674 lines
18 KiB
Plaintext
674 lines
18 KiB
Plaintext
* $NetBSD: round.sa,v 1.3 1994/10/26 07:49:24 cgd Exp $
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* MOTOROLA MICROPROCESSOR & MEMORY TECHNOLOGY GROUP
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* M68000 Hi-Performance Microprocessor Division
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* M68040 Software Package
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*
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* M68040 Software Package Copyright (c) 1993, 1994 Motorola Inc.
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* All rights reserved.
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*
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* THE SOFTWARE is provided on an "AS IS" basis and without warranty.
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* To the maximum extent permitted by applicable law,
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* MOTOROLA DISCLAIMS ALL WARRANTIES WHETHER EXPRESS OR IMPLIED,
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* INCLUDING IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A
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* PARTICULAR PURPOSE and any warranty against infringement with
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* regard to the SOFTWARE (INCLUDING ANY MODIFIED VERSIONS THEREOF)
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* and any accompanying written materials.
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*
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* To the maximum extent permitted by applicable law,
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* IN NO EVENT SHALL MOTOROLA BE LIABLE FOR ANY DAMAGES WHATSOEVER
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* (INCLUDING WITHOUT LIMITATION, DAMAGES FOR LOSS OF BUSINESS
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* PROFITS, BUSINESS INTERRUPTION, LOSS OF BUSINESS INFORMATION, OR
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* OTHER PECUNIARY LOSS) ARISING OF THE USE OR INABILITY TO USE THE
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* SOFTWARE. Motorola assumes no responsibility for the maintenance
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* and support of the SOFTWARE.
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*
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* You are hereby granted a copyright license to use, modify, and
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* distribute the SOFTWARE so long as this entire notice is retained
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* without alteration in any modified and/or redistributed versions,
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* and that such modified versions are clearly identified as such.
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* No licenses are granted by implication, estoppel or otherwise
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* under any patents or trademarks of Motorola, Inc.
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*
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* round.sa 3.4 7/29/91
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*
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* handle rounding and normalization tasks
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*
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ROUND IDNT 2,1 Motorola 040 Floating Point Software Package
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section 8
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include fpsp.h
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*
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* round --- round result according to precision/mode
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*
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* a0 points to the input operand in the internal extended format
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* d1(high word) contains rounding precision:
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* ext = $0000xxxx
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* sgl = $0001xxxx
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* dbl = $0002xxxx
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* d1(low word) contains rounding mode:
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* RN = $xxxx0000
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* RZ = $xxxx0001
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* RM = $xxxx0010
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* RP = $xxxx0011
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* d0{31:29} contains the g,r,s bits (extended)
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*
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* On return the value pointed to by a0 is correctly rounded,
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* a0 is preserved and the g-r-s bits in d0 are cleared.
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* The result is not typed - the tag field is invalid. The
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* result is still in the internal extended format.
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*
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* The INEX bit of USER_FPSR will be set if the rounded result was
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* inexact (i.e. if any of the g-r-s bits were set).
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*
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xdef round
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round:
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* If g=r=s=0 then result is exact and round is done, else set
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* the inex flag in status reg and continue.
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*
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bsr.b ext_grs ;this subroutine looks at the
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* :rounding precision and sets
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* ;the appropriate g-r-s bits.
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tst.l d0 ;if grs are zero, go force
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bne.w rnd_cont ;lower bits to zero for size
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swap d1 ;set up d1.w for round prec.
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bra.w truncate
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rnd_cont:
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*
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* Use rounding mode as an index into a jump table for these modes.
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*
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or.l #inx2a_mask,USER_FPSR(a6) ;set inex2/ainex
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lea mode_tab,a1
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move.l (a1,d1.w*4),a1
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jmp (a1)
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*
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* Jump table indexed by rounding mode in d1.w. All following assumes
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* grs != 0.
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*
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mode_tab:
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dc.l rnd_near
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dc.l rnd_zero
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dc.l rnd_mnus
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dc.l rnd_plus
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*
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* ROUND PLUS INFINITY
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*
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* If sign of fp number = 0 (positive), then add 1 to l.
