Subversion Repositories openrisc_2011-10-31

//
//      $Id: get_op.S,v 1.2 2001-09-27 12:01:22 chris Exp $
//
//      get_op.sa 3.6 5/19/92
//
//      get_op.sa 3.5 4/26/91
//
//  Description: This routine is called by the unsupported format/data
// type exception handler ('unsupp' - vector 55) and the unimplemented
// instruction exception handler ('unimp' - vector 11).  'get_op'
// determines the opclass (0, 2, or 3) and branches to the
// opclass handler routine.  See 68881/2 User's Manual table 4-11
// for a description of the opclasses.
//
// For UNSUPPORTED data/format (exception vector 55) and for
// UNIMPLEMENTED instructions (exception vector 11) the following
// applies:
//
// - For unnormalized numbers (opclass 0, 2, or 3) the
// number(s) is normalized and the operand type tag is updated.
//              
// - For a packed number (opclass 2) the number is unpacked and the
// operand type tag is updated.
//
// - For denormalized numbers (opclass 0 or 2) the number(s) is not
// changed but passed to the next module.  The next module for
// unimp is do_func, the next module for unsupp is res_func.
//
// For UNSUPPORTED data/format (exception vector 55) only the
// following applies:
//
// - If there is a move out with a packed number (opclass 3) the
// number is packed and written to user memory.  For the other
// opclasses the number(s) are written back to the fsave stack
// and the instruction is then restored back into the '040.  The
// '040 is then able to complete the instruction.
//
// For example:
// fadd.x fpm,fpn where the fpm contains an unnormalized number.
// The '040 takes an unsupported data trap and gets to this
// routine.  The number is normalized, put back on the stack and
// then an frestore is done to restore the instruction back into
// the '040.  The '040 then re-executes the fadd.x fpm,fpn with
// a normalized number in the source and the instruction is
// successful.
//              
// Next consider if in the process of normalizing the un-
// normalized number it becomes a denormalized number.  The
// routine which converts the unnorm to a norm (called mk_norm)
// detects this and tags the number as a denorm.  The routine
// res_func sees the denorm tag and converts the denorm to a
// norm.  The instruction is then restored back into the '040
// which re_executes the instruction.
//
//
//              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//      THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA 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.

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

        |section        8

#include "fpsp.defs"

        .global PIRN,PIRZRM,PIRP
        .global SMALRN,SMALRZRM,SMALRP
        .global BIGRN,BIGRZRM,BIGRP

PIRN:
        .long 0x40000000,0xc90fdaa2,0x2168c235    //pi
PIRZRM:
        .long 0x40000000,0xc90fdaa2,0x2168c234    //pi
PIRP:
        .long 0x40000000,0xc90fdaa2,0x2168c235    //pi

//round to nearest
SMALRN:
        .long 0x3ffd0000,0x9a209a84,0xfbcff798    //log10(2)
        .long 0x40000000,0xadf85458,0xa2bb4a9a    //e
        .long 0x3fff0000,0xb8aa3b29,0x5c17f0bc    //log2(e)
        .long 0x3ffd0000,0xde5bd8a9,0x37287195    //log10(e)
        .long 0x00000000,0x00000000,0x00000000    //0.0
// round to zero;round to negative infinity
SMALRZRM:
        .long 0x3ffd0000,0x9a209a84,0xfbcff798    //log10(2)
        .long 0x40000000,0xadf85458,0xa2bb4a9a    //e
        .long 0x3fff0000,0xb8aa3b29,0x5c17f0bb    //log2(e)
        .long 0x3ffd0000,0xde5bd8a9,0x37287195    //log10(e)
        .long 0x00000000,0x00000000,0x00000000    //0.0
// round to positive infinity
SMALRP:
        .long 0x3ffd0000,0x9a209a84,0xfbcff799    //log10(2)
        .long 0x40000000,0xadf85458,0xa2bb4a9b    //e
        .long 0x3fff0000,0xb8aa3b29,0x5c17f0bc    //log2(e)
        .long 0x3ffd0000,0xde5bd8a9,0x37287195    //log10(e)
        .long 0x00000000,0x00000000,0x00000000    //0.0

