GNU Arm Embedded Toolchain

-fpromote-loop-indices not valid?

Asked by Moses McKnight

I just found this project linked from onARM.com

I've been using CodeSourcery lite and have used the option -fpromote-loop-indices for optimization. When I try to compile my project with arm-none-eabi-gcc-4_6-20111208 from this site it says that is not a valid option.

I can compile my project if I remove this option, but it does result in slightly more program memory usage than the same project compiled with CodeSourcery GCC Lite.

Is there an alternative to this that I can use?

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Joey Ye (jinyun-ye) said : 		#1

Moses,

Thanks for trying GNU Tools for ARM Embedded Processors and your question. This project is based on GCC trunk and official release branches. The option -fpromote-loop-indices wasn't accepted by GCC trunk or 4.6 offical release branch, so it is not a valide option in this project or GCC trunk/4.6 branch. I don't know alternative option to this so far.

Nevertheless, we are continously improving trunk and this branch. We hope other optimizations can improve your project's memory usage. It will be great if possible, you can share a small program demostrate the memory usage problem so that we can analyze and optimize in future?

Thanks - Joey

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Jiangning Liu (liujiangning) said : 		#2

Moses,

Actually the optimization implemented by this option should have been solved in GCC >=4.6 by alternative solution, i.e. the improvement in scalar evolution pass. Therefore this release needn't command line option -fpromote-loop-indices any longer.

Do you still any special case exposing the same problem with this release? If yes, could you help to post the cases you have, so we can look into for solutions. Anyway, this option(optimization) itself shouldn't increase program memory usage.

However, I'm assuming your question has nothing to do with this command line option at all and your point should be the memory usage of binaries generated by this compiler release may be a little bit high for some cases. Technically speaking, it is possible, but it is still case by case.

It would be great if you can provide us any real examples here.

Thanks,
-Jiangning

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