The document discusses intermediate code generation in compilers. It describes how an intermediate representation is produced that bridges the analysis and synthesis phases of translation. Examples of intermediate representations discussed include 3-address code, stack machine code, graphical representations like control flow graphs and trees. Specific compiler techniques like common subexpression elimination are also covered.

1. Intermediate Code Generator
Dr.P.Kumaran
AP/CSE

2. Intermediate Code Generations
An intermediate representation of the final machine language
code is produced. This phase bridges the analysis and synthesis
phases of translation.
Example
temp1:= int to real (60)
temp2:= id3 * temp1
temp3:= id2 + temp2
id1:= temp3.
id1 = id2 + id3 * id4

3. Phases of Compiler

4. Semantic Analysis
Position:= initial + rate *60
Example

5. • Syntax Directed Definition (SDD)
– Production + Semantic Rules
• Syntax Directed Translation (SDT)
– Production + Semantic Action
Semantic Analysis

6. • Grammar + Semantic Rules= SDD
• SDD for Evaluation of Expression
E  E+T {E.value=E.value+T.value}
E T {E.value=T.value}
T T*F {T.value=T.value*F.value}
T F {T.value=F.value}
F  num {F.value=num.value}
Syntax Directed Definition (SDD)
Example1

7. • 2+3*4
Syntax Directed Definition (SDD) Cont..

8. • Example2
Syntax Directed Definition (SDD) Cont..
L  E {L.val=E.val}
E  E1+ T {E.val= E1.val+ T.val}
E  T {E.val=T.val}
T T1*F {T.val= T1.val*F.val}
TF {T.val=F.val}
F(E) {F.val=E.val}
F digit {F.val=digit.lexval}

9. Syntax Directed Definition (SDD) Cont..
(9+10)

10. SDD  Attribute Types
• Synthesized Attribute value defined by its
child and itself

11. • D  TL {L.inh=T.type}
• T int {T.type=‘integer’}
• Treal {T.type=‘real’}
• L L1,id {L1.inh= L.inh }
addtype{id.entry, L.inh}
• L id addtype{id.entry, L.inh}
Syntax Directed Definition (SDD) Cont..
• Example3

12. • real id1,id2,id3
Syntax Directed Definition (SDD) Cont..

13. SDD  Attribute Types
• Inherited Attribute value defined by its
parent or siblings or itself
S- Attributed Definitions: synthesized
L- Attributed Definitions: Synthesized and
Inherited

14. • E E*T {E.val=E.val*T.val}
• E T {E.val=T.val}
• T  F-T {T.val=F.val – T.val}
• T F {T.val=F.val}
• F 2 {F.val=2}
• F 4 {F.val=4}
Syntax Directed Definition (SDD) Cont..
• Example4

15. • 4-2-4*2
Syntax Directed Definition (SDD) Cont..

16. Example1
Syntax Directed Translation (SDT)
E  E+T {printf(“+”);} 1
E T {} 2
T T*F {printf(“*”);} 3
T F {} 4
F  num {printf(num.val);} 5

17. 2+3*4 (Infix to Postfix conversion) – TDP top
down and left to right
Syntax Directed Translation (SDT) Cont..

18. • 2+3*4 (Infix to Postfix conversion) – BUP
Syntax Directed Translation (SDT) Cont..

19. Example2
Syntax Directed Translation (SDT) Cont..
S xxW {printf(1);}
S  y {printf(2);}
W Sz {printf(3);}

20. • xxxxyzz
Syntax Directed Translation (SDT) Cont..

21. • Graphical IR
– Graph
• Control-Flow Graph
• Dependence Graph
• Call Graph
– Tree
• Parse Tree
• Abstract syntax tree
• Directed acyclic graph
• Linear IR
– 3-Address Code
– Stack Machine Code
– Linear Code
• Hybrid IR
Intermediate Code Generator

22. Graphical IR - Graph
Control-flow graph

23. Graphical IR- Graph
Dependence Graph

24. Graphical IR- Graph
Call Graph

25. Graphical IR - Tree
Parse Tree

26. Graphical IR - Tree
Abstract Syntax Trees
a ×2+ a× 2 × b

27. Graphical IR - Tree
Directed Acyclic Graphs
a ×2+ a× 2 × b

28. ICG- Graphical Representation
• Common Sub Expression Elimination
a= b*-c + b*-c

29. Linear IR
3 Address Code

30. Linear IR
Stack Machine Code

31. 3- Address Code
x:=y op z
x,y, and z names, constants, or temporaries
op  Operator (arithmetic or logical )
Example:
x+y*z
t1:=y*z
t2:=x+t1

32. 3- Address Code
a= b*-c + b*-c

33. • Assignment Statement : x:=y op z
– op  Arithmetic or logical operator
• Assignment Statement : x:= op y
– op Unary Operator
• Copy Statement : x:=y
• Unconditional Jump : goto L
• Conditional Jump : if x relop y goto L
• Procedure call : p(x1,x2,x3,…,xn)
Param x1
Param x2
…………..
Param xn
Call p,n
Type of 3- Address Statements

34. • In compiler the 3 address code is field of records
 Quadruples
 Triples
 Indirect Triples
3- Address Code

35. 3- Address Code
Indirect Triples

36. Examples

37. Example 1

38. Example 2

39. Example 3

40. IMG-DECLARATIONS

41. • D  TL {L.inh=T.type}
• T int {T.type=‘integer’}
• Treal {T.type=‘real’}
• L L1,id {L1.inh= L.inh }
addtype{id.entry, L.inh}
• L id addtype{id.entry, L.inh}
IMG-Declarations

42. • real id1,id2,id3
IMG-Declarations

43. • mktable(previous)
• enter(table,name,type,offset)
• addwidth(table,width)
• enterproc(table,name,newtable)
• lookup(table,name)
IMG-Declarations

44. IMG-Declarations

45. IMG-Declarations

46. IMG-Declarations

47. IMG-Declarations

48. Example 4

49. Example 5

50. Example 6

51. Example 7

52. Example 8

53. Example 9