SlideShare a Scribd company logo

code optimization

Download as PPT, PDF
G
guest9f8315

This document discusses various techniques for code optimization at the compiler level. It begins by defining code optimization and explaining that it aims to make a program more efficient by reducing resources like time and memory usage. Several common optimization techniques are then described, including common subexpression elimination, dead code elimination, and loop optimization. Common subexpression elimination removes redundant computations. Dead code elimination removes code that does not affect program output. Loop optimization techniques like removing loop invariants and induction variables can improve loop performance. The document provides examples to illustrate how each technique works.

EducationTechnology
1 of 46
Downloaded 55 times
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
CODE OPTIMIZATION Presented By: Amita das Jayanti bhattacharya Jaistha Upadhyay
Design Of a Compiler Lexical Analysis Syntax Analysis Intermediate Code Generation Code Generation Code Optimization Table Mgmt Routine Error Handling Routine Source code Object code
What is optimization? In computing, optimization is the process of modifying a system to make some aspect of it work more efficiently or use fewer resources. For instance, a computer program may be optimized so that it executes more rapidly, or is capable of operating with less memory storage or other resources, or draw less power. The system may be a single computer program, a collection of computers or even an entire network such as the internet.
 
Levels' of optimization Optimization can occur at a number of 'levels': Design level At the highest level, the design may be optimized to make best use of the available resources. The implementation of this design will benefit from the use of suitable efficient algorithms and the implementation of these algorithms will benefit from writing good quality code. The architectural design of a system overwhelmingly affects its performance. The choice of algorithm affects efficiency more than any other item of the design. Compile level Use of an optimizing compiler tends to ensure that the executable program is optimized at least as much as the compiler can predict.
Assembly level At the lowest level, writing code using an Assembly language designed for a particular hardware platform will normally produce the most efficient code since the programmer can take advantage of the full repertoire of machine instructions. The operating systems of most machines has been traditionally written in Assembler code for this reason. Runtime Just In Time Compiler and assembler programmers are able to perform runtime optimization.
When to optimize ? Optimization is often performed at the end of the development stage since it reduces readability adds code that is used to improve the performance.
Criteria For optimization An optimization must preserve the meaning of a program : Cannot change the output produced for any input -Can not introduce an error optimization should, on average, speed up programs Transformation should be worth the effort
Improvements can be made at various phases: Source Code : -Algorithms transformations can produce spectacular improvements -Profiling can be helpful to focus a programmer’s attention on important code. Intermediate Code: -Compiler can improve loops, procedure calls and address calculations -Typically only optimizing compilers include this phase Target Code: Compilers can use registers efficiently Peephole transformation can be applied
Types of Code optimization Common Sub-expression Removal Dead Code Optimization Loop Optimization
Common Sub expression elimination Common Sub expression elimination is a optimization that searches for instances of identical expressions (i.e they all evaluate the same value), and analyses whether it is worthwhile replacing with a single variable holding the computed value. a=b * c + g d=b * c * d temp=b * c a=temp + g d=temp * d
Dead Code elimination is a compiler optimization that removes code that does not affect a program. Removing such code has two benefits It shrinks program size, an important consideration in some contexts. It lets the running program avoid executing irrelevant operations, which reduces its running time. Dead Code elimination is of two types Unreachable Code Redundant statement Dead code Optimization:
Unreachable Code In Computer Programming, Unreachable Code or dead code is code that exists in the source code of a program but can never be executed. Program Code If (a>b) m=a elseif (a<b) m=b elseif (a==b) m=0 else m=-1 Optimized Code If (a>b) m=a elseif (a<b) m=b else m=0
Redundant Code Redundant Code is code that is executed but has no effect on the output from a program main(){ int a,b,c,r; a=5; b=6; c=a + b; r=2; r++; printf(“%d”,c); } Adding time & space complexity
Loop optimization Loop optimization plays an important role in improving the performance of the source code by reducing overheads associated with executing loops. Loop Optimization can be done by removing: Loop invariant Induction variables
Loop Invariant i = 1 s= 0 do{ s= s + i a =5 i = i + 1 { while (i < =n) i = 1 s= 0 a =5 do{ s= s + i i = i + 1 { while (i < =n) Bringing a=5 outside the do while loop, is called code motion.
Induction variables i = 1 s= 0 S1=0 S2=0 while (i < =n) { s= s + a[ i ] t1 = i * 4 s= s + b[ t1 ] t2 = t1 +2 s2= s2 + c[ t2 ] i = i + 1 } i = 1 s= 0 S1=0 S2=0 t2=0 while (i < =n) { s= s + a[ i ] t1 = t1+ 4 s= s + b[ t1 ] s2= s2 + c[t1 +2 ] i = i + 1 } t1,t2 are induction variables. i is inducing t1 and t1 is inducing t2 “ +” replaced “ * ”, t1 was made independent of i
 
 
 
 
Common Sub-expression Removal It is used to remove redundant computations which usually improves the execution time of a program.
 
