sim/erc32/float.c

   1 /*
   2  * This file is part of SIS.
   3  *
   4  * SIS, SPARC instruction simulator. Copyright (C) 1995 Jiri Gaisler, European
   5  * Space Agency
   6  *
   7  * This program is free software; you can redistribute it and/or modify it under
   8  * the terms of the GNU General Public License as published by the Free
   9  * Software Foundation; either version 2 of the License, or (at your option)
  10  * any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful, but WITHOUT
  13  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  15  * more details.
  16  *
  17  * You should have received a copy of the GNU General Public License along with
  18  * this program; if not, write to the Free Software Foundation, Inc., 675
  19  * Mass Ave, Cambridge, MA 02139, USA.
  20  *
  21  *
  22  * This file implements the interface between the host and the simulated
  23  * FPU. IEEE trap handling is done as follows:
  24  * 1. In the host, all IEEE traps are masked
  25  * 2. After each simulated FPU instruction, check if any exception occured
  26  *    by reading the exception bits from the host FPU status register
  27  *    (get_accex()).
  28  * 3. Propagate any exceptions to the simulated FSR.
  29  * 4. Clear host exception bits
  30  *
  31  *
  32  * This can also be done using ieee_flags() library routine on sun.
  33  */
  34
  35 #include "sis.h"
  36
  37 /* Forward declarations */
  38
  39 extern uint32   _get_sw PARAMS ((void));
  40 extern uint32   _get_cw PARAMS ((void));
  41 static void     __setfpucw PARAMS ((unsigned short fpu_control));
  42
  43 /* This host dependent routine should return the accrued exceptions */
  44 int
  45 get_accex()
  46 {
  47 #ifdef sparc
  48     return ((_get_fsr_raw() >> 5) & 0x1F);
  49 #elif i386
  50     uint32 accx;
  51
  52     accx = _get_sw() & 0x3f;
  53     accx = ((accx & 1) << 4) | ((accx & 2) >> 1) | ((accx & 4) >> 1) |
  54            (accx & 8) | ((accx & 16) >> 2) | ((accx & 32) >> 5);
  55     return(accx);
  56 #else
  57     return(0);
  58 #warning no fpu trap support for this target
  59 #endif
  60
  61 }
  62
  63 /* How to clear the accrued exceptions */
  64 void
  65 clear_accex()
  66 {
  67 #ifdef sparc
  68     set_fsr((_get_fsr_raw() & ~0x3e0));
  69 #elif i386
  70     asm("
  71 .text
  72         fnclex
  73
  74     ");
  75 #else
  76 #warning no fpu trap support for this target
  77 #endif
  78 }
  79
  80 /* How to map SPARC FSR onto the host */
  81 void
  82 set_fsr(fsr)
  83 uint32 fsr;
  84 {
  85 #ifdef sparc
  86         _set_fsr_raw(fsr & ~0x0f800000);
  87 #elif i386
  88      void __setfpucw(unsigned short fpu_control);
  89      uint32 rawfsr;
  90
  91      fsr >>= 30;
  92      switch (fsr) {
  93         case 0:
  94         case 2: break;
  95         case 1: fsr = 3;
  96         case 3: fsr = 1;
  97      }
  98      rawfsr = _get_cw();
  99      rawfsr |= (fsr << 10) | 0x3ff;
 100      __setfpucw(rawfsr);
 101 #else
 102 #warning no fpu trap support for this target
 103 #endif
 104 }
 105
 106
 107 /* Host dependent support functions */
 108
 109 #ifdef sparc
 110
 111     asm("
 112
 113 .text
 114         .align 4
 115         .global __set_fsr_raw,_set_fsr_raw
 116 __set_fsr_raw:
 117 _set_fsr_raw:
 118         save %sp,-104,%sp
 119         st %i0,[%fp+68]
 120         ld [%fp+68], %fsr
 121         mov 0,%i0
 122         ret
 123         restore
 124
 125         .align 4
 126         .global __get_fsr_raw
 127         .global _get_fsr_raw
 128 __get_fsr_raw:
 129 _get_fsr_raw:
 130         save %sp,-104,%sp
 131         st %fsr,[%fp+68]
 132         ld [%fp+68], %i0
 133         ret
 134         restore
 135
 136     ");
 137
 138 #elif i386
 139
 140     asm("
 141
 142 .text
 143         .align 8
 144 .globl _get_sw,__get_sw
 145 __get_sw:
 146 _get_sw:
 147         pushl %ebp
 148         movl %esp,%ebp
 149         movl $0,%eax
 150         fnstsw %ax
 151         movl %ebp,%esp
 152         popl %ebp
 153         ret
 154
 155         .align 8
 156 .globl _get_cw,__get_cw
 157 __get_cw:
 158 _get_cw:
 159         pushl %ebp
 160         movl %esp,%ebp
 161         subw $2,%esp
 162         fnstcw -2(%ebp)
 163         movw -2(%ebp),%eax
 164         movl %ebp,%esp
 165         popl %ebp
 166         ret
 167
 168
 169     ");
 170
 171
 172 #else
 173 #warning no fpu trap support for this target
 174 #endif
 175
 176 #if i386
 177 /* #if defined _WIN32 || defined __GO32__ */
 178 /* This is so floating exception handling works on NT
 179    These definitions are from the linux fpu_control.h, which
 180    doesn't exist on NT.
 181
 182    default to:
 183      - extended precision
 184      - rounding to nearest
 185      - exceptions on overflow, zero divide and NaN
 186 */
 187 #define _FPU_DEFAULT  0x1372
 188 #define _FPU_RESERVED 0xF0C0  /* Reserved bits in cw */
 189
 190 static void
 191 __setfpucw(unsigned short fpu_control)
 192 {
 193   volatile unsigned short cw;
 194
 195   /* If user supplied _fpu_control, use it ! */
 196   if (!fpu_control)
 197   {
 198     /* use defaults */
 199     fpu_control = _FPU_DEFAULT;
 200   }
 201   /* Get Control Word */
 202   __asm__ volatile ("fnstcw %0" : "=m" (cw) : );
 203
 204   /* mask in */
 205   cw &= _FPU_RESERVED;
 206   cw = cw | (fpu_control & ~_FPU_RESERVED);
 207
 208   /* set cw */
 209   __asm__ volatile ("fldcw %0" :: "m" (cw));
 210 }
 211 /* #endif */
 212 #endif