[fpc-devel] Class field reordering
Hi, I've implemented an optimization that reorders the instance fields of Delphi-style classes (and only of Delphi-style classes) to minimise memory gaps caused by alignment differences and odd sizes. The effect is the same as when you would change the order of the fields in the source code to achieve this effect. In general, I think this should be safe since unlike records and TP-style objects, a Delphi class is normally never blockwritten to disk or so. There is a switch to disable this transformation, but I'm wondering whether anyone sees a problem with enabling it by default when -O2 or higher is used. It works fine with at least the compiler and Lazarus without any ill effects, saving a small amount of memory for both (about 2.5MB on 87MB for the Darwin/x86-64 compiler compiling itslf, and 2.5MB on 62.7MB for a Carbon/i386 Lazarus right after startup and loading some source files). Jonas PS: a similar reordering could be performed for local variables, although the implementation would be quite different. Additionally, different kinds of reordering, e.g. targeting cache improvements by putting fields/local variables often used together next to each other, could also be implemented in the future. ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
[fpc-devel] Class field reordering
Hi, I've implemented an optimization that reorders the instance fields of Delphi-style classes (and only of Delphi-style classes) to minimise memory gaps caused by alignment differences and odd sizes. The effect is the same as when you would change the order of the fields in the source code to achieve this effect. In general, I think this should be safe since unlike records and TP-style objects, a Delphi class is normally never blockwritten to disk or so. There is a switch to disable this transformation, but I'm wondering whether anyone sees a problem with enabling it by default when -O2 or higher is used. It works fine with at least the compiler and Lazarus without any ill effects, saving a small amount of memory for both (about 2.5MB on 87MB for the Darwin/x86-64 compiler compiling itslf, and 2.5MB on 62.7MB for a Carbon/i386 Lazarus right after startup and loading some source files). Jonas PS: a similar reordering could be performed for local variables, although the implementation would be quite different. Additionally, different kinds of reordering, e.g. targeting cache improvements by putting fields/local variables often used together next to each other, could also be implemented in the future. ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] Class field reordering
On Jul 13, 2012, at 6:44 PM, Jonas Maebe jonas.ma...@elis.ugent.be wrote: Hi, I've implemented an optimization that reorders the instance fields of Delphi-style classes (and only of Delphi-style classes) to minimise memory gaps caused by alignment differences and odd sizes. The effect is the same as when you would change the order of the fields in the source code to achieve this effect. In general, I think this should be safe since unlike records and TP-style objects, a Delphi class is normally never blockwritten to disk or so. There is a switch to disable this transformation, but I'm wondering whether anyone sees a problem with enabling it by default when -O2 or higher is used. It works fine with at least the compiler and Lazarus without any ill effects, saving a small amount of memory for both (about 2.5MB on 87MB for the Darwin/x86-64 compiler compiling itslf, and 2.5MB on 62.7MB for a Carbon/i386 Lazarus right after startup and loading some source files). Jonas PS: a similar reordering could be performed for local variables, although the implementation would be quite different. Additionally, different kinds of reordering, e.g. targeting cache improvements by putting fields/local variables often used together next to each other, could also be implemented in the future. ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] Class field reordering
On Saturday 14 July 2012 01:44:39 Jonas Maebe wrote: Hi, I've implemented an optimization that reorders the instance fields of Delphi-style classes (and only of Delphi-style classes) to minimise memory gaps caused by alignment differences and odd sizes. The effect is the same as when you would change the order of the fields in the source code to achieve this effect. I sometimes need cracker classes in MSEide and MSEgui to fix bugs and make extensinsions for FCL classes in order to access private fields (examples TDataset, TParam, TField, TFiler, TReader, TWriter, TComponent). Is it guaranteed that the local definitions have the same layout as the definition in the FCL unit? Martin ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] Class field reordering
On Saturday 14 July 2012 07:50:58 Martin Schreiber wrote: On Saturday 14 July 2012 01:44:39 Jonas Maebe wrote: Hi, I've implemented an optimization that reorders the instance fields of Delphi-style classes (and only of Delphi-style classes) to minimise memory gaps caused by alignment differences and odd sizes. The effect is the same as when you would change the order of the fields in the source code to achieve this effect. I sometimes need cracker classes in MSEide and MSEgui to fix bugs and make extensinsions for FCL classes in order to access private fields (examples TDataset, TParam, TField, TFiler, TReader, TWriter, TComponent). Is it guaranteed that the local definitions have the same layout as the definition in the FCL unit? Hmm, up to now I listed in the cracker classes fields up to the last private field I need to access so the cracker classes would not brake by changing or adding successive fields in the original classes. I assume now it is necessary to always list all fields of the original class. Martin ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
