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107 lines
2.7 KiB
C#
107 lines
2.7 KiB
C#
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using System;
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namespace ChocolArm64.Decoders
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{
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static class DecoderHelper
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{
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public struct BitMask
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{
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public long WMask;
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public long TMask;
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public int Pos;
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public int Shift;
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public bool IsUndefined;
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public static BitMask Invalid => new BitMask { IsUndefined = true };
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}
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public static BitMask DecodeBitMask(int opCode, bool immediate)
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{
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int immS = (opCode >> 10) & 0x3f;
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int immR = (opCode >> 16) & 0x3f;
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int n = (opCode >> 22) & 1;
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int sf = (opCode >> 31) & 1;
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int length = BitUtils.HighestBitSet32((~immS & 0x3f) | (n << 6));
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if (length < 1 || (sf == 0 && n != 0))
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{
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return BitMask.Invalid;
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}
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int size = 1 << length;
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int levels = size - 1;
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int s = immS & levels;
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int r = immR & levels;
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if (immediate && s == levels)
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{
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return BitMask.Invalid;
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}
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long wMask = BitUtils.FillWithOnes(s + 1);
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long tMask = BitUtils.FillWithOnes(((s - r) & levels) + 1);
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if (r > 0)
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{
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wMask = BitUtils.RotateRight(wMask, r, size);
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wMask &= BitUtils.FillWithOnes(size);
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}
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return new BitMask()
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{
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WMask = BitUtils.Replicate(wMask, size),
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TMask = BitUtils.Replicate(tMask, size),
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Pos = immS,
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Shift = immR
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};
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}
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public static long DecodeImm8Float(long imm, int size)
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{
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int e = 0, f = 0;
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switch (size)
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{
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case 0: e = 8; f = 23; break;
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case 1: e = 11; f = 52; break;
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default: throw new ArgumentOutOfRangeException(nameof(size));
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}
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long value = (imm & 0x3f) << f - 4;
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long eBit = (imm >> 6) & 1;
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long sBit = (imm >> 7) & 1;
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if (eBit != 0)
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{
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value |= (1L << e - 3) - 1 << f + 2;
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}
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value |= (eBit ^ 1) << f + e - 1;
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value |= sBit << f + e;
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return value;
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}
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public static long DecodeImm26_2(int opCode)
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{
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return ((long)opCode << 38) >> 36;
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}
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public static long DecodeImmS19_2(int opCode)
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{
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return (((long)opCode << 40) >> 43) & ~3;
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}
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public static long DecodeImmS14_2(int opCode)
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{
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return (((long)opCode << 45) >> 48) & ~3;
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}
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}
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}
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