Ryujinx/ARMeilleure/CodeGen/Arm64/CodeGenCommon.cs

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using ARMeilleure.IntermediateRepresentation;
using System;
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)
{
ulong value = operand.Value;
if (operand.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 == ulong.MaxValue)
{
immN = 0;
immS = 0;
immR = 0;
return false;
}
int bitLength = CountSequence(value);
if ((value >> bitLength) != 0)
{
bitLength += CountSequence(value >> bitLength);
}
int bitLengthLog2 = BitOperations.Log2((uint)bitLength);
int bitLengthPow2 = 1 << bitLengthLog2;
if (bitLengthPow2 < bitLength)
{
bitLengthLog2++;
bitLengthPow2 <<= 1;
}
int selectedESize = 64;
int repetitions = 1;
int onesCount = BitOperations.PopCount(value);
if (bitLengthPow2 < 64 && (value >> bitLengthPow2) != 0)
{
for (int eSizeLog2 = bitLengthLog2; eSizeLog2 < 6; eSizeLog2++)
{
bool match = true;
int eSize = 1 << eSizeLog2;
ulong mask = (1UL << eSize) - 1;
ulong eValue = value & mask;
for (int e = 1; e < 64 / eSize; e++)
{
if (((value >> (e * eSize)) & mask) != eValue)
{
match = false;
break;
}
}
if (match)
{
selectedESize = eSize;
repetitions = 64 / eSize;
onesCount = BitOperations.PopCount(eValue);
break;
}
}
}
// Find rotation. We have two cases, one where the highest bit is 0
// and one where it is 1.
// If it's 1, we just need to count the number of 1 bits on the MSB to find the right rotation.
// If it's 0, we just need to count the number of 0 bits on the LSB to find the left rotation,
// then we can convert it to the right rotation shift by subtracting the value from the element size.
int rotation;
long vHigh = (long)(value << (64 - selectedESize));
if (vHigh < 0)
{
rotation = BitOperations.LeadingZeroCount(~(ulong)vHigh);
}
else
{
rotation = (selectedESize - BitOperations.TrailingZeroCount(value)) & (selectedESize - 1);
}
// Reconstruct value and see if it matches. If not, we can't encode.
ulong reconstructed = onesCount == 64 ? ulong.MaxValue : RotateRight((1UL << onesCount) - 1, rotation, selectedESize);
for (int bit = 32; bit >= selectedESize; bit >>= 1)
{
reconstructed |= reconstructed << bit;
}
if (reconstructed != value || onesCount == 0)
{
immN = 0;
immS = 0;
immR = 0;
return false;
}
immR = rotation;
// immN indicates that there are no repetitions.
// The MSB of immS indicates the amount of repetitions, and the LSB the number of bits set.
if (repetitions == 1)
{
immN = 1;
immS = 0;
}
else
{
immN = 0;
immS = (0xf80 >> BitOperations.Log2((uint)repetitions)) & 0x3f;
}
immS |= onesCount - 1;
return true;
}
private static int CountSequence(ulong value)
{
return BitOperations.TrailingZeroCount(value) + BitOperations.TrailingZeroCount(~value);
}
private static ulong RotateRight(ulong bits, int shift, int size)
{
return (bits >> shift) | ((bits << (size - shift)) & (size == 64 ? ulong.MaxValue : (1UL << size) - 1));
}
}
}