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//
//      $Id: x_operr.S,v 1.2 2001-09-27 12:01:22 chris Exp $
//
//      x_operr.sa 3.5 7/1/91
//
//      fpsp_operr --- FPSP handler for operand error exception
//
//      See 68040 User's Manual pp. 9-44f
//
// Note 1: For trap disabled 040 does the following:
// If the dest is a fp reg, then an extended precision non_signaling
// NAN is stored in the dest reg.  If the dest format is b, w, or l and
// the source op is a NAN, then garbage is stored as the result (actually
// the upper 32 bits of the mantissa are sent to the integer unit). If
// the dest format is integer (b, w, l) and the operr is caused by
// integer overflow, or the source op is inf, then the result stored is
// garbage.
// There are three cases in which operr is incorrectly signaled on the 
// 040.  This occurs for move_out of format b, w, or l for the largest 
// negative integer (-2^7 for b, -2^15 for w, -2^31 for l).
//
//        On opclass = 011 fmove.(b,w,l) that causes a conversion
//        overflow -> OPERR, the exponent in wbte (and fpte) is:
//              byte    56 - (62 - exp)
//              word    48 - (62 - exp)
//              long    32 - (62 - exp)
//
//                      where exp = (true exp) - 1
//
//  So, wbtemp and fptemp will contain the following on erroneously
//        signalled operr:
//                      fpts = 1
//                      fpte = $4000  (15 bit externally)
//              byte    fptm = $ffffffff ffffff80
//              word    fptm = $ffffffff ffff8000
//              long    fptm = $ffffffff 80000000
//
// Note 2: For trap enabled 040 does the following:
// If the inst is move_out, then same as Note 1.
// If the inst is not move_out, the dest is not modified.
// The exceptional operand is not defined for integer overflow 
// during a move_out.
//

//              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//      THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA 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_OPERR:        //idnt    2,1 | Motorola 040 Floating Point Software Package

        |section        8

#include "fpsp.defs"

        |xref   mem_write
        |xref   real_operr
        |xref   real_inex
        |xref   get_fline
        |xref   fpsp_done
        |xref   reg_dest

        .global fpsp_operr
fpsp_operr:
//
        link            %a6,#-LOCAL_SIZE
        fsave           -(%a7)
        moveml          %d0-%d1/%a0-%a1,USER_DA(%a6)
        fmovemx %fp0-%fp3,USER_FP0(%a6)
        fmoveml %fpcr/%fpsr/%fpiar,USER_FPCR(%a6)

//
// Check if this is an opclass 3 instruction.
//  If so, fall through, else branch to operr_end
//
        btstb   #TFLAG,T_BYTE(%a6)
        beqs    operr_end

//
// If the destination size is B,W,or L, the operr must be 
// handled here.
//
        movel   CMDREG1B(%a6),%d0
        bfextu  %d0{#3:#3},%d0  //0=long, 4=word, 6=byte
        cmpib   #0,%d0          //determine size; check long
        beq     operr_long
        cmpib   #4,%d0          //check word
        beq     operr_word
        cmpib   #6,%d0          //check byte
        beq     operr_byte

//
// The size is not B,W,or L, so the operr is handled by the 
// kernel handler.  Set the operr bits and clean up, leaving
// only the integer exception frame on the stack, and the 
// fpu in the original exceptional state.
//
operr_end:
        bsetb           #operr_bit,FPSR_EXCEPT(%a6)
        bsetb           #aiop_bit,FPSR_AEXCEPT(%a6)

        moveml          USER_DA(%a6),%d0-%d1/%a0-%a1
        fmovemx USER_FP0(%a6),%fp0-%fp3
        fmoveml USER_FPCR(%a6),%fpcr/%fpsr/%fpiar
        frestore        (%a7)+
        unlk            %a6
        bral            real_operr

operr_long:
        moveql  #4,%d1          //write size to d1
        moveb   STAG(%a6),%d0   //test stag for nan
        andib   #0xe0,%d0               //clr all but tag
        cmpib   #0x60,%d0               //check for nan
        beq     operr_nan       
        cmpil   #0x80000000,FPTEMP_LO(%a6) //test if ls lword is special
        bnes    chklerr         //if not equal, check for incorrect operr
        bsr     check_upper     //check if exp and ms mant are special
        tstl    %d0
        bnes    chklerr         //if d0 is true, check for incorrect operr
        movel   #0x80000000,%d0 //store special case result
        bsr     operr_store
        bra     not_enabled     //clean and exit
//
//      CHECK FOR INCORRECTLY GENERATED OPERR EXCEPTION HERE
//
chklerr:
        movew   FPTEMP_EX(%a6),%d0
        andw    #0x7FFF,%d0     //ignore sign bit
        cmpw    #0x3FFE,%d0     //this is the only possible exponent value
        bnes    chklerr2
fixlong:
        movel   FPTEMP_LO(%a6),%d0
        bsr     operr_store
        bra     not_enabled
chklerr2:
        movew   FPTEMP_EX(%a6),%d0
        andw    #0x7FFF,%d0     //ignore sign bit
        cmpw    #0x4000,%d0
        bcc     store_max       //exponent out of range

