R/ChocolArm64/Decoder/ADecoderHelper.cs

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2018-02-04 23:08:20 +00:00
using System;
namespace ChocolArm64.Decoder
{
static class ADecoderHelper
{
public struct BitMask
{
public long WMask;
public long TMask;
public int Pos;
public int Shift;
public bool IsUndefined;
public static BitMask Invalid => new BitMask { IsUndefined = true };
}
public static BitMask DecodeBitMask(int OpCode, bool Immediate)
{
int ImmS = (OpCode >> 10) & 0x3f;
int ImmR = (OpCode >> 16) & 0x3f;
int N = (OpCode >> 22) & 1;
int SF = (OpCode >> 31) & 1;
int Length = ABitUtils.HighestBitSet32((~ImmS & 0x3f) | (N << 6));
if (Length < 1 || (SF == 0 && N != 0))
{
return BitMask.Invalid;
}
int Size = 1 << Length;
int Levels = Size - 1;
int S = ImmS & Levels;
int R = ImmR & Levels;
if (Immediate && S == Levels)
{
return BitMask.Invalid;
}
long WMask = ABitUtils.FillWithOnes(S + 1);
long TMask = ABitUtils.FillWithOnes(((S - R) & Levels) + 1);
if (R > 0)
{
WMask = ABitUtils.RotateRight(WMask, R, Size);
WMask &= ABitUtils.FillWithOnes(Size);
}
return new BitMask()
{
WMask = ABitUtils.Replicate(WMask, Size),
TMask = ABitUtils.Replicate(TMask, Size),
Pos = ImmS,
Shift = ImmR
};
}
public static long DecodeImm8Float(long Imm, int Size)
{
int E = 0, F = 0;
switch (Size)
{
case 0: E = 8; F = 23; break;
case 1: E = 11; F = 52; break;
default: throw new ArgumentOutOfRangeException(nameof(Size));
}
long Value = (Imm & 0x3f) << F - 4;
long EBit = (Imm >> 6) & 1;
long SBit = (Imm >> 7) & 1;
if (EBit != 0)
{
Value |= (1L << E - 3) - 1 << F + 2;
}
Value |= (EBit ^ 1) << F + E - 1;
Value |= SBit << F + E;
return Value;
}
public static long DecodeImm26_2(int OpCode)
{
return ((long)OpCode << 38) >> 36;
}
public static long DecodeImmS19_2(int OpCode)
{
return (((long)OpCode << 40) >> 43) & ~3;
}
public static long DecodeImmS14_2(int OpCode)
{
return (((long)OpCode << 45) >> 48) & ~3;
}
}
}