Hello everybody. I need some help with gcc optimizations and I don't know where I can get it. The objective of my work is to estimate how many machine instructions I can save in a program execution employing compiler optimizations. I am working with ARM architecture. Anyway, I have understood that main gcc optimizations are architecture-independent. In the gcc user's manual I have read that flags -O, -O1, -O2, -O3 and -Os activate different optimization flags (starting with "-f", I think), but not all of them are available individually. If I switch on all flags available individually for -O1 (-fdefer-pop, -fmerge-constants...) they have no effect in obtained machine code, but if I compile with -O1 option, there is a reduction of about 50% in machine instructions number with respect to basic compilation. With these results, I suppose that -O1 performs more actions that are not reported in any document I have found in The Internet. I have downloaded the gcc source-code but it is too difficult for me to understand it. My question is: where can I get full information about gcc optimizations and how they are performed? And another question: would be possible to get a benchmark or similar for compiler optimizations? That is, some set of programs that estimate the save that a compiler can achieve. I know it depends on the algotihms compiled, employed architecture and more (please, don't remember me that...). I just need an estimation. That would be great for my work. I hope your answer. Thank you very much. I really think you are developing a great job.