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*
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rnd_plus:
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swap d1 ;set up d1 for round prec.
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tst.b LOCAL_SGN(a0) ;check for sign
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bmi.w truncate ;if positive then truncate
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move.l #$ffffffff,d0 ;force g,r,s to be all f's
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lea add_to_l,a1
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move.l (a1,d1.w*4),a1
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jmp (a1)
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*
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* ROUND MINUS INFINITY
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*
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* If sign of fp number = 1 (negative), then add 1 to l.
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*
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rnd_mnus:
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swap d1 ;set up d1 for round prec.
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tst.b LOCAL_SGN(a0) ;check for sign
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bpl.w truncate ;if negative then truncate
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move.l #$ffffffff,d0 ;force g,r,s to be all f's
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lea add_to_l,a1
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move.l (a1,d1.w*4),a1
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jmp (a1)
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*
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* ROUND ZERO
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*
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* Always truncate.
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rnd_zero:
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swap d1 ;set up d1 for round prec.
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bra.w truncate
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*
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*
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* ROUND NEAREST
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*
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* If (g=1), then add 1 to l and if (r=s=0), then clear l
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* Note that this will round to even in case of a tie.
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*
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rnd_near:
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swap d1 ;set up d1 for round prec.
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add.l d0,d0 ;shift g-bit to c-bit
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bcc.w truncate ;if (g=1) then
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lea add_to_l,a1
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move.l (a1,d1.w*4),a1
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jmp (a1)
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*
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* ext_grs --- extract guard, round and sticky bits
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*
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* Input: d1 = PREC:ROUND
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* Output: d0{31:29}= guard, round, sticky
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*
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* The ext_grs extract the guard/round/sticky bits according to the
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* selected rounding precision. It is called by the round subroutine
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* only. All registers except d0 are kept intact. d0 becomes an
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* updated guard,round,sticky in d0{31:29}
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*
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* Notes: the ext_grs uses the round PREC, and therefore has to swap d1
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* prior to usage, and needs to restore d1 to original.
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*
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ext_grs:
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swap d1 ;have d1.w point to round precision
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tst.w d1
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bne.b sgl_or_dbl
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bra.b end_ext_grs
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sgl_or_dbl:
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movem.l d2/d3,-(a7) ;make some temp registers
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cmpi.w #1,d1
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bne.b grs_dbl
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grs_sgl:
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bfextu LOCAL_HI(a0){24:2},d3 ;sgl prec. g-r are 2 bits right
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move.l #30,d2 ;of the sgl prec. limits
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lsl.l d2,d3 ;shift g-r bits to MSB of d3
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move.l LOCAL_HI(a0),d2 ;get word 2 for s-bit test
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andi.l #$0000003f,d2 ;s bit is the or of all other
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bne.b st_stky ;bits to the right of g-r
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tst.l LOCAL_LO(a0) ;test lower mantissa
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bne.b st_stky ;if any are set, set sticky
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tst.l d0 ;test original g,r,s
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bne.b st_stky ;if any are set, set sticky
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bra.b end_sd ;if words 3 and 4 are clr, exit
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grs_dbl:
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bfextu LOCAL_LO(a0){21:2},d3 ;dbl-prec. g-r are 2 bits right
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move.l #30,d2 ;of the dbl prec. limits
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lsl.l d2,d3 ;shift g-r bits to the MSB of d3
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move.l LOCAL_LO(a0),d2 ;get lower mantissa for s-bit test
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andi.l #$000001ff,d2 ;s bit is the or-ing of all
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bne.b st_stky ;other bits to the right of g-r
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tst.l d0 ;test word original g,r,s
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bne.b st_stky ;if any are set, set sticky
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bra.b end_sd ;if clear, exit
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st_stky:
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bset #rnd_stky_bit,d3
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end_sd:
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move.l d3,d0 ;return grs to d0
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movem.l (a7)+,d2/d3 ;restore scratch registers
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end_ext_grs:
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swap d1 ;restore d1 to original
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rts