//round to nearest
BIGRN:
        .long 0x3ffe0000,0xb17217f7,0xd1cf79ac    //ln(2)
        .long 0x40000000,0x935d8ddd,0xaaa8ac17    //ln(10)
        .long 0x3fff0000,0x80000000,0x00000000    //10 ^ 0

        .global PTENRN
PTENRN:
        .long 0x40020000,0xA0000000,0x00000000    //10 ^ 1
        .long 0x40050000,0xC8000000,0x00000000    //10 ^ 2
        .long 0x400C0000,0x9C400000,0x00000000    //10 ^ 4
        .long 0x40190000,0xBEBC2000,0x00000000    //10 ^ 8
        .long 0x40340000,0x8E1BC9BF,0x04000000    //10 ^ 16
        .long 0x40690000,0x9DC5ADA8,0x2B70B59E    //10 ^ 32
        .long 0x40D30000,0xC2781F49,0xFFCFA6D5    //10 ^ 64
        .long 0x41A80000,0x93BA47C9,0x80E98CE0    //10 ^ 128
        .long 0x43510000,0xAA7EEBFB,0x9DF9DE8E    //10 ^ 256
        .long 0x46A30000,0xE319A0AE,0xA60E91C7    //10 ^ 512
        .long 0x4D480000,0xC9767586,0x81750C17    //10 ^ 1024
        .long 0x5A920000,0x9E8B3B5D,0xC53D5DE5    //10 ^ 2048
        .long 0x75250000,0xC4605202,0x8A20979B    //10 ^ 4096
//round to minus infinity
BIGRZRM:
        .long 0x3ffe0000,0xb17217f7,0xd1cf79ab    //ln(2)
        .long 0x40000000,0x935d8ddd,0xaaa8ac16    //ln(10)
        .long 0x3fff0000,0x80000000,0x00000000    //10 ^ 0

        .global PTENRM
PTENRM:
        .long 0x40020000,0xA0000000,0x00000000    //10 ^ 1
        .long 0x40050000,0xC8000000,0x00000000    //10 ^ 2
        .long 0x400C0000,0x9C400000,0x00000000    //10 ^ 4
        .long 0x40190000,0xBEBC2000,0x00000000    //10 ^ 8
        .long 0x40340000,0x8E1BC9BF,0x04000000    //10 ^ 16
        .long 0x40690000,0x9DC5ADA8,0x2B70B59D    //10 ^ 32
        .long 0x40D30000,0xC2781F49,0xFFCFA6D5    //10 ^ 64
        .long 0x41A80000,0x93BA47C9,0x80E98CDF    //10 ^ 128
        .long 0x43510000,0xAA7EEBFB,0x9DF9DE8D    //10 ^ 256
        .long 0x46A30000,0xE319A0AE,0xA60E91C6    //10 ^ 512
        .long 0x4D480000,0xC9767586,0x81750C17    //10 ^ 1024
        .long 0x5A920000,0x9E8B3B5D,0xC53D5DE5    //10 ^ 2048
        .long 0x75250000,0xC4605202,0x8A20979A    //10 ^ 4096
//round to positive infinity
BIGRP:
        .long 0x3ffe0000,0xb17217f7,0xd1cf79ac    //ln(2)
        .long 0x40000000,0x935d8ddd,0xaaa8ac17    //ln(10)
        .long 0x3fff0000,0x80000000,0x00000000    //10 ^ 0

        .global PTENRP
PTENRP:
        .long 0x40020000,0xA0000000,0x00000000    //10 ^ 1
        .long 0x40050000,0xC8000000,0x00000000    //10 ^ 2
        .long 0x400C0000,0x9C400000,0x00000000    //10 ^ 4
        .long 0x40190000,0xBEBC2000,0x00000000    //10 ^ 8
        .long 0x40340000,0x8E1BC9BF,0x04000000    //10 ^ 16
        .long 0x40690000,0x9DC5ADA8,0x2B70B59E    //10 ^ 32
        .long 0x40D30000,0xC2781F49,0xFFCFA6D6    //10 ^ 64
        .long 0x41A80000,0x93BA47C9,0x80E98CE0    //10 ^ 128
        .long 0x43510000,0xAA7EEBFB,0x9DF9DE8E    //10 ^ 256
        .long 0x46A30000,0xE319A0AE,0xA60E91C7    //10 ^ 512
        .long 0x4D480000,0xC9767586,0x81750C18    //10 ^ 1024
        .long 0x5A920000,0x9E8B3B5D,0xC53D5DE6    //10 ^ 2048
        .long 0x75250000,0xC4605202,0x8A20979B    //10 ^ 4096

