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619 lines
19 KiB
Plaintext
619 lines
19 KiB
Plaintext
;
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; File: GetOp.a
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;
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; Contains: FPU Emulation Package routines to handle Unsupported format/data types
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;
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; Originally Written by: Motorola Inc.
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; Adapted to Apple/MPW: Jon Okada
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;
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; Copyright: © 1990, 1991 by Apple Computer, Inc., all rights reserved.
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;
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; This file is used in these builds: Mac32
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;
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; Change History (most recent first):
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;
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; <4> 5/24/91 BG Further streamlined "mk_norm" to treat opclass 0 and opclass 3
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; cases the same.
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; <3> 4/13/91 BG Fixed a bug which caused incorrect exception flags and results
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; for unnormalized extended input with denormal values.
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; <2> 3/30/91 BG Rolling in Jon Okada's latest changes.
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; <1> 12/14/90 BG First checked into TERROR/BBS.
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; getop.a
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; Based upon Motorola file 'get_op.sa'.
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; CHANGE LOG:
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; 04 Jan 91 JPO Moved constant tables for FMOVECR operation to
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; file 'constants.a'. Renamed labels "opclass3"
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; and "not_fmovecr" to "gopclass3" and "gnot_fmovecr",
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; respectively.
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; 13 Mar 91 JPO Refined test for packed decimal SRC for unsupported
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; data/format exception (opclass 2).
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; 11 Apr 91 JPO Cleaned up subroutine "mk_norm" to properly handle
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; unnormalized input with subnormal (denormal) values
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; for both unimplemented instruction and unsupported
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; format exception handlers. Note that tag masks are
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; byte-wide.
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; 17 Apr 91 JPO Further streamlined "mk_norm" to treat opclass 0 and
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; opclass 3 cases the same.
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;
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*
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* get_op.sa 3.1 12/10/90
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*
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* Description: This routine is called by the unsupported format/data
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* type exception handler ('unsupp' - vector 55) and the unimplemented
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* instruction exception handler ('unimp' - vector 11). 'get_op'
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* determines the opclass (0, 2, or 3) and branches to the
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* opclass handler routine. See 68881/2 User's Manual table 4-11
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* for a description of the opclasses.
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*
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* For UNSUPPORTED data/format (exception vector 55) and for
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* UNIMPLEMENTED instructions (exception vector 11) the following
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* applies:
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*
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* - For unnormormalized numbers (opclass 0, 2, or 3) the
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* number(s) is normalized and the operand type tag is updated.
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*
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* - For a packed number (opclass 2) the number is unpacked and the
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* operand type tag is updated.
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*
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* - For denormalized numbers (opclass 0 or 2) the number(s) is not
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* changed but passed to the next module. The next module for
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* unimp is do_func, the next module for unsupp is res_func.
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*
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* For UNSUPPORTED data/format (exception vector 55) only the
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* following applies:
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*
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* - If there is a move out with a packed number (opclass 3) the
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* number is packed and written to user memory. For the other
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* opclasses the number(s) are written back to the fsave stack
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* and the instruction is then restored back into the '040. The
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* '040 is then able to complete the instruction.
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*
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* For example:
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* fadd.x fpm,fpn where the fpm contains an unnormalized number.
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* The '040 takes an unsupported data trap and gets to this
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* routine. The number is normalized, put back on the stack and
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* then an frestore is done to restore the instruction back into
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* the '040. The '040 then re-executes the fadd.x fpm,fpn with
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* a normalized number in the source and the instruction is
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* successful.
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*
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* Next consider if in the process of normalizing the un-
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* normalized number it becomes a denormalized number. The
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* routine which converts the unnorm to a norm (called mk_norm)
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* detects this and tags the number as a denorm. The routine
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* res_func sees the denorm tag and converts the denorm to a
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* norm. The instruction is then restored back into the '040
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* which re_executess the instruction.
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*
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*
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* Copyright (C) Motorola, Inc. 1990
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* All Rights Reserved
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*
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* THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA
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* The copyright notice above does not evidence any
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* actual or intended publication of such source code.