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******************** Local Equates
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ad_1_sgl equ $00000100 constant to add 1 to l-bit in sgl prec
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ad_1_dbl equ $00000800 constant to add 1 to l-bit in dbl prec
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*Jump table for adding 1 to the l-bit indexed by rnd prec
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add_to_l:
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dc.l add_ext
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dc.l add_sgl
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dc.l add_dbl
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dc.l add_dbl
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*
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* ADD SINGLE
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*
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add_sgl:
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add.l #ad_1_sgl,LOCAL_HI(a0)
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bcc.b scc_clr ;no mantissa overflow
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roxr.w LOCAL_HI(a0) ;shift v-bit back in
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roxr.w LOCAL_HI+2(a0) ;shift v-bit back in
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add.w #$1,LOCAL_EX(a0) ;and incr exponent
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scc_clr:
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tst.l d0 ;test for rs = 0
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bne.b sgl_done
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andi.w #$fe00,LOCAL_HI+2(a0) ;clear the l-bit
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sgl_done:
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andi.l #$ffffff00,LOCAL_HI(a0) ;truncate bits beyond sgl limit
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clr.l LOCAL_LO(a0) ;clear d2
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rts
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*
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* ADD EXTENDED
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*
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add_ext:
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addq.l #1,LOCAL_LO(a0) ;add 1 to l-bit
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bcc.b xcc_clr ;test for carry out
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addq.l #1,LOCAL_HI(a0) ;propogate carry
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bcc.b xcc_clr
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roxr.w LOCAL_HI(a0) ;mant is 0 so restore v-bit
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roxr.w LOCAL_HI+2(a0) ;mant is 0 so restore v-bit
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roxr.w LOCAL_LO(a0)
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roxr.w LOCAL_LO+2(a0)
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add.w #$1,LOCAL_EX(a0) ;and inc exp
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xcc_clr:
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tst.l d0 ;test rs = 0
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bne.b add_ext_done
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andi.b #$fe,LOCAL_LO+3(a0) ;clear the l bit
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add_ext_done:
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rts
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*
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* ADD DOUBLE
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*
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add_dbl:
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add.l #ad_1_dbl,LOCAL_LO(a0)
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bcc.b dcc_clr
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addq.l #1,LOCAL_HI(a0) ;propogate carry
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bcc.b dcc_clr
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roxr.w LOCAL_HI(a0) ;mant is 0 so restore v-bit
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roxr.w LOCAL_HI+2(a0) ;mant is 0 so restore v-bit
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roxr.w LOCAL_LO(a0)
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roxr.w LOCAL_LO+2(a0)
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add.w #$1,LOCAL_EX(a0) ;incr exponent
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dcc_clr:
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tst.l d0 ;test for rs = 0
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bne.b dbl_done
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andi.w #$f000,LOCAL_LO+2(a0) ;clear the l-bit
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dbl_done:
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andi.l #$fffff800,LOCAL_LO(a0) ;truncate bits beyond dbl limit
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rts
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error:
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rts
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*
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* Truncate all other bits
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*
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trunct:
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dc.l end_rnd
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dc.l sgl_done
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dc.l dbl_done
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dc.l dbl_done
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truncate:
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lea trunct,a1
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move.l (a1,d1.w*4),a1
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jmp (a1)
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end_rnd:
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rts
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*
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* NORMALIZE
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*
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* These routines (nrm_zero & nrm_set) normalize the unnorm. This
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* is done by shifting the mantissa left while decrementing the
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* exponent.
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*
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* NRM_SET shifts and decrements until there is a 1 set in the integer
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* bit of the mantissa (msb in d1).
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*
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* NRM_ZERO shifts and decrements until there is a 1 set in the integer
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* bit of the mantissa (msb in d1) unless this would mean the exponent
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* would go less than 0. In that case the number becomes a denorm - the
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* exponent (d0) is set to 0 and the mantissa (d1 & d2) is not
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* normalized.
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*
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* Note that both routines have been optimized (for the worst case) and
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* therefore do not have the easy to follow decrement/shift loop.
