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AInstEmitSimdCvt: Half-precision to single-precision conversion (#235)

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Merry 2018-07-12 19:51:02 +01:00 committed by gdkchan
parent c590201b2a
commit 1e35b99f74
2 changed files with 40 additions and 4 deletions
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8
Instruction/AInstEmitSimdCvt.cs
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@ -45,10 +45,10 @@ namespace ChocolArm64.Instruction
{
if (SizeF == 0)
{
//TODO: This need the half precision floating point type,
//that is not yet supported on .NET. We should probably
//do our own implementation on the meantime.
throw new NotImplementedException();
EmitVectorExtractZx(Context, Op.Rn, Part + Index, 1);
Context.Emit(OpCodes.Conv_U2);
Context.EmitCall(typeof(ASoftFloat), nameof(ASoftFloat.ConvertHalfToSingle));
}
else /* if (SizeF == 1) */
{

36
Instruction/ASoftFloat.cs
View file

@ -225,5 +225,41 @@ namespace ChocolArm64.Instruction
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)));
}
}
}