        |xref   nrm_zero
        |xref   decbin
        |xref   round

        .global    get_op
        .global    uns_getop
        .global    uni_getop
get_op:
        clrb    DY_MO_FLG(%a6)
        tstb    UFLG_TMP(%a6)   //test flag for unsupp/unimp state
        beq     uni_getop

uns_getop:
        btstb   #direction_bit,CMDREG1B(%a6)
        bne     opclass3        //branch if a fmove out (any kind)
        btstb   #6,CMDREG1B(%a6)
        beqs    uns_notpacked

        bfextu  CMDREG1B(%a6){#3:#3},%d0
        cmpb    #3,%d0
        beq     pack_source     //check for a packed src op, branch if so
uns_notpacked:
        bsr     chk_dy_mo       //set the dyadic/monadic flag
        tstb    DY_MO_FLG(%a6)
        beqs    src_op_ck       //if monadic, go check src op
//                              ;else, check dst op (fall through)

        btstb   #7,DTAG(%a6)
        beqs    src_op_ck       //if dst op is norm, check src op
        bras    dst_ex_dnrm     //else, handle destination unnorm/dnrm

uni_getop:
        bfextu  CMDREG1B(%a6){#0:#6},%d0 //get opclass and src fields
        cmpil   #0x17,%d0               //if op class and size fields are $17, 
//                              ;it is FMOVECR; if not, continue
//
// If the instruction is fmovecr, exit get_op.  It is handled
// in do_func and smovecr.sa.
//
        bne     not_fmovecr     //handle fmovecr as an unimplemented inst
        rts

not_fmovecr:
        btstb   #E1,E_BYTE(%a6) //if set, there is a packed operand
        bne     pack_source     //check for packed src op, branch if so

// The following lines of are coded to optimize on normalized operands
        moveb   STAG(%a6),%d0
        orb     DTAG(%a6),%d0   //check if either of STAG/DTAG msb set
        bmis    dest_op_ck      //if so, some op needs to be fixed
        rts

dest_op_ck:
        btstb   #7,DTAG(%a6)    //check for unsupported data types in
        beqs    src_op_ck       //the destination, if not, check src op
        bsr     chk_dy_mo       //set dyadic/monadic flag
        tstb    DY_MO_FLG(%a6)  //
        beqs    src_op_ck       //if monadic, check src op
//
// At this point, destination has an extended denorm or unnorm.
//
dst_ex_dnrm:
        movew   FPTEMP_EX(%a6),%d0 //get destination exponent
        andiw   #0x7fff,%d0     //mask sign, check if exp = 0000
        beqs    src_op_ck       //if denorm then check source op.
//                              ;denorms are taken care of in res_func 
//                              ;(unsupp) or do_func (unimp)
//                              ;else unnorm fall through
        leal    FPTEMP(%a6),%a0 //point a0 to dop - used in mk_norm
        bsr     mk_norm         //go normalize - mk_norm returns:
//                              ;L_SCR1{7:5} = operand tag 
//                              ;       (000 = norm, 100 = denorm)
//                              ;L_SCR1{4} = fpte15 or ete15 
//                              ;       0 = exp >  $3fff
//                              ;       1 = exp <= $3fff
//                              ;and puts the normalized num back 
//                              ;on the fsave stack
//
        moveb L_SCR1(%a6),DTAG(%a6) //write the new tag & fpte15 
//                              ;to the fsave stack and fall 
//                              ;through to check source operand
//
src_op_ck:
        btstb   #7,STAG(%a6)
        beq     end_getop       //check for unsupported data types on the
//                              ;source operand
        btstb   #5,STAG(%a6)
        bnes    src_sd_dnrm     //if bit 5 set, handle sgl/dbl denorms
//
// At this point only unnorms or extended denorms are possible.
//
src_ex_dnrm:
        movew   ETEMP_EX(%a6),%d0 //get source exponent
        andiw   #0x7fff,%d0     //mask sign, check if exp = 0000
        beq     end_getop       //if denorm then exit, denorms are 
//                              ;handled in do_func
        leal    ETEMP(%a6),%a0  //point a0 to sop - used in mk_norm
        bsr     mk_norm         //go normalize - mk_norm returns:
//                              ;L_SCR1{7:5} = operand tag 
//                              ;       (000 = norm, 100 = denorm)
//                              ;L_SCR1{4} = fpte15 or ete15 
//                              ;       0 = exp >  $3fff
//                              ;       1 = exp <= $3fff
//                              ;and puts the normalized num back 
//                              ;on the fsave stack
//
        moveb   L_SCR1(%a6),STAG(%a6) //write the new tag & ete15 
        rts                     //end_getop