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* GET_OP IDNT 2,1 Motorola 040 Floating Point Software Package
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get_op:
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clr.b DY_MO_FLG(a6)
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tst.b UFLG_TMP(a6) ;test flag for unsupp/unimp state
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beq.b uni_getop
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uns_getop:
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btst.b #direction_bit,CMDREG1B(a6)
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bne.w gopclass3 ;branch if a fmove out (any kind) - label RENAMED <1/4/91, JPO>
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btst.b #6,CMDREG1B(a6) ; opclass 2 (memory to reg)? <3/13/91, JPO>
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beq.b @1 ; no. opclass 0 (reg to reg) <3/13/91, JPO>
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bfextu CMDREG1B(a6){3:3},d0
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cmp.b #3,d0
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beq.w pack_source ;check for a packed src op, branch if so
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@1: ; label ADDED <3/13/91, JPO>
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bsr chk_dy_mo ;set the dyadic/monadic flag
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tst.b DY_MO_FLG(a6)
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beq.b src_op_ck ;if monadic, go check src op
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* ;else, check dst op (fall through)
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btst.b #7,DTAG(a6)
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beq.b src_op_ck ;if dst op is norm, check src op
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bra.b dst_ex_dnrm ;else, handle destination unnorm/dnrm
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uni_getop:
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bfextu CMDREG1B(a6){0:6},d0 ;get opclass and src fields
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cmpi.l #$17,d0 ;if op class and size fields are $17,
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* ;it is FMOVECR; if not, continue
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*
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* If the instruction is fmovecr, exit get_op. It is handled
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* in do_func and smovecr.sa.
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*
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bne.b gnot_fmovecr ;handle fmovecr as an unimplemented inst - label RENAMED <1/4/91, JPO>
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rts
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gnot_fmovecr: ; label RENAMED <1/4/91, JPO>
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btst.b #E1,E_BYTE(a6) ;if set, there is a packed operand
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bne.w pack_source ;check for packed src op, branch if so
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* The following lines of are coded to optimize on normalized operands
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move.b STAG(a6),d0
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or.b DTAG(a6),d0 ;check if either of STAG/DTAG msb set
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bmi.b dest_op_ck ;if so, some op needs to be fixed
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rts
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dest_op_ck:
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btst.b #7,DTAG(a6) ;check for unsupported data types in
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beq.b src_op_ck ;the destination, if not, check src op
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bsr chk_dy_mo ;set dyadic/monadic flag
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tst.b DY_MO_FLG(a6) ;
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beq.b src_op_ck ;if monadic, check src op
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*
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* At this point, destination has an extended denorm or unnorm.
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*
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dst_ex_dnrm:
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move.w FPTEMP_EX(a6),d0 ;get destination exponent
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andi.w #$7fff,d0 ;mask sign, check if exp = 0000
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beq.b src_op_ck ;if denorm then check source op.
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* ;denorms are taken care of in res_func
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* ;(unsupp) or do_func (unimp)
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* ;else unnorm fall through
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lea.l FPTEMP(a6),a0 ;point a0 to dop - used in mk_norm
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bsr mk_norm ;go normalize - mk_norm returns:
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* ;L_SCR1{7:5} = operand tag
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* ; (000 = norm, 100 = denorm)
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* ;L_SCR1{4} = fpte15 or ete15
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* ; 0 = exp > $3fff
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* ; 1 = exp <= $3fff
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* ;and puts the normalized num back
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* ;on the fsave stack
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*
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move.b L_SCR1(a6),DTAG(a6) ;write the new tag & fpte15
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* ;to the fsave stack and fall
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* ;through to check source operand
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*
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src_op_ck:
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btst.b #7,STAG(a6)
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beq.w end_getop ;check for unsupported data types on the
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* ;source operand
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btst.b #5,STAG(a6)
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bne.b src_sd_dnrm ;if bit 5 set, handle sgl/dbl denorms
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*
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* At this point only unnorms or extended denorms are possible.
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*
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src_ex_dnrm:
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move.w ETEMP_EX(a6),d0 ;get source exponent
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andi.w #$7fff,d0 ;mask sign, check if exp = 0000
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beq.w end_getop ;if denorm then exit, denorms are
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* ;handled in do_func
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lea.l ETEMP(a6),a0 ;point a0 to sop - used in mk_norm
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bsr mk_norm ;go normalize - mk_norm returns:
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* ;L_SCR1{7:5} = operand tag
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* ; (000 = norm, 100 = denorm)
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* ;L_SCR1{4} = fpte15 or ete15
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* ; 0 = exp > $3fff
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* ; 1 = exp <= $3fff
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* ;and puts the normalized num back
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* ;on the fsave stack
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*
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move.b L_SCR1(a6),STAG(a6) ;write the new tag & ete15
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rts ;end_getop
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*
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* At this point, only single or double denorms are possible.
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* If the inst is not fmove, normalize the source. If it is,
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* do nothing to the input.