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*
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* NRM_ZERO
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*
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* Distance to first 1 bit in mantissa = X
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* Distance to 0 from exponent = Y
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* If X < Y
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* Then
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* nrm_set
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* Else
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* shift mantissa by Y
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* set exponent = 0
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*
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*input:
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* FP_SCR1 = exponent, ms mantissa part, ls mantissa part
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*output:
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* L_SCR1{4} = fpte15 or ete15 bit
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*
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xdef nrm_zero
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nrm_zero:
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move.w LOCAL_EX(a0),d0
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cmp.w #64,d0 ;see if exp > 64
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bmi.b d0_less
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bsr nrm_set ;exp > 64 so exp won't exceed 0
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rts
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d0_less:
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movem.l d2/d3/d5/d6,-(a7)
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move.l LOCAL_HI(a0),d1
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move.l LOCAL_LO(a0),d2
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bfffo d1{0:32},d3 ;get the distance to the first 1
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* ;in ms mant
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beq.b ms_clr ;branch if no bits were set
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cmp.w d3,d0 ;of X>Y
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bmi.b greater ;then exp will go past 0 (neg) if
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* ;it is just shifted
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bsr nrm_set ;else exp won't go past 0
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movem.l (a7)+,d2/d3/d5/d6
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rts
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greater:
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move.l d2,d6 ;save ls mant in d6
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lsl.l d0,d2 ;shift ls mant by count
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lsl.l d0,d1 ;shift ms mant by count
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move.l #32,d5
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sub.l d0,d5 ;make op a denorm by shifting bits
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lsr.l d5,d6 ;by the number in the exp, then
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* ;set exp = 0.
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or.l d6,d1 ;shift the ls mant bits into the ms mant
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clr.l d0 ;same as if decremented exp to 0
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* ;while shifting
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move.w d0,LOCAL_EX(a0)
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move.l d1,LOCAL_HI(a0)
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move.l d2,LOCAL_LO(a0)
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movem.l (a7)+,d2/d3/d5/d6
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rts
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ms_clr:
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bfffo d2{0:32},d3 ;check if any bits set in ls mant
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beq.b all_clr ;branch if none set
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add.w #32,d3
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cmp.w d3,d0 ;if X>Y
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bmi.b greater ;then branch
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bsr nrm_set ;else exp won't go past 0
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movem.l (a7)+,d2/d3/d5/d6
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rts
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all_clr:
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clr.w LOCAL_EX(a0) ;no mantissa bits set. Set exp = 0.
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movem.l (a7)+,d2/d3/d5/d6
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rts
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*
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* NRM_SET
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*
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xdef nrm_set
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nrm_set:
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move.l d7,-(a7)
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bfffo LOCAL_HI(a0){0:32},d7 ;find first 1 in ms mant to d7)
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beq.b lower ;branch if ms mant is all 0's
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move.l d6,-(a7)
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sub.w d7,LOCAL_EX(a0) ;sub exponent by count
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move.l LOCAL_HI(a0),d0 ;d0 has ms mant
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move.l LOCAL_LO(a0),d1 ;d1 has ls mant
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lsl.l d7,d0 ;shift first 1 to j bit position
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move.l d1,d6 ;copy ls mant into d6
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lsl.l d7,d6 ;shift ls mant by count
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move.l d6,LOCAL_LO(a0) ;store ls mant into memory
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moveq.l #32,d6
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sub.l d7,d6 ;continue shift
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lsr.l d6,d1 ;shift off all bits but those that will
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* ;be shifted into ms mant
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or.l d1,d0 ;shift the ls mant bits into the ms mant
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move.l d0,LOCAL_HI(a0) ;store ms mant into memory
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movem.l (a7)+,d7/d6 ;restore registers
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rts
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*
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* We get here if ms mant was = 0, and we assume ls mant has bits
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* set (otherwise this would have been tagged a zero not a denorm).
