net.mograsim.machine/src/net/mograsim/machine/isa/AsmFloatOperand.java

   1 package net.mograsim.machine.isa;
   2
   3 import java.math.BigDecimal;
   4 import java.math.BigInteger;
   5
   6 import net.mograsim.logic.core.types.Bit;
   7 import net.mograsim.logic.core.types.BitVector;
   8 import net.mograsim.logic.core.types.BitVector.BitVectorMutator;
   9 import net.mograsim.machine.isa.types.AsmNumberFormatException;
  10
  11 public class AsmFloatOperand implements AsmOperand
  12 {
  13         private final int size;
  14         private final int mantissa;
  15         private final int exponent;
  16
  17         public AsmFloatOperand(int size)
  18         {
  19                 this.size = size;
  20                 switch (size)
  21                 {
  22                 case 8:
  23                         exponent = 4;
  24                         mantissa = 3;
  25                         break;
  26                 case 16:
  27                         exponent = 5;
  28                         mantissa = 10;
  29                         break;
  30                 case 32:
  31                         exponent = 8;
  32                         mantissa = 23;
  33                         break;
  34                 case 64:
  35                         exponent = 11;
  36                         mantissa = 52;
  37                         break;
  38                 case 128:
  39                         exponent = 15;
  40                         mantissa = 112;
  41                         break;
  42                 default:
  43                         if (size > 128 && size % 32 == 0)
  44                         {
  45                                 exponent = (int) Math.round(Math.log(size) / Math.log(2)) - 13;
  46                                 mantissa = size - exponent - 1;
  47                         } else
  48                         {
  49                                 throw new IllegalArgumentException("Illegal floating point size: " + size);
  50                         }
  51                 }
  52         }
  53
  54         public AsmFloatOperand(int exponent, int mantissa)
  55         {
  56                 if (exponent < 1 || mantissa < 1)
  57                         throw new IllegalArgumentException("illegal floating point specification: e=" + exponent + ", m=" + mantissa);
  58                 this.exponent = exponent;
  59                 this.mantissa = mantissa;
  60                 this.size = exponent + mantissa + 1;
  61         }
  62
  63         @Override
  64         public int getSize()
  65         {
  66                 return size;
  67         }
  68
  69         @Override
  70         public BitVector parse(String s) throws AsmNumberFormatException
  71         {
  72                 String cleaned = s.replace("_", "").toLowerCase();
  73                 int len = cleaned.length();
  74                 BigInteger res;
  75                 try
  76                 {
  77                         return bigDecToBitVector(new BigDecimal(cleaned));
  78                 }
  79                 catch (NumberFormatException e)
  80                 {
  81                         throw new AsmNumberFormatException(e, "Error parsing %s: no valid float format", s);
  82                 }
  83         }
  84
  85         BitVector bigDecToBitVector(BigDecimal bi) throws AsmNumberFormatException
  86         {
  87                 BigInteger raw = bi.unscaledValue();
  88                 int mantLen = raw.bitLength();
  89 //              bi.
  90                 int bitLength = raw.bitLength() - (bi.signum() - 1) / 2;
  91                 if (bitLength > size)
  92                         throw new AsmNumberFormatException("Error parsing %s: bit count %d exceeds size %d", bi, bitLength, size);
  93                 BitVectorMutator bvm = BitVectorMutator.ofLength(size);
  94                 for (int i = 0; i < size; i++)
  95                         bvm.setLSBit(i, Bit.of(raw.testBit(i)));
  96                 return bvm.toBitVector();
  97         }
  98 }