## Finite Constants: Characterizations of a New Decidable Set of
Constants

**Bernhard Steffen and Jens Knoop**
*Abstract:* *Constant propagation* - the replacement
of program terms which represent a unique value at run time by
their values - is a classical program optimization method. In spite
of being treated for years, constant propagation still has been in
the unsatisfactory phase of heuristics. We enhance the known
constant propagation techniques to obtain an algorithm which is
*optimal* for programs without loops. Fundamental is the
introduction of a new decidable set of constants, the *finite
constants*. This set has two different characterizations: a
denotational one, which directly specifies our iterative algorithm
and an operational one, which delivers the completeness or
optimality of this algorithm for programs without loops. The
algorithm is implemented in a commercial compiler project.

*ECS-LFCS-89-79*

This report is an extended version of a paper which appeared in
MFCS'89, Lecture Notes in Computer Science, Springer-Verlag,
1989.

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