Peephole optimization is a type of Code Optimization performed on a small part of the code. It is performed on the very small set of instructions in a segment of code.
The small set of instructions or small part of code on which peephole optimization is performed is known as peephole or window.
It basically works on the theory of replacement in which a part of code is replaced by shorter and faster code without change in output.
Peephole is the machine dependent optimization.
Objectives of Peephole Optimization:
The objective of peephole optimization is:
- To improve performance
- To To reduce memory footprint
- To reduce code size
Peephole Optimization Techniques:
- Redundant load and store elimination:
In this technique the redundancy is eliminated.
Initial code: y = x + 5; i = y; z = i; w = z * 3; Optimized code: y = x + 5; i = y; w = y * 3;
- Constant folding:
The code that can be simplified by user itself, is simplified.
Initial code: x = 2 * 3; Optimized code: x = 6;
- Strength Reduction:
The operators that consume higher execution time are replaced by the operators consuming less execution time.
Initial code: y = x * 2; Optimized code: y = x + x; or y = x << 1; Initial code: y = x / 2; Optimized code: y = x >> 1;
- Null sequences:
Useless operations are deleted.
- Combine operations:
Several operations are replaced by a single equivalent operation.
- Compiler Design | Loop Optimization
- Compiler Design | Code Optimization
- Compiler Design | Introduction of Compiler design
- Compiler Design | Phases of a Compiler
- Compiler Design | Bootstrapping
- Compiler Design | Linker
- Compiler Design | Assembler
- Compiler Design | Why FIRST and FOLLOW?
- Compiler Design | Lexical Analysis
- Compiler Design | Classification of top down parsers
- Compiler Design | FIRST Set in Syntax Analysis
- Compiler Design | Runtime Environments
- Error Handling in Compiler Design
- Compiler Design | Input Buffering
- Labeling Algorithm in Compiler Design
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