        movel   FPTEMP_LO(%a6),%d0
        andl    #0x7FFF0000,%d0 //look for all 1's on bits 30-16
        cmpl    #0x7FFF0000,%d0
        beqs    fixlong

        tstl    FPTEMP_LO(%a6)
        bpls    chklepos
        cmpl    #0xFFFFFFFF,FPTEMP_HI(%a6)
        beqs    fixlong
        bra     store_max
chklepos:
        tstl    FPTEMP_HI(%a6)
        beqs    fixlong
        bra     store_max

operr_word:
        moveql  #2,%d1          //write size to d1
        moveb   STAG(%a6),%d0   //test stag for nan
        andib   #0xe0,%d0               //clr all but tag
        cmpib   #0x60,%d0               //check for nan
        beq     operr_nan       
        cmpil   #0xffff8000,FPTEMP_LO(%a6) //test if ls lword is special
        bnes    chkwerr         //if not equal, check for incorrect operr
        bsr     check_upper     //check if exp and ms mant are special
        tstl    %d0
        bnes    chkwerr         //if d0 is true, check for incorrect operr
        movel   #0x80000000,%d0 //store special case result
        bsr     operr_store
        bra     not_enabled     //clean and exit
//
//      CHECK FOR INCORRECTLY GENERATED OPERR EXCEPTION HERE
//
chkwerr:
        movew   FPTEMP_EX(%a6),%d0
        andw    #0x7FFF,%d0     //ignore sign bit
        cmpw    #0x3FFE,%d0     //this is the only possible exponent value
        bnes    store_max
        movel   FPTEMP_LO(%a6),%d0
        swap    %d0
        bsr     operr_store
        bra     not_enabled

operr_byte:
        moveql  #1,%d1          //write size to d1
        moveb   STAG(%a6),%d0   //test stag for nan
        andib   #0xe0,%d0               //clr all but tag
        cmpib   #0x60,%d0               //check for nan
        beqs    operr_nan       
        cmpil   #0xffffff80,FPTEMP_LO(%a6) //test if ls lword is special
        bnes    chkberr         //if not equal, check for incorrect operr
        bsr     check_upper     //check if exp and ms mant are special
        tstl    %d0
        bnes    chkberr         //if d0 is true, check for incorrect operr
        movel   #0x80000000,%d0 //store special case result
        bsr     operr_store
        bra     not_enabled     //clean and exit
//
//      CHECK FOR INCORRECTLY GENERATED OPERR EXCEPTION HERE
//
chkberr:
        movew   FPTEMP_EX(%a6),%d0
        andw    #0x7FFF,%d0     //ignore sign bit
        cmpw    #0x3FFE,%d0     //this is the only possible exponent value
        bnes    store_max
        movel   FPTEMP_LO(%a6),%d0
        asll    #8,%d0
        swap    %d0
        bsr     operr_store
        bra     not_enabled

//
// This operr condition is not of the special case.  Set operr
// and aiop and write the portion of the nan to memory for the
// given size.
//
operr_nan:
        orl     #opaop_mask,USER_FPSR(%a6) //set operr & aiop

        movel   ETEMP_HI(%a6),%d0       //output will be from upper 32 bits
        bsr     operr_store
        bra     end_operr
//
// Store_max loads the max pos or negative for the size, sets
// the operr and aiop bits, and clears inex and ainex, incorrectly
// set by the 040.
//
store_max:
        orl     #opaop_mask,USER_FPSR(%a6) //set operr & aiop
        bclrb   #inex2_bit,FPSR_EXCEPT(%a6)
        bclrb   #ainex_bit,FPSR_AEXCEPT(%a6)
        fmovel  #0,%FPSR
        
        tstw    FPTEMP_EX(%a6)  //check sign
        blts    load_neg
        movel   #0x7fffffff,%d0
        bsr     operr_store
        bra     end_operr
load_neg:
        movel   #0x80000000,%d0
        bsr     operr_store
        bra     end_operr

