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 |       For details on the license for this file, please see the
  55 |       file, README, in this same directory.
  56
  57 |SINT    idnt    2,1 | Motorola 040 Floating Point Software Package
  58
  59         |section        8
  60
  61 #include "fpsp.h"
  62
  63         |xref   dnrm_lp
  64         |xref   nrm_set
  65         |xref   round
  66         |xref   t_inx2
  67         |xref   ld_pone
  68         |xref   ld_mone
  69         |xref   ld_pzero
  70         |xref   ld_mzero
  71         |xref   snzrinx
  72
  73 |
  74 |       FINT
  75 |
  76         .global sint
  77 sint:
  78         bfextu  FPCR_MODE(%a6){#2:#2},%d1       |use user's mode for rounding
  79 |                                       ;implicitly has extend precision
  80 |                                       ;in upper word.
  81         movel   %d1,L_SCR1(%a6)         |save mode bits
  82         bras    sintexc
  83
  84 |
  85 |       FINT with extended denorm inputs.
  86 |
  87         .global sintd
  88 sintd:
  89         btstb   #5,FPCR_MODE(%a6)
  90         beq     snzrinx         |if round nearest or round zero, +/- 0
  91         btstb   #4,FPCR_MODE(%a6)
  92         beqs    rnd_mns
  93 rnd_pls:
  94         btstb   #sign_bit,LOCAL_EX(%a0)
  95         bnes    sintmz
  96         bsr     ld_pone         |if round plus inf and pos, answer is +1
  97         bra     t_inx2
  98 rnd_mns:
  99         btstb   #sign_bit,LOCAL_EX(%a0)
 100         beqs    sintpz
 101         bsr     ld_mone         |if round mns inf and neg, answer is -1
 102         bra     t_inx2
 103 sintpz:
 104         bsr     ld_pzero
 105         bra     t_inx2
 106 sintmz:
 107         bsr     ld_mzero
 108         bra     t_inx2
 109
 110 |
 111 |       FINTRZ
 112 |
 113         .global sintrz
 114 sintrz:
 115         movel   #1,L_SCR1(%a6)          |use rz mode for rounding
 116 |                                       ;implicitly has extend precision
 117 |                                       ;in upper word.
 118         bras    sintexc
 119 |
 120 |       SINTDO
 121 |
 122 |       Input:  a0 points to an IEEE extended format operand
 123 |       Output: fp0 has the result
 124 |
 125 | Exceptions:
 126 |
 127 | If the subroutine results in an inexact operation, the inx2 and
 128 | ainx bits in the USER_FPSR are set.
 129 |
 130 |
 131         .global sintdo
 132 sintdo:
 133         bfextu  FPCR_MODE(%a6){#2:#2},%d1       |use user's mode for rounding
 134 |                                       ;implicitly has ext precision
 135 |                                       ;in upper word.
 136         movel   %d1,L_SCR1(%a6)         |save mode bits
 137 |
 138 | Real work of sint is in sintexc
 139 |
 140 sintexc:
 141         bclrb   #sign_bit,LOCAL_EX(%a0) |convert to internal extended
 142 |                                       ;format
 143         sne     LOCAL_SGN(%a0)
 144         cmpw    #0x403e,LOCAL_EX(%a0)   |check if (unbiased) exp > 63
 145         bgts    out_rnge                        |branch if exp < 63
 146         cmpw    #0x3ffd,LOCAL_EX(%a0)   |check if (unbiased) exp < 0
 147         bgt     in_rnge                 |if 63 >= exp > 0, do calc
 148 |
 149 | Input is less than zero.  Restore sign, and check for directed
 150 | rounding modes.  L_SCR1 contains the rmode in the lower byte.
