Reaching definitions analysis in Compiler Design - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a reaching definition in data flow analysis.

Compiler Design

A definition of a variable reaches a point in the program if there is a path from the definition to that point with no intervening [1] to the variable.

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Ause

Bredefinition

Cloop

Dbranch

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing 'use' with 'redefinition'.

Thinking loops stop reaching definitions.

A reaching definition means the variable's value is not changed (redefined) along the path to that point.

2fill in blank

medium

Complete the code to describe the purpose of reaching definitions analysis.

Compiler Design

Reaching definitions analysis helps to find all definitions of variables that may reach a given [1] in the program.

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Ause

Bstatement

Cassignment

Dloop

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'assignment' instead of 'use'.

Confusing 'statement' with 'use'.

The analysis finds definitions that can reach a variable's use (where the variable is read).

3fill in blank

hard

Fix the error in the statement about the direction of reaching definitions analysis.

Compiler Design

Reaching definitions analysis is a [1]-flow data flow analysis.

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Aforward

Bcyclic

Csideways

Dbackward

Attempts:

3 left

💡 Hint

Common Mistakes

Thinking it is backward-flow analysis.

Confusing flow direction terms.

Reaching definitions analysis proceeds forward through the control flow graph, from definitions to uses.

4fill in blank

hard

Fill both blanks to complete the data flow equation for reaching definitions.

Compiler Design

OUT[B] = GEN[B] [1] (IN[B] [2] KILL[B])

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Aunion

Bintersection

C-

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using intersection instead of union.

Using addition instead of subtraction for kill set.

The output set of block B is the union of generated definitions and the input set minus killed definitions.

5fill in blank

hard

Fill all three blanks to complete the iterative algorithm step for reaching definitions.

Compiler Design

IN[B] = \bigcup_[1] \in preds(B)} OUT[2]\nRepeat until [3] changes.

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AP

B[P]

Cno

Dnothing

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect notation for predecessors.

Thinking the algorithm stops immediately.

IN[B] is the union of OUT sets of all predecessors P of B. The process repeats until no changes occur.