fpu/ferr.cc

   1 /////////////////////////////////////////////////////////////////////////
   2 // $Id: ferr.cc,v 1.13 2008/09/02 19:46:30 sshwarts Exp $
   3 /////////////////////////////////////////////////////////////////////////
   4 //
   5 //   Copyright (c) 2003 Stanislav Shwartsman
   6 //          Written by Stanislav Shwartsman [sshwarts at sourceforge net]
   7 //
   8 //  This library is free software; you can redistribute it and/or
   9 //  modify it under the terms of the GNU Lesser General Public
  10 //  License as published by the Free Software Foundation; either
  11 //  version 2 of the License, or (at your option) any later version.
  12 //
  13 //  This library is distributed in the hope that it will be useful,
  14 //  but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 //  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16 //  Lesser General Public License for more details.
  17 //
  18 //  You should have received a copy of the GNU Lesser General Public
  19 //  License along with this library; if not, write to the Free Software
  20 //  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
  21 //
  22 /////////////////////////////////////////////////////////////////////////
  23
  24 #define NEED_CPU_REG_SHORTCUTS 1
  25 #include "bochs.h"
  26 #include "cpu/cpu.h"
  27 #define LOG_THIS BX_CPU_THIS_PTR
  28
  29 #if BX_SUPPORT_FPU
  30
  31 #include "softfloat-specialize.h"
  32
  33 void BX_CPU_C::FPU_stack_overflow(void)
  34 {
  35   /* The masked response */
  36   if (BX_CPU_THIS_PTR the_i387.is_IA_masked())
  37   {
  38     BX_CPU_THIS_PTR the_i387.FPU_push();
  39     BX_WRITE_FPU_REG(floatx80_default_nan, 0);
  40   }
  41   FPU_exception(FPU_EX_Stack_Overflow);
  42 }
  43
  44 void BX_CPU_C::FPU_stack_underflow(int stnr, int pop_stack)
  45 {
  46   /* The masked response */
  47   if (BX_CPU_THIS_PTR the_i387.is_IA_masked())
  48   {
  49     BX_WRITE_FPU_REG(floatx80_default_nan, stnr);
  50     if (pop_stack)
  51         BX_CPU_THIS_PTR the_i387.FPU_pop();
  52   }
  53   FPU_exception(FPU_EX_Stack_Underflow);
  54 }
  55
  56 /* Returns unmasked exceptions if occured */
  57 unsigned BX_CPU_C::FPU_exception(unsigned exception, bx_bool is_mem)
  58 {
  59   /* Extract only the bits which we use to set the status word */
  60   exception &= (FPU_SW_Exceptions_Mask);
  61
  62   /* Set the corresponding exception bits */
  63   FPU_PARTIAL_STATUS |= exception;
  64
  65   unsigned unmasked = FPU_PARTIAL_STATUS & ~FPU_CONTROL_WORD & FPU_CW_Exceptions_Mask;
  66
  67   /* Set summary bits iff exception isn't masked */
  68   if (unmasked)
  69     FPU_PARTIAL_STATUS |= (FPU_SW_Summary | FPU_SW_Backward);
  70
  71   if (exception & (FPU_SW_Stack_Fault | FPU_EX_Precision))
  72   {
  73     if (! (exception & FPU_SW_C1)) {
  74       /* This bit distinguishes over- from underflow for a stack fault,
  75            and roundup from round-down for precision loss. */
  76       FPU_PARTIAL_STATUS &= ~FPU_SW_C1;
  77     }
  78   }
  79
  80   // If #P unmasked exception occured the result still has to be
  81   // written to the destination.
  82   unmasked &= ~FPU_CW_Precision;
  83
  84   // If unmasked overflow or underflow occurs and destination is a memory
  85   // location, the TOS and destination operands remain unchanged and no
  86   // result is stored in the memory. If the destination is in the register
  87   // stack, adjusted resulting value is stored in the destination operand.
  88   if (! is_mem)
  89     unmasked &= ~(FPU_CW_Underflow | FPU_CW_Overflow);
  90
  91   return unmasked;
  92 }
  93
  94 #endif