arch/m68k/fpsp040/x_ovfl.S

   1 |
   2 |       x_ovfl.sa 3.5 7/1/91
   3 |
   4 |       fpsp_ovfl --- FPSP handler for overflow exception
   5 |
   6 |       Overflow occurs when a floating-point intermediate result is
   7 |       too large to be represented in a floating-point data register,
   8 |       or when storing to memory, the contents of a floating-point
   9 |       data register are too large to be represented in the
  10 |       destination format.
  11 |
  12 | Trap disabled results
  13 |
  14 | If the instruction is move_out, then garbage is stored in the
  15 | destination.  If the instruction is not move_out, then the
  16 | destination is not affected.  For 68881 compatibility, the
  17 | following values should be stored at the destination, based
  18 | on the current rounding mode:
  19 |
  20 |  RN   Infinity with the sign of the intermediate result.
  21 |  RZ   Largest magnitude number, with the sign of the
  22 |       intermediate result.
  23 |  RM   For pos overflow, the largest pos number. For neg overflow,
  24 |       -infinity
  25 |  RP   For pos overflow, +infinity. For neg overflow, the largest
  26 |       neg number
  27 |
  28 | Trap enabled results
  29 | All trap disabled code applies.  In addition the exceptional
  30 | operand needs to be made available to the users exception handler
  31 | with a bias of $6000 subtracted from the exponent.
  32 |
  33 |
  34
  35 |               Copyright (C) Motorola, Inc. 1990
  36 |                       All Rights Reserved
  37 |
  38 |       THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA
  39 |       The copyright notice above does not evidence any
  40 |       actual or intended publication of such source code.
  41
  42 X_OVFL: |idnt    2,1 | Motorola 040 Floating Point Software Package
  43
  44         |section        8
  45
  46 #include "fpsp.h"
  47
  48         |xref   ovf_r_x2
  49         |xref   ovf_r_x3
  50         |xref   store
  51         |xref   real_ovfl
  52         |xref   real_inex
  53         |xref   fpsp_done
  54         |xref   g_opcls
  55         |xref   b1238_fix
  56
  57         .global fpsp_ovfl
  58 fpsp_ovfl:
  59         link            %a6,#-LOCAL_SIZE
  60         fsave           -(%a7)
  61         moveml          %d0-%d1/%a0-%a1,USER_DA(%a6)
  62         fmovemx %fp0-%fp3,USER_FP0(%a6)
  63         fmoveml %fpcr/%fpsr/%fpiar,USER_FPCR(%a6)
  64
  65 |
  66 |       The 040 doesn't set the AINEX bit in the FPSR, the following
  67 |       line temporarily rectifies this error.
  68 |
  69         bsetb   #ainex_bit,FPSR_AEXCEPT(%a6)
  70 |
  71         bsrl    ovf_adj         |denormalize, round & store interm op
  72 |
  73 |       if overflow traps not enabled check for inexact exception
  74 |
  75         btstb   #ovfl_bit,FPCR_ENABLE(%a6)
  76         beqs    ck_inex
  77 |
  78         btstb           #E3,E_BYTE(%a6)
  79         beqs            no_e3_1
  80         bfextu          CMDREG3B(%a6){#6:#3},%d0        |get dest reg no
  81         bclrb           %d0,FPR_DIRTY_BITS(%a6) |clr dest dirty bit
  82         bsrl            b1238_fix
  83         movel           USER_FPSR(%a6),FPSR_SHADOW(%a6)
  84         orl             #sx_mask,E_BYTE(%a6)
  85 no_e3_1:
  86         moveml          USER_DA(%a6),%d0-%d1/%a0-%a1
  87         fmovemx USER_FP0(%a6),%fp0-%fp3
  88         fmoveml USER_FPCR(%a6),%fpcr/%fpsr/%fpiar
  89         frestore        (%a7)+
  90         unlk            %a6
  91         bral            real_ovfl
  92 |
  93 | It is possible to have either inex2 or inex1 exceptions with the
  94 | ovfl.  If the inex enable bit is set in the FPCR, and either
  95 | inex2 or inex1 occurred, we must clean up and branch to the
  96 | real inex handler.
