1 files changed, 167 insertions, 0 deletions
diff --git a/src/ARMeilleure/Decoders/DecoderHelper.cs b/src/ARMeilleure/Decoders/DecoderHelper.cs
new file mode 100644
index 00000000..5227e6a1
--- /dev/null
+++ b/src/ARMeilleure/Decoders/DecoderHelper.cs
@@ -0,0 +1,167 @@
+using ARMeilleure.Common;
+
+namespace ARMeilleure.Decoders
+{
+    static class DecoderHelper
+    {
+        static DecoderHelper()
+        {
+            Imm8ToFP32Table = BuildImm8ToFP32Table();
+            Imm8ToFP64Table = BuildImm8ToFP64Table();
+        }
+
+        public static readonly uint[]  Imm8ToFP32Table;
+        public static readonly ulong[] Imm8ToFP64Table;
+
+        private static uint[] BuildImm8ToFP32Table()
+        {
+            uint[] tbl = new uint[256];
+
+            for (int idx = 0; idx < tbl.Length; idx++)
+            {
+                tbl[idx] = ExpandImm8ToFP32((uint)idx);
+            }
+
+            return tbl;
+        }
+
+        private static ulong[] BuildImm8ToFP64Table()
+        {
+            ulong[] tbl = new ulong[256];
+
+            for (int idx = 0; idx < tbl.Length; idx++)
+            {
+                tbl[idx] = ExpandImm8ToFP64((ulong)idx);
+            }
+
+            return tbl;
+        }
+
+        // abcdefgh -> aBbbbbbc defgh000 00000000 00000000 (B = ~b)
+        private static uint ExpandImm8ToFP32(uint imm)
+        {
+            uint MoveBit(uint bits, int from, int to)
+            {
+                return ((bits >> from) & 1U) << to;
+            }
+
+            return MoveBit(imm, 7, 31) | MoveBit(~imm, 6, 30) |
+                   MoveBit(imm, 6, 29) | MoveBit( imm, 6, 28) |
+                   MoveBit(imm, 6, 27) | MoveBit( imm, 6, 26) |
+                   MoveBit(imm, 6, 25) | MoveBit( imm, 5, 24) |
+                   MoveBit(imm, 4, 23) | MoveBit( imm, 3, 22) |
+                   MoveBit(imm, 2, 21) | MoveBit( imm, 1, 20) |
+                   MoveBit(imm, 0, 19);
+        }
+
+        // abcdefgh -> aBbbbbbb bbcdefgh 00000000 00000000 00000000 00000000 00000000 00000000 (B = ~b)
+        private static ulong ExpandImm8ToFP64(ulong imm)
+        {
+            ulong MoveBit(ulong bits, int from, int to)
+            {
+                return ((bits >> from) & 1UL) << to;
+            }
+
+            return MoveBit(imm, 7, 63) | MoveBit(~imm, 6, 62) |
+                   MoveBit(imm, 6, 61) | MoveBit( imm, 6, 60) |
+                   MoveBit(imm, 6, 59) | MoveBit( imm, 6, 58) |
+                   MoveBit(imm, 6, 57) | MoveBit( imm, 6, 56) |
+                   MoveBit(imm, 6, 55) | MoveBit( imm, 6, 54) |
+                   MoveBit(imm, 5, 53) | MoveBit( imm, 4, 52) |
+                   MoveBit(imm, 3, 51) | MoveBit( imm, 2, 50) |
+                   MoveBit(imm, 1, 49) | MoveBit( imm, 0, 48);
+        }
+
+        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 = BitUtils.HighestBitSet((~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 = BitUtils.FillWithOnes(s + 1);
+            long tMask = BitUtils.FillWithOnes(((s - r) & levels) + 1);
+
+            if (r > 0)
+            {
+                wMask  = BitUtils.RotateRight(wMask, r, size);
+                wMask &= BitUtils.FillWithOnes(size);
+            }
+
+            return new BitMask()
+            {
+                WMask = BitUtils.Replicate(wMask, size),
+                TMask = BitUtils.Replicate(tMask, size),
+
+                Pos   = immS,
+                Shift = immR
+            };
+        }
+
+        public static long DecodeImm24_2(int opCode)
+        {
+            return ((long)opCode << 40) >> 38;
+        }
+
+        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;
+        }
+
+        public static bool VectorArgumentsInvalid(bool q, params int[] args)
+        {
+            if (q)
+            {
+                for (int i = 0; i < args.Length; i++)
+                {
+                    if ((args[i] & 1) == 1)
+                    {
+                        return true;
+                    }
+                }
+            }
+            return false;
+        }
+    }
+}
+\ No newline at end of file