integer n = UInt(Rn); integer t = UInt(Rt); boolean tagchecked = wback || n != 31; boolean wb_unknown = FALSE; Constraint c; if wback && n == t && n != 31 then c = ConstrainUnpredictable(Unpredictable_WBOVERLAPLD); assert c IN {Constraint_WBSUPPRESS, Constraint_UNKNOWN, Constraint_UNDEF, Constraint_NOP}; case c of when Constraint_WBSUPPRESS wback = FALSE; // writeback is suppressed when Constraint_UNKNOWN wb_unknown = TRUE; // writeback is UNKNOWN when Constraint_UNDEF UNDEFINED; when Constraint_NOP EndOfInstruction();

bits(64) address; bits(32) data; boolean privileged = PSTATE.EL != EL0; AccessDescriptor accdesc = CreateAccDescGPR(MemOp_LOAD, FALSE, privileged, tagchecked); if n == 31 then CheckSPAlignment(); address = SP[]; else address = X[n, 64]; if !postindex then address = GenerateAddress(address, offset, accdesc); data = Mem[address, 4, accdesc]; X[t, 64] = SignExtend(data, 64); if wback then if wb_unknown then address = bits(64) UNKNOWN; elsif postindex then address = GenerateAddress(address, offset, accdesc); if n == 31 then SP[] = address; else X[n, 64] = address;