//
// At this point, only single or double denorms are possible.
// If the inst is not fmove, normalize the source.  If it is,
// do nothing to the input.
//
src_sd_dnrm:
        btstb   #4,CMDREG1B(%a6)        //differentiate between sgl/dbl denorm
        bnes    is_double
is_single:
        movew   #0x3f81,%d1     //write bias for sgl denorm
        bras    common          //goto the common code
is_double:
        movew   #0x3c01,%d1     //write the bias for a dbl denorm
common:
        btstb   #sign_bit,ETEMP_EX(%a6) //grab sign bit of mantissa
        beqs    pos     
        bset    #15,%d1         //set sign bit because it is negative
pos:
        movew   %d1,ETEMP_EX(%a6)
//                              ;put exponent on stack

        movew   CMDREG1B(%a6),%d1
        andw    #0xe3ff,%d1     //clear out source specifier
        orw     #0x0800,%d1     //set source specifier to extended prec
        movew   %d1,CMDREG1B(%a6)       //write back to the command word in stack
//                              ;this is needed to fix unsupp data stack
        leal    ETEMP(%a6),%a0  //point a0 to sop
        
        bsr     mk_norm         //convert sgl/dbl denorm to norm
        moveb   L_SCR1(%a6),STAG(%a6) //put tag into source tag reg - d0
        rts                     //end_getop
//
// At this point, the source is definitely packed, whether
// instruction is dyadic or monadic is still unknown
//
pack_source:
        movel   FPTEMP_LO(%a6),ETEMP(%a6)       //write ms part of packed 
//                              ;number to etemp slot
        bsr     chk_dy_mo       //set dyadic/monadic flag
        bsr     unpack

        tstb    DY_MO_FLG(%a6)
        beqs    end_getop       //if monadic, exit
//                              ;else, fix FPTEMP
pack_dya:
        bfextu  CMDREG1B(%a6){#6:#3},%d0 //extract dest fp reg
        movel   #7,%d1
        subl    %d0,%d1
        clrl    %d0
        bsetl   %d1,%d0         //set up d0 as a dynamic register mask
        fmovemx %d0,FPTEMP(%a6) //write to FPTEMP

        btstb   #7,DTAG(%a6)    //check dest tag for unnorm or denorm
        bne     dst_ex_dnrm     //else, handle the unnorm or ext denorm
//
// Dest is not denormalized.  Check for norm, and set fpte15 
// accordingly.
//
        moveb   DTAG(%a6),%d0
        andib   #0xf0,%d0               //strip to only dtag:fpte15
        tstb    %d0             //check for normalized value
        bnes    end_getop       //if inf/nan/zero leave get_op
        movew   FPTEMP_EX(%a6),%d0
        andiw   #0x7fff,%d0
        cmpiw   #0x3fff,%d0     //check if fpte15 needs setting
        bges    end_getop       //if >= $3fff, leave fpte15=0
        orb     #0x10,DTAG(%a6)
        bras    end_getop

//
// At this point, it is either an fmoveout packed, unnorm or denorm
//
opclass3:
        clrb    DY_MO_FLG(%a6)  //set dyadic/monadic flag to monadic
        bfextu  CMDREG1B(%a6){#4:#2},%d0
        cmpib   #3,%d0
        bne     src_ex_dnrm     //if not equal, must be unnorm or denorm
//                              ;else it is a packed move out
//                              ;exit
end_getop:
        rts

