ChocolArm64/Instruction/ASoftFloat.cs

537 lines
16 KiB
C#

using System;
namespace ChocolArm64.Instruction
{
static class ASoftFloat
{
static ASoftFloat()
{
InvSqrtEstimateTable = BuildInvSqrtEstimateTable();
RecipEstimateTable = BuildRecipEstimateTable();
}
private static readonly byte[] RecipEstimateTable;
private static readonly byte[] InvSqrtEstimateTable;
private static byte[] BuildInvSqrtEstimateTable()
{
byte[] Table = new byte[512];
for (ulong index = 128; index < 512; index++)
{
ulong a = index;
if (a < 256)
{
a = (a << 1) + 1;
}
else
{
a = (a | 1) << 1;
}
ulong b = 256;
while (a * (b + 1) * (b + 1) < (1ul << 28))
{
b++;
}
b = (b + 1) >> 1;
Table[index] = (byte)(b & 0xFF);
}
return Table;
}
private static byte[] BuildRecipEstimateTable()
{
byte[] Table = new byte[256];
for (ulong index = 0; index < 256; index++)
{
ulong a = index | 0x100;
a = (a << 1) + 1;
ulong b = 0x80000 / a;
b = (b + 1) >> 1;
Table[index] = (byte)(b & 0xFF);
}
return Table;
}
public static float InvSqrtEstimate(float x)
{
return (float)InvSqrtEstimate((double)x);
}
public static double InvSqrtEstimate(double x)
{
ulong x_bits = (ulong)BitConverter.DoubleToInt64Bits(x);
ulong x_sign = x_bits & 0x8000000000000000;
long x_exp = (long)((x_bits >> 52) & 0x7FF);
ulong scaled = x_bits & ((1ul << 52) - 1);
if (x_exp == 0x7FF && scaled != 0)
{
// NaN
return BitConverter.Int64BitsToDouble((long)(x_bits | 0x0008000000000000));
}
if (x_exp == 0)
{
if (scaled == 0)
{
// Zero -> Infinity
return BitConverter.Int64BitsToDouble((long)(x_sign | 0x7FF0000000000000));
}
// Denormal
while ((scaled & (1 << 51)) == 0)
{
scaled <<= 1;
x_exp--;
}
scaled <<= 1;
}
if (x_sign != 0)
{
// Negative -> NaN
return BitConverter.Int64BitsToDouble((long)0x7FF8000000000000);
}
if (x_exp == 0x7ff && scaled == 0)
{
// Infinity -> Zero
return BitConverter.Int64BitsToDouble((long)x_sign);
}
if (((ulong)x_exp & 1) == 1)
{
scaled >>= 45;
scaled &= 0xFF;
scaled |= 0x80;
}
else
{
scaled >>= 44;
scaled &= 0xFF;
scaled |= 0x100;
}
ulong result_exp = ((ulong)(3068 - x_exp) / 2) & 0x7FF;
ulong estimate = (ulong)InvSqrtEstimateTable[scaled];
ulong fraction = estimate << 44;
ulong result = x_sign | (result_exp << 52) | fraction;
return BitConverter.Int64BitsToDouble((long)result);
}
public static float RecipEstimate(float x)
{
return (float)RecipEstimate((double)x);
}
public static double RecipEstimate(double x)
{
ulong x_bits = (ulong)BitConverter.DoubleToInt64Bits(x);
ulong x_sign = x_bits & 0x8000000000000000;
ulong x_exp = (x_bits >> 52) & 0x7FF;
ulong scaled = x_bits & ((1ul << 52) - 1);
if (x_exp >= 2045)
{
if (x_exp == 0x7ff && scaled != 0)
{
// NaN
return BitConverter.Int64BitsToDouble((long)(x_bits | 0x0008000000000000));
}
// Infinity, or Out of range -> Zero
return BitConverter.Int64BitsToDouble((long)x_sign);
}
if (x_exp == 0)
{
if (scaled == 0)
{
// Zero -> Infinity
return BitConverter.Int64BitsToDouble((long)(x_sign | 0x7FF0000000000000));
}
// Denormal
if ((scaled & (1ul << 51)) == 0)
{
x_exp = ~0ul;
scaled <<= 2;
}
else
{
scaled <<= 1;
}
}
scaled >>= 44;
scaled &= 0xFF;
ulong result_exp = (2045 - x_exp) & 0x7FF;
ulong estimate = (ulong)RecipEstimateTable[scaled];
ulong fraction = estimate << 44;
if (result_exp == 0)
{
fraction >>= 1;
fraction |= 1ul << 51;
}
else if (result_exp == 0x7FF)
{
result_exp = 0;
fraction >>= 2;
fraction |= 1ul << 50;
}
ulong result = x_sign | (result_exp << 52) | fraction;
