A computer program consists of a sequence of instructions. In the simplest case, these instructions are carried out in order, one by one, starting with the first. When a branch instruction is encountered, however, the sequence is broken: execution jumps to either an earlier or a later part of the code. Branches may be unconditional ("always jump from here to line X") or conditional ("jump from here to line X only if condition Y holds").

Branching is a necessary feature of computer code. However, it can come into conflict with the technique called pipelining, which is used in modern processors to accelerate code execution. Pipelining simply means getting several instructions (perhaps as many as 5 or 10) executing all at once, rather than waiting to finish each instruction before commencing the next. This can be done because each assembly-level instruction actually consists of a whole series of hardware-level...