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//
//      $Id: bugfix.S,v 1.2 2001-09-27 12:01:22 chris Exp $
//
//      bugfix.sa 3.2 1/31/91
//
//      This file contains workarounds for bugs in the 040
//      relating to the Floating-Point Software Package (FPSP)
//
//      Fixes for bugs: 1238
//
//      Bug: 1238 
//
//
//    /* The following dirty_bit clear should be left in
//     * the handler permanently to improve throughput.
//     * The dirty_bits are located at bits [23:16] in
//     * longword $08 in the busy frame $4x60.  Bit 16
//     * corresponds to FP0, bit 17 corresponds to FP1,
//     * and so on.
//     */
//    if  (E3_exception_just_serviced)   {
//         dirty_bit[cmdreg3b[9:7]] = 0;
//         }
//
//    if  (fsave_format_version != $40)  {goto NOFIX}
//
//    if !(E3_exception_just_serviced)   {goto NOFIX}
//    if  (cupc == 0000000)              {goto NOFIX}
//    if  ((cmdreg1b[15:13] != 000) &&
//         (cmdreg1b[15:10] != 010001))  {goto NOFIX}
//    if (((cmdreg1b[15:13] != 000) || ((cmdreg1b[12:10] != cmdreg2b[9:7]) &&
//                                    (cmdreg1b[12:10] != cmdreg3b[9:7]))  ) &&
//       ((cmdreg1b[ 9: 7] != cmdreg2b[9:7]) &&
//        (cmdreg1b[ 9: 7] != cmdreg3b[9:7])) )  {goto NOFIX}
//
//    /* Note: for 6d43b or 8d43b, you may want to add the following code
//     * to get better coverage.  (If you do not insert this code, the part
//     * won't lock up; it will simply get the wrong answer.)
//     * Do NOT insert this code for 10d43b or later parts.
//     *
//     *  if (fpiarcu == integer stack return address) {
//     *       cupc = 0000000;
//     *       goto NOFIX;
//     *       }
//     */
//
//    if (cmdreg1b[15:13] != 000)   {goto FIX_OPCLASS2}
//    FIX_OPCLASS0:
//    if (((cmdreg1b[12:10] == cmdreg2b[9:7]) ||
//       (cmdreg1b[ 9: 7] == cmdreg2b[9:7])) &&
//      (cmdreg1b[12:10] != cmdreg3b[9:7]) &&
//      (cmdreg1b[ 9: 7] != cmdreg3b[9:7]))  {  /* xu conflict only */
//      /* We execute the following code if there is an
//         xu conflict and NOT an nu conflict */
//
//      /* first save some values on the fsave frame */
//      stag_temp     = STAG[fsave_frame];
//      cmdreg1b_temp = CMDREG1B[fsave_frame];
//      dtag_temp     = DTAG[fsave_frame];
//      ete15_temp    = ETE15[fsave_frame];
//
//      CUPC[fsave_frame] = 0000000;
//      FRESTORE
//      FSAVE
//
//      /* If the xu instruction is exceptional, we punt.
//       * Otherwise, we would have to include OVFL/UNFL handler
//       * code here to get the correct answer.
//       */
//      if (fsave_frame_format == $4060) {goto KILL_PROCESS}
//
//      fsave_frame = /* build a long frame of all zeros */
//      fsave_frame_format = $4060;  /* label it as long frame */
//
//      /* load it with the temps we saved */
//      STAG[fsave_frame]     =  stag_temp;
//      CMDREG1B[fsave_frame] =  cmdreg1b_temp;
//      DTAG[fsave_frame]     =  dtag_temp;
//      ETE15[fsave_frame]    =  ete15_temp;
//
//      /* Make sure that the cmdreg3b dest reg is not going to
//       * be destroyed by a FMOVEM at the end of all this code.
//       * If it is, you should move the current value of the reg
//       * onto the stack so that the reg will loaded with that value.
//       */
//
//      /* All done.  Proceed with the code below */
//    }
//
//    etemp  = FP_reg_[cmdreg1b[12:10]];
//    ete15  = ~ete14;
//    cmdreg1b[15:10] = 010010;
//    clear(bug_flag_procIDxxxx);
//    FRESTORE and return;
//
//
//    FIX_OPCLASS2:
//    if ((cmdreg1b[9:7] == cmdreg2b[9:7]) &&
//      (cmdreg1b[9:7] != cmdreg3b[9:7]))  {  /* xu conflict only */
//      /* We execute the following code if there is an
//         xu conflict and NOT an nu conflict */
//
//      /* first save some values on the fsave frame */
//      stag_temp     = STAG[fsave_frame];
//      cmdreg1b_temp = CMDREG1B[fsave_frame];
//      dtag_temp     = DTAG[fsave_frame];
//      ete15_temp    = ETE15[fsave_frame];
//      etemp_temp    = ETEMP[fsave_frame];
//
//      CUPC[fsave_frame] = 0000000;
//      FRESTORE
//      FSAVE
//
//
//      /* If the xu instruction is exceptional, we punt.
//       * Otherwise, we would have to include OVFL/UNFL handler
//       * code here to get the correct answer.
//       */
//      if (fsave_frame_format == $4060) {goto KILL_PROCESS}
//
//      fsave_frame = /* build a long frame of all zeros */
//      fsave_frame_format = $4060;  /* label it as long frame */
//
//      /* load it with the temps we saved */
//      STAG[fsave_frame]     =  stag_temp;
//      CMDREG1B[fsave_frame] =  cmdreg1b_temp;
//      DTAG[fsave_frame]     =  dtag_temp;
//      ETE15[fsave_frame]    =  ete15_temp;
//      ETEMP[fsave_frame]    =  etemp_temp;
//
//      /* Make sure that the cmdreg3b dest reg is not going to
//       * be destroyed by a FMOVEM at the end of all this code.
//       * If it is, you should move the current value of the reg
//       * onto the stack so that the reg will loaded with that value.
//       */
//
//      /* All done.  Proceed with the code below */
//    }
//
//    if (etemp_exponent == min_sgl)   etemp_exponent = min_dbl;
//    if (etemp_exponent == max_sgl)   etemp_exponent = max_dbl;
//    cmdreg1b[15:10] = 010101;
//    clear(bug_flag_procIDxxxx);
//    FRESTORE and return;
//
//
//    NOFIX:
//    clear(bug_flag_procIDxxxx);
//    FRESTORE and return;
//