return BitConverter.Int64BitsToDouble((long)result);
}
public static float RecipStep(float op1, float op2)
{
return (float)RecipStep((double)op1, (double)op2);
}
public static double RecipStep(double op1, double op2)
{
op1 = -op1;
ulong op1_bits = (ulong)BitConverter.DoubleToInt64Bits(op1);
ulong op2_bits = (ulong)BitConverter.DoubleToInt64Bits(op2);
ulong op1_sign = op1_bits & 0x8000000000000000;
ulong op2_sign = op2_bits & 0x8000000000000000;
ulong op1_other = op1_bits & 0x7FFFFFFFFFFFFFFF;
ulong op2_other = op2_bits & 0x7FFFFFFFFFFFFFFF;
bool inf1 = op1_other == 0x7FF0000000000000;
bool inf2 = op2_other == 0x7FF0000000000000;
bool zero1 = op1_other == 0;
bool zero2 = op2_other == 0;
if ((inf1 && zero2) || (zero1 && inf2))
{
return 2.0;
}
else if (inf1 || inf2)
{
// Infinity
return BitConverter.Int64BitsToDouble((long)(0x7FF0000000000000 | (op1_sign ^ op2_sign)));
}
return 2.0 + op1 * op2;
}
public static float ConvertHalfToSingle(ushort x)
{
uint x_sign = (uint)(x >> 15) & 0x0001;
uint x_exp = (uint)(x >> 10) & 0x001F;
uint x_mantissa = (uint)x & 0x03FF;
if (x_exp == 0 && x_mantissa == 0)
{
// Zero
return BitConverter.Int32BitsToSingle((int)(x_sign << 31));
}
if (x_exp == 0x1F)
{
// NaN or Infinity
return BitConverter.Int32BitsToSingle((int)((x_sign << 31) | 0x7F800000 | (x_mantissa << 13)));
}
int exponent = (int)x_exp - 15;
if (x_exp == 0)
{
// Denormal
x_mantissa <<= 1;
while ((x_mantissa & 0x0400) == 0)
{
x_mantissa <<= 1;
exponent--;
}
x_mantissa &= 0x03FF;
}
uint new_exp = (uint)((exponent + 127) & 0xFF) << 23;
return BitConverter.Int32BitsToSingle((int)((x_sign << 31) | new_exp | (x_mantissa << 13)));
}
public static float MaxNum(float op1, float op2)
{
uint op1_bits = (uint)BitConverter.SingleToInt32Bits(op1);
uint op2_bits = (uint)BitConverter.SingleToInt32Bits(op2);
if (IsQNaN(op1_bits) && !IsQNaN(op2_bits))
{
op1 = float.NegativeInfinity;
}
else if (!IsQNaN(op1_bits) && IsQNaN(op2_bits))
{
op2 = float.NegativeInfinity;
}
return Max(op1, op2);
}
public static double MaxNum(double op1, double op2)
{
ulong op1_bits = (ulong)BitConverter.DoubleToInt64Bits(op1);
ulong op2_bits = (ulong)BitConverter.DoubleToInt64Bits(op2);
if (IsQNaN(op1_bits) && !IsQNaN(op2_bits))
{
op1 = double.NegativeInfinity;
}
else if (!IsQNaN(op1_bits) && IsQNaN(op2_bits))
{
op2 = double.NegativeInfinity;
}
return Max(op1, op2);
}
public static float Max(float op1, float op2)
{
// Fast path
if (op1 > op2)
{
return op1;
}
if (op1 < op2 || (op1 == op2 && op2 != 0))
{
return op2;
}
uint op1_bits = (uint)BitConverter.SingleToInt32Bits(op1);
uint op2_bits = (uint)BitConverter.SingleToInt32Bits(op2);
// Handle NaN cases
if (ProcessNaNs(op1_bits, op2_bits, out uint op_bits))
{
return BitConverter.Int32BitsToSingle((int)op_bits);
}
// Return the most positive zero
if ((op1_bits & op2_bits) == 0x80000000u)
{
return BitConverter.Int32BitsToSingle(int.MinValue);
}
return 0;
}
public static double Max(double op1, double op2)
{
// Fast path
if (op1 > op2)
{
return op1;
}
if (op1 < op2 || (op1 == op2 && op2 != 0))
{
return op2;
}
ulong op1_bits = (ulong)BitConverter.DoubleToInt64Bits(op1);
ulong op2_bits = (ulong)BitConverter.DoubleToInt64Bits(op2);
// Handle NaN cases
if (ProcessNaNs(op1_bits, op2_bits, out ulong op_bits))
{
return BitConverter.Int64BitsToDouble((long)op_bits);
}
// Return the most positive zero
if ((op1_bits & op2_bits) == 0x8000000000000000ul)
{
