Compiler level optimization

How code optimization is achieved in compiler design?
The key areas of code optimization in compiler design are instruction scheduling, register allocation, loop unrolling, dead code elimination, constant propagation, and function inlining.
These techniques aim to make code faster, more efficient, and smaller while preserving its functionality..
How does GCC optimization work?
The compiler optimizes to reduce the size of the binary instead of execution speed.
If you do not specify an optimization option, gcc attempts to reduce the compilation time and to make debugging always yield the result expected from reading the source code..
How is code optimized?
We say that code optimization is writing or rewriting code so a program uses the least possible memory or disk space, minimizes its CPU time or network bandwidth, or makes the best use of additional cores.
In practice, we sometimes default to another definition: Writing less code..
Why do we need code optimization?
Code optimization is essential to enhance the execution and efficiency of a source code.
It is mandatory to deliver efficient target code by lowering the number of instructions in a program..
Machine-Independent Optimization Techniques:
Compile Time Evaluation.
Common Subexpression Elimination.
Variable Propagation.
Dead Code Elimination.
Optimization level -O0
-O0 disables all optimizations.
This optimization level is the default.
Using -O0 results in a faster compilation and build time, but produces slower code than the other optimization levels.
Code size and stack usage are significantly higher at -O0 than at other optimization levels.
Optimization level -Os
-Os aims to provide high performance without a significant increase in code size.
Depending on your application, the performance provided by -Os might be similar to -O2 or -O3 . -Os provides code size reduction compared to -O3 .
So, for optimization, such code or dead code is eliminated.
The code which is never executed during the program (Dead code) takes time so, for optimization and speed, it is eliminated from the code.
Eliminating the dead code increases the speed of the program as the compiler does not have to translate the dead code.

The degree to which the compiler will optimize the code it generates is controlled by the -O flag. 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.

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

Turning on optimization makes the compiler attempt to improve the performance and/or code size at the expense of compilation time and possibly the ability to debug the program. If you use multiple -O options, with or without level numbers, the last such option is the one that is effective.

Compiler level optimization

How code optimization is achieved in compiler design?

How does GCC optimization work?

How is code optimized?

Why do we need code optimization?