 
 
 
 
 
Three Address Code of Quick Sort i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto (5) j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto (9) if i >= j goto (23) t 6 = 4 * i x = a[t 6 ] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 t 7 = 4 * I t 8 = 4 * j t 9 = a[t 8 ] a[t 7 ] = t 9 t 10 = 4 * j a[t 10 ] = x goto (5) t 11 = 4 * I x = a[t 11 ] t 12 = 4 * i t 13 = 4 * n t 14 = a[t 13 ] a[t 12 ] = t 14 t 15 = 4 * n a[t 15 ] = x 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Find The Basic Block i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto (5) j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto (9) if i >= j goto (23) t 6 = 4 * i x = a[t 6 ] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 t 7 = 4 * I t 8 = 4 * j t 9 = a[t 8 ] a[t 7 ] = t 9 t 10 = 4 * j a[t 10 ] = x goto (5) t 11 = 4 * i x = a[t 11 ] t 12 = 4 * i t 13 = 4 * n t 14 = a[t 13 ] a[t 12 ] = t 14 t 15 = 4 * n a[t 15 ] = x 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Flow Graph if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 t 6 = 4 * i x = a[t 6 ] t 7 = 4 * i t 8 = 4 * j t 9 = a[t 8 ] a[t 7 ] = t 9 t 10 = 4 * j a[t 10 ] = x goto B 2 t 11 = 4 * i x = a[t 11 ] t 12 = 4 * i t 13 = 4 * n t 14 = a[t 13 ] a[t 12 ] = t 14 t 15 = 4 * n a[t 15 ] = x B 1 B 2 B 3 B 4 B 5 B 6
Common Subexpression Elimination if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 t 6 = 4 * i x = a[t 6 ] t 7 = 4 * i t 8 = 4 * j t 9 = a[t 8 ] a[t 7 ] = t 9 t 10 = 4 * j a[t 10 ] = x goto B 2 t 11 = 4 * i x = a[t 11 ] t 12 = 4 * i t 13 = 4 * n t 14 = a[t 13 ] a[t 12 ] = t 14 t 15 = 4 * n a[t 15 ] = x B 1 B 2 B 3 B 4 B 5 B 6
Common Subexpression Elimination if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 t 6 = 4 * i x = a[t 6 ] t 8 = 4 * j t 9 = a[t 8 ] a[ t 6 ] = t 9 t 10 = 4 * j a[t 10 ] = x goto B 2 t 11 = 4 * i x = a[t 11 ] t 12 = 4 * i t 13 = 4 * n t 14 = a[t 13 ] a[t 12 ] = t 14 t 15 = 4 * n a[t 15 ] = x B 1 B 2 B 3 B 4 B 5 B 6
Common Subexpression Elimination if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 t 6 = 4 * i x = a[t 6 ] t 8 = 4 * j t 9 = a[t 8 ] a[ t 6 ] = t 9 a[ t 8 ] = x goto B 2 t 11 = 4 *i x = a[t 11 ] t 12 = 4 * i t 13 = 4 * n t 14 = a[t 13 ] a[t 12 ] = t 14 t 15 = 4 * n a[t 15 ] = x B 1 B 2 B 3 B 4 B 5 B 6
Common Subexpression Elimination if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 t 6 = 4 * i x = a[t 6 ] t 8 = 4 * j t 9 = a[t 8 ] a[ t 6 ] = t 9 a[ t 8 ] = x goto B 2 t 11 = 4 * i x = a[t 11 ] t 12 = 4 * i t 13 = 4 * n t 14 = a[t 13 ] a[t 12 ] = t 14 t 15 = 4 * n a[t 15 ] = x B 1 B 2 B 3 B 4 B 5 B 6
