source: rtems/bsps/m68k/shared/fpsp/x_store.S @ b82a4b4

#include "fpsp-namespace.h"
//
//
//      x_store.sa 3.2 1/24/91
//
//      store --- store operand to memory or register
//
//      Used by underflow and overflow handlers.
//
//      a6 = points to fp value to be stored.
//

//              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//      THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA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.

X_STORE:        //idnt    2,1 | Motorola 040 Floating Point Software Package

        |section        8

fpreg_mask:
        .byte   0x80,0x40,0x20,0x10,0x08,0x04,0x02,0x01

#include "fpsp.defs"

        |xref   mem_write
        |xref   get_fline
        |xref   g_opcls
        |xref   g_dfmtou
        |xref   reg_dest

        .global dest_ext
        .global dest_dbl
        .global dest_sgl

        .global store
store:
        btstb   #E3,E_BYTE(%a6)
        beqs    E1_sto
E3_sto:
        movel   CMDREG3B(%a6),%d0
        bfextu  %d0{#6:#3},%d0          //isolate dest. reg from cmdreg3b
sto_fp:
        lea     fpreg_mask,%a1
        moveb   (%a1,%d0.w),%d0         //convert reg# to dynamic register mask
        tstb    LOCAL_SGN(%a0)
        beqs    is_pos
        bsetb   #sign_bit,LOCAL_EX(%a0)
is_pos:
        fmovemx (%a0),%d0               //move to correct register
//
//      if fp0-fp3 is being modified, we must put a copy
//      in the USER_FPn variable on the stack because all exception
//      handlers restore fp0-fp3 from there.
//
        cmpb    #0x80,%d0
        bnes    not_fp0
        fmovemx %fp0-%fp0,USER_FP0(%a6)
        rts
not_fp0:
        cmpb    #0x40,%d0
        bnes    not_fp1
        fmovemx %fp1-%fp1,USER_FP1(%a6)
        rts
not_fp1:
        cmpb    #0x20,%d0
        bnes    not_fp2
        fmovemx %fp2-%fp2,USER_FP2(%a6)
        rts
not_fp2:
        cmpb    #0x10,%d0
        bnes    not_fp3
        fmovemx %fp3-%fp3,USER_FP3(%a6)
        rts
not_fp3:
        rts

E1_sto:
        bsrl    g_opcls         //returns opclass in d0
        cmpib   #3,%d0
        beq     opc011          //branch if opclass 3
        movel   CMDREG1B(%a6),%d0
        bfextu  %d0{#6:#3},%d0  //extract destination register
        bras    sto_fp

opc011:
        bsrl    g_dfmtou        //returns dest format in d0
//                              ;ext=00, sgl=01, dbl=10
        movel   %a0,%a1         //save source addr in a1
        movel   EXC_EA(%a6),%a0 //get the address
        cmpil   #0,%d0          //if dest format is extended
        beq     dest_ext        //then branch
        cmpil   #1,%d0          //if dest format is single
        beq     dest_sgl        //then branch
//
//      fall through to dest_dbl
//

