LDAPURSB Load-acquire RCpc register signed byte (unscaled) This instruction calculates an address from a base register and an immediate offset, loads a signed byte from memory, sign-extends it, and writes it to a register. The instruction has memory ordering semantics as described in Load-Acquire, Load-AcquirePC, and Store-Release, except that: There is no ordering requirement, separate from the requirements of a Load-AcquirePC or a Store-Release, created by having a Store-Release followed by a Load-AcquirePC instruction. The reading of a value written by a Store-Release by a Load-AcquirePC instruction by the same observer does not make the write of the Store-Release globally observed. This difference in memory ordering is not described in the pseudocode. For information about addressing modes, see Load/Store addressing modes. If PSTATE.DIT is 1, the timing of this instruction is insensitive to the value of the data being loaded or stored. 0 0 0 1 1 0 0 1 1 x 0 0 0 1 LDAPURSB <Wt>, [<Xn|SP>{, #<simm>}] 0 LDAPURSB <Xt>, [<Xn|SP>{, #<simm>}] if !IsFeatureImplemented(FEAT_LRCPC2) then UNDEFINED; constant bits(64) offset = SignExtend(imm9, 64); <Wt> Is the 32-bit name of the general-purpose register to be transferred, encoded in the "Rt" field. <Xn|SP> Is the 64-bit name of the general-purpose base register or stack pointer, encoded in the "Rn" field. <simm> Is the optional signed immediate byte offset, in the range -256 to 255, defaulting to 0 and encoded in the "imm9" field. <Xt> Is the 64-bit name of the general-purpose register to be transferred, encoded in the "Rt" field. constant integer t = UInt(Rt); constant integer n = UInt(Rn); constant integer datasize = 8; constant integer regsize = 64 >> UInt(opc<0>); constant boolean tagchecked = n != 31; bits(64) address; constant AccessDescriptor accdesc = CreateAccDescLDAcqPC(tagchecked); if n == 31 then CheckSPAlignment(); address = SP[]; else address = X[n, 64]; address = AddressAdd(address, offset, accdesc); constant bits(datasize) data = Mem[address, datasize DIV 8, accdesc]; X[t, regsize] = SignExtend(data, regsize);