/*
    NetWinder Floating Point Emulator
    (c) Corel Computer Corporation, 1998
    (c) Philip Blundell, 1999

    Direct questions, comments to Scott Bambrough <scottb@corelcomputer.com>

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include "config.h"
#include "milieu.h"
#include "softfloat.h"
#include "fpopcode.h"
#include "fpa11.h"
#include "fpa11.inl"
#include "fpmodule.h"
#include "fpmodule.inl"

extern flag floatx80_is_nan(floatx80);
extern flag float64_is_nan( float64);
extern flag float32_is_nan( float32);

void SetRoundingMode(const unsigned int opcode);

unsigned int PerformFLT(const unsigned int opcode);
unsigned int PerformFIX(const unsigned int opcode);

static unsigned int
PerformComparison(const unsigned int opcode);

unsigned int EmulateCPRT(const unsigned int opcode)
{
  unsigned int nRc = 1;

  //fp_printk("EmulateCPRT(0x%08x)\n",opcode);

  if (opcode & 0x800000)
  {
     /* This is some variant of a comparison (PerformComparison will
	sort out which one).  Since most of the other CPRT
	instructions are oddball cases of some sort or other it makes
	sense to pull this out into a fast path.  */
     return PerformComparison(opcode);
  }

  /* Hint to GCC that we'd like a jump table rather than a load of CMPs */
  switch ((opcode & 0x700000) >> 20)
  {
    case  FLT_CODE >> 20: nRc = PerformFLT(opcode); break;
    case  FIX_CODE >> 20: nRc = PerformFIX(opcode); break;
    
    case  WFS_CODE >> 20: writeFPSR(readRegister(getRd(opcode))); break;
    case  RFS_CODE >> 20: writeRegister(getRd(opcode),readFPSR()); break;

#if 0
    /* ?? Not at all sure about the mode checks here.  Linux never
       calls the emulator from a non-USR fault but we always run in SVC
       mode.  Is there even any point trying to emulate the way FPA11
       behaves in this respect?

       No - and I quote: 'The FPCR may only be present in some
       implementations: it is there to control the hardware in an
       implementation-specific manner, ...  The user mode of the
       ARM is not permitted to use this register, and the WFC and
       RFC instructions will trap if tried from user mode.'
       Therefore, we do not provide the RFC and WFC instructions.
        (rmk, 3/05/1999)
     */
    case  WFC_CODE >> 20:
    {
       int mode = 0;
       __asm__ volatile ("mrs %0, cpsr; and %0, %0, #0x1f;" : : "g" (mode));
       nRc = (0x13 == mode) ? 1 : 0;	/* in SVC processor mode? */
       if (nRc) writeFPCR(readRegister(getRd(opcode)));
    }
    break;
    
    case  RFC_CODE >> 20:
    {
       int mode = 0;
       __asm__ volatile ("mrs %0, cpsr; and %0, %0, #0x1f;" : : "g" (mode));
       nRc = (0x13 == mode) ? 1 : 0;	/* in SVC processor mode? */
       if (nRc) writeRegister(getRd(opcode),readFPCR()); break;
    }
    break;
#endif

    default: nRc = 0;
  }
  
  return nRc;
}

unsigned int PerformFLT(const unsigned int opcode)
{
   unsigned int nRc = 1;
   SetRoundingMode(opcode);
   SetRoundingPrecision(opcode);
   
   switch (opcode & MASK_ROUNDING_PRECISION)
   {
      case ROUND_SINGLE:
      {
        fpa11->fpreg[getFn(opcode)].fType = typeSingle;
        fpa11->fpreg[getFn(opcode)].fValue.fSingle =
	   int32_to_float32(readRegister(getRd(opcode)));
      }
      break;

      case ROUND_DOUBLE:
      {
        fpa11->fpreg[getFn(opcode)].fType = typeDouble;
        fpa11->fpreg[getFn(opcode)].fValue.fDouble =
            int32_to_float64(readRegister(getRd(opcode)));
      }
      break;
        
      case ROUND_EXTENDED:
      {
        fpa11->fpreg[getFn(opcode)].fType = typeExtended;
        fpa11->fpreg[getFn(opcode)].fValue.fExtended =
	   int32_to_floatx80(readRegister(getRd(opcode)));
      }
      break;
      
      default: nRc = 0;
  }
  
  return nRc;
}

unsigned int PerformFIX(const unsigned int opcode)
{
   unsigned int nRc = 1;
   unsigned int Fn = getFm(opcode);
   