//              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.

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

        |section        8

#include "fpsp.defs"

        |xref   fpsp_fmt_error

        .global b1238_fix
b1238_fix:
//
// This code is entered only on completion of the handling of an 
// nu-generated ovfl, unfl, or inex exception.  If the version 
// number of the fsave is not $40, this handler is not necessary.
// Simply branch to fix_done and exit normally.
//
        cmpib   #VER_40,4(%a7)
        bne     fix_done
//
// Test for cu_savepc equal to zero.  If not, this is not a bug
// #1238 case.
//
        moveb   CU_SAVEPC(%a6),%d0
        andib   #0xFE,%d0
        beq     fix_done        //if zero, this is not bug #1238

//
// Test the register conflict aspect.  If opclass0, check for
// cu src equal to xu dest or equal to nu dest.  If so, go to 
// op0.  Else, or if opclass2, check for cu dest equal to
// xu dest or equal to nu dest.  If so, go to tst_opcl.  Else,
// exit, it is not the bug case.
//
// Check for opclass 0.  If not, go and check for opclass 2 and sgl.
//
        movew   CMDREG1B(%a6),%d0
        andiw   #0xE000,%d0             //strip all but opclass
        bne     op2sgl                  //not opclass 0, check op2
//
// Check for cu and nu register conflict.  If one exists, this takes
// priority over a cu and xu conflict. 
//
        bfextu  CMDREG1B(%a6){#3:#3},%d0        //get 1st src 
        bfextu  CMDREG3B(%a6){#6:#3},%d1        //get 3rd dest
        cmpb    %d0,%d1
        beqs    op0                     //if equal, continue bugfix
//
// Check for cu dest equal to nu dest.  If so, go and fix the 
// bug condition.  Otherwise, exit.
//
        bfextu  CMDREG1B(%a6){#6:#3},%d0        //get 1st dest 
        cmpb    %d0,%d1                 //cmp 1st dest with 3rd dest
        beqs    op0                     //if equal, continue bugfix
//
// Check for cu and xu register conflict.
//
        bfextu  CMDREG2B(%a6){#6:#3},%d1        //get 2nd dest
        cmpb    %d0,%d1                 //cmp 1st dest with 2nd dest
        beqs    op0_xu                  //if equal, continue bugfix
        bfextu  CMDREG1B(%a6){#3:#3},%d0        //get 1st src 
        cmpb    %d0,%d1                 //cmp 1st src with 2nd dest
        beq     op0_xu
        bne     fix_done                //if the reg checks fail, exit
//
// We have the opclass 0 situation.
//
op0:
        bfextu  CMDREG1B(%a6){#3:#3},%d0        //get source register no
        movel   #7,%d1
        subl    %d0,%d1
        clrl    %d0
        bsetl   %d1,%d0
        fmovemx %d0,ETEMP(%a6)          //load source to ETEMP

        moveb   #0x12,%d0
        bfins   %d0,CMDREG1B(%a6){#0:#6}        //opclass 2, extended
//
//      Set ETEMP exponent bit 15 as the opposite of ete14
//
        btst    #6,ETEMP_EX(%a6)                //check etemp exponent bit 14
