Code Optimization

One of the Newton 2.x OS Q&As
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This document was exported on 7/23/97.

Code Optimization (9/15/93)

Q: Does the compiler in the Newton Toolkit reorder expressions or fold floating point constants? Can the order of evaluation be forced (as with ANSI C)?

A: The current version of the compiler doesn't do any serious optimization, such as eliminating subexpressions, or reordering functions; however, this may change in future products. (Note: NTK 1.6 added constant folding, so for example 2+3 will be replaced with 5 by the compiler.) In the meantime, you need to write your code as clearly as possible without relying too heavily on the ordering of functions inside expressions.

The current version of the NTK compiler dead-strips conditional statements from your application code if the boolean expression is a simple constant. This feature allows you to compile your code conditionally.

For example, if you define a kDebugMode constant in your project and have in your application a statement conditioned by the value of kDebugMode, the NTK compiler removes the entire if/then statement from your application code when the value of kDebugMode is NIL. 

constant kDebugMode := true;         // define in Project Data
if kDebugMode then Print(...);     // in application code


When you change the value of the kDebugMode constant to NIL, then the compiler strips out the entire if/then statement.