 151 |
 152 un_rnge:
 153         btstb   #1,L_SCR1+3(%a6)                |check for rn and rz
 154         beqs    un_rnrz
 155         tstb    LOCAL_SGN(%a0)          |check for sign
 156         bnes    un_rmrp_neg
 157 |
 158 | Sign is +.  If rp, load +1.0, if rm, load +0.0
 159 |
 160         cmpib   #3,L_SCR1+3(%a6)                |check for rp
 161         beqs    un_ldpone               |if rp, load +1.0
 162         bsr     ld_pzero                |if rm, load +0.0
 163         bra     t_inx2
 164 un_ldpone:
 165         bsr     ld_pone
 166         bra     t_inx2
 167 |
 168 | Sign is -.  If rm, load -1.0, if rp, load -0.0
 169 |
 170 un_rmrp_neg:
 171         cmpib   #2,L_SCR1+3(%a6)                |check for rm
 172         beqs    un_ldmone               |if rm, load -1.0
 173         bsr     ld_mzero                |if rp, load -0.0
 174         bra     t_inx2
 175 un_ldmone:
 176         bsr     ld_mone
 177         bra     t_inx2
 178 |
 179 | Rmode is rn or rz; return signed zero
 180 |
 181 un_rnrz:
 182         tstb    LOCAL_SGN(%a0)          |check for sign
 183         bnes    un_rnrz_neg
 184         bsr     ld_pzero
 185         bra     t_inx2
 186 un_rnrz_neg:
 187         bsr     ld_mzero
 188         bra     t_inx2
 189
 190 |
 191 | Input is greater than 2^63.  All bits are significant.  Return
 192 | the input.
 193 |
 194 out_rnge:
 195         bfclr   LOCAL_SGN(%a0){#0:#8}   |change back to IEEE ext format
 196         beqs    intps
 197         bsetb   #sign_bit,LOCAL_EX(%a0)
 198 intps:
 199         fmovel  %fpcr,-(%sp)
 200         fmovel  #0,%fpcr
 201         fmovex LOCAL_EX(%a0),%fp0       |if exp > 63
 202 |                                       ;then return X to the user
 203 |                                       ;there are no fraction bits
 204         fmovel  (%sp)+,%fpcr
 205         rts
 206
 207 in_rnge:
 208 |                                       ;shift off fraction bits
 209         clrl    %d0                     |clear d0 - initial g,r,s for
 210 |                                       ;dnrm_lp
 211         movel   #0x403e,%d1             |set threshold for dnrm_lp
 212 |                                       ;assumes a0 points to operand
 213         bsr     dnrm_lp
 214 |                                       ;returns unnormalized number
 215 |                                       ;pointed by a0
 216 |                                       ;output d0 supplies g,r,s
 217 |                                       ;used by round
 218         movel   L_SCR1(%a6),%d1         |use selected rounding mode
 219 |
 220 |
 221         bsr     round                   |round the unnorm based on users
 222 |                                       ;input  a0 ptr to ext X
 223 |                                       ;       d0 g,r,s bits
 224 |                                       ;       d1 PREC/MODE info
 225 |                                       ;output a0 ptr to rounded result
 226 |                                       ;inexact flag set in USER_FPSR
 227 |                                       ;if initial grs set
 228 |
 229 | normalize the rounded result and store value in fp0
 230 |
 231         bsr     nrm_set                 |normalize the unnorm
 232 |                                       ;Input: a0 points to operand to
 233 |                                       ;be normalized
 234 |                                       ;Output: a0 points to normalized
 235 |                                       ;result
 236         bfclr   LOCAL_SGN(%a0){#0:#8}
 237         beqs    nrmrndp
 238         bsetb   #sign_bit,LOCAL_EX(%a0) |return to IEEE extended format
 239 nrmrndp:
 240         fmovel  %fpcr,-(%sp)
 241         fmovel  #0,%fpcr
 242         fmovex LOCAL_EX(%a0),%fp0       |move result to fp0
 243         fmovel  (%sp)+,%fpcr
 244         rts
 245
 246         |end