        beq     setete15
        bclr    #etemp15_bit,STAG(%a6)
        bra     finish
setete15:
        bset    #etemp15_bit,STAG(%a6)
        bra     finish

//
// We have the case in which a conflict exists between the cu src or
// dest and the dest of the xu.  We must clear the instruction in 
// the cu and restore the state, allowing the instruction in the
// xu to complete.  Remember, the instruction in the nu
// was exceptional, and was completed by the appropriate handler.
// If the result of the xu instruction is not exceptional, we can
// restore the instruction from the cu to the frame and continue
// processing the original exception.  If the result is also
// exceptional, we choose to kill the process.
//
//      Items saved from the stack:
//      
//              $3c stag     - L_SCR1
//              $40 cmdreg1b - L_SCR2
//              $44 dtag     - L_SCR3
//
// The cu savepc is set to zero, and the frame is restored to the
// fpu.
//
op0_xu:
        movel   STAG(%a6),L_SCR1(%a6)   
        movel   CMDREG1B(%a6),L_SCR2(%a6)       
        movel   DTAG(%a6),L_SCR3(%a6)
        andil   #0xe0000000,L_SCR3(%a6)
        moveb   #0,CU_SAVEPC(%a6)
        movel   (%a7)+,%d1              //save return address from bsr
        frestore (%a7)+
        fsave   -(%a7)
//
// Check if the instruction which just completed was exceptional.
// 
        cmpw    #0x4060,(%a7)
        beq     op0_xb
// 
// It is necessary to isolate the result of the instruction in the
// xu if it is to fp0 - fp3 and write that value to the USER_FPn
// locations on the stack.  The correct destination register is in 
// cmdreg2b.
//
        bfextu  CMDREG2B(%a6){#6:#3},%d0        //get dest register no
        cmpil   #3,%d0
        bgts    op0_xi
        beqs    op0_fp3
        cmpil   #1,%d0
        blts    op0_fp0
        beqs    op0_fp1
op0_fp2:
        fmovemx %fp2-%fp2,USER_FP2(%a6)
        bras    op0_xi
op0_fp1:
        fmovemx %fp1-%fp1,USER_FP1(%a6)
        bras    op0_xi
op0_fp0:
        fmovemx %fp0-%fp0,USER_FP0(%a6)
        bras    op0_xi
op0_fp3:
        fmovemx %fp3-%fp3,USER_FP3(%a6)
//
// The frame returned is idle.  We must build a busy frame to hold
// the cu state information and setup etemp.
//
op0_xi:
        movel   #22,%d0         //clear 23 lwords
        clrl    (%a7)
op0_loop:
        clrl    -(%a7)
        dbf     %d0,op0_loop
        movel   #0x40600000,-(%a7)
        movel   L_SCR1(%a6),STAG(%a6)
        movel   L_SCR2(%a6),CMDREG1B(%a6)
        movel   L_SCR3(%a6),DTAG(%a6)
        moveb   #0x6,CU_SAVEPC(%a6)
        movel   %d1,-(%a7)              //return bsr return address
        bfextu  CMDREG1B(%a6){#3:#3},%d0        //get source register no
        movel   #7,%d1
        subl    %d0,%d1
        clrl    %d0
        bsetl   %d1,%d0
        fmovemx %d0,ETEMP(%a6)          //load source to ETEMP

