1 files changed, 91 insertions, 0 deletions
diff --git a/src/ARMeilleure/CodeGen/Arm64/CodeGenCommon.cs b/src/ARMeilleure/CodeGen/Arm64/CodeGenCommon.cs
new file mode 100644
index 00000000..8d1e597b
--- /dev/null
+++ b/src/ARMeilleure/CodeGen/Arm64/CodeGenCommon.cs
@@ -0,0 +1,91 @@
+using ARMeilleure.IntermediateRepresentation;
+using System.Numerics;
+
+namespace ARMeilleure.CodeGen.Arm64
+{
+    static class CodeGenCommon
+    {
+        public const int TcAddressRegister = 8;
+        public const int ReservedRegister = 17;
+
+        public static bool ConstFitsOnSImm7(int value, int scale)
+        {
+            return (((value >> scale) << 25) >> (25 - scale)) == value;
+        }
+
+        public static bool ConstFitsOnSImm9(int value)
+        {
+            return ((value << 23) >> 23) == value;
+        }
+
+        public static bool ConstFitsOnUImm12(int value)
+        {
+            return (value & 0xfff) == value;
+        }
+
+        public static bool ConstFitsOnUImm12(int value, OperandType type)
+        {
+            int scale = Assembler.GetScaleForType(type);
+            return (((value >> scale) & 0xfff) << scale) == value;
+        }
+
+        public static bool TryEncodeBitMask(Operand operand, out int immN, out int immS, out int immR)
+        {
+            return TryEncodeBitMask(operand.Type, operand.Value, out immN, out immS, out immR);
+        }
+
+        public static bool TryEncodeBitMask(OperandType type, ulong value, out int immN, out int immS, out int immR)
+        {
+            if (type == OperandType.I32)
+            {
+                value |= value << 32;
+            }
+
+            return TryEncodeBitMask(value, out immN, out immS, out immR);
+        }
+
+        public static bool TryEncodeBitMask(ulong value, out int immN, out int immS, out int immR)
+        {
+            // Some special values also can't be encoded:
+            // 0 can't be encoded because we need to subtract 1 from onesCount (which would became negative if 0).
+            // A value with all bits set can't be encoded because it is reserved according to the spec, because:
+            // Any value AND all ones will be equal itself, so it's effectively a no-op.
+            // Any value OR all ones will be equal all ones, so one can just use MOV.
+            // Any value XOR all ones will be equal its inverse, so one can just use MVN.
+            if (value == 0 || value == ulong.MaxValue)
+            {
+                immN = 0;
+                immS = 0;
+                immR = 0;
+
+                return false;
+            }
+
+            // Normalize value, rotating it such that the LSB is 1: Ensures we get a complete element that has not
+            // been cut-in-half across the word boundary.
+            int rotation = BitOperations.TrailingZeroCount(value & (value + 1));
+            ulong rotatedValue = ulong.RotateRight(value, rotation);
+
+            // Now that we have a complete element in the LSB with the LSB = 1, determine size and number of ones
+            // in element.
+            int elementSize = BitOperations.TrailingZeroCount(rotatedValue & (rotatedValue + 1));
+            int onesInElement = BitOperations.TrailingZeroCount(~rotatedValue);
+
+            // Check the value is repeating; also ensures element size is a power of two.
+            if (ulong.RotateRight(value, elementSize) != value)
+            {
+                immN = 0;
+                immS = 0;
+                immR = 0;
+
+                return false;
+            }
+
+            immN = (elementSize >> 6) & 1;
+            immS = (((~elementSize + 1) << 1) | (onesInElement - 1)) & 0x3f;
+            immR = (elementSize - rotation) & (elementSize - 1);
+
+            return true;
+        }
+    }
+}
+\ No newline at end of file