml		(%a7)+,%d2/%d3
+	leal		ETEMP(%a6),%a0
+	bra		t_resdnrm
+
+|
+| Source is outside of 2^14 range.  Test the sign and branch
+| to the appropriate exception handler.
+|
+src_out:
+	tstb		L_SCR1(%a6)
+	beqs		scro_pos
+	orl		#0x8000,%d1
+scro_pos:
+	movel		FPTEMP_HI(%a6),ETEMP_HI(%a6)
+	movel		FPTEMP_LO(%a6),ETEMP_LO(%a6)
+	tstw		ETEMP(%a6)
+	blts		res_neg
+res_pos:
+	movew		%d1,ETEMP(%a6)	|result in ETEMP
+	bra		t_ovfl2
+res_neg:
+	movew		%d1,ETEMP(%a6)	|result in ETEMP
+	leal		ETEMP(%a6),%a0
+	bra		t_unfl
+	|end