  97 |
  98 ck_inex:
  99 |       move.b          FPCR_ENABLE(%a6),%d0
 100 |       and.b           FPSR_EXCEPT(%a6),%d0
 101 |       andi.b          #$3,%d0
 102         btstb           #inex2_bit,FPCR_ENABLE(%a6)
 103         beqs            ovfl_exit
 104 |
 105 | Inexact enabled and reported, and we must take an inexact exception.
 106 |
 107 take_inex:
 108         btstb           #E3,E_BYTE(%a6)
 109         beqs            no_e3_2
 110         bfextu          CMDREG3B(%a6){#6:#3},%d0        |get dest reg no
 111         bclrb           %d0,FPR_DIRTY_BITS(%a6) |clr dest dirty bit
 112         bsrl            b1238_fix
 113         movel           USER_FPSR(%a6),FPSR_SHADOW(%a6)
 114         orl             #sx_mask,E_BYTE(%a6)
 115 no_e3_2:
 116         moveb           #INEX_VEC,EXC_VEC+1(%a6)
 117         moveml          USER_DA(%a6),%d0-%d1/%a0-%a1
 118         fmovemx USER_FP0(%a6),%fp0-%fp3
 119         fmoveml USER_FPCR(%a6),%fpcr/%fpsr/%fpiar
 120         frestore        (%a7)+
 121         unlk            %a6
 122         bral            real_inex
 123
 124 ovfl_exit:
 125         bclrb   #E3,E_BYTE(%a6) |test and clear E3 bit
 126         beqs    e1_set
 127 |
 128 | Clear dirty bit on dest resister in the frame before branching
 129 | to b1238_fix.
 130 |
 131         bfextu          CMDREG3B(%a6){#6:#3},%d0        |get dest reg no
 132         bclrb           %d0,FPR_DIRTY_BITS(%a6) |clr dest dirty bit
 133         bsrl            b1238_fix               |test for bug1238 case
 134
 135         movel           USER_FPSR(%a6),FPSR_SHADOW(%a6)
 136         orl             #sx_mask,E_BYTE(%a6)
 137         moveml          USER_DA(%a6),%d0-%d1/%a0-%a1
 138         fmovemx USER_FP0(%a6),%fp0-%fp3
 139         fmoveml USER_FPCR(%a6),%fpcr/%fpsr/%fpiar
 140         frestore        (%a7)+
 141         unlk            %a6
 142         bral            fpsp_done
 143 e1_set:
 144         moveml          USER_DA(%a6),%d0-%d1/%a0-%a1
 145         fmovemx USER_FP0(%a6),%fp0-%fp3
 146         fmoveml USER_FPCR(%a6),%fpcr/%fpsr/%fpiar
 147         unlk            %a6
 148         bral            fpsp_done
 149
 150 |
 151 |       ovf_adj
 152 |
 153 ovf_adj:
 154 |
 155 | Have a0 point to the correct operand.
 156 |
 157         btstb   #E3,E_BYTE(%a6) |test E3 bit
 158         beqs    ovf_e1
 159
 160         lea     WBTEMP(%a6),%a0
 161         bras    ovf_com
 162 ovf_e1:
 163         lea     ETEMP(%a6),%a0
 164
 165 ovf_com:
 166         bclrb   #sign_bit,LOCAL_EX(%a0)
 167         sne     LOCAL_SGN(%a0)
 168
 169         bsrl    g_opcls         |returns opclass in d0
 170         cmpiw   #3,%d0          |check for opclass3
 171         bnes    not_opc011
 172
 173 |
 174 | FPSR_CC is saved and restored because ovf_r_x3 affects it. The
 175 | CCs are defined to be 'not affected' for the opclass3 instruction.
 176 |
 177         moveb   FPSR_CC(%a6),L_SCR1(%a6)
 178         bsrl    ovf_r_x3        |returns a0 pointing to result
 179         moveb   L_SCR1(%a6),FPSR_CC(%a6)
 180         bral    store           |stores to memory or register
 181
 182 not_opc011:
 183         bsrl    ovf_r_x2        |returns a0 pointing to result
 184         bral    store           |stores to memory or register
 185
 186         |end