Common Subexpression Elimination if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 t 6 = 4 * i x = a[t 6 ] t 8 = 4 * j t 9 = a[t 8 ] a[ t 6 ] = t 9 a[ t 8 ] = x goto B 2 t 11 = 4 * i x = a[t 11 ] t 13 = 4 * n t 14 = a[t 13 ] a[ t 11 ] = t 14 t 15 = 4 * n a[t 15 ] = x B 1 B 2 B 3 B 4 B 5 B 6
Common Subexpression Elimination if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 t 6 = 4 * i x = a[t 6 ] t 8 = 4 * j t 9 = a[t 8 ] a[ t 6 ] = t 9 a[ t 8 ] = x goto B 2 t 11 = 4 * i x = a[t 11 ] t 13 = 4 * n t 14 = a[t 13 ] a[ t 11 ] = t 14 a[ t 13 ] = x B 1 B 2 B 3 B 4 B 5 B 6
Common Subexpression Elimination if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 t 6 = 4 * i x = a[t 6 ] t 8 = 4 * j t 9 = a[t 8 ] a[ t 6 ] = t 9 a[ t 8 ] = x goto B 2 t 11 = 4 * i x = a[t 11 ] t 13 = 4 * n t 14 = a[t 13 ] a[ t 11 ] = t 14 a[ t 13 ] = x B 1 B 2 B 3 B 4 B 5 B 6
Common Subexpression Elimination if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 x = a[ t 2 ] t 8 = 4 * j t 9 = a[t 8 ] a[ t 2 ] = t 9 a[ t 8 ] = x goto B 2 t 11 = 4 * i x = a[t 11 ] t 13 = 4 * n t 14 = a[t 13 ] a[ t 11 ] = t 14 a[ t 13 ] = x B 1 B 2 B 3 B 4 B 5 B 6
Common Subexpression Elimination if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 x = t 3 t 8 = 4 * j t 9 = a[t 8 ] a[ t 2 ] = t 9 a[ t 8 ] = x goto B 2 t 11 = 4 * i x = a[t 11 ] t 13 = 4 * n t 14 = a[t 13 ] a[ t 11 ] = t 14 a[ t 13 ] = x B 1 B 2 B 3 B 4 B 5 B 6
Common Subexpression Elimination if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 x = t 3 a[ t 2 ] = t 5 a[ t 4 ] = x goto B 2 t 11 = 4 * i x = a[t 11 ] t 13 = 4 * n t 14 = a[t 13 ] a[ t 11 ] = t 14 a[ t 13 ] = x B 1 B 2 B 3 B 4 B 5 B 6
Common Subexpression Elimination if i >= j goto B 6 Similarly for B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 x = t 3 a[ t 2 ] = t 5 a[ t 4 ] = x goto B 2 x = t 3 t 14 = a[t 1 ] a[ t 2 ] = t 14 a[ t 1 ] = x B 1 B 2 B 3 B 4 B 5 B 6
Dead Code Elimination if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 x = t 3 a[ t 2 ] = t 5 a[ t 4 ] = x goto B 2 x = t 3 t 14 = a[t 1 ] a[ t 2 ] = t 14 a[ t 1 ] = x B 1 B 2 B 3 B 4 B 5 B 6
Dead Code Elimination if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 a[ t 2 ] = t 5 a[ t 4 ] = t 3 goto B 2 t 14 = a[t 1 ] a[ t 2 ] = t 14 a[ t 1 ] = t 3 B 1 B 2 B 3 B 4 B 5 B 6
Reduction in Strength if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 a[ t 2 ] = t 5 a[ t 4 ] = t 3 goto B 2 t 14 = a[t 1 ] a[ t 2 ] = t 14 a[ t 1 ] = t 3 B 1 B 2 B 3 B 4 B 5 B 6
Reduction in Strength if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] t 2 = 4 * i t 4 = 4 * j t 2 = t 2 + 4 t 3 = a[t 2 ] if t 3 < v goto B 2 t 4 = t 4 - 4 t 5 = a[t 4 ] if t 5 > v goto B 3 a[ t 2 ] = t 5 a[ t 4 ] = t 3 goto B 2 t 14 = a[t 1 ] a[ t 2 ] = t 14 a[ t 1 ] = t 3 B 1 B 2 B 3 B 4 B 5 B 6

