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What is the primary advantage of using postfix notation in expressions?
What is the primary advantage of using postfix notation in expressions?
What is the standard form of a three-address statement?
What is the standard form of a three-address statement?
How many references are typically involved in a standard three-address statement?
How many references are typically involved in a standard three-address statement?
What is the role of internal nodes in a syntax tree?
What is the role of internal nodes in a syntax tree?
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What does a syntax tree represent in relation to a parse tree?
What does a syntax tree represent in relation to a parse tree?
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What are temporary variables in three-address code typically referred to as?
What are temporary variables in three-address code typically referred to as?
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Which of the following is NOT a method for representing three-address code?
Which of the following is NOT a method for representing three-address code?
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How does creating a syntax tree improve expression representation?
How does creating a syntax tree improve expression representation?
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What happens to control when the expression E is false within a while loop?
What happens to control when the expression E is false within a while loop?
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What is the characteristic of a postfix syntax-directed translation (SDT)?
What is the characteristic of a postfix syntax-directed translation (SDT)?
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Which of the following correctly defines the function of S1.NEXT in a while loop implementation?
Which of the following correctly defines the function of S1.NEXT in a while loop implementation?
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In parser stack implementation of postfix SDTs, what is primarily stored in the parser stack?
In parser stack implementation of postfix SDTs, what is primarily stored in the parser stack?
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How is control managed in the translation syntax for a while loop?
How is control managed in the translation syntax for a while loop?
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What does the semantic rule 'E.FALSE = S.NEXT' indicate in the context of a while loop?
What does the semantic rule 'E.FALSE = S.NEXT' indicate in the context of a while loop?
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In the context of postfix SDTs, which semantic rule corresponds to 'S.CODE = GEN(S.BEGIN '− ') || E.CODE || GEN(E.TRUE '− ') || S1.CODE'?
In the context of postfix SDTs, which semantic rule corresponds to 'S.CODE = GEN(S.BEGIN '− ') || E.CODE || GEN(E.TRUE '− ') || S1.CODE'?
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What is the significance of the label S.BEGIN in the control flow of a while loop?
What is the significance of the label S.BEGIN in the control flow of a while loop?
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What happens when reduction occurs at the top of the stack during syntax-directed translation?
What happens when reduction occurs at the top of the stack during syntax-directed translation?
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In an SDT with actions inside the production, when are the actions performed if using a bottom-up parser?
In an SDT with actions inside the production, when are the actions performed if using a bottom-up parser?
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What should be done to a grammar that contains left recursion to enable parsing with a top-down parser?
What should be done to a grammar that contains left recursion to enable parsing with a top-down parser?
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In L-attributed definitions used in SDT, where should the actions for inherited attributes be placed?
In L-attributed definitions used in SDT, where should the actions for inherited attributes be placed?
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In the provided production P ⇢ Pr | q, how is it transformed after eliminating left recursion?
In the provided production P ⇢ Pr | q, how is it transformed after eliminating left recursion?
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What is an example of a synthesized attribute in the provided productions?
What is an example of a synthesized attribute in the provided productions?
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How are arithmetic expression references, like A[i] + B[j], converted into intermediate representations in syntax-directed translation?
How are arithmetic expression references, like A[i] + B[j], converted into intermediate representations in syntax-directed translation?
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What is an outcome of using synthesized attributes in syntax-directed translation?
What is an outcome of using synthesized attributes in syntax-directed translation?
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Study Notes
Syntax Directed Translation in Compiler Design
- Parsers use Context-Free Grammars (CFGs) to validate input strings and produce output for the next compiler phase.
- Outputs can be parse trees or abstract syntax trees.
- Syntax Directed Translation (SDT) interleaves semantic analysis with syntax analysis.
- Conceptually, SDT parses the input, builds a parse tree, then traverses the tree to evaluate semantic rules at every node.
- Semantic rule evaluation can generate code, manage the symbol table, produce error messages, or perform other actions.
Definition
- Syntax Directed Translation augments the grammar.
- SDT involves passing information (bottom-up and/or top-down) to the parse tree, attaching attributes to nodes.
- Attributes can be lexical values, constants, and attributes associated with non-terminals.
- SDT generally constructs a parse tree, evaluating attribute values at the nodes in a specific order.
Example
- A grammar example for expressions with addition and multiplication is given.
- Semantic analysis can be performed using SDT rules.
- An example of how semantic analysis happens is presented with a sample input and its corresponding parse tree; showing how attribute values are calculated at the parse tree's different nodes in a left-to-right bottom-up evaluation.
Intermediate Code Generation in Compiler Design
- A compiler uses a frontend to translate a source program into intermediate code.
- The backend uses this intermediate code to generate target code.
- The role of intermediate code is platform independence.
- Portability is enhanced.
- Efficient code generation and code optimization can occur through intermediate code.
Advantages of Syntax Directed Translation
- Implementation is easier.
- Separates concerns of parsing and translation.
- Modularity and extensibility are facilitated when designing compilers.
Disadvantages of Syntax Directed Translation
- Limited expressiveness compared to other methods (like attribute grammars).
- Can be inflexible for complex translation rules.
- Limited error recovery capabilities, which could impact error messages and diagnostics.
Intermediate Code Representations
- Postfix notation (reverse Polish notation) places operators after operands (e.g., a + b becomes ab+).
- Three-address code has a maximum of three references per statement (two for operands, one for result).
- Example, the expression a+bc will compile to: T1 = bc ; T2 = a+T1;
Syntax Tree
- Condensed representation of a parse tree.
- Simplifies visual representation of the program's syntactic structure.
- Relocates operators and keywords and places them within parent nodes.
Intermediate code generation advantages
- Implementation is easier.
- Facilitates code optimization.
- Platform-independent: code can run on multiple platforms without modification.
- Code reuse: Intermediate code can be reused for other platforms or languages.
- Easier debugging: Closer to source code, thus allowing for easier debugging.
Intermediate code generation disadvantages
- Increased compilation time.
- Additional memory usage.
- Increased complexity.
- Reduced performance (than generating machine code directly)
Abstract Translation Scheme
- An abstract translation scheme describes how to translate programming constructions into intermediate code.
- Includes examples for if-then, if-then-else, and while-loop constructs.
Control Statements
- Statements like if–then,if–then–else, and while–do, which change the flow of the program's execution.
- These are translated by generating jump instructions, based on the Boolean expression's result.
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Description
This quiz explores the concept of Syntax Directed Translation (SDT) in the context of compiler design. It covers the role of parsers, Context-Free Grammars (CFGs), and how semantic rules are evaluated within parse trees. Test your understanding of SDT's integration with both syntax and semantic analysis in compilers.