//
// Sets the DY_MO_FLG correctly. This is used only on if it is an
// unsupported data type exception.  Set if dyadic.
//
chk_dy_mo:
        movew   CMDREG1B(%a6),%d0       
        btstl   #5,%d0          //testing extension command word
        beqs    set_mon         //if bit 5 = 0 then monadic
        btstl   #4,%d0          //know that bit 5 = 1
        beqs    set_dya         //if bit 4 = 0 then dyadic
        andiw   #0x007f,%d0     //get rid of all but extension bits {6:0}
        cmpiw   #0x0038,%d0     //if extension = $38 then fcmp (dyadic)
        bnes    set_mon
set_dya:
        st      DY_MO_FLG(%a6)  //set the inst flag type to dyadic
        rts
set_mon:
        clrb    DY_MO_FLG(%a6)  //set the inst flag type to monadic
        rts
//
//      MK_NORM
//
// Normalizes unnormalized numbers, sets tag to norm or denorm, sets unfl
// exception if denorm.
//
// CASE opclass 0x0 unsupp
//      mk_norm till msb set
//      set tag = norm
//
// CASE opclass 0x0 unimp
//      mk_norm till msb set or exp = 0
//      if integer bit = 0
//         tag = denorm
//      else
//         tag = norm
//
// CASE opclass 011 unsupp
//      mk_norm till msb set or exp = 0
//      if integer bit = 0
//         tag = denorm
//         set unfl_nmcexe = 1
//      else
//         tag = norm
//
// if exp <= $3fff
//   set ete15 or fpte15 = 1
// else set ete15 or fpte15 = 0

// input:
//      a0 = points to operand to be normalized
// output:
//      L_SCR1{7:5} = operand tag (000 = norm, 100 = denorm)
//      L_SCR1{4}   = fpte15 or ete15 (0 = exp > $3fff, 1 = exp <=$3fff)
//      the normalized operand is placed back on the fsave stack
mk_norm:        
        clrl    L_SCR1(%a6)
        bclrb   #sign_bit,LOCAL_EX(%a0)
        sne     LOCAL_SGN(%a0)  //transform into internal extended format

        cmpib   #0x2c,1+EXC_VEC(%a6) //check if unimp
        bnes    uns_data        //branch if unsupp
        bsr     uni_inst        //call if unimp (opclass 0x0)
        bras    reload
uns_data:
        btstb   #direction_bit,CMDREG1B(%a6) //check transfer direction
        bnes    bit_set         //branch if set (opclass 011)
        bsr     uns_opx         //call if opclass 0x0
        bras    reload
bit_set:
        bsr     uns_op3         //opclass 011
reload:
        cmpw    #0x3fff,LOCAL_EX(%a0) //if exp > $3fff
        bgts    end_mk          //   fpte15/ete15 already set to 0
        bsetb   #4,L_SCR1(%a6)  //else set fpte15/ete15 to 1
//                              ;calling routine actually sets the 
//                              ;value on the stack (along with the 
//                              ;tag), since this routine doesn't 
//                              ;know if it should set ete15 or fpte15
//                              ;ie, it doesn't know if this is the 
//                              ;src op or dest op.
end_mk:
        bfclr   LOCAL_SGN(%a0){#0:#8}
        beqs    end_mk_pos
        bsetb   #sign_bit,LOCAL_EX(%a0) //convert back to IEEE format
end_mk_pos:
        rts
//
//     CASE opclass 011 unsupp
//
uns_op3:
        bsr     nrm_zero        //normalize till msb = 1 or exp = zero
        btstb   #7,LOCAL_HI(%a0)        //if msb = 1
        bnes    no_unfl         //then branch
set_unfl:
        orw     #dnrm_tag,L_SCR1(%a6) //set denorm tag
        bsetb   #unfl_bit,FPSR_EXCEPT(%a6) //set unfl exception bit
no_unfl:
        rts
//
//     CASE opclass 0x0 unsupp
//
uns_opx:
        bsr     nrm_zero        //normalize the number
        btstb   #7,LOCAL_HI(%a0)        //check if integer bit (j-bit) is set 
        beqs    uns_den         //if clear then now have a denorm
uns_nrm:
        orb     #norm_tag,L_SCR1(%a6) //set tag to norm
        rts
uns_den:
        orb     #dnrm_tag,L_SCR1(%a6) //set tag to denorm
        rts
//
//     CASE opclass 0x0 unimp
//
uni_inst:
        bsr     nrm_zero
        btstb   #7,LOCAL_HI(%a0)        //check if integer bit (j-bit) is set 
        beqs    uni_den         //if clear then now have a denorm
uni_nrm:
        orb     #norm_tag,L_SCR1(%a6) //set tag to norm
        rts
uni_den:
        orb     #dnrm_tag,L_SCR1(%a6) //set tag to denorm
        rts

