Rational Developer for System z
Enterprise PL/I for z/OS, Version 3.8, Programming Guide

OPTIMIZE

You can specify the OPTIMIZE option to improve the speed of your program; otherwise, the compiler makes only basic optimization efforts.

Choosing OPTIMIZE(2) directs the compiler to generate code for better performance. Usually, the resultant code is shorter than when the program is compiled under NOOPTIMIZE. Sometimes, however, a longer sequence of instructions runs faster than a shorter sequence. This occurs, for instance, when a branch table is created for a SELECT statement where the values in the WHEN clauses contain gaps. The increased number of instructions generated is usually offset by the execution of fewer instructions in other places.

Choosing OPTIMIZE(3) directs the compiler to generate even better code. However, when you specify the OPTIMIZE(3) option, the compilation will take longer (and sometimes much, much longer) than when you specify OPTIMIZE(2).


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