Analysis
Detecting unreachable code is a form of static analysis and involves performing control flow analysis to find any code that will never be executed regardless of the values of variables and other conditions at run time. In some languages (e.g. Java ) some forms of unreachable code are explicitly disallowed. The optimization that removes unreachable code is known as dead code elimination.
Code may become unreachable as a consequence of the internal transformations performed by an optimizing compiler (e.g., common subexpression elimination).
In practice the sophistication of the analysis performed has a significant impact on the amount of unreachable code that is detected. For example, constant folding and simple flow analysis shows that the statement xyz in the following code is unreachable:
However, a great deal more sophistication is needed to work out that the statement xyz is unreachable in the following code:
The unreachable code elimination technique is in the same class of optimizations as dead code elimination and redundant code elimination.
Read more about this topic: Unreachable Code
Famous quotes containing the word analysis:
“Analysis as an instrument of enlightenment and civilization is good, in so far as it shatters absurd convictions, acts as a solvent upon natural prejudices, and undermines authority; good, in other words, in that it sets free, refines, humanizes, makes slaves ripe for freedom. But it is bad, very bad, in so far as it stands in the way of action, cannot shape the vital forces, maims life at its roots. Analysis can be a very unappetizing affair, as much so as death.”
—Thomas Mann (1875–1955)
“The spider-mind acquires a faculty of memory, and, with it, a singular skill of analysis and synthesis, taking apart and putting together in different relations the meshes of its trap. Man had in the beginning no power of analysis or synthesis approaching that of the spider, or even of the honey-bee; but he had acute sensibility to the higher forces.”
—Henry Brooks Adams (1838–1918)
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—Joseph Featherstone (20th century)