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//
//      $Id: gen_except.S,v 1.2 2001-09-27 12:01:22 chris Exp $
//
//      gen_except.sa 3.7 1/16/92
//
//      gen_except --- FPSP routine to detect reportable exceptions
//      
//      This routine compares the exception enable byte of the
//      user_fpcr on the stack with the exception status byte
//      of the user_fpsr. 
//
//      Any routine which may report an exceptions must load
//      the stack frame in memory with the exceptional operand(s).
//
//      Priority for exceptions is:
//
//      Highest:        bsun
//                      snan
//                      operr
//                      ovfl
//                      unfl
//                      dz
//                      inex2
//      Lowest:         inex1
//
//      Note: The IEEE standard specifies that inex2 is to be
//      reported if ovfl occurs and the ovfl enable bit is not
//      set but the inex2 enable bit is.  
//
//
//              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//      THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA 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.

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

        |section 8

#include "fpsp.defs"

        |xref   real_trace
        |xref   fpsp_done
        |xref   fpsp_fmt_error

exc_tbl:
        .long   bsun_exc
        .long   commonE1
        .long   commonE1
        .long   ovfl_unfl
        .long   ovfl_unfl
        .long   commonE1
        .long   commonE3
        .long   commonE3
        .long   no_match

        .global gen_except
gen_except:
        cmpib   #IDLE_SIZE-4,1(%a7)     //test for idle frame
        beq     do_check                //go handle idle frame
        cmpib   #UNIMP_40_SIZE-4,1(%a7) //test for orig unimp frame
        beqs    unimp_x                 //go handle unimp frame
        cmpib   #UNIMP_41_SIZE-4,1(%a7) //test for rev unimp frame
        beqs    unimp_x                 //go handle unimp frame
        cmpib   #BUSY_SIZE-4,1(%a7)     //if size <> $60, fmt error
        bnel    fpsp_fmt_error
        leal    BUSY_SIZE+LOCAL_SIZE(%a7),%a1 //init a1 so fpsp.h
//                                      ;equates will work
// Fix up the new busy frame with entries from the unimp frame
//
        movel   ETEMP_EX(%a6),ETEMP_EX(%a1) //copy etemp from unimp
        movel   ETEMP_HI(%a6),ETEMP_HI(%a1) //frame to busy frame
        movel   ETEMP_LO(%a6),ETEMP_LO(%a1) 
        movel   CMDREG1B(%a6),CMDREG1B(%a1) //set inst in frame to unimp
        movel   CMDREG1B(%a6),%d0               //fix cmd1b to make it
        andl    #0x03c30000,%d0         //work for cmd3b
        bfextu  CMDREG1B(%a6){#13:#1},%d1       //extract bit 2
        lsll    #5,%d1                  
        swap    %d1
        orl     %d1,%d0                 //put it in the right place
        bfextu  CMDREG1B(%a6){#10:#3},%d1       //extract bit 3,4,5
        lsll    #2,%d1
        swap    %d1
        orl     %d1,%d0                 //put them in the right place
        movel   %d0,CMDREG3B(%a1)               //in the busy frame
//
// Or in the FPSR from the emulation with the USER_FPSR on the stack.
//
        fmovel  %FPSR,%d0               
        orl     %d0,USER_FPSR(%a6)
        movel   USER_FPSR(%a6),FPSR_SHADOW(%a1) //set exc bits
        orl     #sx_mask,E_BYTE(%a1)
        bra     do_clean

