1. Migrating Embedded Systems from Assembler to C Using the Fermat Transformation System

2. Pigs from Sausages? Extracting the logic and business rules from evolved legacy systems Automatically migrate them to a new High Level Language Re-host them

3. Why bother? Increased Speed/Capacity Better Price/Performance Larger, more complex systems Cost per function point: –Assembler: £48.00 –PL/1: £39.00 –C: £21.00 Pressure to Migrate to HLL

4. Case Study – Tenovis Gmbh & Co. Specialists in Convergent Networking 200,000 Clients 6000 Employees Revenues over 950 million euros

5. Tenovis Challenge Private Branch eXchange (PBX) system Four Hardware Platforms Installed in 18 countries 800,000 lines of C 544,000 lines of 186 assembler in 318 source files Problems: –Backlog of enhancements –Availability and functionality of the processor

6. SML’s Challenge To migrate the assembler to high-level structured, maintainable C code suitable for porting to more modern processor and also suitable for implementing the backlog of enhancements. The migrated code should meet the coding standards used within the existing C code.

7. FermaT Transformation System Nearly 20 years research and development (> 120 man years) Core technology research @ Oxford and Durham University Migration projects to validate this research funded by IBM, CAA & DTI Used extensively in Y2K projects FermaT Workbench Transformation System

8. Fermat Architecture

9. What is WSL Wide Spectrum Language –From low-level constructs to high-level abstract specifications –Unique transform capability Fermat product set is implemented in MetaWSL WSL is now in the Public Domain under a GUL licence

10. Case Study – Phase 1 Migration of a single 3,000 line source file –Develop a 186 to WSL parser –Modify the existing WSL to C parser –Implement 186-specific WSL transformations

11. Case Study – Phase 2 Mini Call Control –Self contained subsystem –67,000 lines of assembler –41 source files

12. Phase 2 - Requirements Use existing C header files where available Use of the “function parameter table” Translate selected subroutines directly to HLL code Translate bitfield operations into C record fields Eliminate stack usage where possible Detect jump tables and generate appropriate switch statements Generate switch statements instead of nested if statements Can ignore segment addressing for this application

13. Phase 2 - Process 5 iterations of the Mini Call Control Customer feedback on each iteration Update the parsers or transformations Regenerate the C code automatically Final iteration C code was compiled installed and tested

14. Final Migration 2.6Ghz PC with 512Mb of RAM All 318 source files processed in 1.5 hours 1,436,031 transformations: –4,500 transformations per source file –275 transformations per second Largest source file was 8,348 lines –73,393 transformations –370 seconds CPU time –42Mb RAM 506,672 lines of C code plus 37,047 lines of header files generated

15. Results At least 6 bugs were discovered in the system via the migration process “Hey, this really looks like C!” Test environment: “soft switch” between C and Assembler Versions on a PC linked to the hardware.

16. Cost Savings Estimate for Manual translation: 67 man months Actual customer effort for automated translation: SML’s actual effort 52 man days Less than 10% of manual effort Larger systems will achieve even greater savings

17. Advantages of Automated Reengineering Scalability Rapid turnaround of the subsystem Customisability Low resource requirements Low Impact on ongoing development Enables porting to different hardware and/or software platform Removes dependence on limited resources

18. Conclusion Assembler to C using the FermaT Migration System and Workbench is a practical solution to the high costs and skills shortage in assembler maintenance and to the problem of migrating legacy assembler systems to a more modern platform.

19. The future for Fermat Currently assembler to C and COBOL Pascal to C Assembler/Pascal to C Output to Java Joint 3 year research project with DeMontfort University to extend the use of WSL and Fermat

20. Further Resources www.artechhouse.com

21. Further Resources The Fermat Transformation System is available under GNU GPL (General Public Licence) www.dur.ac.uk/~dcs0mpw/fermat.html www.cse.dmu.ac.uk/~mward/fermat.ht ml