        moveb   #0x12,%d0
        bfins   %d0,CMDREG1B(%a6){#0:#6}        //opclass 2, extended
//
//      Set ETEMP exponent bit 15 as the opposite of ete14
//
        btst    #6,ETEMP_EX(%a6)                //check etemp exponent bit 14
        beq     op0_sete15
        bclr    #etemp15_bit,STAG(%a6)
        bra     finish
op0_sete15:
        bset    #etemp15_bit,STAG(%a6)
        bra     finish

//
// The frame returned is busy.  It is not possible to reconstruct
// the code sequence to allow completion.  We will jump to 
// fpsp_fmt_error and allow the kernel to kill the process.
//
op0_xb:
        jmp     fpsp_fmt_error

//
// Check for opclass 2 and single size.  If not both, exit.
//
op2sgl:
        movew   CMDREG1B(%a6),%d0
        andiw   #0xFC00,%d0             //strip all but opclass and size
        cmpiw   #0x4400,%d0             //test for opclass 2 and size=sgl
        bne     fix_done                //if not, it is not bug 1238
//
// Check for cu dest equal to nu dest or equal to xu dest, with 
// a cu and nu conflict taking priority an nu conflict.  If either,
// go and fix the bug condition.  Otherwise, exit.
//
        bfextu  CMDREG1B(%a6){#6:#3},%d0        //get 1st dest 
        bfextu  CMDREG3B(%a6){#6:#3},%d1        //get 3rd dest
        cmpb    %d0,%d1                 //cmp 1st dest with 3rd dest
        beq     op2_com                 //if equal, continue bugfix
        bfextu  CMDREG2B(%a6){#6:#3},%d1        //get 2nd dest 
        cmpb    %d0,%d1                 //cmp 1st dest with 2nd dest
        bne     fix_done                //if the reg checks fail, exit
//
// We have the case in which a conflict exists between the cu src or
// dest and the dest of the xu.  We must clear the instruction in 
// the cu and restore the state, allowing the instruction in the
// xu to complete.  Remember, the instruction in the nu
// was exceptional, and was completed by the appropriate handler.
// If the result of the xu instruction is not exceptional, we can
// restore the instruction from the cu to the frame and continue
// processing the original exception.  If the result is also
// exceptional, we choose to kill the process.
//
//      Items saved from the stack:
//      
//              $3c stag     - L_SCR1
//              $40 cmdreg1b - L_SCR2
//              $44 dtag     - L_SCR3
//              etemp        - FP_SCR2
//
// The cu savepc is set to zero, and the frame is restored to the
// fpu.
//
op2_xu:
        movel   STAG(%a6),L_SCR1(%a6)   
        movel   CMDREG1B(%a6),L_SCR2(%a6)       
        movel   DTAG(%a6),L_SCR3(%a6)   
        andil   #0xe0000000,L_SCR3(%a6)
        moveb   #0,CU_SAVEPC(%a6)
        movel   ETEMP(%a6),FP_SCR2(%a6)
        movel   ETEMP_HI(%a6),FP_SCR2+4(%a6)
        movel   ETEMP_LO(%a6),FP_SCR2+8(%a6)
        movel   (%a7)+,%d1              //save return address from bsr