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*
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src_sd_dnrm:
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btst.b #4,CMDREG1B(a6) ;differentiate between sgl/dbl denorm
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bne.b is_double
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is_single:
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move.w #$3f81,d1 ;write bias for sgl denorm
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bra.b common ;goto the common code
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is_double:
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move.w #$3c01,d1 ;write the bias for a dbl denorm
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common:
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btst.b #sign_bit,ETEMP_EX(a6) ;grab sign bit of mantissa
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beq.b pos
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bset #15,d1 ;set sign bit because it is negative
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pos:
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move.w d1,ETEMP_EX(a6)
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* ;put exponent on stack
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move.w CMDREG1B(a6),d1
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and.w #$e3ff,d1 ;clear out source specifier
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or.w #$0800,d1 ;set source specifier to extended prec
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move.w d1,CMDREG1B(a6) ;write back to the command word in stack
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* ;this is needed to fix unsupp data stack
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lea.l ETEMP(a6),a0 ;point a0 to sop
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bsr mk_norm ;convert sgl/dbl denorm to norm
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move.b L_SCR1(a6),STAG(a6) ;put tag into source tag reg - d0
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rts ;end_getop
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*
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* At this point, the source is definitely packed, whether
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* instruction is dyadic or monadic is still unknown
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*
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pack_source:
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move.l FPTEMP_LO(a6),ETEMP(a6) ;write ms part of packed
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* ;number to etemp slot
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bsr.b chk_dy_mo ;set dyadic/monadic flag
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bsr unpack
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tst.b DY_MO_FLG(a6)
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beq.b end_getop ;if monadic, exit
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* ;else, fix FPTEMP
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pack_dya:
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bfextu CMDREG1B(a6){6:3},d0 ;extract dest fp reg
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move.l #7,d1
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sub.l d0,d1
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clr.l d0
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bset.l d1,d0 ;set up d0 as a dynamic register mask
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fmovem.x d0,FPTEMP(a6) ;write to FPTEMP
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btst.b #7,DTAG(a6) ;check dest tag for unnorm or denorm
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bne.w dst_ex_dnrm ;else, handle the unnorm or ext denorm
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*
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* Dest is not denormalized. Check for norm, and set fpte15
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* accordingly.
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*
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move.b DTAG(a6),d0
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andi.b #$f0,d0 ;strip to only dtag:fpte15
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tst.b d0 ;check for normalized value
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bne.b end_getop ;if inf/nan/zero leave get_op
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move.w FPTEMP_EX(a6),d0
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andi.w #$7fff,d0
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cmpi.w #$3fff,d0 ;check if fpte15 needs setting
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bge.b end_getop ;if >= $3fff, leave fpte15=0
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or.b #$10,DTAG(a6)
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bra.b end_getop
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*
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* At this point, it is either an fmoveout packed, unnorm or denorm
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*
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gopclass3: ; label renamed <1/4/91, JPO>
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clr.b DY_MO_FLG(a6) ;set dyadic/monadic flag to monadic
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bfextu CMDREG1B(a6){4:2},d0
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cmpi.b #3,d0
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bne.w src_ex_dnrm ;if not equal, must be unnorm or denorm
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* ;else it is a packed move out
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* ;exit
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end_getop:
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rts
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*
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* Sets the DY_MO_FLG correctly. This is used only on if it is an
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* unuspported data type exception. Set if dyadic.