More Related Content

PPT
Code Optimization
guest9f8315
 
PPT
code optimization 1...code optimization-1221849738688969-9
Sanjeev Raaz
 
PDF
طراحی الگوریتم فصل 1
Saeed Sarshar
 
PDF
number-theory
ครูนิก อดิศักดิ์
 
PDF
Real problem2 p
Thanuphong Ngoapm
 
PDF
Results after modifying errors
MaRwa Hamed
 
PDF
Function problem p
Thanuphong Ngoapm
 
DOC
Hw3 abdo khalaf
Abdo Khalaf
 
Code Optimization
guest9f8315
 
code optimization 1...code optimization-1221849738688969-9
Sanjeev Raaz
 
طراحی الگوریتم فصل 1
Saeed Sarshar
 
number-theory
ครูนิก อดิศักดิ์
 
Real problem2 p
Thanuphong Ngoapm
 
Results after modifying errors
MaRwa Hamed
 
Function problem p
Thanuphong Ngoapm
 
Hw3 abdo khalaf
Abdo Khalaf
 

What's hot (12)

PDF
3人ゲームの混合戦略ナッシュ均衡を求める ゲーム理論 BASIC 演習1の補足
ssusere0a682
 
PDF
ข้อสอบ Pat 1 + เฉลย
AunJan
 
PDF
ゲーム理論BASIC 演習37 -3人ゲームの混合戦略ナッシュ均衡を求める-
ssusere0a682
 
DOCX
Hw solution 5
Abdo Khalaf
 
PDF
Key pat1 3-52 math
Arisara Fungthanakul
 
DOC
Niem khuccuoi kyam
1bidvn1616
 
PDF
matrices
ครูนิก อดิศักดิ์
 
PDF
Change of subject
Josephine Thong
 
PDF
7 วิชา คณิต the brain
Jamescoolboy
 
PDF
Sistemas de comunicacion 4ta edicion - bruce a. carlson solutions manual
luis hernando rodriguez montenegro
 
PDF
communication-systems-4th-edition-2002-carlson-solution-manual
amirhosseinozgoli
 
ODP
Dominator tree
sean chen
 
3人ゲームの混合戦略ナッシュ均衡を求める ゲーム理論 BASIC 演習1の補足
ssusere0a682
 
ข้อสอบ Pat 1 + เฉลย
AunJan
 
ゲーム理論BASIC 演習37 -3人ゲームの混合戦略ナッシュ均衡を求める-
ssusere0a682
 
Hw solution 5
Abdo Khalaf
 
Key pat1 3-52 math
Arisara Fungthanakul
 
Niem khuccuoi kyam
1bidvn1616
 
matrices
ครูนิก อดิศักดิ์
 
Change of subject
Josephine Thong
 
7 วิชา คณิต the brain
Jamescoolboy
 
Sistemas de comunicacion 4ta edicion - bruce a. carlson solutions manual
luis hernando rodriguez montenegro
 
communication-systems-4th-edition-2002-carlson-solution-manual
amirhosseinozgoli
 
Dominator tree
sean chen
 
Ad

Similar to code optimization (20)

PPT
code optimization
Sanjeev Raaz
 
PPT
457418.-Compiler-Design-Code-optimization.ppt
Incredible20
 
PDF
System dynamics 3rd edition palm solutions manual
SextonMales
 
PDF
Solutions manual for business math 10th edition by cleaves
CooKi5472
 
PDF
ブロックチェーン: 「 書き換え不可能な記録」によって 社会はどう変化するか?
Yoshiharu Ikutani
 
PPTX
Integral calculus
Santhanam Krishnan
 
PPT
Lec38
Nikhil Chilwant
 
PDF
Metodologia de la programación - expresiones
Mar_Angeles
 
PDF
Vector_2_lyst174817261564123456789273.pdf
bachubhavish07
 
PPTX
Compiler Optimization Presentation
19magnet
 
DOCX
Solución guía n°1 operaciones combinadas
Francisco Gaete Garrido
 
PDF
kintone university 03-1. AD+カスタマイズ入門第6版 サンプル
Yudai Shibuya
 
PDF
HIDRAULICA DE CANALES
Dennis Ventura Huaman
 
PDF
Boas mathematical methods in the physical sciences 3ed instructors solutions...
Praveen Prashant
 
PDF
Complete solutions-mathematical-methods-in-the-physical-sciences-3rd-edition
Aba Dula
 
PPTX
Arrays in c
CGC Technical campus,Mohali
 
DOCX
Math worksheet4
Ric Dagdagan
 
PDF
AtCoder Regular Contest 038 解説
AtCoder Inc.
 