        frestore (%a7)+
        fsave   -(%a7)
//
// Check if the instruction which just completed was exceptional.
// 
        cmpw    #0x4060,(%a7)
        beq     op2_xb
// 
// It is necessary to isolate the result of the instruction in the
// xu if it is to fp0 - fp3 and write that value to the USER_FPn
// locations on the stack.  The correct destination register is in 
// cmdreg2b.
//
        bfextu  CMDREG2B(%a6){#6:#3},%d0        //get dest register no
        cmpil   #3,%d0
        bgts    op2_xi
        beqs    op2_fp3
        cmpil   #1,%d0
        blts    op2_fp0
        beqs    op2_fp1
op2_fp2:
        fmovemx %fp2-%fp2,USER_FP2(%a6)
        bras    op2_xi
op2_fp1:
        fmovemx %fp1-%fp1,USER_FP1(%a6)
        bras    op2_xi
op2_fp0:
        fmovemx %fp0-%fp0,USER_FP0(%a6)
        bras    op2_xi
op2_fp3:
        fmovemx %fp3-%fp3,USER_FP3(%a6)
//
// The frame returned is idle.  We must build a busy frame to hold
// the cu state information and fix up etemp.
//
op2_xi:
        movel   #22,%d0         //clear 23 lwords
        clrl    (%a7)
op2_loop:
        clrl    -(%a7)
        dbf     %d0,op2_loop
        movel   #0x40600000,-(%a7)
        movel   L_SCR1(%a6),STAG(%a6)
        movel   L_SCR2(%a6),CMDREG1B(%a6)
        movel   L_SCR3(%a6),DTAG(%a6)
        moveb   #0x6,CU_SAVEPC(%a6)
        movel   FP_SCR2(%a6),ETEMP(%a6)
        movel   FP_SCR2+4(%a6),ETEMP_HI(%a6)
        movel   FP_SCR2+8(%a6),ETEMP_LO(%a6)
        movel   %d1,-(%a7)
        bra     op2_com

//
// We have the opclass 2 single source situation.
//
op2_com:
        moveb   #0x15,%d0
        bfins   %d0,CMDREG1B(%a6){#0:#6}        //opclass 2, double

        cmpw    #0x407F,ETEMP_EX(%a6)   //single +max
        bnes    case2
        movew   #0x43FF,ETEMP_EX(%a6)   //to double +max
        bra     finish
case2:  
        cmpw    #0xC07F,ETEMP_EX(%a6)   //single -max
        bnes    case3
        movew   #0xC3FF,ETEMP_EX(%a6)   //to double -max
        bra     finish
case3:  
        cmpw    #0x3F80,ETEMP_EX(%a6)   //single +min
        bnes    case4
        movew   #0x3C00,ETEMP_EX(%a6)   //to double +min
        bra     finish
case4:
        cmpw    #0xBF80,ETEMP_EX(%a6)   //single -min
        bne     fix_done
        movew   #0xBC00,ETEMP_EX(%a6)   //to double -min
        bra     finish
//
// The frame returned is busy.  It is not possible to reconstruct
// the code sequence to allow completion.  fpsp_fmt_error causes
// an fline illegal instruction to be executed.
//
// You should replace the jump to fpsp_fmt_error with a jump
// to the entry point used to kill a process. 
//
op2_xb:
        jmp     fpsp_fmt_error

//
// Enter here if the case is not of the situations affected by
// bug #1238, or if the fix is completed, and exit.
//
finish:
fix_done:
        rts

        |end