Slicing of Esterel

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Slicing of Esterel

• Static Slicing A program transformation that
  extracts a subset of program based on specific
  criterion.
• Slice preserves the behavior of original program
  w.r.t the slicing criterion.
• Esterel A synchronous language. Used to model
  control behavior of reactive systems.
• Applications of slicing
• Program understanding
• Debugging
• Formal Verification

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Example of Slice

• read ( n )
• i 1
• sum 0
• prod 1
• while ( i lt n )
• sum sum i
• prod prod i
• i i 1
• print ( sum )
• print ( prod )
• Slicing Criterion ltlineno, variablegt

• read ( n )
• i 1
• sum 0
• while ( i lt n )
• sum sum i
• i i 1
• print ( sum )
• Slice w.r.t lt10, sumgt

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Esterel Slicer
Reduced Esterel Program Slice
Esterel Program
Slicing Criterion ltlineno, output signalgt
The behavior of slice and original program must
be same w.r.t the slicing criterion.
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Architecture of Slicer
AST CFG
Parser Front end
Esterel Program
Data Flow Analysis
DDS
CDS
Control Flow Analysis
PDG
Slicing Algorithm
Slicing Criterion
Slice
5
Example

• loop
• emit S1
• pause
• present S2 then emit S3
• emit S2
• emit S1
• end
• Slicing Criterion lt 5, S3 gt