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hw1-sols

# hw1-sols - CS 243 Assignment 1 Assignment 1 Dataflow...

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Unformatted text preview: CS 243 Assignment 1 Assignment 1 Dataflow Analysis Due: January 25, 11:00 am This is a written assignment, every student must hand in his or her homework. Bring your homework to class on January 25. SCPD students may submit their homework by e-mail via [email protected] or give your homework to the courier. 1. Compute the available expressions (Chapter 9.2.6 in ALSU) on entry and exit for each basic block in the flow graph below. entry t = x+y; c = a+b; b = t+c; a = t+c; b = 4; c = t+c; a = x+y; exit Solution: The most common error here was assuming that t + c was available after the expression c = t + c . Block In Out Entry- ∅ B1 ∅ { x+y, a+b } B2 { x+y, a+b } { x+y, t+c } B3 { x+y } { x+y, t+c } B4 { x+y } { x+y } B5 { x+y, t+c } { x+y } B6 { x+y } { x+y } Exit { x+y }- Winter 2011/2012 page 1 of 4 CS 243 Assignment 1 2. Is the following a meet operator? Please answer yes or no. No explanation is encessary. a. Maximum value (on integers) b. Product (on integers) c. Addition (on integers) d. Product mod 2 (on the set { 0, 1 } ) e. Addition mod 2 (on the set { 0, 1 } ) f. The GCD function (on integers) Solution: All the “no” answers failed because they were not idempotent (i.e., x ∧ x...
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hw1-sols - CS 243 Assignment 1 Assignment 1 Dataflow...

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