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I can examine the optimization using profiler, size of the executable file and time to take for the execution.
I can get the result of the optimization. But I have these questions,
Thanks in advance.
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The degree to which the compiler will optimize the code it generates is controlled by the -O flag. No optimization. In the absence of any version of the -O flag, the compiler generates straightforward code with no instruction reordering or other attempt at performance improvement. -O or -O2.
Optimize Program Algorithm For any code, you should always allocate some time to think the right algorithm to use. So, the first task is to select and improve the algorithm which will be frequently used in the code. 2. Avoid Type Conversion Whenever possible, plan to use the same type of variables for processing.
you can get an idea of optimization using the option -fdump-tree-optimized with gcc .
and you'll get an optimised file. you cannot run the code but using that you can get an idea of optimization . dont forget to include -O2 or -O3 or some other level.
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Usually the code isn't optimized as C. Usually optimization passes are done long after the C has been converted into some form of intermediate representation that is easier for a compiler to work with in memory. Therefore, a direct answer to your question is that the optimized C code never exists.
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A C compiler does not usually produce optimized C at any stage. Rather, the compiler turns C into a simplified internal representation, and most compiler optimizations will be done on one or more of those intermediate representations. Then the compiler generates assembly or a binary from that.
The closest you can get is probably to compile a file to assembly with no optimization and again with highest optimization, and then compare the assembly output. You will have to have a good grasp of assembly language to do that. If you are using gcc, read about the -S and -O switches for how to do (or not do) this.
If your goal is to write faster code, then, your best bet is to write better C by using better algorithms and data structures at the C level by carefully using the profiler.
If your goal is just to understand optimization, try Program Optimization and Compiler Optimization on Wikipedia for some general information.
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