return BitConverter.Int64BitsToDouble(long.MinValue);
}
return 0;
}
public static float MinNum(float op1, float op2)
{
uint op1_bits = (uint)BitConverter.SingleToInt32Bits(op1);
uint op2_bits = (uint)BitConverter.SingleToInt32Bits(op2);
if (IsQNaN(op1_bits) && !IsQNaN(op2_bits))
{
op1 = float.PositiveInfinity;
}
else if (!IsQNaN(op1_bits) && IsQNaN(op2_bits))
{
op2 = float.PositiveInfinity;
}
return Min(op1, op2);
}
public static double MinNum(double op1, double op2)
{
ulong op1_bits = (ulong)BitConverter.DoubleToInt64Bits(op1);
ulong op2_bits = (ulong)BitConverter.DoubleToInt64Bits(op2);
if (IsQNaN(op1_bits) && !IsQNaN(op2_bits))
{
op1 = double.PositiveInfinity;
}
else if (!IsQNaN(op1_bits) && IsQNaN(op2_bits))
{
op2 = double.PositiveInfinity;
}
return Min(op1, op2);
}
public static float Min(float op1, float op2)
{
// Fast path
if (op1 < op2)
{
return op1;
}
if (op1 > op2 || (op1 == op2 && op2 != 0))
{
return op2;
}
uint op1_bits = (uint)BitConverter.SingleToInt32Bits(op1);
uint op2_bits = (uint)BitConverter.SingleToInt32Bits(op2);
// Handle NaN cases
if (ProcessNaNs(op1_bits, op2_bits, out uint op_bits))
{
return BitConverter.Int32BitsToSingle((int)op_bits);
}
// Return the most negative zero
if ((op1_bits | op2_bits) == 0x80000000u)
{
return BitConverter.Int32BitsToSingle(int.MinValue);
}
return 0;
}
public static double Min(double op1, double op2)
{
// Fast path
if (op1 < op2)
{
return op1;
}
if (op1 > op2 || (op1 == op2 && op2 != 0))
{
return op2;
}
ulong op1_bits = (ulong)BitConverter.DoubleToInt64Bits(op1);
ulong op2_bits = (ulong)BitConverter.DoubleToInt64Bits(op2);
// Handle NaN cases
if (ProcessNaNs(op1_bits, op2_bits, out ulong op_bits))
{
return BitConverter.Int64BitsToDouble((long)op_bits);
}
// Return the most negative zero
if ((op1_bits | op2_bits) == 0x8000000000000000ul)
{
return BitConverter.Int64BitsToDouble(long.MinValue);
}
return 0;
}
private static bool ProcessNaNs(uint op1_bits, uint op2_bits, out uint op_bits)
{
if (IsSNaN(op1_bits))
{
op_bits = op1_bits | (1u << 22); // op1 is SNaN, return QNaN op1
}
else if (IsSNaN(op2_bits))
{
op_bits = op2_bits | (1u << 22); // op2 is SNaN, return QNaN op2
}
else if (IsQNaN(op1_bits))
{
op_bits = op1_bits; // op1 is QNaN, return QNaN op1
}
else if (IsQNaN(op2_bits))
{
op_bits = op2_bits; // op2 is QNaN, return QNaN op2
}
else
{
op_bits = 0;
return false;
}
return true;
}
private static bool ProcessNaNs(ulong op1_bits, ulong op2_bits, out ulong op_bits)
{
if (IsSNaN(op1_bits))
{
op_bits = op1_bits | (1ul << 51); // op1 is SNaN, return QNaN op1
}
else if (IsSNaN(op2_bits))
{
op_bits = op2_bits | (1ul << 51); // op2 is SNaN, return QNaN op2
}
else if (IsQNaN(op1_bits))
{
op_bits = op1_bits; // op1 is QNaN, return QNaN op1
}
else if (IsQNaN(op2_bits))
{
op_bits = op2_bits; // op2 is QNaN, return QNaN op2
}
else
{
op_bits = 0;
return false;
}
return true;
}
private static bool IsQNaN(uint op_bits)
{
return (op_bits & 0x007FFFFF) != 0 &&
(op_bits & 0x7FC00000) == 0x7FC00000;
}
private static bool IsQNaN(ulong op_bits)
{
return (op_bits & 0x000FFFFFFFFFFFFF) != 0 &&
(op_bits & 0x7FF8000000000000) == 0x7FF8000000000000;
}
private static bool IsSNaN(uint op_bits)
{
return (op_bits & 0x007FFFFF) != 0 &&
(op_bits & 0x7FC00000) == 0x7F800000;
}
private static bool IsSNaN(ulong op_bits)
{
return (op_bits & 0x000FFFFFFFFFFFFF) != 0 &&
(op_bits & 0x7FF8000000000000) == 0x7FF0000000000000;
}
}
}