People are perfectly capable of writing spaghetti code in structured programming languages (without goto) and such programs are always reducible in the sense of

People are perfectly capable of writing spaghetti code in structured programming languages (without goto) and such programs are always reducible in the sense of this article. Actually, I have a hunch that every program that is reducible in the standard compiler sense is also reducible in the sense of the article, but the converse does not hold. 1 -> 2 -> 3 -> 4, 1 -> 3 -> 2 is irreducible in the compiler sense (there is a loop with two entries) but reducible in the sense of the article (first merge 2 and 3, then delete self loop, an acyclic graph remains which is trivially reducible).