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*
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lower:
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move.w LOCAL_EX(a0),d0 ;d0 has exponent
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move.l LOCAL_LO(a0),d1 ;d1 has ls mant
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sub.w #32,d0 ;account for ms mant being all zeros
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bfffo d1{0:32},d7 ;find first 1 in ls mant to d7)
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sub.w d7,d0 ;subtract shift count from exp
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lsl.l d7,d1 ;shift first 1 to integer bit in ms mant
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move.w d0,LOCAL_EX(a0) ;store ms mant
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move.l d1,LOCAL_HI(a0) ;store exp
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clr.l LOCAL_LO(a0) ;clear ls mant
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move.l (a7)+,d7
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rts
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*
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* denorm --- denormalize an intermediate result
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*
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* Used by underflow.
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*
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* Input:
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* a0 points to the operand to be denormalized
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* (in the internal extended format)
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*
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* d0: rounding precision
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* Output:
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* a0 points to the denormalized result
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* (in the internal extended format)
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*
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* d0 is guard,round,sticky
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*
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* d0 comes into this routine with the rounding precision. It
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* is then loaded with the denormalized exponent threshold for the
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* rounding precision.
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*
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xdef denorm
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denorm:
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btst.b #6,LOCAL_EX(a0) ;check for exponents between $7fff-$4000
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beq.b no_sgn_ext
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bset.b #7,LOCAL_EX(a0) ;sign extend if it is so
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no_sgn_ext:
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tst.b d0 ;if 0 then extended precision
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bne.b not_ext ;else branch
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clr.l d1 ;load d1 with ext threshold
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clr.l d0 ;clear the sticky flag
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bsr dnrm_lp ;denormalize the number
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tst.b d1 ;check for inex
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beq.w no_inex ;if clr, no inex
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bra.b dnrm_inex ;if set, set inex
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not_ext:
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cmpi.l #1,d0 ;if 1 then single precision
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beq.b load_sgl ;else must be 2, double prec
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load_dbl:
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move.w #dbl_thresh,d1 ;put copy of threshold in d1
|
|
move.l d1,d0 ;copy d1 into d0
|
|
sub.w LOCAL_EX(a0),d0 ;diff = threshold - exp
|
|
cmp.w #67,d0 ;if diff > 67 (mant + grs bits)
|
|
bpl.b chk_stky ;then branch (all bits would be
|
|
* ; shifted off in denorm routine)
|
|
clr.l d0 ;else clear the sticky flag
|
|
bsr dnrm_lp ;denormalize the number
|
|
tst.b d1 ;check flag
|
|
beq.b no_inex ;if clr, no inex
|
|
bra.b dnrm_inex ;if set, set inex
|
|
|
|
load_sgl:
|
|
move.w #sgl_thresh,d1 ;put copy of threshold in d1
|
|
move.l d1,d0 ;copy d1 into d0
|
|
sub.w LOCAL_EX(a0),d0 ;diff = threshold - exp
|
|
cmp.w #67,d0 ;if diff > 67 (mant + grs bits)
|
|
bpl.b chk_stky ;then branch (all bits would be
|
|
* ; shifted off in denorm routine)
|
|
clr.l d0 ;else clear the sticky flag
|
|
bsr dnrm_lp ;denormalize the number
|
|
tst.b d1 ;check flag
|
|
beq.b no_inex ;if clr, no inex
|
|
bra.b dnrm_inex ;if set, set inex
|
|
|
|
chk_stky:
|
|
tst.l LOCAL_HI(a0) ;check for any bits set
|
|
bne.b set_stky
|
|
tst.l LOCAL_LO(a0) ;check for any bits set
|
|
bne.b set_stky
|
|
bra.b clr_mant
|
|
set_stky:
|
|
or.l #inx2a_mask,USER_FPSR(a6) ;set inex2/ainex
|
|
move.l #$20000000,d0 ;set sticky bit in return value
|
|
clr_mant:
|
|
move.w d1,LOCAL_EX(a0) ;load exp with threshold
|
|
clr.l LOCAL_HI(a0) ;set d1 = 0 (ms mantissa)
|
|
clr.l LOCAL_LO(a0) ;set d2 = 0 (ms mantissa)
|
|
rts
|
|
dnrm_inex:
|
|
or.l #inx2a_mask,USER_FPSR(a6) ;set inex2/ainex
|
|
no_inex:
|
|
rts
|
|
|
|
*
|
|
* dnrm_lp --- normalize exponent/mantissa to specified threshhold
|
|
*
|
|
* Input:
|
|
* a0 points to the operand to be denormalized
|
|
* d0{31:29} initial guard,round,sticky
|
|
* d1{15:0} denormalization threshold
|
|
* Output:
|
|
* a0 points to the denormalized operand
|
|
* d0{31:29} final guard,round,sticky
|
|
* d1.b inexact flag: all ones means inexact result
|
|
*
|
|
* The LOCAL_LO and LOCAL_GRS parts of the value are copied to FP_SCR2
|
|
* so that bfext can be used to extract the new low part of the mantissa.