//
// This routine stores the data in d0, for the given size in d1,
// to memory or data register as required.  A read of the fline
// is required to determine the destination.
//
operr_store:
        movel   %d0,L_SCR1(%a6) //move write data to L_SCR1
        movel   %d1,-(%a7)      //save register size
        bsrl    get_fline       //fline returned in d0
        movel   (%a7)+,%d1
        bftst   %d0{#26:#3}             //if mode is zero, dest is Dn
        bnes    dest_mem
//
// Destination is Dn.  Get register number from d0. Data is on
// the stack at (a7). D1 has size: 1=byte,2=word,4=long/single
//
        andil   #7,%d0          //isolate register number
        cmpil   #4,%d1
        beqs    op_long         //the most frequent case
        cmpil   #2,%d1
        bnes    op_con
        orl     #8,%d0
        bras    op_con
op_long:
        orl     #0x10,%d0
op_con:
        movel   %d0,%d1         //format size:reg for reg_dest
        bral    reg_dest        //call to reg_dest returns to caller
//                              ;of operr_store
//
// Destination is memory.  Get <ea> from integer exception frame
// and call mem_write.
//
dest_mem:
        leal    L_SCR1(%a6),%a0 //put ptr to write data in a0
        movel   EXC_EA(%a6),%a1 //put user destination address in a1
        movel   %d1,%d0         //put size in d0
        bsrl    mem_write
        rts
//
// Check the exponent for $c000 and the upper 32 bits of the 
// mantissa for $ffffffff.  If both are true, return d0 clr
// and store the lower n bits of the least lword of FPTEMP
// to d0 for write out.  If not, it is a real operr, and set d0.
//
check_upper:
        cmpil   #0xffffffff,FPTEMP_HI(%a6) //check if first byte is all 1's
        bnes    true_operr      //if not all 1's then was true operr
        cmpiw   #0xc000,FPTEMP_EX(%a6) //check if incorrectly signalled
        beqs    not_true_operr  //branch if not true operr
        cmpiw   #0xbfff,FPTEMP_EX(%a6) //check if incorrectly signalled
        beqs    not_true_operr  //branch if not true operr
true_operr:
        movel   #1,%d0          //signal real operr
        rts
not_true_operr:
        clrl    %d0             //signal no real operr
        rts

//
// End_operr tests for operr enabled.  If not, it cleans up the stack
// and does an rte.  If enabled, it cleans up the stack and branches
// to the kernel operr handler with only the integer exception
// frame on the stack and the fpu in the original exceptional state
// with correct data written to the destination.
//
end_operr:
        btstb           #operr_bit,FPCR_ENABLE(%a6)
        beqs            not_enabled
enabled:
        moveml          USER_DA(%a6),%d0-%d1/%a0-%a1
        fmovemx USER_FP0(%a6),%fp0-%fp3
        fmoveml USER_FPCR(%a6),%fpcr/%fpsr/%fpiar
        frestore        (%a7)+
        unlk            %a6
        bral            real_operr

not_enabled:
//
// It is possible to have either inex2 or inex1 exceptions with the
// operr.  If the inex enable bit is set in the FPCR, and either
// inex2 or inex1 occurred, we must clean up and branch to the
// real inex handler.
//
ck_inex:
        moveb   FPCR_ENABLE(%a6),%d0
        andb    FPSR_EXCEPT(%a6),%d0
        andib   #0x3,%d0
        beq     operr_exit
//
// Inexact enabled and reported, and we must take an inexact exception.
//
take_inex:
        moveb           #INEX_VEC,EXC_VEC+1(%a6)
        movel           USER_FPSR(%a6),FPSR_SHADOW(%a6)
        orl             #sx_mask,E_BYTE(%a6)
        moveml          USER_DA(%a6),%d0-%d1/%a0-%a1
        fmovemx USER_FP0(%a6),%fp0-%fp3
        fmoveml USER_FPCR(%a6),%fpcr/%fpsr/%fpiar
        frestore        (%a7)+
        unlk            %a6
        bral            real_inex
//
// Since operr is only an E1 exception, there is no need to frestore
// any state back to the fpu.
//
operr_exit:
        moveml          USER_DA(%a6),%d0-%d1/%a0-%a1
        fmovemx USER_FP0(%a6),%fp0-%fp3
        fmoveml USER_FPCR(%a6),%fpcr/%fpsr/%fpiar
        unlk            %a6
        bral            fpsp_done

        |end