//
//      Decimal to binary conversion
//
// Special cases of inf and NaNs are completed outside of decbin.  
// If the input is an snan, the snan bit is not set.
// 
// input:
//      ETEMP(a6)       - points to packed decimal string in memory
// output:
//      fp0     - contains packed string converted to extended precision
//      ETEMP   - same as fp0
unpack:
        movew   CMDREG1B(%a6),%d0       //examine command word, looking for fmove's
        andw    #0x3b,%d0
        beq     move_unpack     //special handling for fmove: must set FPSR_CC

        movew   ETEMP(%a6),%d0  //get word with inf information
        bfextu  %d0{#20:#12},%d1        //get exponent into d1
        cmpiw   #0x0fff,%d1     //test for inf or NaN
        bnes    try_zero        //if not equal, it is not special
        bfextu  %d0{#17:#3},%d1 //get SE and y bits into d1
        cmpiw   #7,%d1          //SE and y bits must be on for special
        bnes    try_zero        //if not on, it is not special
//input is of the special cases of inf and NaN
        tstl    ETEMP_HI(%a6)   //check ms mantissa
        bnes    fix_nan         //if non-zero, it is a NaN
        tstl    ETEMP_LO(%a6)   //check ls mantissa
        bnes    fix_nan         //if non-zero, it is a NaN
        bra     finish          //special already on stack
fix_nan:
        btstb   #signan_bit,ETEMP_HI(%a6) //test for snan
        bne     finish
        orl     #snaniop_mask,USER_FPSR(%a6) //always set snan if it is so
        bra     finish
try_zero:
        movew   ETEMP_EX+2(%a6),%d0 //get word 4
        andiw   #0x000f,%d0     //clear all but last ni(y)bble
        tstw    %d0             //check for zero.
        bne     not_spec
        tstl    ETEMP_HI(%a6)   //check words 3 and 2
        bne     not_spec
        tstl    ETEMP_LO(%a6)   //check words 1 and 0
        bne     not_spec
        tstl    ETEMP(%a6)      //test sign of the zero
        bges    pos_zero
        movel   #0x80000000,ETEMP(%a6) //write neg zero to etemp
        clrl    ETEMP_HI(%a6)
        clrl    ETEMP_LO(%a6)
        bra     finish
pos_zero:
        clrl    ETEMP(%a6)
        clrl    ETEMP_HI(%a6)
        clrl    ETEMP_LO(%a6)
        bra     finish

not_spec:
        fmovemx %fp0-%fp1,-(%a7)        //save fp0 - decbin returns in it
        bsr     decbin
        fmovex %fp0,ETEMP(%a6)  //put the unpacked sop in the fsave stack
        fmovemx (%a7)+,%fp0-%fp1
        fmovel  #0,%FPSR                //clr fpsr from decbin
        bra     finish

//
// Special handling for packed move in:  Same results as all other
// packed cases, but we must set the FPSR condition codes properly.
//
move_unpack:
        movew   ETEMP(%a6),%d0  //get word with inf information
        bfextu  %d0{#20:#12},%d1        //get exponent into d1
        cmpiw   #0x0fff,%d1     //test for inf or NaN
        bnes    mtry_zero       //if not equal, it is not special
        bfextu  %d0{#17:#3},%d1 //get SE and y bits into d1
        cmpiw   #7,%d1          //SE and y bits must be on for special
        bnes    mtry_zero       //if not on, it is not special
//input is of the special cases of inf and NaN
        tstl    ETEMP_HI(%a6)   //check ms mantissa
        bnes    mfix_nan                //if non-zero, it is a NaN
        tstl    ETEMP_LO(%a6)   //check ls mantissa
        bnes    mfix_nan                //if non-zero, it is a NaN
//input is inf
        orl     #inf_mask,USER_FPSR(%a6) //set I bit
        tstl    ETEMP(%a6)      //check sign
        bge     finish
        orl     #neg_mask,USER_FPSR(%a6) //set N bit
        bra     finish          //special already on stack
mfix_nan:
        orl     #nan_mask,USER_FPSR(%a6) //set NaN bit
        moveb   #nan_tag,STAG(%a6)      //set stag to NaN
        btstb   #signan_bit,ETEMP_HI(%a6) //test for snan
        bnes    mn_snan
        orl     #snaniop_mask,USER_FPSR(%a6) //set snan bit
        btstb   #snan_bit,FPCR_ENABLE(%a6) //test for snan enabled
        bnes    mn_snan
        bsetb   #signan_bit,ETEMP_HI(%a6) //force snans to qnans
mn_snan:
        tstl    ETEMP(%a6)      //check for sign
        bge     finish          //if clr, go on
        orl     #neg_mask,USER_FPSR(%a6) //set N bit
        bra     finish