PPTX
Lecture 12 data structures and algorithms
Aakash deep Singhal
 
PPT
Matematicas iv.
gabyjab
 
code optimization
Sanjeev Raaz
 
457418.-Compiler-Design-Code-optimization.ppt
Incredible20
 
System dynamics 3rd edition palm solutions manual
SextonMales
 
Solutions manual for business math 10th edition by cleaves
CooKi5472
 
ブロックチェーン: 「 書き換え不可能な記録」によって 社会はどう変化するか?
Yoshiharu Ikutani
 
Integral calculus
Santhanam Krishnan
 
Lec38
Nikhil Chilwant
 
Metodologia de la programación - expresiones
Mar_Angeles
 
Vector_2_lyst174817261564123456789273.pdf
bachubhavish07
 
Compiler Optimization Presentation
19magnet
 
Solución guía n°1 operaciones combinadas
Francisco Gaete Garrido
 
kintone university 03-1. AD+カスタマイズ入門第6版 サンプル
Yudai Shibuya
 
HIDRAULICA DE CANALES
Dennis Ventura Huaman
 
Boas mathematical methods in the physical sciences 3ed instructors solutions...
Praveen Prashant
 
Complete solutions-mathematical-methods-in-the-physical-sciences-3rd-edition
Aba Dula
 
Arrays in c
CGC Technical campus,Mohali
 
Math worksheet4
Ric Dagdagan
 
AtCoder Regular Contest 038 解説
AtCoder Inc.
 
Lecture 12 data structures and algorithms
Aakash deep Singhal
 
Matematicas iv.
gabyjab
 
Ad

Recently uploaded (20)

PDF
The Lost Whites of Pakistan by Jahanzaib Mughal.pdf
jahanzaibmughal6
 
PPTX
IMMUNITY IMMUNITY refers to protection against infection, and the immune syst...
shilpa939953
 
PDF
Anesthesia in Laparoscopic Surgery in India
mohitsuren827
 
PDF
Chinmaya Tiranga quiz Grand Finale.pdf
Nitin Suresh
 
PDF
Complications of Minimal Access Surgery at WLH
mohitsuren827
 
PDF
ANTIBIOTICS.pptx.pdf………………… xxxxxxxxxxxxx
HakHe
 
PPTX
master seminar digital applications in india
ananyaray35
 
PDF
FourierSeries-QuestionsWithAnswers(Part-A).pdf
Raji Murugan
 
PDF
Black Hat USA 2025 - Micro ICS Summit - ICS/OT Threat Landscape
Chris Sistrunk
 
PPTX
school management -TNTEU- B.Ed., Semester II Unit 1.pptx
NihumathunnisaH
 
PDF
Supply Chain Operations Speaking Notes -ICLT Program
labyankof
 
PPTX
Lesson notes of climatology university.
sgladness67
 
PDF
Classroom Observation Tools for Teachers
Nicaramirez
 
PPTX
Final Presentation General Medicine 03-08-2024.pptx
ZaheerAhmad228692
 
PPTX
GDM (1) (1).pptx small presentation for students
shrawanbpkihs
 
PDF
Chapter 2 Heredity, Prenatal Development, and Birth.pdf
MarjorieLopezTiu
 
PPTX
PPT- ENG7_QUARTER1_LESSON1_WEEK1. IMAGERY -DESCRIPTIONS pptx.pptx
KMDee
 
PPTX
Cell Structure & Organelles in detailed.
DHANASHREESIVAKUMAR
 
PDF
OBE - B.A.(HON'S) IN INTERIOR ARCHITECTURE -Ar.MOHIUDDIN.pdf
ArchitectAFMMohiuddi
 
PDF
Saundersa Comprehensive Review for the NCLEX-RN Examination.pdf
sreejithcareers
 
The Lost Whites of Pakistan by Jahanzaib Mughal.pdf
jahanzaibmughal6
 
IMMUNITY IMMUNITY refers to protection against infection, and the immune syst...
shilpa939953
 
Anesthesia in Laparoscopic Surgery in India
mohitsuren827
 
Chinmaya Tiranga quiz Grand Finale.pdf
Nitin Suresh
 
Complications of Minimal Access Surgery at WLH
mohitsuren827
 
ANTIBIOTICS.pptx.pdf………………… xxxxxxxxxxxxx
HakHe
 
master seminar digital applications in india
ananyaray35
 
FourierSeries-QuestionsWithAnswers(Part-A).pdf
Raji Murugan
 
Black Hat USA 2025 - Micro ICS Summit - ICS/OT Threat Landscape
Chris Sistrunk
 
school management -TNTEU- B.Ed., Semester II Unit 1.pptx
NihumathunnisaH
 
Supply Chain Operations Speaking Notes -ICLT Program
labyankof
 
Lesson notes of climatology university.
sgladness67
 
Classroom Observation Tools for Teachers
Nicaramirez
 
Final Presentation General Medicine 03-08-2024.pptx
ZaheerAhmad228692
 
GDM (1) (1).pptx small presentation for students
shrawanbpkihs
 
Chapter 2 Heredity, Prenatal Development, and Birth.pdf
MarjorieLopezTiu
 
PPT- ENG7_QUARTER1_LESSON1_WEEK1. IMAGERY -DESCRIPTIONS pptx.pptx
KMDee
 
Cell Structure & Organelles in detailed.
DHANASHREESIVAKUMAR
 
OBE - B.A.(HON'S) IN INTERIOR ARCHITECTURE -Ar.MOHIUDDIN.pdf
ArchitectAFMMohiuddi
 
