Compiler Designs and Constructions

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Compiler Designs and Constructions

• Chapter 10 Intermediate Code Generation (part I)
• Objectives
• Dr. Mohsen Chitsaz

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Intermediate Language (Code)

• Why Intermediate Language and not the Target
  Language?
• Advantages of Intermediate Code

Pascal
Back-End
Fortran
Inter. Code
---gt 68000 ---gt 8086
C
My Compiler
Front-End
3

• Definition
• Back-End
• Intermediate ---gt Machine Code
• Front-End
• Programming Languages ---gt Intermediate

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Intermediate Code Generation

• C AB
• What are the values of A and B?
• A.Place
• B.Place
• C.Place
• Translate
• Gen(Temp1 A.Place B.Place)
• Gen(C.Place Temp1)

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Notation and Definition
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Notation and Definition
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1-Assignment Statement

• A ---gt id E
• E ---gt E E
• E ---gt E E
• E ---gt - E
• E ---gt ( E )
• E ---gt id

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Code Generation for Assignment Statement
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Mixed Mode Translation (Type)

• E.Mode to pass the Type
• C A B

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• E ---gt E1 E2
• E.Place NewTemp()
• If E1.ModeInt and E2.Mode Int THEN
• E.Mode Int
• Gen(E.Place E1.Place E2.Place)
• ELSE
• If E1.Mode Real and E2.Mode Real THEN
• E.Mode Real
• Gen(E.Place E1.Place E2.Place)
• ELSE

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• If E1.Mode Int THEN
• TNewTemp()
• Gen(T Int_To_Real E1.Place)
• Gen(E.Place T E2.Place)
• E.Mode Real
• ELSE
• T NewTemp()
• Gen(T Int_To_Real E2.Place)
• Gen(E.Place E2.Place T)
• E.Mode Real

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2-Translation of Boolean Expression

• Logical Values
• Conditional Expression
• 1- E ---gt E OR E
• 2- E ---gt E AND E
• 3- E ---gt NOT E
• 4- E ---gt (E)
• 5- E ---gt id Rel.op id
• 6- E ---gt TRUE
• 7- E ---gt FALSE

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Method1 Using Quadruples

• Assumption
• Left association
• True1
• False0
• Example
• a OR b AND NOT c
• t1 NOT c
• t2 b AND t1
• t3 a OR t2

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Translation of Boolean Expression con.

• Example a lt b
• 0 IF altb GOTO ( )
• 1 t1 0
• 2 GOTO ( )
• 3 t1 1
• 4
• IF altb THEN 1 ELSE 0

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Translation of Boolean Expression con.

• Example
• A lt b OR c
• 0 IF a lt b GOTO ( 3 )
• 1 t1 0
• 2 GOTO ( 4 )
• 3 t1 1
• 4 t2 t1 OR c
• 5

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Translation of Boolean Expression con.

• 7- E ---gt FALSE
• E.Place NewTemp()
• Gen(E.Place 0)
• 6- E ---gt TRUE
• E.Place NewTemp()
• Gen(E.Place 1)

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Translation of Boolean Expression con.

• 5- E ---gt id1 Rel.op id2
• E.Place NewTemp()
• Gen(IF id1.Place Rel.op id2.Place GOTO
  nextQuad2)
• Gen(E.Place 0)
• Gen(GOTO nextQuad1)
• Gen(E.Place 1)

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Translation of Boolean Expression con.

• 4- E ---gt (E1)
• E.Place E1.Place
• 3- E ---gt NOT E1
• E.Place NewTemp()
• Gen(E.Place NOT E1.Place)
• 2- E ---gt E1 AND E2
• E.Place NewTemp()
• Gen(E.Place E1.Place AND E2.Place)
• 1- E ---gt E1 OR E2

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Example

• altb OR cltd AND eltf