Optimizing compiler:
*Compiler optimizing is a compiler that tries to minimize or maximize some attributes of an executable computer program.
*The requirements are to minimize a program's execution time, memory requirement,and power consumption.
* It has some code optimization problems are NP-complete, or even undecidable.
*We have types of Compiler optimizations are:
- Peephole optimizations
- local optimizations
- global optimizations
- Prescient store optimizations
- Loop optimizations
- Machine code optimizations
1.peephole optimiztions:
* The compilation process after machine code has been generated.
*A multiplication of a value by 2 might be more efficiently executed by left-shifting the value or by adding the value to itself
2.Local optimizations:
* Information local to a basic block.
* Basic blocks have no control flow, these optimizations need very little analysis.
3.Global optimizations:
*These are also called "intraprocedural methods" and act on whole functions
*This gives them more information to work with but often makes expensive computations necessary.
*Worst case assumptions have to be made when function calls occur or global variables are accessed
4.Prescient store optimizations
*The process needs some way of knowing ahead of time what value will be stored by the assignment.
* The purpose of this relaxation is to allow compiler optimization to perform certain kinds of code rearrangement that preserve the semantics of properly synchronized programs
5.Loop optimizations
*These act on the statements which make up a loop, such as a for loop.
*Loop optimizations can have a significant impact because many programs spend a large percentage of their time inside loops.
6.Machine code optimization:
*These analyze the executable task image of the program after all of an executable machine code has been linked.
*Some of the techniques that can be applied in a more limited scope, such as macro compression are more effective when the entire executable task image is available for analysis.
7. link-time optimization:
*These analyze all of a program's source code.
*The greater quantity of information extracted means that optimizations can be more effective compared to when they only have access to local information.
*This kind of optimization can also allow new techniques to be performed.
