Re: spaghetti code (Preston Briggs)
Mon, 2 Mar 1992 18:58:30 GMT

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Newsgroups: comp.compilers
From: (Preston Briggs)
Keywords: optimize, analysis
Organization: Rice University, Houston
References: 92-03-005
Date: Mon, 2 Mar 1992 18:58:30 GMT (Aubrey de Grey) writes:

>but as far as I can see the problem of optimising spaghetti
>code as opposed to structured code is one of turning each procedure into a
>form where no pair of jumps (forward or backward) is linked. (A pair of
>jumps is linked when each jump encloses exactly one end of the other.)

No. "Linked loops" are no problem. They're just nested in a perhaps
non-intuitive fashion. The optimizer has no problem with them.
The only "problem" is irreducible loops (loops with more than one
entry) and they aren't that bad a problem since node-splitting can
always be applied.

>statement1; <-------
>label1; |
>statement2; <---- |
>label2; | |
>statement3; | |
>if condition1 then goto label1; >------
>statement4; |
>if condition2 then goto label2; >---

In this case, there's just a loop nest with 2 loops.
The outer nest includes statements 2, 3, and 4.
The inner loop includes statements 3 and 4.

Preston Briggs

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