Compiler Design and Analysis Overview

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Questions and Answers

What are the main objectives of code optimization?

Improves code readability.

Increases the complexity of the code.

Reduces the number of lines of code.

Saves space and time. (correct)

Which of the following is NOT a code optimization method?

Constant folding

Copy propagation

Code commenting (correct)

Dead code elimination

What is the purpose of 'Constant Folding' in code optimization?

Simplifying expressions with constants. (correct)

Replacing variables with their values.

Reordering code to improve efficiency.

Removing unnecessary code.

Which optimization technique replaces expensive operations with cheaper ones?

Strength reduction Signup and view all the answers

What is the main purpose of 'Dead Code Elimination' in optimization?

Eliminating code that is unreachable. Signup and view all the answers

In the given code example, which line(s) would be considered a basic block leader?

Line 1, Line 2, Line 5, Line 8, Line 9, Line 10 Signup and view all the answers

In the given code example, which statement is NOT amenable to constant folding?

t1 = 5 * i Signup and view all the answers

Which optimization can be applied to the statement `x = 2 * y`?

Strength reduction Signup and view all the answers

What type of attribute is computed at a node based on its parent or sibling?

Inherited Attribute Signup and view all the answers

In which type of grammar are attributes synthesized only and placed at the end of a production?

S-Attributed Grammar Signup and view all the answers

What does the computation of a synthesized attribute depend on?

Child Nodes Signup and view all the answers

What is an example of an inherited attribute in the context provided?

A.x from S AB Signup and view all the answers

Which attribute type does not allow for attributes from sibling nodes to be referenced?

Synthesized Attribute Signup and view all the answers

Which of the following statements is true regarding the evaluation of L-Attributed Grammar?

Only left siblings contribute to attribute computation Signup and view all the answers

What does an expression of type E E1 + T denote in terms of synthesized attributes?

E.val is the sum of E1.val and T.val Signup and view all the answers

In a syntax-directed definition, how are synthesized attributes typically evaluated?

In a topological order Signup and view all the answers

What information does the First Set provide in the context of parsing?

It includes the extreme left terminal from which the string of a variable starts. Signup and view all the answers

Which of the following statements about the Follow Set is true?

It always contains the end-of-input marker $. Signup and view all the answers

What is the first step in constructing a parsing table for LL(1) parsers?

Remove left recursion if any. Signup and view all the answers

Which of the following describes a Top-Down Parser (specifically LL(1))?

It cannot handle left recursion. Signup and view all the answers

How is the Follow Set for a non-terminal B in the production A --> αBβ determined?

It includes the terminals derived from β. Signup and view all the answers

What is a characteristic of ambiguous grammar?

It can lead to multiple valid parsing trees for the same string. Signup and view all the answers

When performing left factoring, what is the main goal?

To eliminate common prefixes in production rules. Signup and view all the answers

Which of these is true regarding the deployment of DPDA in parsers?

They are primarily used for context-free grammars. Signup and view all the answers

What is a key characteristic of Bottom-UP Parsers?

They cannot parse ambiguous grammar. Signup and view all the answers

What is the purpose of shift entries in a Bottom-UP Parser?

To represent terminal symbols and their transitions. Signup and view all the answers

How does the LR (1) parser differ from the LR (0) parser?

LR (1) includes lookahead symbols to enhance parsing. Signup and view all the answers

What does the 'follow' set represent in parsing?

The symbols that can appear immediately after a non-terminal in a string. Signup and view all the answers

In which parser is the reduce operation performed for each production in the item set?

LR (0) Parser Signup and view all the answers

What is typically done to handle an unambiguous grammar that lacks a parser?

Expand the grammar and employ another parsing technique. Signup and view all the answers

Which of the following is NOT a type of entry in a Bottom-UP Parser?

Parse Entry Signup and view all the answers

What is a primary function of the Basic Algorithm for Construction in parsing?

To augment the grammar and establish item sets. Signup and view all the answers

What type of grammar is utilized in synthesizing types according to the definitions given?

S-attributed Grammar Signup and view all the answers

Which of the following statements about L-attributed grammars is true?