//
// Frame is an unimp frame possible resulting from an fmove <ea>,fp0
// that caused an exception
//
// a1 is modified to point into the new frame allowing fpsp equates
// to be valid.
//
unimp_x:
        cmpib   #UNIMP_40_SIZE-4,1(%a7) //test for orig unimp frame
        bnes    test_rev
        leal    UNIMP_40_SIZE+LOCAL_SIZE(%a7),%a1
        bras    unimp_con
test_rev:
        cmpib   #UNIMP_41_SIZE-4,1(%a7) //test for rev unimp frame
        bnel    fpsp_fmt_error          //if not $28 or $30
        leal    UNIMP_41_SIZE+LOCAL_SIZE(%a7),%a1
        
unimp_con:
//
// Fix up the new unimp frame with entries from the old unimp frame
//
        movel   CMDREG1B(%a6),CMDREG1B(%a1) //set inst in frame to unimp
//
// Or in the FPSR from the emulation with the USER_FPSR on the stack.
//
        fmovel  %FPSR,%d0               
        orl     %d0,USER_FPSR(%a6)
        bra     do_clean

//
// Frame is idle, so check for exceptions reported through
// USER_FPSR and set the unimp frame accordingly.  
// A7 must be incremented to the point before the
// idle fsave vector to the unimp vector.
//
        
do_check:
        addl    #4,%a7                  //point A7 back to unimp frame
//
// Or in the FPSR from the emulation with the USER_FPSR on the stack.
//
        fmovel  %FPSR,%d0               
        orl     %d0,USER_FPSR(%a6)
//
// On a busy frame, we must clear the nmnexc bits.
//
        cmpib   #BUSY_SIZE-4,1(%a7)     //check frame type
        bnes    check_fr                //if busy, clr nmnexc
        clrw    NMNEXC(%a6)             //clr nmnexc & nmcexc
        btstb   #5,CMDREG1B(%a6)                //test for fmove out
        bnes    frame_com
        movel   USER_FPSR(%a6),FPSR_SHADOW(%a6) //set exc bits
        orl     #sx_mask,E_BYTE(%a6)
        bras    frame_com
check_fr:
        cmpb    #UNIMP_40_SIZE-4,1(%a7)
        beqs    frame_com
        clrw    NMNEXC(%a6)
frame_com:
        moveb   FPCR_ENABLE(%a6),%d0    //get fpcr enable byte
        andb    FPSR_EXCEPT(%a6),%d0    //and in the fpsr exc byte
        bfffo   %d0{#24:#8},%d1         //test for first set bit
        leal    exc_tbl,%a0             //load jmp table address
        subib   #24,%d1                 //normalize bit offset to 0-8
        movel   (%a0,%d1.w*4),%a0               //load routine address based
//                                      ;based on first enabled exc
        jmp     (%a0)                   //jump to routine
//
// Bsun is not possible in unimp or unsupp
//
bsun_exc:
        bra     do_clean
//
// The typical work to be done to the unimp frame to report an 
// exception is to set the E1/E3 byte and clr the U flag.
// commonE1 does this for E1 exceptions, which are snan, 
// operr, and dz.  commonE3 does this for E3 exceptions, which 
// are inex2 and inex1, and also clears the E1 exception bit
// left over from the unimp exception.
//
commonE1:
        bsetb   #E1,E_BYTE(%a6)         //set E1 flag
        bra     commonE                 //go clean and exit

commonE3:
        tstb    UFLG_TMP(%a6)           //test flag for unsup/unimp state
        bnes    unsE3
uniE3:
        bsetb   #E3,E_BYTE(%a6)         //set E3 flag
        bclrb   #E1,E_BYTE(%a6)         //clr E1 from unimp
        bra     commonE

unsE3:
        tstb    RES_FLG(%a6)
        bnes    unsE3_0 
unsE3_1:
        bsetb   #E3,E_BYTE(%a6)         //set E3 flag
unsE3_0:
        bclrb   #E1,E_BYTE(%a6)         //clr E1 flag
        movel   CMDREG1B(%a6),%d0
        andl    #0x03c30000,%d0         //work for cmd3b
        bfextu  CMDREG1B(%a6){#13:#1},%d1       //extract bit 2
        lsll    #5,%d1                  
        swap    %d1
        orl     %d1,%d0                 //put it in the right place
        bfextu  CMDREG1B(%a6){#10:#3},%d1       //extract bit 3,4,5
        lsll    #2,%d1
        swap    %d1
        orl     %d1,%d0                 //put them in the right place
        movel   %d0,CMDREG3B(%a6)               //in the busy frame