mtry_zero:
        movew   ETEMP_EX+2(%a6),%d0 //get word 4
        andiw   #0x000f,%d0     //clear all but last ni(y)bble
        tstw    %d0             //check for zero.
        bnes    mnot_spec
        tstl    ETEMP_HI(%a6)   //check words 3 and 2
        bnes    mnot_spec
        tstl    ETEMP_LO(%a6)   //check words 1 and 0
        bnes    mnot_spec
        tstl    ETEMP(%a6)      //test sign of the zero
        bges    mpos_zero
        orl     #neg_mask+z_mask,USER_FPSR(%a6) //set N and Z
        movel   #0x80000000,ETEMP(%a6) //write neg zero to etemp
        clrl    ETEMP_HI(%a6)
        clrl    ETEMP_LO(%a6)
        bras    finish
mpos_zero:
        orl     #z_mask,USER_FPSR(%a6) //set Z
        clrl    ETEMP(%a6)
        clrl    ETEMP_HI(%a6)
        clrl    ETEMP_LO(%a6)
        bras    finish

mnot_spec:
        fmovemx %fp0-%fp1,-(%a7)        //save fp0 ,fp1 - decbin returns in fp0
        bsr     decbin
        fmovex %fp0,ETEMP(%a6)
//                              ;put the unpacked sop in the fsave stack
        fmovemx (%a7)+,%fp0-%fp1

finish:
        movew   CMDREG1B(%a6),%d0       //get the command word
        andw    #0xfbff,%d0     //change the source specifier field to 
//                              ;extended (was packed).
        movew   %d0,CMDREG1B(%a6)       //write command word back to fsave stack
//                              ;we need to do this so the 040 will 
//                              ;re-execute the inst. without taking 
//                              ;another packed trap.

fix_stag:
//Converted result is now in etemp on fsave stack, now set the source 
//tag (stag) 
//      if (ete =$7fff) then INF or NAN
//              if (etemp = $x.0----0) then
//                      stag = INF
//              else
//                      stag = NAN
//      else
//              if (ete = $0000) then
//                      stag = ZERO
//              else
//                      stag = NORM
//
// Note also that the etemp_15 bit (just right of the stag) must
// be set accordingly.  
//
        movew           ETEMP_EX(%a6),%d1
        andiw           #0x7fff,%d1   //strip sign
        cmpw            #0x7fff,%d1
        bnes            z_or_nrm
        movel           ETEMP_HI(%a6),%d1
        bnes            is_nan
        movel           ETEMP_LO(%a6),%d1
        bnes            is_nan
is_inf:
        moveb           #0x40,STAG(%a6)
        movel           #0x40,%d0
        rts
is_nan:
        moveb           #0x60,STAG(%a6)
        movel           #0x60,%d0
        rts
z_or_nrm:
        tstw            %d1  
        bnes            is_nrm
is_zro:
// For a zero, set etemp_15
        moveb           #0x30,STAG(%a6)
        movel           #0x20,%d0
        rts
is_nrm:
// For a norm, check if the exp <= $3fff; if so, set etemp_15
        cmpiw           #0x3fff,%d1
        bles            set_bit15
        moveb           #0,STAG(%a6)
        bras            end_is_nrm
set_bit15:
        moveb           #0x10,STAG(%a6)
end_is_nrm:
        movel           #0,%d0
end_fix:
        rts
 
end_get:
        rts
        |end