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*
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chk_dy_mo:
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move.w CMDREG1B(a6),d0
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btst.l #5,d0 ;testing extension command word
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beq.b set_mon ;if bit 5 = 0 then monadic
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btst.l #4,d0 ;know that bit 5 = 1
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beq.b set_dya ;if bit 4 = 0 then dyadic
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andi.w #$007f,d0 ;get rid of all but extension bits {6:0}
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cmpi.w #$0038,d0 ;if extension = $38 then fcmp (dyadic)
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bne.b set_mon
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set_dya:
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st.b DY_MO_FLG(a6) ;set the inst flag type to dyadic
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rts
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set_mon:
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clr.b DY_MO_FLG(a6) ;set the inst flag type to monadic
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rts
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*
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* MK_NORM - MODIFIED <4/17/91, JPO>
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*
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* Normalizes unnormalized numbers, sets tag to norm or denorm
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*
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* mk_norm till msb set or exp = 0
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* if integer bit = 0
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* tag = denorm
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* else
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* tag = norm
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*
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* if exp <= $3fff
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* set ete15 or fpte15 = 1
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* else
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* set ete15 or fpte15 = 0
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*
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* input:
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* a0 = points to operand to be normalized
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* output:
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* L_SCR1{7:5} = operand tag (000 = norm, 100 = denorm)
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* L_SCR1{4} = fpte15 or ete15 (0 = exp > $3fff, 1 = exp <=$3fff)
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* the normalized operand is placed back on the fsave stack
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mk_norm:
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clr.l L_SCR1(a6)
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bclr.b #sign_bit,LOCAL_EX(a0)
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sne LOCAL_SGN(a0) ;transform into internal extended format
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; cmpi.b #$2c,1+EXC_VEC(a6) ;check if unimp - DELETED <4/17/91, JPO> <T4> thru next <T4>
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; bne.b uns_data ;branch if unsupp - DELETED <4/17/91, JPO>
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; bsr.b uni_inst ;call if unimp (opclass 0x0) - DELETED <4/17/91, JPO>
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; bra.b reload ; DELETED <4/11/91, JPO>
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; beq.b uni_inst ; unimplemented <4/11/91, JPO> - DELETED <4/17/91, JPO>
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;uns_data: ; label DELETED - <4/11/91, JPO>
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; btst.b #direction_bit,CMDREG1B(a6) ;check transfer direction - DELETED <4/17/91, JPO> <T4>
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; bne.b bit_set ;branch if set (opclass 011) - DELETED <4/11/91, JPO>
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; bsr.b uns_opx ;call if opclass 0x0 - DELETED <4/11/91, JPO>
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; bra.b reload ; DELETED <4/11/91, JPO>
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;
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; bne.b uns_op3 ; opclass 011 <4/11/91, JPO> - DELETED <4/17/91, JPO> <T4>
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;bit_set: ; label DELETED <4/11/91, JPO>
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; bsr.b uns_op3 ;opclass 011 - DELETED <4/11/91, JPO>
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;
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; CASE opclass 0 unsupported or unimplemented - MOVED inline from below <4/11/91, JPO>
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;
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;uni_inst: ; label DELETED <4/17/91, JPO> <T4>
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bsr nrm_zero ; <4/11/91, JPO>
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btst.b #7,LOCAL_HI(a0) ;check if integer bit (j-bit) is set
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; beq.b uns_den ;if clear then now have a denorm - DELETED <4/11/91, JPO>
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bne.b reload ;if set, now have a norm <4/11/91, JPO>
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; or.w #norm_tag,L_SCR1(a6) ;set tag to norm - DELETED <4/11/91, JPO>
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; rts ; DELETED <4/11/91, JPO>
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;uns_den: ; label DELETED <4/11/91, JPO>
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; or.w #dnrm_tag,L_SCR1(a6) ;set tag to norm - DELETED <4/11/91, JPO>
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or.b #dnrm_tag,L_SCR1(a6) ; set byte tag to denorm <4/11/91, JPO> <T3>
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reload:
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cmp.w #$3fff,LOCAL_EX(a0) ;if exp > $3fff
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bgt.b end_mk ; fpte15/ete15 already set to 0
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bset.b #4,L_SCR1(a6) ;else set fpte15/ete15 to 1
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* ;calling routine actually sets the
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* ;value on the stack (along with the
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* ;tag), since this routine doesn't
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* ;know if it should set ete15 or fpte15
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* ;ie, it doesn't know if this is the
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* ;src op or dest op.