commonE:
        bclrb   #UFLAG,T_BYTE(%a6)      //clr U flag from unimp
        bra     do_clean                //go clean and exit
//
// No bits in the enable byte match existing exceptions.  Check for
// the case of the ovfl exc without the ovfl enabled, but with
// inex2 enabled.
//
no_match:
        btstb   #inex2_bit,FPCR_ENABLE(%a6) //check for ovfl/inex2 case
        beqs    no_exc                  //if clear, exit
        btstb   #ovfl_bit,FPSR_EXCEPT(%a6) //now check ovfl
        beqs    no_exc                  //if clear, exit
        bras    ovfl_unfl               //go to unfl_ovfl to determine if
//                                      ;it is an unsupp or unimp exc
        
// No exceptions are to be reported.  If the instruction was 
// unimplemented, no FPU restore is necessary.  If it was
// unsupported, we must perform the restore.
no_exc:
        tstb    UFLG_TMP(%a6)   //test flag for unsupp/unimp state
        beqs    uni_no_exc
uns_no_exc:
        tstb    RES_FLG(%a6)    //check if frestore is needed
        bne     do_clean        //if clear, no frestore needed
uni_no_exc:
        moveml  USER_DA(%a6),%d0-%d1/%a0-%a1
        fmovemx USER_FP0(%a6),%fp0-%fp3
        fmoveml USER_FPCR(%a6),%fpcr/%fpsr/%fpiar
        unlk    %a6
        bra     finish_up
//
// Unsupported Data Type Handler:
// Ovfl:
//   An fmoveout that results in an overflow is reported this way.
// Unfl:
//   An fmoveout that results in an underflow is reported this way.
//
// Unimplemented Instruction Handler:
// Ovfl:
//   Only scosh, setox, ssinh, stwotox, and scale can set overflow in 
//   this manner.
// Unfl:
//   Stwotox, setox, and scale can set underflow in this manner.
//   Any of the other Library Routines such that f(x)=x in which
//   x is an extended denorm can report an underflow exception. 
//   It is the responsibility of the exception-causing exception 
//   to make sure that WBTEMP is correct.
//
//   The exceptional operand is in FP_SCR1.
//
ovfl_unfl:
        tstb    UFLG_TMP(%a6)   //test flag for unsupp/unimp state
        beqs    ofuf_con
//
// The caller was from an unsupported data type trap.  Test if the
// caller set CU_ONLY.  If so, the exceptional operand is expected in
// FPTEMP, rather than WBTEMP.
//
        tstb    CU_ONLY(%a6)            //test if inst is cu-only
        beq     unsE3
//      move.w  #$fe,CU_SAVEPC(%a6)
        clrb    CU_SAVEPC(%a6)
        bsetb   #E1,E_BYTE(%a6)         //set E1 exception flag
        movew   ETEMP_EX(%a6),FPTEMP_EX(%a6)
        movel   ETEMP_HI(%a6),FPTEMP_HI(%a6)
        movel   ETEMP_LO(%a6),FPTEMP_LO(%a6)
        bsetb   #fptemp15_bit,DTAG(%a6) //set fpte15
        bclrb   #UFLAG,T_BYTE(%a6)      //clr U flag from unimp
        bra     do_clean                //go clean and exit

ofuf_con:
        moveb   (%a7),VER_TMP(%a6)      //save version number
        cmpib   #BUSY_SIZE-4,1(%a7)     //check for busy frame
        beqs    busy_fr                 //if unimp, grow to busy
        cmpib   #VER_40,(%a7)           //test for orig unimp frame
        bnes    try_41                  //if not, test for rev frame
        moveql  #13,%d0                 //need to zero 14 lwords
        bras    ofuf_fin
try_41:
        cmpib   #VER_41,(%a7)           //test for rev unimp frame
        bnel    fpsp_fmt_error          //if neither, exit with error
        moveql  #11,%d0                 //need to zero 12 lwords