   SetRoundingMode(opcode);

   switch (fpa11->fpreg[Fn].fType)
   {
      case typeSingle:
      {
         writeRegister(getRd(opcode),
	               float32_to_int32(fpa11->fpreg[Fn].fValue.fSingle));
      }
      break;

      case typeDouble:
      {
         writeRegister(getRd(opcode),
	               float64_to_int32(fpa11->fpreg[Fn].fValue.fDouble));
      }
      break;
      	               
      case typeExtended:
      {
         writeRegister(getRd(opcode),
	               floatx80_to_int32(fpa11->fpreg[Fn].fValue.fExtended));
      }
      break;
      
      default: nRc = 0;
  }
  
  return nRc;
}

   
static unsigned int __inline__
PerformComparisonOperation(floatx80 Fn, floatx80 Fm)
{
   unsigned int flags = 0;

   /* test for less than condition */
   if (floatx80_lt(Fn,Fm))
   {
      flags |= CC_NEGATIVE;
   }
  
   /* test for equal condition */
   if (floatx80_eq(Fn,Fm))
   {
      flags |= CC_ZERO;
   }

   /* test for greater than or equal condition */
   if (floatx80_lt(Fm,Fn))
   {
      flags |= CC_CARRY;
   }
   
   writeConditionCodes(flags);
   return 1;
}

/* This instruction sets the flags N, Z, C, V in the FPSR. */
   
static unsigned int PerformComparison(const unsigned int opcode)
{
   unsigned int Fn, Fm;
   floatx80 rFn, rFm;
   int e_flag = opcode & 0x400000;	/* 1 if CxFE */
   int n_flag = opcode & 0x200000;	/* 1 if CNxx */
   unsigned int flags = 0;

   //fp_printk("PerformComparison(0x%08x)\n",opcode);

   Fn = getFn(opcode);
   Fm = getFm(opcode);

   /* Check for unordered condition and convert all operands to 80-bit
      format.
      ?? Might be some mileage in avoiding this conversion if possible.
      Eg, if both operands are 32-bit, detect this and do a 32-bit
      comparison (cheaper than an 80-bit one).  */
   switch (fpa11->fpreg[Fn].fType)
   {
      case typeSingle: 
        //fp_printk("single.\n");
	if (float32_is_nan(fpa11->fpreg[Fn].fValue.fSingle))
	   goto unordered;
        rFn = float32_to_floatx80(fpa11->fpreg[Fn].fValue.fSingle);
      break;

      case typeDouble: 
        //fp_printk("double.\n");
	if (float64_is_nan(fpa11->fpreg[Fn].fValue.fDouble))
	   goto unordered;
        rFn = float64_to_floatx80(fpa11->fpreg[Fn].fValue.fDouble);
      break;
      
      case typeExtended: 
        //fp_printk("extended.\n");
	if (floatx80_is_nan(fpa11->fpreg[Fn].fValue.fExtended))
	   goto unordered;
        rFn = fpa11->fpreg[Fn].fValue.fExtended;
      break;
      
      default: return 0;
   }

   if (CONSTANT_FM(opcode))
   {
     //fp_printk("Fm is a constant: #%d.\n",Fm);
     rFm = getExtendedConstant(Fm);
     if (floatx80_is_nan(rFm))
        goto unordered;
   }
   else
   {
     //fp_printk("Fm = r%d which contains a ",Fm);
      switch (fpa11->fpreg[Fm].fType)
      {
         case typeSingle: 
           //fp_printk("single.\n");
	   if (float32_is_nan(fpa11->fpreg[Fm].fValue.fSingle))
	      goto unordered;
           rFm = float32_to_floatx80(fpa11->fpreg[Fm].fValue.fSingle);
         break;

         case typeDouble: 
           //fp_printk("double.\n");
	   if (float64_is_nan(fpa11->fpreg[Fm].fValue.fDouble))
	      goto unordered;
           rFm = float64_to_floatx80(fpa11->fpreg[Fm].fValue.fDouble);
         break;
      
         case typeExtended: 
           //fp_printk("extended.\n");
	   if (floatx80_is_nan(fpa11->fpreg[Fm].fValue.fExtended))
	      goto unordered;
           rFm = fpa11->fpreg[Fm].fValue.fExtended;
         break;
      
         default: return 0;
      }
   }

   if (n_flag)
   {
      rFm.high ^= 0x8000;
   }

   return PerformComparisonOperation(rFn,rFm);

 unordered:
   /* ?? The FPA data sheet is pretty vague about this, in particular
      about whether the non-E comparisons can ever raise exceptions.
      This implementation is based on a combination of what it says in
      the data sheet, observation of how the Acorn emulator actually
      behaves (and how programs expect it to) and guesswork.  */
   flags |= CC_OVERFLOW;

   if (BIT_AC & readFPSR()) flags |= CC_CARRY;

   if (e_flag) float_raise(float_flag_invalid);

   writeConditionCodes(flags);
   return 1;
}
