18C5T13 Lecture Notes - Lecture 4: Common Subexpression Elimination, Instruction Set, Loop Fission And Fusion

• School: Jawaharlal Nehru Technological University - JNTU Kakinada
• Department: Engineering
• Course: 18C5T13

Document Summary

Code optimization is required to produce an efficient target code. Elimination of unnecessary instructions in object code or the replacement of one sequence of instruction by a faster sequence of instructions that does the same thing is usually called code improvement or code optimization. In code optimization, we need to take care of the semantic equivalence of the source program. The improvement over the program efficiency must be achieved without changing the algorithm of the program. Code becomes inefficient because of two factors: such as, programmer & Code optimization can be performed in different phases of a compiler. In front end: programmer can make use of efficient algorithm. In icg phase: apply transformations on loops, procedure calls and address calculation. In code generation: use registers, select appropriate instructions and apply peephole optimization. Optimization is of two types such as, machine dependent optimization and machine independent optimization.