LARA

Applications of Data-Flow Analysis

  1. optimization
  2. correctness

Optimization

Brief list of data-flow analyses and their uses - from Tiger book, sav08, papers

Checks:

  • initialization analysis
  • protocol usage analysis
  • array bounds checks

Some optimizations:

  • common subexpression elimination using available expression analysis
    • avoid recomputing (automatically or manually generated) identical expressions
  • constant propagation
    • use constants instead of variables if variable value is known
  • copy propagation
    • use another variable with the same name
  • dead code elimination
    • remove unnecessary code
  • automatically generate code for parallel machines

Consider code: 

  x = complexComputationF(a.f,b.g);
  y = complexComputationG(c.f,d.g);
  z = x + y;
  c.f = e;
  u = complexComputationF(a.f,b.g);

Questions:

  • can we compute complexComputationF and complexComputationG in parallel?
  • does u compute same results as x ?
  • what areas of memory do functions
    • read
    • write
  • can a and c both refer to the same object?
    • alias analysis

References:

Correctness

ASTREE Analyzer

“In Nov. 2003, ASTRÉE was able to prove completely automatically the absence of any RTE in the primary flight control software of the Airbus A340 fly-by-wire system, a program of 132,000 lines of C analyzed in 1h20 on a 2.8 GHz 32-bit PC using 300 Mb of memory (and 50mn on a 64-bit AMD Athlon™ 64 using 580 Mb of memory).”

Some Commercial Tools

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