Undefined instruction fault in ARM64 assembly code

The UDF (Undefined Instruction) error in ARM64 occurs when the processor encounters an unrecognized or unsupported instruction. This error is deliberately triggered by the UDF opcode (0xD65F03C0) or invalid instruction encodings, causing a synchronous exception.

During development, the UDF instruction is often used to mark unreachable code or debug specific execution paths. However, it should not appear in production code, as it always halts execution and raises an exception. The exception is categorized as a data abort or instruction abort, depending on context, and the ESR_ELx (Exception Syndrome Register) identifies the cause.

How can developers ensure that the UDF instruction does not accidentally remain in production code? What tools or techniques can be used to detect and remove such instructions before deployment? Are there implementation-specific differences in how ARM64 processors (e.g., Cortex-A series, Apple M1/M2) handle the UDF instruction that could affect debugging or exception handling?