CPUs guarantee what they guarantee, and if they guarantee that a certain instruction takes an operand-independent time then it does. For example a RISC-V CPU i

CPUs guarantee what they guarantee, and if they guarantee that a certain instruction takes an operand-independent time then it does. For example a RISC-V CPU implementing the Zkt extension is required to implement a whole bunch of logical and arithmetic integer operations with operand-independent timing. This includes the two "branchless move" instructions from the Zicond extension, czero.eqz and czero.nez.