Study Guide Primary Topics

Question 1

What is semantic analysis?

Answer 1

The phase of the compiler that checks the source program for semantic consistency with the language definition.

Question 2

What is a synthesized attribute?

Answer 2

Of a non terminal A at a parse tree node N is directly defined by a semantic rule associated with production at N (node value determined from child node(s))

Question 3

What is an inherited attribute?

Answer 3

For a nonterminal B at a parse-tree node N is defined by a semantic rule associated with the production at the parent of N (node gets value from parent/sibling nodes)

Question 4

What are attribute grammars?

Answer 4

Syntax-defined definitions whose semantic rules have no side effects.

Question 5

What is a side effect?

Answer 5

Any action or rule application that results in an effect, such as printing or evaluating a value.

Question 6

What is the purpose of the semantic analyzer?

Answer 6

Checking and verifying data types. Last chance to weed out inconsistent/incorrect programs at the front end.

Question 7

What are the jobs of the semantic analyzer (know at least 3)

Answer 7

1. Type checking
2. Type coercion/conversion
3. Variable deceleration and use
4. Access control and scope checking
5. Function parameter count and consistency
6. Store discovered/synthesized/inherited attributes in the IR or symbol table

Question 8

What is intermediate representation?

Answer 8

Data structure used by compiler to represent source code.

Question 9

What are data types?

Answer 9

A collection or grouping of data values and the operations that can be performed on them.

Question 10

What is a type system?

Answer 10

feature of a language, the collection of all its data types, data operations, and rules for how types can be combined or coerced

Question 11

Language Type: Static

Answer 11

Type-checking performed at compile time.

Question 12

Language Type: Dynamic

Answer 12

Type checking performed at run time

Question 13

Language Type: Explicit

Answer 13

Types declared in source code

Question 14

Language Type: Implicit

Answer 14

Type checking in compiler

Question 15

Language Type: Safe

Answer 15

Cannot violate rules and structure of type system

Question 16

Language Type: Unsafe

Answer 16

Can violate rules and structure of type system

Question 17

Language Type: Atomic

Answer 17

Types provided by language and recognized by compiler

Question 18

Language Type: Composite

Answer 18

Types that are built up from atomic types

Question 19

Why do we use data types?

Answer 19

They give us a way of specifying the context of data

Question 20

Why do we use type systems?

Answer 20

Ensures that everything is typed and all types agree with each other

Question 21

Benefits of a type system?

Answer 21

Correctness, performance, expressiveness

Question 22

What is data flow analysis?

Answer 22

Process of tracing how values make their way through a program

Question 23

What are the benefits (3) of data flow analysis?

Answer 23

1. Knowing when data is alive and in-scope (visible)
2. Knowing if a variable changes and when/if it changes at all
3. Knowing if a variable is declared but never used

Question 24

What is code generation/what does it do?

Answer 24

Takes intermediate representation, translates into machine code.
optimized TAC → code generation → machine code

Question 25

What kind of optimizations can be done? Know three

Answer 25

Constant folding
Copy propagation
Reduction in strength
Substitution of in-line code
Common subexpression elimination
Loop optimization