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end_mk:
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bfclr LOCAL_SGN(a0){0:8}
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beq.b end_mk_pos
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bset.b #sign_bit,LOCAL_EX(a0) ;convert back to IEEE format
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end_mk_pos:
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rts
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;*
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;* CASE opclass 011 unsupp - modified from subroutine to inline <4/11/91, JPO> <T4> thru next <T4>
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;* then DELETED <4/17/91 JPO>
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;uns_op3:
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; bsr nrm_zero ;normalize till msb = 1 or exp = zero
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; btst.b #7,LOCAL_HI(a0) ;if msb = 1
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; bne.b no_unfl ;then branch
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;set_unfl:
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; or.w #dnrm_tag,L_SCR1(a6) ;set denorm tag - DELETED <4/11/91, JPO>
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; or.b #dnrm_tag,L_SCR1(a6) ; set denorm in byte tag <4/11/91, JPO>
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; bset.b #unfl_bit,FPSR_EXCEPT(a6) ;set unfl exception bit
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no_unfl:
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; rts ; DELETED <4/11/91, JPO>
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; bra.b reload ; finish up mk_norm <4/11/91, JPO> <T4>
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*
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* CASE opclass 0x0 unsupp - routine DELETED <4/11/91, JPO>
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*
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;uns_opx:
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; bsr nrm_zero ;normalize the number
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|
; or.w #norm_tag,L_SCR1(a6) ;set tag to norm
|
|
; rts
|
|
*
|
|
* CASE opclass 0x0 unimp - routine MOVED inline above <4/11/91, JPO>
|
|
*
|
|
;uni_inst:
|
|
; bsr nrm_zero
|
|
; btst.b #7,LOCAL_HI(a0) ;check if integer bit (j-bit) is set
|
|
; beq.b uns_den ;if clear then now have a denorm
|
|
;uns_nrm:
|
|
; or.w #norm_tag,L_SCR1(a6) ;set tag to norm
|
|
; rts
|
|
;uns_den:
|
|
; or.w #dnrm_tag,L_SCR1(a6) ;set tag to norm
|
|
; rts <T3>
|
|
|
|
*
|
|
* 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:
|
|
move.w CMDREG1B(a6),d0 ;examine command word, looking for fmove's
|
|
and.w #$3b,d0
|
|
beq move_unpack ;special handling for fmove: must set FPSR_CC
|
|
|
|
move.w ETEMP(a6),d0 ;get word with inf information
|
|
bfextu d0{20:12},d1 ;get exponent into d1
|
|
cmpi.w #$0fff,d1 ;test for inf or NaN
|
|
bne.b try_zero ;if not equal, it is not special
|
|
bfextu d0{17:3},d1 ;get SE and y bits into d1
|
|
cmpi.w #7,d1 ;SE and y bits must be on for special
|
|
bne.b try_zero ;if not on, it is not special
|
|
*input is of the special cases of inf and NaN
|
|
tst.l ETEMP_HI(a6) ;check ms mantissa
|
|
bne.b fix_nan ;if non-zero, it is a NaN
|
|
tst.l ETEMP_LO(a6) ;check ls mantissa
|
|
bne.b fix_nan ;if non-zero, it is a NaN
|
|
bra.w finish ;special already on stack
|
|
fix_nan:
|
|
btst.b #signan_bit,ETEMP_HI(a6) ;test for snan
|
|
bne.w finish
|
|
or.l #snaniop_mask,USER_FPSR(a6) ;always set snan if it is so
|
|
bra.w finish
|
|
try_zero:
|
|
move.w ETEMP_EX+2(a6),d0 ;get word 4
|
|
andi.w #$000f,d0 ;clear all but last ni(y)bble
|
|
tst.w d0 ;check for zero.