Saundersa Comprehensive Review for the NCLEX-RN Examination.pdf
sreejithcareers
 

code optimization

  • 1. CODE OPTIMIZATION Presented By: Amita das Jayanti bhattacharya Jaistha Upadhyay
  • 2. Design Of a Compiler Lexical Analysis Syntax Analysis Intermediate Code Generation Code Generation Code Optimization Table Mgmt Routine Error Handling Routine Source code Object code
  • 3. What is optimization? In computing, optimization is the process of modifying a system to make some aspect of it work more efficiently or use fewer resources. For instance, a computer program may be optimized so that it executes more rapidly, or is capable of operating with less memory storage or other resources, or draw less power. The system may be a single computer program, a collection of computers or even an entire network such as the internet.
  • 4.  
  • 5. Levels' of optimization Optimization can occur at a number of 'levels': Design level At the highest level, the design may be optimized to make best use of the available resources. The implementation of this design will benefit from the use of suitable efficient algorithms and the implementation of these algorithms will benefit from writing good quality code. The architectural design of a system overwhelmingly affects its performance. The choice of algorithm affects efficiency more than any other item of the design. Compile level Use of an optimizing compiler tends to ensure that the executable program is optimized at least as much as the compiler can predict.
  • 6. Assembly level At the lowest level, writing code using an Assembly language designed for a particular hardware platform will normally produce the most efficient code since the programmer can take advantage of the full repertoire of machine instructions. The operating systems of most machines has been traditionally written in Assembler code for this reason. Runtime Just In Time Compiler and assembler programmers are able to perform runtime optimization.
  • 7. When to optimize ? Optimization is often performed at the end of the development stage since it reduces readability adds code that is used to improve the performance.
  • 8. Criteria For optimization An optimization must preserve the meaning of a program : Cannot change the output produced for any input -Can not introduce an error optimization should, on average, speed up programs Transformation should be worth the effort
  • 9. Improvements can be made at various phases: Source Code : -Algorithms transformations can produce spectacular improvements -Profiling can be helpful to focus a programmer’s attention on important code. Intermediate Code: -Compiler can improve loops, procedure calls and address calculations -Typically only optimizing compilers include this phase Target Code: Compilers can use registers efficiently Peephole transformation can be applied
  • 10. Types of Code optimization Common Sub-expression Removal Dead Code Optimization Loop Optimization
  • 11. Common Sub expression elimination Common Sub expression elimination is a optimization that searches for instances of identical expressions (i.e they all evaluate the same value), and analyses whether it is worthwhile replacing with a single variable holding the computed value. a=b * c + g d=b * c * d temp=b * c a=temp + g d=temp * d
  • 12. Dead Code elimination is a compiler optimization that removes code that does not affect a program. Removing such code has two benefits It shrinks program size, an important consideration in some contexts. It lets the running program avoid executing irrelevant operations, which reduces its running time. Dead Code elimination is of two types Unreachable Code Redundant statement Dead code Optimization:
  • 13. Unreachable Code In Computer Programming, Unreachable Code or dead code is code that exists in the source code of a program but can never be executed. Program Code If (a>b) m=a elseif (a<b) m=b elseif (a==b) m=0 else m=-1 Optimized Code If (a>b) m=a elseif (a<b) m=b else m=0
  • 14. Redundant Code Redundant Code is code that is executed but has no effect on the output from a program main(){ int a,b,c,r; a=5; b=6; c=a + b; r=2; r++; printf(“%d”,c); } Adding time & space complexity
  • 15. Loop optimization Loop optimization plays an important role in improving the performance of the source code by reducing overheads associated with executing loops. Loop Optimization can be done by removing: Loop invariant Induction variables
  • 16. Loop Invariant i = 1 s= 0 do{ s= s + i a =5 i = i + 1 { while (i < =n) i = 1 s= 0 a =5 do{ s= s + i i = i + 1 { while (i < =n) Bringing a=5 outside the do while loop, is called code motion.
  • 17. Induction variables i = 1 s= 0 S1=0 S2=0 while (i < =n) { s= s + a[ i ] t1 = i * 4 s= s + b[ t1 ] t2 = t1 +2 s2= s2 + c[ t2 ] i = i + 1 } i = 1 s= 0 S1=0 S2=0 t2=0 while (i < =n) { s= s + a[ i ] t1 = t1+ 4 s= s + b[ t1 ] s2= s2 + c[t1 +2 ] i = i + 1 } t1,t2 are induction variables. i is inducing t1 and t1 is inducing t2 “ +” replaced “ * ”, t1 was made independent of i
  • 18.  
  • 19.  
  • 20.  
  • 21.  
  • 22. Common Sub-expression Removal It is used to remove redundant computations which usually improves the execution time of a program.
  • 23.  
  • 24.  
  • 25.  
  • 26.  
  • 27.  
  • 28.  
  • 29. Three Address Code of Quick Sort i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto (5) j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto (9) if i >= j goto (23) t 6 = 4 * i x = a[t 6 ] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 t 7 = 4 * I t 8 = 4 * j t 9 = a[t 8 ] a[t 7 ] = t 9 t 10 = 4 * j a[t 10 ] = x goto (5) t 11 = 4 * I x = a[t 11 ] t 12 = 4 * i t 13 = 4 * n t 14 = a[t 13 ] a[t 12 ] = t 14 t 15 = 4 * n a[t 15 ] = x 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
  • 30. Find The Basic Block i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto (5) j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto (9) if i >= j goto (23) t 6 = 4 * i x = a[t 6 ] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 t 7 = 4 * I t 8 = 4 * j t 9 = a[t 8 ] a[t 7 ] = t 9 t 10 = 4 * j a[t 10 ] = x goto (5) t 11 = 4 * i x = a[t 11 ] t 12 = 4 * i t 13 = 4 * n t 14 = a[t 13 ] a[t 12 ] = t 14 t 15 = 4 * n a[t 15 ] = x 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
  • 31. Flow Graph if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 t 6 = 4 * i x = a[t 6 ] t 7 = 4 * i t 8 = 4 * j t 9 = a[t 8 ] a[t 7 ] = t 9 t 10 = 4 * j a[t 10 ] = x goto B 2 t 11 = 4 * i x = a[t 11 ] t 12 = 4 * i t 13 = 4 * n t 14 = a[t 13 ] a[t 12 ] = t 14 t 15 = 4 * n a[t 15 ] = x B 1 B 2 B 3 B 4 B 5 B 6
  • 32. Common Subexpression Elimination if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 t 6 = 4 * i x = a[t 6 ] t 7 = 4 * i t 8 = 4 * j t 9 = a[t 8 ] a[t 7 ] = t 9 t 10 = 4 * j a[t 10 ] = x goto B 2 t 11 = 4 * i x = a[t 11 ] t 12 = 4 * i t 13 = 4 * n t 14 = a[t 13 ] a[t 12 ] = t 14 t 15 = 4 * n a[t 15 ] = x B 1 B 2 B 3 B 4 B 5 B 6
  • 33. Common Subexpression Elimination if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 t 6 = 4 * i x = a[t 6 ] t 8 = 4 * j t 9 = a[t 8 ] a[ t 6 ] = t 9 t 10 = 4 * j a[t 10 ] = x goto B 2 t 11 = 4 * i x = a[t 11 ] t 12 = 4 * i t 13 = 4 * n t 14 = a[t 13 ] a[t 12 ] = t 14 t 15 = 4 * n a[t 15 ] = x B 1 B 2 B 3 B 4 B 5 B 6