ofuf_fin:
        clrl    (%a7)
loop1:
        clrl    -(%a7)                  //clear and dec a7
        dbra    %d0,loop1
        moveb   VER_TMP(%a6),(%a7)
        moveb   #BUSY_SIZE-4,1(%a7)             //write busy fmt word.
busy_fr:
        movel   FP_SCR1(%a6),WBTEMP_EX(%a6)     //write
        movel   FP_SCR1+4(%a6),WBTEMP_HI(%a6)   //exceptional op to
        movel   FP_SCR1+8(%a6),WBTEMP_LO(%a6)   //wbtemp
        bsetb   #E3,E_BYTE(%a6)                 //set E3 flag
        bclrb   #E1,E_BYTE(%a6)                 //make sure E1 is clear
        bclrb   #UFLAG,T_BYTE(%a6)              //clr U flag
        movel   USER_FPSR(%a6),FPSR_SHADOW(%a6)
        orl     #sx_mask,E_BYTE(%a6)
        movel   CMDREG1B(%a6),%d0               //fix cmd1b to make it
        andl    #0x03c30000,%d0         //work for cmd3b
        bfextu  CMDREG1B(%a6){#13:#1},%d1       //extract bit 2
        lsll    #5,%d1                  
        swap    %d1
        orl     %d1,%d0                 //put it in the right place
        bfextu  CMDREG1B(%a6){#10:#3},%d1       //extract bit 3,4,5
        lsll    #2,%d1
        swap    %d1
        orl     %d1,%d0                 //put them in the right place
        movel   %d0,CMDREG3B(%a6)               //in the busy frame

//
// Check if the frame to be restored is busy or unimp.
//** NOTE *** Bug fix for errata (0d43b #3)
// If the frame is unimp, we must create a busy frame to 
// fix the bug with the nmnexc bits in cases in which they
// are set by a previous instruction and not cleared by
// the save. The frame will be unimp only if the final 
// instruction in an emulation routine caused the exception
// by doing an fmove <ea>,fp0.  The exception operand, in
// internal format, is in fptemp.
//
do_clean:
        cmpib   #UNIMP_40_SIZE-4,1(%a7)
        bnes    do_con
        moveql  #13,%d0                 //in orig, need to zero 14 lwords
        bras    do_build
do_con:
        cmpib   #UNIMP_41_SIZE-4,1(%a7)
        bnes    do_restore              //frame must be busy
        moveql  #11,%d0                 //in rev, need to zero 12 lwords

do_build:
        moveb   (%a7),VER_TMP(%a6)
        clrl    (%a7)
loop2:
        clrl    -(%a7)                  //clear and dec a7
        dbra    %d0,loop2
//
// Use a1 as pointer into new frame.  a6 is not correct if an unimp or
// busy frame was created as the result of an exception on the final
// instruction of an emulation routine.
//
// We need to set the nmcexc bits if the exception is E1. Otherwise,
// the exc taken will be inex2.
//
        leal    BUSY_SIZE+LOCAL_SIZE(%a7),%a1   //init a1 for new frame
        moveb   VER_TMP(%a6),(%a7)      //write busy fmt word
        moveb   #BUSY_SIZE-4,1(%a7)
        movel   FP_SCR1(%a6),WBTEMP_EX(%a1)     //write
        movel   FP_SCR1+4(%a6),WBTEMP_HI(%a1)   //exceptional op to
        movel   FP_SCR1+8(%a6),WBTEMP_LO(%a1)   //wbtemp
//      btst.b  #E1,E_BYTE(%a1)
//      beq.b   do_restore
        bfextu  USER_FPSR(%a6){#17:#4},%d0      //get snan/operr/ovfl/unfl bits
        bfins   %d0,NMCEXC(%a1){#4:#4}  //and insert them in nmcexc
        movel   USER_FPSR(%a6),FPSR_SHADOW(%a1) //set exc bits
        orl     #sx_mask,E_BYTE(%a1)
        
