arch/m68k/fpsp040/sint.S

   1 |
   2 |       sint.sa 3.1 12/10/90
   3 |
   4 |       The entry point sINT computes the rounded integer
   5 |       equivalent of the input argument, sINTRZ computes
   6 |       the integer rounded to zero of the input argument.
   7 |
   8 |       Entry points sint and sintrz are called from do_func
   9 |       to emulate the fint and fintrz unimplemented instructions,
  10 |       respectively.  Entry point sintdo is used by bindec.
  11 |
  12 |       Input: (Entry points sint and sintrz) Double-extended
  13 |               number X in the ETEMP space in the floating-point
  14 |               save stack.
  15 |              (Entry point sintdo) Double-extended number X in
  16 |               location pointed to by the address register a0.
  17 |              (Entry point sintd) Double-extended denormalized
  18 |               number X in the ETEMP space in the floating-point
  19 |               save stack.
  20 |
  21 |       Output: The function returns int(X) or intrz(X) in fp0.
  22 |
  23 |       Modifies: fp0.
  24 |
  25 |       Algorithm: (sint and sintrz)
  26 |
  27 |       1. If exp(X) >= 63, return X.
  28 |          If exp(X) < 0, return +/- 0 or +/- 1, according to
  29 |          the rounding mode.
  30 |
  31 |       2. (X is in range) set rsc = 63 - exp(X). Unnormalize the
  32 |          result to the exponent $403e.
  33 |
  34 |       3. Round the result in the mode given in USER_FPCR. For
  35 |          sintrz, force round-to-zero mode.
  36 |
  37 |       4. Normalize the rounded result; store in fp0.
  38 |
  39 |       For the denormalized cases, force the correct result
  40 |       for the given sign and rounding mode.
  41 |
  42 |                       Sign(X)
  43 |               RMODE   +    -
  44 |               -----  --------
  45 |                RN    +0   -0
  46 |                RZ    +0   -0
  47 |                RM    +0   -1
  48 |                RP    +1   -0
  49 |
  50 |
  51 |               Copyright (C) Motorola, Inc. 1990
  52 |                       All Rights Reserved
  53 |
  54 |       THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA
  55 |       The copyright notice above does not evidence any
  56 |       actual or intended publication of such source code.
  57
  58 |SINT    idnt    2,1 | Motorola 040 Floating Point Software Package
  59
  60         |section        8
  61
  62 #include "fpsp.h"
  63
  64         |xref   dnrm_lp
  65         |xref   nrm_set
  66         |xref   round
  67         |xref   t_inx2
  68         |xref   ld_pone
  69         |xref   ld_mone
  70         |xref   ld_pzero
  71         |xref   ld_mzero
  72         |xref   snzrinx
  73
  74 |
  75 |       FINT
  76 |
  77         .global sint
  78 sint:
  79         bfextu  FPCR_MODE(%a6){#2:#2},%d1       |use user's mode for rounding
  80 |                                       ;implicitly has extend precision
  81 |                                       ;in upper word.
  82         movel   %d1,L_SCR1(%a6)         |save mode bits
  83         bras    sintexc
  84
  85 |
  86 |       FINT with extended denorm inputs.
  87 |
  88         .global sintd
  89 sintd:
  90         btstb   #5,FPCR_MODE(%a6)
  91         beq     snzrinx         |if round nearest or round zero, +/- 0
  92         btstb   #4,FPCR_MODE(%a6)
  93         beqs    rnd_mns
  94 rnd_pls:
  95         btstb   #sign_bit,LOCAL_EX(%a0)
  96         bnes    sintmz
  97         bsr     ld_pone         |if round plus inf and pos, answer is +1
  98         bra     t_inx2
  99 rnd_mns:
 100         btstb   #sign_bit,LOCAL_EX(%a0)
 101         beqs    sintpz
 102         bsr     ld_mone         |if round mns inf and neg, answer is -1
 103         bra     t_inx2
 104 sintpz:
 105         bsr     ld_pzero
 106         bra     t_inx2
 107 sintmz:
 108         bsr     ld_mzero
 109         bra     t_inx2
 110
 111 |
 112 |       FINTRZ
 113 |
 114         .global sintrz
 115 sintrz:
 116         movel   #1,L_SCR1(%a6)          |use rz mode for rounding
 117 |                                       ;implicitly has extend precision
 118 |                                       ;in upper word.
 119         bras    sintexc
 120 |
 121 |       SINTDO
 122 |
 123 |       Input:  a0 points to an IEEE extended format operand
 124 |       Output: fp0 has the result
 125 |
 126 | Exceptions:
 127 |
 128 | If the subroutine results in an inexact operation, the inx2 and
 129 | ainx bits in the USER_FPSR are set.
 130 |
 131 |
 132         .global sintdo
 133 sintdo:
 134         bfextu  FPCR_MODE(%a6){#2:#2},%d1       |use user's mode for rounding
 135 |                                       ;implicitly has ext precision
 136 |                                       ;in upper word.
