RCWCLR, RCWCLRA, RCWCLRL, RCWCLRAL Read check write atomic bit clear on doubleword in memory This instruction atomically loads a 64-bit doubleword from memory, performs a bitwise AND with the complement of the value held in a register on it, and conditionally stores the result back to memory. Storing of the result back to memory is conditional on RCW 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. RCWCLRA and RCWCLRAL load from memory with acquire semantics. RCWCLRL and RCWCLRAL store to memory with release semantics. RCWCLR 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 0 1 1 1 0 0 0 1 1 0 0 1 0 0 0 0 RCWCLR <Xs>, <Xt>, [<Xn|SP>] 1 0 RCWCLRA <Xs>, <Xt>, [<Xn|SP>] 1 1 RCWCLRAL <Xs>, <Xt>, [<Xn|SP>] 0 1 RCWCLRL <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 = FALSE; 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_BIC, 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