do_restore:
        moveml  USER_DA(%a6),%d0-%d1/%a0-%a1
        fmovemx USER_FP0(%a6),%fp0-%fp3
        fmoveml USER_FPCR(%a6),%fpcr/%fpsr/%fpiar
        frestore (%a7)+
        tstb    RES_FLG(%a6)    //RES_FLG indicates a "continuation" frame
        beq     cont
        bsr     bug1384
cont:
        unlk    %a6
//
// If trace mode enabled, then go to trace handler.  This handler 
// cannot have any fp instructions.  If there are fp inst's and an 
// exception has been restored into the machine then the exception 
// will occur upon execution of the fp inst.  This is not desirable 
// in the kernel (supervisor mode).  See MC68040 manual Section 9.3.8.
//
finish_up:
        btstb   #7,(%a7)                //test T1 in SR
        bnes    g_trace
        btstb   #6,(%a7)                //test T0 in SR
        bnes    g_trace
        bral    fpsp_done
//
// Change integer stack to look like trace stack
// The address of the instruction that caused the
// exception is already in the integer stack (is
// the same as the saved friar)
//
// If the current frame is already a 6-word stack then all
// that needs to be done is to change the vector# to TRACE.
// If the frame is only a 4-word stack (meaning we got here
// on an Unsupported data type exception), then we need to grow
// the stack an extra 2 words and get the FPIAR from the FPU.
//
g_trace:
        bftst   EXC_VEC-4(%sp){#0:#4}
        bne     g_easy

        subw    #4,%sp          // make room
        movel   4(%sp),(%sp)
        movel   8(%sp),4(%sp)
        subw    #BUSY_SIZE,%sp
        fsave   (%sp)
        fmovel  %fpiar,BUSY_SIZE+EXC_EA-4(%sp)
        frestore (%sp)
        addw    #BUSY_SIZE,%sp

g_easy:
        movew   #TRACE_VEC,EXC_VEC-4(%a7)
        bral    real_trace
//
//  This is a work-around for hardware bug 1384.
//
bug1384:
        link    %a5,#0
        fsave   -(%sp)
        cmpib   #0x41,(%sp)     // check for correct frame
        beq     frame_41
        bgt     nofix           // if more advanced mask, do nada

frame_40:
        tstb    1(%sp)          // check to see if idle
        bne     notidle
idle40:
        clrl    (%sp)           // get rid of old fsave frame
        movel  %d1,USER_D1(%a6)  // save d1
        movew   #8,%d1          // place unimp frame instead
loop40: clrl    -(%sp)
        dbra    %d1,loop40
        movel  USER_D1(%a6),%d1  // restore d1
        movel   #0x40280000,-(%sp)
        frestore (%sp)+
        unlk    %a5     
        rts

frame_41:
        tstb    1(%sp)          // check to see if idle
        bne     notidle 
idle41:
        clrl    (%sp)           // get rid of old fsave frame
        movel  %d1,USER_D1(%a6)  // save d1
        movew   #10,%d1         // place unimp frame instead
loop41: clrl    -(%sp)
        dbra    %d1,loop41
        movel  USER_D1(%a6),%d1  // restore d1
        movel   #0x41300000,-(%sp)
        frestore (%sp)+
        unlk    %a5     
        rts

notidle:
        bclrb   #etemp15_bit,-40(%a5) 
        frestore (%sp)+
        unlk    %a5     
        rts

nofix:
        frestore (%sp)+
        unlk    %a5     
        rts

        |end