In
computing
Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes, and development of both hardware and software. Computing has scientific, e ...
, jump threading is a
compiler optimization
In computing, an optimizing compiler is a compiler that tries to minimize or maximize some attributes of an executable computer program. Common requirements are to minimize a program's execution time, memory footprint, storage size, and power con ...
of one jump directly to a second jump. If the second condition is a subset or inverse of the first, it can be eliminated, or threaded through the first jump.
This is easily done in a single pass through the program, following acyclic chained jumps until the compiler arrives at a fixed point.
Example
The following
pseudocode
In computer science, pseudocode is a plain language description of the steps in an algorithm or another system. Pseudocode often uses structural conventions of a normal programming language, but is intended for human reading rather than machine re ...
demonstrates when a jump may be threaded.
10. a = SomeNumber();
20. IF a > 10 GOTO 50
...
50. IF a > 0 GOTO 100
...
The jump on line 50 will always be taken if the jump on line 20 is taken. Therefore, for as long as line 100 is within the reachable range of the jump (or the size of the jump doesn't matter), the jump on line 20 may safely be modified to jump directly to line 100.
See also
*
Switch (programming)
*
Spaghetti code
Spaghetti code is a pejorative phrase for unstructured and difficult-to- maintain source code. Spaghetti code can be caused by several factors, such as volatile project requirements, lack of programming style rules, and software engineers with ins ...
*
Branch displacement optimization
References
Compiler optimizations
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