  • 34. Common Subexpression Elimination if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 t 6 = 4 * i x = a[t 6 ] t 8 = 4 * j t 9 = a[t 8 ] a[ t 6 ] = t 9 a[ t 8 ] = x goto B 2 t 11 = 4 *i x = a[t 11 ] t 12 = 4 * i t 13 = 4 * n t 14 = a[t 13 ] a[t 12 ] = t 14 t 15 = 4 * n a[t 15 ] = x B 1 B 2 B 3 B 4 B 5 B 6
  • 35. Common Subexpression Elimination if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 t 6 = 4 * i x = a[t 6 ] t 8 = 4 * j t 9 = a[t 8 ] a[ t 6 ] = t 9 a[ t 8 ] = x goto B 2 t 11 = 4 * i x = a[t 11 ] t 12 = 4 * i t 13 = 4 * n t 14 = a[t 13 ] a[t 12 ] = t 14 t 15 = 4 * n a[t 15 ] = x B 1 B 2 B 3 B 4 B 5 B 6
  • 36. Common Subexpression Elimination if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 t 6 = 4 * i x = a[t 6 ] t 8 = 4 * j t 9 = a[t 8 ] a[ t 6 ] = t 9 a[ t 8 ] = x goto B 2 t 11 = 4 * i x = a[t 11 ] t 13 = 4 * n t 14 = a[t 13 ] a[ t 11 ] = t 14 t 15 = 4 * n a[t 15 ] = x B 1 B 2 B 3 B 4 B 5 B 6
  • 37. Common Subexpression Elimination if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 t 6 = 4 * i x = a[t 6 ] t 8 = 4 * j t 9 = a[t 8 ] a[ t 6 ] = t 9 a[ t 8 ] = x goto B 2 t 11 = 4 * i x = a[t 11 ] t 13 = 4 * n t 14 = a[t 13 ] a[ t 11 ] = t 14 a[ t 13 ] = x B 1 B 2 B 3 B 4 B 5 B 6
  • 38. Common Subexpression Elimination if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 t 6 = 4 * i x = a[t 6 ] t 8 = 4 * j t 9 = a[t 8 ] a[ t 6 ] = t 9 a[ t 8 ] = x goto B 2 t 11 = 4 * i x = a[t 11 ] t 13 = 4 * n t 14 = a[t 13 ] a[ t 11 ] = t 14 a[ t 13 ] = x B 1 B 2 B 3 B 4 B 5 B 6
  • 39. Common Subexpression Elimination if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 x = a[ t 2 ] t 8 = 4 * j t 9 = a[t 8 ] a[ t 2 ] = t 9 a[ t 8 ] = x goto B 2 t 11 = 4 * i x = a[t 11 ] t 13 = 4 * n t 14 = a[t 13 ] a[ t 11 ] = t 14 a[ t 13 ] = x B 1 B 2 B 3 B 4 B 5 B 6
  • 40. Common Subexpression Elimination if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 x = t 3 t 8 = 4 * j t 9 = a[t 8 ] a[ t 2 ] = t 9 a[ t 8 ] = x goto B 2 t 11 = 4 * i x = a[t 11 ] t 13 = 4 * n t 14 = a[t 13 ] a[ t 11 ] = t 14 a[ t 13 ] = x B 1 B 2 B 3 B 4 B 5 B 6
  • 41. Common Subexpression Elimination if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 x = t 3 a[ t 2 ] = t 5 a[ t 4 ] = x goto B 2 t 11 = 4 * i x = a[t 11 ] t 13 = 4 * n t 14 = a[t 13 ] a[ t 11 ] = t 14 a[ t 13 ] = x B 1 B 2 B 3 B 4 B 5 B 6
  • 42. Common Subexpression Elimination if i >= j goto B 6 Similarly for B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 x = t 3 a[ t 2 ] = t 5 a[ t 4 ] = x goto B 2 x = t 3 t 14 = a[t 1 ] a[ t 2 ] = t 14 a[ t 1 ] = x B 1 B 2 B 3 B 4 B 5 B 6
  • 43. Dead Code Elimination if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 x = t 3 a[ t 2 ] = t 5 a[ t 4 ] = x goto B 2 x = t 3 t 14 = a[t 1 ] a[ t 2 ] = t 14 a[ t 1 ] = x B 1 B 2 B 3 B 4 B 5 B 6
  • 44. Dead Code Elimination if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 a[ t 2 ] = t 5 a[ t 4 ] = t 3 goto B 2 t 14 = a[t 1 ] a[ t 2 ] = t 14 a[ t 1 ] = t 3 B 1 B 2 B 3 B 4 B 5 B 6
  • 45. Reduction in Strength if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] i = i + 1 t 2 = 4 * i t 3 = a[t 2 ] if t 3 < v goto B 2 j = j – 1 t 4 = 4 * j t 5 = a[t 4 ] if t 5 > v goto B 3 a[ t 2 ] = t 5 a[ t 4 ] = t 3 goto B 2 t 14 = a[t 1 ] a[ t 2 ] = t 14 a[ t 1 ] = t 3 B 1 B 2 B 3 B 4 B 5 B 6
  • 46. Reduction in Strength if i >= j goto B 6 i = m - 1 j = n t 1 =4 * n v = a[t 1 ] t 2 = 4 * i t 4 = 4 * j t 2 = t 2 + 4 t 3 = a[t 2 ] if t 3 < v goto B 2 t 4 = t 4 - 4 t 5 = a[t 4 ] if t 5 > v goto B 3 a[ t 2 ] = t 5 a[ t 4 ] = t 3 goto B 2 t 14 = a[t 1 ] a[ t 2 ] = t 14 a[ t 1 ] = t 3 B 1 B 2 B 3 B 4 B 5 B 6