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Intermediate Code Generation

Intermediate Code Generation. Prepared By: Abhisekh Biswas - 04CS3002. Intermediate Code. Intermediate Code is generated using the Parse rule Producing a language from the input language. Utility of Intermediate Code Generation.

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Intermediate Code Generation

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  1. Intermediate Code Generation Prepared By: Abhisekh Biswas - 04CS3002

  2. Intermediate Code Intermediate Code is generated using the Parse rule Producing a language from the input language.

  3. Utility of Intermediate Code Generation 1. Suppose We have n-source languages and m-Target languages. Without Intermediate code we will change each source language into target language directly. So, for each source-target pair we will need a compiler. Hence we will require (n*m) Compilers, one for each pair. If we Use Intermediate code We will require n-Compilers to convert each source language into Intermediate code and m-Compilers to convert Intermediate code into m-target languages. Thus We require only (n+m) Compilers.

  4. Retargeting is facilitated; a compiler for a different machine can be created by attaching a Back-end (which generate Target Code) for the new machine to an existing Front-end (which generate Intermediate Code). • A machine Independent Code-Optimizer can be applied to the Intermediate code. • Intermediate code is simple enough to be easily converted to any target code. • Complex enough to represent all the complex structure of high level language.

  5. Types of Intermediate Code • High Level Representation. • Low level Representation.

  6. Code Optimization • See the total intermediate instruction and optimize. • Find Redundancy in Code.

  7. -find common subexpression • -check for dependency • -detect dead codes • TWO BASIC TYPES OF OPTIMIZATION: • 1>machine dependent i.e utilizing hardware specification for max efficiency.but range of compatibility is small. • 2>machine independent,

  8. Syntax Tree is optimization of high level language. Suppose we have following code: if(x<0) then x=3*(y+1) else y=y+1;

  9. ifstat if assign then exp elsestat ; id relop id = exp id exp exp * exp ) ( exp + exp id id

  10. elsestat exp else id exp = exp exp + id id

  11. We Can see A DAG gives the same information but in a more compact manner because common sub-expression are identified. • PostFix Notation can be used to represent tree in linearized manner.In PostFix Notation edges of tree do not appear explicitly.

  12. Three Address Code • Another way to represent tree in lenearized form is Three-address-code Notation. • In Three Address Code method internal nodes are given names. It is a low level Intermediate code representation.

  13. Example x=y op z where x, y and z are names, constants or Compiler generated temporaries. where op stands for any operator.

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