1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
|
using System.Numerics;
namespace Ryujinx.Cpu.LightningJit.CodeGen.Arm64
{
static class CodeGenCommon
{
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 &= uint.MaxValue;
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;
}
}
}
|
