Is a reducable flow graph necessary?

"Derek M. Jones" <>
14 Apr 2006 14:13:38 -0400

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Is a reducable flow graph necessary? (Derek M. Jones) (2006-04-14)
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From: "Derek M. Jones" <>
Newsgroups: comp.compilers
Date: 14 Apr 2006 14:13:38 -0400
Organization: ntl Cablemodem News Service
References: 06-04-097
Keywords: optimize
Posted-Date: 14 Apr 2006 14:13:38 EDT


One of the reasons given for why goto statements should
not be used is that their use can result in a function's
control flow graph being irreducible.

Irreducible? So what you say. Well some (many?) graph
transformation algorithms only work for reducible graphs.

Why do we need to perform graph transformations? Well, they
are used by various optimization and static analysis algorithms.

Why don't these algorithms use one of the iterative techniques
(which don't require reducible graphs)? Inertia, the courses they
were taught only used the graph transformation algorithms, ...

Does anybody know of an optimization/code analysis algorithm
that cannot be implemented using an iterative technique?

Are any of the graph transformation approaches significantly
better than the equivalent iterative technique (ie, in storage
space requirements or running time)?

It seems to me that for practical purposes iterative techniques
are as good anything else out there.

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