 137         movel   %d1,L_SCR1(%a6)         |save mode bits
 138 |
 139 | Real work of sint is in sintexc
 140 |
 141 sintexc:
 142         bclrb   #sign_bit,LOCAL_EX(%a0) |convert to internal extended
 143 |                                       ;format
 144         sne     LOCAL_SGN(%a0)
 145         cmpw    #0x403e,LOCAL_EX(%a0)   |check if (unbiased) exp > 63
 146         bgts    out_rnge                        |branch if exp < 63
 147         cmpw    #0x3ffd,LOCAL_EX(%a0)   |check if (unbiased) exp < 0
 148         bgt     in_rnge                 |if 63 >= exp > 0, do calc
 149 |
 150 | Input is less than zero.  Restore sign, and check for directed
 151 | rounding modes.  L_SCR1 contains the rmode in the lower byte.
 152 |
 153 un_rnge:
 154         btstb   #1,L_SCR1+3(%a6)                |check for rn and rz
 155         beqs    un_rnrz
 156         tstb    LOCAL_SGN(%a0)          |check for sign
 157         bnes    un_rmrp_neg
 158 |
 159 | Sign is +.  If rp, load +1.0, if rm, load +0.0
 160 |
 161         cmpib   #3,L_SCR1+3(%a6)                |check for rp
 162         beqs    un_ldpone               |if rp, load +1.0
 163         bsr     ld_pzero                |if rm, load +0.0
 164         bra     t_inx2
 165 un_ldpone:
 166         bsr     ld_pone
 167         bra     t_inx2
 168 |
 169 | Sign is -.  If rm, load -1.0, if rp, load -0.0
 170 |
 171 un_rmrp_neg:
 172         cmpib   #2,L_SCR1+3(%a6)                |check for rm
 173         beqs    un_ldmone               |if rm, load -1.0
 174         bsr     ld_mzero                |if rp, load -0.0
 175         bra     t_inx2
 176 un_ldmone:
 177         bsr     ld_mone
 178         bra     t_inx2
 179 |
 180 | Rmode is rn or rz; return signed zero
 181 |
 182 un_rnrz:
 183         tstb    LOCAL_SGN(%a0)          |check for sign
 184         bnes    un_rnrz_neg
 185         bsr     ld_pzero
 186         bra     t_inx2
 187 un_rnrz_neg:
 188         bsr     ld_mzero
 189         bra     t_inx2
 190
 191 |
 192 | Input is greater than 2^63.  All bits are significant.  Return
 193 | the input.
 194 |
 195 out_rnge:
 196         bfclr   LOCAL_SGN(%a0){#0:#8}   |change back to IEEE ext format
 197         beqs    intps
 198         bsetb   #sign_bit,LOCAL_EX(%a0)
 199 intps:
 200         fmovel  %fpcr,-(%sp)
 201         fmovel  #0,%fpcr
 202         fmovex LOCAL_EX(%a0),%fp0       |if exp > 63
 203 |                                       ;then return X to the user
 204 |                                       ;there are no fraction bits
 205         fmovel  (%sp)+,%fpcr
 206         rts
 207
 208 in_rnge:
 209 |                                       ;shift off fraction bits
 210         clrl    %d0                     |clear d0 - initial g,r,s for
 211 |                                       ;dnrm_lp
 212         movel   #0x403e,%d1             |set threshold for dnrm_lp
 213 |                                       ;assumes a0 points to operand
 214         bsr     dnrm_lp
 215 |                                       ;returns unnormalized number
 216 |                                       ;pointed by a0
 217 |                                       ;output d0 supplies g,r,s
 218 |                                       ;used by round
 219         movel   L_SCR1(%a6),%d1         |use selected rounding mode
 220 |
 221 |
 222         bsr     round                   |round the unnorm based on users
 223 |                                       ;input  a0 ptr to ext X
 224 |                                       ;       d0 g,r,s bits
 225 |                                       ;       d1 PREC/MODE info
 226 |                                       ;output a0 ptr to rounded result
 227 |                                       ;inexact flag set in USER_FPSR
 228 |                                       ;if initial grs set
 229 |
 230 | normalize the rounded result and store value in fp0
 231 |
 232         bsr     nrm_set                 |normalize the unnorm
 233 |                                       ;Input: a0 points to operand to
 234 |                                       ;be normalized
 235 |                                       ;Output: a0 points to normalized
 236 |                                       ;result
 237         bfclr   LOCAL_SGN(%a0){#0:#8}
 238         beqs    nrmrndp
 239         bsetb   #sign_bit,LOCAL_EX(%a0) |return to IEEE extended format
 240 nrmrndp:
 241         fmovel  %fpcr,-(%sp)
 242         fmovel  #0,%fpcr
 243         fmovex LOCAL_EX(%a0),%fp0       |move result to fp0
 244         fmovel  (%sp)+,%fpcr
 245         rts
 246
 247         |end