Author: Gerd Isenberg
Date: 03:27:09 10/21/02
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On October 18, 2002 at 15:34:12, Bo Persson wrote: >On October 18, 2002 at 09:11:30, Gerd Isenberg wrote: > >>On October 17, 2002 at 19:29:30, Peter Fendrich wrote: >> >>>Is there any reason why 'protected' data should have better performance than >>>'public'? What could the compier do with this extra information? >>>Peter >> >>Hi Peter, >> >>access qualification has no impact on performance. Another thing are 'const' >>functions. The information that a function does not change anything inside this >>object permits the compiler to do additional optimizations, eg. holding data >>members in registers. >> >>Gerd > >No! > >The compiler can see for itself whether you change the data or not. If you >declare a member function const and then try to change the object anyway, the >compiler complains. Because it can tell! > > > > >Bo Persson >bop2@telia.com from AMD Athlon™ Processor x86 Code Optimization Guide: Chapter 3 C Source-Level Optimizations Use Const Type Qualifier Use the “const” type qualifier as much as possible. This optimization makes code more robust and may enable higher performance code to be generated due to the additional information available to the compiler. For example, the C standard allows compilers to not allocate storage for objects that are declared “const” if their address is never taken. Gerd
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