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namespace ARMeilleure.Decoders
{
class OpCodeMemImm : OpCodeMem
{
public long Immediate { get; protected set; }
public bool WBack { get; protected set; }
public bool PostIdx { get; protected set; }
protected bool Unscaled { get; }
private enum MemOp
{
Unscaled = 0,
PostIndexed = 1,
Unprivileged = 2,
PreIndexed = 3,
Unsigned
}
public new static OpCode Create(InstDescriptor inst, ulong address, int opCode) => new OpCodeMemImm(inst, address, opCode);
public OpCodeMemImm(InstDescriptor inst, ulong address, int opCode) : base(inst, address, opCode)
{
Extend64 = ((opCode >> 22) & 3) == 2;
WBack = ((opCode >> 24) & 1) == 0;
// The type is not valid for the Unsigned Immediate 12-bits encoding,
// because the bits 11:10 are used for the larger Immediate offset.
MemOp type = WBack ? (MemOp)((opCode >> 10) & 3) : MemOp.Unsigned;
PostIdx = type == MemOp.PostIndexed;
Unscaled = type == MemOp.Unscaled ||
type == MemOp.Unprivileged;
// Unscaled and Unprivileged doesn't write back,
// but they do use the 9-bits Signed Immediate.
if (Unscaled)
{
WBack = false;
}
if (WBack || Unscaled)
{
// 9-bits Signed Immediate.
Immediate = (opCode << 11) >> 23;
}
else
{
// 12-bits Unsigned Immediate.
Immediate = ((opCode >> 10) & 0xfff) << Size;
}
}
}
}
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