|
|
* Dnrm_lp can be called with a0 pointing to ETEMP or WBTEMP and there
|
|
* is no LOCAL_GRS scratch word following it on the fsave frame.
|
|
*
|
|
xdef dnrm_lp
|
|
dnrm_lp:
|
|
move.l d2,-(sp) ;save d2 for temp use
|
|
btst.b #E3,E_BYTE(a6) ;test for type E3 exception
|
|
beq.b not_E3 ;not type E3 exception
|
|
bfextu WBTEMP_GRS(a6){6:3},d2 ;extract guard,round, sticky bit
|
|
move.l #29,d0
|
|
lsl.l d0,d2 ;shift g,r,s to their postions
|
|
move.l d2,d0
|
|
not_E3:
|
|
move.l (sp)+,d2 ;restore d2
|
|
move.l LOCAL_LO(a0),FP_SCR2+LOCAL_LO(a6)
|
|
move.l d0,FP_SCR2+LOCAL_GRS(a6)
|
|
move.l d1,d0 ;copy the denorm threshold
|
|
sub.w LOCAL_EX(a0),d1 ;d1 = threshold - uns exponent
|
|
ble.b no_lp ;d1 <= 0
|
|
cmp.w #32,d1
|
|
blt.b case_1 ;0 = d1 < 32
|
|
cmp.w #64,d1
|
|
blt.b case_2 ;32 <= d1 < 64
|
|
bra.w case_3 ;d1 >= 64
|
|
*
|
|
* No normalization necessary
|
|
*
|
|
no_lp:
|
|
clr.b d1 ;set no inex2 reported
|
|
move.l FP_SCR2+LOCAL_GRS(a6),d0 ;restore original g,r,s
|
|
rts
|
|
*
|
|
* case (0<d1<32)
|
|
*
|
|
case_1:
|
|
move.l d2,-(sp)
|
|
move.w d0,LOCAL_EX(a0) ;exponent = denorm threshold
|
|
move.l #32,d0
|
|
sub.w d1,d0 ;d0 = 32 - d1
|
|
bfextu LOCAL_EX(a0){d0:32},d2
|
|
bfextu d2{d1:d0},d2 ;d2 = new LOCAL_HI
|
|
bfextu LOCAL_HI(a0){d0:32},d1 ;d1 = new LOCAL_LO
|
|
bfextu FP_SCR2+LOCAL_LO(a6){d0:32},d0 ;d0 = new G,R,S
|
|
move.l d2,LOCAL_HI(a0) ;store new LOCAL_HI
|
|
move.l d1,LOCAL_LO(a0) ;store new LOCAL_LO
|
|
clr.b d1
|
|
bftst d0{2:30}
|
|
beq.b c1nstky
|
|
bset.l #rnd_stky_bit,d0
|
|
st.b d1
|
|
c1nstky:
|
|
move.l FP_SCR2+LOCAL_GRS(a6),d2 ;restore original g,r,s
|
|
andi.l #$e0000000,d2 ;clear all but G,R,S
|
|
tst.l d2 ;test if original G,R,S are clear
|
|
beq.b grs_clear
|
|
or.l #$20000000,d0 ;set sticky bit in d0
|
|
grs_clear:
|
|
andi.l #$e0000000,d0 ;clear all but G,R,S
|
|
move.l (sp)+,d2
|
|
rts
|
|
*
|
|
* case (32<=d1<64)
|
|
*
|
|
case_2:
|
|
move.l d2,-(sp)
|
|
move.w d0,LOCAL_EX(a0) ;unsigned exponent = threshold
