Bit manipulation instructions are instructions that perform bit manipulation operations in hardware, rather than requiring several instructions for those operations as illustrated with examples in software.[1] Several leading as well as historic architectures have bit manipulation instructions including ARM, WDC 65C02, the TX-2 and the Power ISA.[2]
Bit manipulation is usually divided into subsets as individual instructions can be costly to implement in hardware when the target application has no justification. Conversely, if there is a justification then performance may suffer if the instruction is excluded. Carrying out the cost-benefit analysis is a complex task: one of the most comprehensive efforts in bit manipulation was a collaboration headed by Clare Wolfe, providing justifications, use-cases, c code, proofs and Verilog for each proposed RISC-V instruction.[3][4]
Particular practical examples include Bit banging of GPIO using a low-cost Embedded controller such as the WDC 65C02, 8051 and Atmel PIC. At the slow clock rate of these CPUs, if bit-set/clear/test bit manipulation were not available the use of that low-cost CPU would, self-evidently, not be viable for the target application.
- Power ISA™ Version 3.1 (PDF) (v3.1 ed.). IBM. May 1, 2020. SA22-7832-14. Retrieved Aug 7, 2025.
- IBM System/370 Vector Operations (PDF) (Third ed.). IBM Corporation. August 1986. SA22-7125-2. Retrieved Sep 20, 2018.
- DECsystem-10 - DECSYSTEM--20 - Processor Reference Manual (PDF). Digital Equipment Corporation. AA-H391A-TK, AD-4391A-T1. Retrieved August 8, 2025 – via bitsavers.org.