//
//      dest_dbl --- write double precision value to user space
//
//Input
//      a0 -> destination address
//      a1 -> source in extended precision
//Output
//      a0 -> destroyed
//      a1 -> destroyed
//      d0 -> 0
//
//Changes extended precision to double precision.
// Note: no attempt is made to round the extended value to double.
//      dbl_sign = ext_sign
//      dbl_exp = ext_exp - $3fff(ext bias) + $7ff(dbl bias)
//      get rid of ext integer bit
//      dbl_mant = ext_mant{62:12}
//
//              ---------------   ---------------    ---------------
//  extended ->  |s|    exp    |   |1| ms mant   |    | ls mant     |
//              ---------------   ---------------    ---------------
//               95         64    63 62       32      31     11   0
//                                   |                       |
//                                   |                       |
//                                   |                       |
//                                   v                       v
//                            ---------------   ---------------
//  double   ->               |s|exp| mant  |   |  mant       |
//                            ---------------   ---------------
//                            63     51   32   31              0
//
dest_dbl:
        clrl    %d0             //clear d0
        movew   LOCAL_EX(%a1),%d0       //get exponent
        subw    #0x3fff,%d0     //subtract extended precision bias
        cmpw    #0x4000,%d0     //check if inf
        beqs    inf             //if so, special case
        addw    #0x3ff,%d0      //add double precision bias
        swap    %d0             //d0 now in upper word
        lsll    #4,%d0          //d0 now in proper place for dbl prec exp
        tstb    LOCAL_SGN(%a1)
        beqs    get_mant        //if positive, go process mantissa
        bsetl   #31,%d0         //if negative, put in sign information
//                              ; before continuing
        bras    get_mant        //go process mantissa
inf:
        movel   #0x7ff00000,%d0 //load dbl inf exponent
        clrl    LOCAL_HI(%a1)   //clear msb
        tstb    LOCAL_SGN(%a1)
        beqs    dbl_inf         //if positive, go ahead and write it
        bsetl   #31,%d0         //if negative put in sign information
dbl_inf:
        movel   %d0,LOCAL_EX(%a1)       //put the new exp back on the stack
        bras    dbl_wrt
get_mant:
        movel   LOCAL_HI(%a1),%d1       //get ms mantissa
        bfextu  %d1{#1:#20},%d1 //get upper 20 bits of ms
        orl     %d1,%d0         //put these bits in ms word of double
        movel   %d0,LOCAL_EX(%a1)       //put the new exp back on the stack
        movel   LOCAL_HI(%a1),%d1       //get ms mantissa
        movel   #21,%d0         //load shift count
        lsll    %d0,%d1         //put lower 11 bits in upper bits
        movel   %d1,LOCAL_HI(%a1)       //build lower lword in memory
        movel   LOCAL_LO(%a1),%d1       //get ls mantissa
        bfextu  %d1{#0:#21},%d0 //get ls 21 bits of double
        orl     %d0,LOCAL_HI(%a1)       //put them in double result
dbl_wrt:
        movel   #0x8,%d0                //byte count for double precision number
        exg     %a0,%a1         //a0=supervisor source, a1=user dest
        bsrl    mem_write       //move the number to the user's memory
        rts
//
//      dest_sgl --- write single precision value to user space
//
//Input
//      a0 -> destination address
//      a1 -> source in extended precision
//
//Output
//      a0 -> destroyed
//      a1 -> destroyed
//      d0 -> 0
//
//Changes extended precision to single precision.
//      sgl_sign = ext_sign
//      sgl_exp = ext_exp - $3fff(ext bias) + $7f(sgl bias)
//      get rid of ext integer bit
//      sgl_mant = ext_mant{62:12}
//
//              ---------------   ---------------    ---------------
//  extended ->  |s|    exp    |   |1| ms mant   |    | ls mant     |
//              ---------------   ---------------    ---------------
//               95         64    63 62    40 32      31     12   0
//                                   |     |
//                                   |     |
//                                   |     |
//                                   v     v
//                            ---------------
//  single   ->               |s|exp| mant  |
//                            ---------------
//                            31     22     0
//
dest_sgl:
        clrl    %d0
        movew   LOCAL_EX(%a1),%d0       //get exponent
        subw    #0x3fff,%d0     //subtract extended precision bias
        cmpw    #0x4000,%d0     //check if inf
        beqs    sinf            //if so, special case
        addw    #0x7f,%d0               //add single precision bias
        swap    %d0             //put exp in upper word of d0
        lsll    #7,%d0          //shift it into single exp bits
        tstb    LOCAL_SGN(%a1)
        beqs    get_sman        //if positive, continue
        bsetl   #31,%d0         //if negative, put in sign first
        bras    get_sman        //get mantissa
sinf:
        movel   #0x7f800000,%d0 //load single inf exp to d0
        tstb    LOCAL_SGN(%a1)
        beqs    sgl_wrt         //if positive, continue
        bsetl   #31,%d0         //if negative, put in sign info
        bras    sgl_wrt

get_sman:
        movel   LOCAL_HI(%a1),%d1       //get ms mantissa
        bfextu  %d1{#1:#23},%d1 //get upper 23 bits of ms
        orl     %d1,%d0         //put these bits in ms word of single

sgl_wrt:
        movel   %d0,L_SCR1(%a6) //put the new exp back on the stack
        movel   #0x4,%d0                //byte count for single precision number
        tstl    %a0             //users destination address
        beqs    sgl_Dn          //destination is a data register
        exg     %a0,%a1         //a0=supervisor source, a1=user dest
        leal    L_SCR1(%a6),%a0 //point a0 to data
        bsrl    mem_write       //move the number to the user's memory
        rts
sgl_Dn:
        bsrl    get_fline       //returns fline word in d0
        andw    #0x7,%d0                //isolate register number
        movel   %d0,%d1         //d1 has size:reg formatted for reg_dest
        orl     #0x10,%d1               //reg_dest wants size added to reg#
        bral    reg_dest        //size is X, rts in reg_dest will
//                              ;return to caller of dest_sgl

dest_ext:
        tstb    LOCAL_SGN(%a1)  //put back sign into exponent word
        beqs    dstx_cont
        bsetb   #sign_bit,LOCAL_EX(%a1)
dstx_cont:
        clrb    LOCAL_SGN(%a1)  //clear out the sign byte

        movel   #0x0c,%d0               //byte count for extended number
        exg     %a0,%a1         //a0=supervisor source, a1=user dest
        bsrl    mem_write       //move the number to the user's memory
        rts

        |end