|
|
sub.w #32,d1 ;d1 now between 0 and 32
|
|
move.l #32,d0
|
|
sub.w d1,d0 ;d0 = 32 - d1
|
|
bfextu LOCAL_EX(a0){d0:32},d2
|
|
bfextu d2{d1:d0},d2 ;d2 = new LOCAL_LO
|
|
bfextu LOCAL_HI(a0){d0:32},d1 ;d1 = new G,R,S
|
|
bftst d1{2:30}
|
|
bne.b c2_sstky ;bra if sticky bit to be set
|
|
bftst FP_SCR2+LOCAL_LO(a6){d0:32}
|
|
bne.b c2_sstky ;bra if sticky bit to be set
|
|
move.l d1,d0
|
|
clr.b d1
|
|
bra.b end_c2
|
|
c2_sstky:
|
|
move.l d1,d0
|
|
bset.l #rnd_stky_bit,d0
|
|
st.b d1
|
|
end_c2:
|
|
clr.l LOCAL_HI(a0) ;store LOCAL_HI = 0
|
|
move.l d2,LOCAL_LO(a0) ;store LOCAL_LO
|
|
move.l FP_SCR2+LOCAL_GRS(a6),d2 ;restore original g,r,s
|
|
andi.l #$e0000000,d2 ;clear all but G,R,S
|
|
tst.l d2 ;test if original G,R,S are clear
|
|
beq.b clear_grs
|
|
or.l #$20000000,d0 ;set sticky bit in d0
|
|
clear_grs:
|
|
andi.l #$e0000000,d0 ;get rid of all but G,R,S
|
|
move.l (sp)+,d2
|
|
rts
|
|
*
|
|
* d1 >= 64 Force the exponent to be the denorm threshold with the
|
|
* correct sign.
|
|
*
|
|
case_3:
|
|
move.w d0,LOCAL_EX(a0)
|
|
tst.w LOCAL_SGN(a0)
|
|
bge.b c3con
|
|
c3neg:
|
|
or.l #$80000000,LOCAL_EX(a0)
|
|
c3con:
|
|
cmp.w #64,d1
|
|
beq.b sixty_four
|
|
cmp.w #65,d1
|
|
beq.b sixty_five
|
|
*
|
|
* Shift value is out of range. Set d1 for inex2 flag and
|
|
* return a zero with the given threshold.
|
|
*
|
|
clr.l LOCAL_HI(a0)
|
|
clr.l LOCAL_LO(a0)
|
|
move.l #$20000000,d0
|
|
st.b d1
|
|
rts
|
|
|
|
sixty_four:
|
|
move.l LOCAL_HI(a0),d0
|
|
bfextu d0{2:30},d1
|
|
andi.l #$c0000000,d0
|
|
bra.b c3com
|
|
|
|
sixty_five:
|
|
move.l LOCAL_HI(a0),d0
|
|
bfextu d0{1:31},d1
|
|
andi.l #$80000000,d0
|
|
lsr.l #1,d0 ;shift high bit into R bit
|
|
|
|
c3com:
|
|
tst.l d1
|
|
bne.b c3ssticky
|
|
tst.l LOCAL_LO(a0)
|
|
bne.b c3ssticky
|
|
tst.b FP_SCR2+LOCAL_GRS(a6)
|
|
bne.b c3ssticky
|
|
clr.b d1
|
|
bra.b c3end
|
|
|
|
c3ssticky:
|
|
bset.l #rnd_stky_bit,d0
|
|
st.b d1
|
|
c3end:
|
|
clr.l LOCAL_HI(a0)
|
|
clr.l LOCAL_LO(a0)
|
|
rts
|
|
|
|
end
|