|
|
bne.b not_spec
|
|
tst.l ETEMP_HI(a6) ;check words 3 and 2
|
|
bne.b not_spec
|
|
tst.l ETEMP_LO(a6) ;check words 1 and 0
|
|
bne.b not_spec
|
|
tst.l ETEMP(a6) ;test sign of the zero
|
|
bge.b pos_zero
|
|
move.l #$80000000,ETEMP(a6) ;write neg zero to etemp
|
|
clr.l ETEMP_HI(a6)
|
|
clr.l ETEMP_LO(a6)
|
|
bra.w finish
|
|
pos_zero:
|
|
clr.l ETEMP(a6)
|
|
clr.l ETEMP_HI(a6)
|
|
clr.l ETEMP_LO(a6)
|
|
bra.w finish
|
|
|
|
not_spec:
|
|
fmovem.x fp0,-(a7) ;save fp0 - decbin returns in it
|
|
bsr decbin
|
|
fmove.x fp0,ETEMP(a6) ;put the unpacked sop in the fsave stack
|
|
fmovem.x (a7)+,fp0
|
|
fmove.l #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:
|
|
move.w ETEMP(a6),d0 ;get word with inf information
|
|
bfextu d0{20:12},d1 ;get exponent into d1
|
|
cmpi.w #$0fff,d1 ;test for inf or NaN
|
|
bne.b mtry_zero ;if not equal, it is not special
|
|
bfextu d0{17:3},d1 ;get SE and y bits into d1
|
|
cmpi.w #7,d1 ;SE and y bits must be on for special
|
|
bne.b mtry_zero ;if not on, it is not special
|
|
*input is of the special cases of inf and NaN
|
|
tst.l ETEMP_HI(a6) ;check ms mantissa
|
|
bne.b mfix_nan ;if non-zero, it is a NaN
|
|
tst.l ETEMP_LO(a6) ;check ls mantissa
|
|
bne.b mfix_nan ;if non-zero, it is a NaN
|
|
*input is inf
|
|
or.l #inf_mask,USER_FPSR(a6) ;set I bit
|
|
tst.l ETEMP(a6) ;check sign
|
|
bge.w finish
|
|
or.l #neg_mask,USER_FPSR(a6) ;set N bit
|
|
bra.w finish ;special already on stack
|
|
mfix_nan:
|
|
or.l #nan_mask,USER_FPSR(a6) ;set NaN bit
|
|
move.b #nan_tag,STAG(a6) ;set stag to NaN
|
|
btst.b #signan_bit,ETEMP_HI(a6) ;test for snan
|
|
bne.b mn_snan
|
|
or.l #snaniop_mask,USER_FPSR(a6) ;set snan bit
|
|
btst.b #snan_bit,FPCR_ENABLE(a6) ;test for snan enabled
|
|
bne.b mn_snan
|
|
bset.b #signan_bit,ETEMP_HI(a6) ;force snans to qnans
|
|
mn_snan:
|
|
tst.l ETEMP(a6) ;check for sign
|
|
bge.b finish ;if clr, go on
|
|
or.l #neg_mask,USER_FPSR(a6) ;set N bit
|
|
bra.b finish
|
|
|
|
mtry_zero:
|
|
move.w ETEMP_EX+2(a6),d0 ;get word 4
|
|
andi.w #$000f,d0 ;clear all but last ni(y)bble
|
|
tst.w d0 ;check for zero.
|
|
bne.b mnot_spec
|
|
tst.l ETEMP_HI(a6) ;check words 3 and 2
|
|
bne.b mnot_spec
|
|
tst.l ETEMP_LO(a6) ;check words 1 and 0
|
|
bne.b mnot_spec
|
|
tst.l ETEMP(a6) ;test sign of the zero
|
|
bge.b mpos_zero
|
|
or.l #neg_mask+z_mask,USER_FPSR(a6) ;set N and Z
|
|
move.l #$80000000,ETEMP(a6) ;write neg zero to etemp
|
|
clr.l ETEMP_HI(a6)
|
|
clr.l ETEMP_LO(a6)
|
|
bra.b finish
|
|
mpos_zero:
|
|
or.l #z_mask,USER_FPSR(a6) ;set Z
|
|
clr.l ETEMP(a6)
|
|
clr.l ETEMP_HI(a6)
|
|
clr.l ETEMP_LO(a6)
|
|
bra.b finish
|
|
|
|
mnot_spec:
|
|
fmovem.x fp0,-(a7) ;save fp0 - decbin returns in it
|
|
bsr decbin
|
|
fmove.x fp0,ETEMP(a6)
|
|
* ;put the unpacked sop in the fsave stack
|
|
fmovem.x (a7)+,fp0
|
|
|
|
finish:
|
|
move.w CMDREG1B(a6),d0 ;get the command word
|
|
and.w #$fbff,d0 ;change the source specifier field to
|
|
* ;extended (was packed).
|
|
move.w 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.
|
|
*
|
|
move.w ETEMP_EX(a6),d1
|
|
andi.w #$7fff,d1 ;strip sign
|
|
cmp.w #$7fff,d1
|
|
bne.b z_or_nrm
|
|
move.l ETEMP_HI(a6),d1
|
|
bne.b is_nan
|
|
move.l ETEMP_LO(a6),d1
|
|
bne.b is_nan
|
|
is_inf:
|
|
move.b #$40,STAG(a6)
|
|
move.l #$40,d0
|
|
rts
|
|
is_nan:
|
|
move.b #$60,STAG(a6)
|
|
move.l #$60,d0
|
|
rts
|
|
z_or_nrm:
|
|
tst.w d1
|
|
bne.b is_nrm
|
|
is_zro:
|
|
* For a zero, set etemp_15
|
|
move.b #$30,STAG(a6)
|
|
move.l #$20,d0
|
|
rts
|
|
is_nrm:
|
|
* For a norm, check if the exp <= $3fff; if so, set etemp_15
|
|
cmpi.w #$3fff,d1
|
|
ble.b set_bit15
|
|
move.b #0,STAG(a6)
|
|
bra.b end_is_nrm
|
|
set_bit15:
|
|
move.b #$10,STAG(a6)
|
|
end_is_nrm:
|
|
move.l #0,d0
|
|
end_fix:
|
|
rts
|
|
|
|
end_get:
|
|
rts
|
|
|
|
|