Every S-attributed grammar can be classified as L-attributed. Signup and view all the answers

What is the maximum number of addresses permissible in 3-address code?

Three addresses Signup and view all the answers

In evaluating expressions for minimum variable requirements, what is the minimum determined from the example given?

3 variables Signup and view all the answers

What is the primary characteristic of Static Single Assignment (SSA) code?

Each variable must have a unique assignment. Signup and view all the answers

When transforming to SSA code, which of the following variables is introduced as additional in the example provided?

r Signup and view all the answers

What does the method of finding the minimum number of variables in 3-address code utilize?

Operator precedence rules Signup and view all the answers

What operation is performed by the synthesizer according to the SDD given?

Assign types based on context Signup and view all the answers

What is the primary purpose of constructing an LL(1) parsing table?

To check if the grammar can be parsed using a top-down approach. Signup and view all the answers

Which of the following indicates the presence of ambiguity in an LL(1) parsing table?

Having multiple items in a single cell. Signup and view all the answers

In the given grammar, what is the follow set for E?

+, $, ) Signup and view all the answers

What is the initial production rule for the variable E after left recursion is removed?

E → TE’ Signup and view all the answers

What indicates that left factoring is not required for the grammar provided?

No two productions start with the same terminal. Signup and view all the answers

What is the first set of the variable T in the given grammar?

id, ( Signup and view all the answers

What does the 'Error' entry in the LL(1) parsing table signify?

No matching production for the terminal. Signup and view all the answers

Which of the following correctly defines the variable F in the context of the provided grammar?

F can produce (E) or id. Signup and view all the answers

Study Notes

Compiler Design

A compiler converts high-level programming language code into low-level machine language.
High-level languages allow for multiple operations in a single statement.
Low-level languages can only handle one operation at a time.
The compiler process involves analysis and synthesis stages.

Analysis Phase

Lexical Analysis:
- Splits the source code into tokens.
- Processes, checks for spelling mistakes.
Syntax Analysis:
- Checks the grammatical structure of the code.
- Uses a parser(e.g., DPDA).
Semantic Analysis: Checks the meaning of the code. (Ex: type mismatches, stack overflow)
Intermediate Code Generation: Creates intermediate representation of the code for easier processing.
Code Optimization: Improves efficiency by reducing redundancy and choosing more efficient representations.

Synthesis Phase

Code Generation: Translates intermediate code into target machine code.

Parsing

Parsing involves checking the grammatical structure of the code.
Context-sensitive grammars describe the rules of programming language syntax.
Parse trees and syntax trees illustrate derivation paths.
Priority and associativity of operators determine parsing sequence.

Compiler Design Concepts (Continued)

Top-down Parsing(Recursive Descent, LL(1))
Bottom-up Parsing (LR(k) family)
Mathematical model of parser (Finite tape, Finite controls, Parsing table, DPDA)
Types of Parsers: Top-down, Bottom-up (Recursive Descent, LL (1), LR(k) family)
Syntax analysis, Parse trees and syntax trees
Removal of Common Prefixes (Left Factor)
First and Follow Sets
Constructing Parsing Tables (LL(1))

Lexical Analysis

Scans the source code character by character, generating tokens.
Handles lexical errors (e.g., incorrect spellings).
Identifies keywords, identifiers, operators, literals.

Syntax-Directed Translation (SDT)

Extends Context-Free Grammars (CFGs) with semantic rules, transforming code meanings.
Inherits or synthesizes attributes to represent meaning.
Parsing trees are annotated with semantic values during traversal.

Intermediate Code and Optimization

Uses intermediate representations (e.g., postfix, 3-address code, abstract syntax trees).
Includes operations such as constant folding, copy propagation, strength reduction, dead code elimination, common subexpression elimination, loop optimization, peephole optimization.
Basic blocks and control flow graphs represent program structure for analysis.

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Description

This quiz covers the fundamental concepts of compiler design, including the critical phases of analysis and synthesis. You will explore lexical, syntax, and semantic analysis, as well as code generation and optimization techniques. Test your understanding of how compilers transform high-level programming languages into machine code.