Static Analysis: DataFlow Analysis IV

1
Static AnalysisData-Flow Analysis IV
( WORKSHOP )
( AMP08 Advanced Models Programs, 2008 )

• Claus Brabrand
• ITU - IT University of Copenhagen
• ( brabrand_at_itu.dk )

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Data-Flow Analyses -)
You havent seen
Very Busy Expressions
backwards
must
?
?
( ? , ? )
?

Available Expressions
Live Variables
( ? , ? )
( ? , ? )
( ? , ? )
?
?
may
forwards
Reaching Definitions
You have seen
3
WORKSHOP
Agenda - Group formation (15) - Workshop
(2h45) - Presentations (4?15)

• 1) Reaching Definitions
• ? (forwards), ? (may / smallest set)
• 2) Live Variables
• ? (backwards), ? (may / smallest set)
• 3) Available Expressions
• ? (forwards), ? (must / largest set)
• 4) Very Busy Expressions
• ? (backwards), ? (must / largest set)

4
WORKSHOP

• 1) Define the problem
• 2) Show that the problem is undecidable
• 3) Define a Lattice
• Check that it is a lattice (and explain how)
• 4) Define monotone transfer functions
• Check that they are monotone (and explain how)
• 5) Pick a program the analysis can analyze
• and make an entire process-diagram (cf. slide
  3)
• 6) Repeat 5) for program analysis cant do
• 7) Explain possible uses of the analysis

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The Language C--

• Syntactic Categories
• Expressions (E ? EXP)
• Statements (S ? STM)
• For simplicity
• Lets assume we only have variables x, y, and
  z !

E n v E E E E E
E E input
S skip v E output E
S1 Sn if E then S else S while E
do S