RCWSSWP, RCWSSWPA, RCWSSWPL, RCWSSWPAL Read check write software swap doubleword in memory This instruction atomically loads a 64-bit doubleword from a memory location, and conditionally stores the value held in a register back to the same memory location. Storing back to memory is conditional on RCW Checks and RCWS Checks. The value initially loaded from memory is returned in the destination register. This instruction updates the condition flags based on the result of the update of memory. RCWSSWPA and RCWSSWPAL load from memory with acquire semantics. RCWSSWPL and RCWSSWPAL store to memory with release semantics. RCWSSWP has neither acquire nor release semantics. If PSTATE.DIT is 1, the timing of this instruction is insensitive to the value of the data being loaded or stored. 0 1 1 1 1 0 0 0 1 1 0 1 0 0 0 0 0 RCWSSWP <Xs>, <Xt>, [<Xn|SP>] 1 0 RCWSSWPA <Xs>, <Xt>, [<Xn|SP>] 1 1 RCWSSWPAL <Xs>, <Xt>, [<Xn|SP>] 0 1 RCWSSWPL <Xs>, <Xt>, [<Xn|SP>] if !IsFeatureImplemented(FEAT_THE) then UNDEFINED; constant integer s = UInt(Rs); constant integer t = UInt(Rt); constant integer n = UInt(Rn); constant boolean soft = TRUE; constant boolean acquire = A == '1' && Rt != '11111'; constant boolean release = R == '1'; constant boolean tagchecked = n != 31; <Xs> Is the 64-bit name of the general-purpose register to be stored, encoded in the "Rs" field. <Xt> Is the 64-bit name of the general-purpose register to be loaded, 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. if IsD128Enabled(PSTATE.EL) then UNDEFINED; bits(64) address; constant bits(64) newdata = X[s, 64]; bits(64) readdata; bits(4) nzcv; constant AccessDescriptor accdesc = CreateAccDescRCW(MemAtomicOp_SWP, soft, acquire, release, tagchecked); if n == 31 then CheckSPAlignment(); address = SP[]; else address = X[n, 64]; constant bits(64) compdata = bits(64) UNKNOWN; // Irrelevant when not executing CAS (nzcv, readdata) = MemAtomicRCW(address, compdata, newdata, accdesc); PSTATE.<N,Z,C,V> = nzcv; X[t, 64] = readdata; // Return the old value when t!=31