1. Compiling ESTEREL circuits into finite states machines BRES Yannis Stage de DEA d’Informatique 1998/1999

2. Esterel constructive semantics Gives, for each statement p p E A new environment E’ E’ A completion code k (terminated, paused or trap exit level) k, A derivative statement p’, to be executed on next step p’, provided an initial environment E :

3. Circuit compilation p E E’k, p’ Thus, each statement p of the language can be compiled into a circuit : E are wires indicating present signals E’ are wires indicating emitted signals k indicates which completing code wire will be on p’ is a another circuit activated by k wire

4. Generated circuits Directed graphs : logical gates (and, or, not, …) registers (memory elements) wires

5. Example of circuit abort sustain O when I

6. Circuits vs. automata Circuits are roughly linear while automata are exponential  No automata for big circuits Up to medium-sized circuits :  Only input/test dependent stuff remain at run-time Automata are faster (run-time minimal) Ex : Motorola measures maximal application speed Control flow computed at compile-time

7. Current compilation chain strlic iclclcscsscoc.strl Esterel source.ic intermediate code.lc linked code.sc circuit code.oc automaton code.ssc sorted circuit code scsscsccausal

8. Future compilation chain strlic iclc lcsc.strl Esterel source.ic intermediate code.lc linked code.sc circuit code.oc automaton code sscoc.ssc sorted circuit code scsscsccausal scoc

9. SSCOC automaton generation Circuit is seen like a set of boolean equations To be evaluated, equations must be sorted ( .ssc) Sorting fails on several kind of cyclic circuits ! Code unmaintained...

10. SCOC automaton compilation Algorithm follows electrical current new informations (hot) propagated informations (cold)

11. SCOC automaton compilation new informations (hot) propagated informations (cold) Building initial state Propagating registers

12. SCOC automaton compilation new informations (hot) propagated informations (cold) Building initial state Propagating registers

13. SCOC automaton compilation new informations (hot) propagated informations (cold) Building initial state Propagating registers

14. SCOC automaton compilation new informations (hot) propagated informations (cold) Building initial state Propagating registers

15. SCOC automaton compilation new informations (hot) propagated informations (cold) Building initial state Propagating registers

16. SCOC automaton compilation new informations (hot) propagated informations (cold) Building initial state Propagating registers

17. SCOC automaton compilation new informations (hot) propagated informations (cold) Building initial state Propagating registers

18. SCOC automaton compilation new informations (hot) propagated informations (cold) Building initial state Propagating registers

19. SCOC automaton compilation new informations (hot) propagated informations (cold) Building initial state Propagating registers

20. SCOC automaton compilation new informations (hot) propagated informations (cold) Building initial state Propagating registers

21. SCOC automaton compilation new informations (hot) propagated informations (cold) Initial state built

22. SCOC automaton compilation new informations (hot) propagated informations (cold) Initial state built Building state 1

23. SCOC automaton compilation new informations (hot) propagated informations (cold) Initial state built Building state 1 Loading registers values

24. SCOC automaton compilation new informations (hot) propagated informations (cold) Initial state built Building state 1 Loading registers values Propagating registers

25. SCOC automaton compilation new informations (hot) propagated informations (cold) Initial state built Building state 1 Loading registers values Propagating registers

26. SCOC automaton compilation new informations (hot) propagated informations (cold) Initial state built Building state 1 Loading registers values Propagating registers

27. SCOC automaton compilation new informations (hot) propagated informations (cold) Initial state built Building state 1 Loading registers values Propagating registers

28. SCOC automaton compilation new informations (hot) propagated informations (cold) Initial state built Building state 1 Loading registers values Propagating registers Forking on input signal I

29. SCOC automaton compilation new informations (hot) propagated informations (cold) Initial state built Building state 1 Loading registers values Propagating registers Forking on input signal I Building branch where I is present

30. SCOC automaton compilation new informations (hot) propagated informations (cold) Initial state built Building state 1 Loading registers values Propagating registers Forking on input signal I Building branch where I is present

31. SCOC automaton compilation new informations (hot) propagated informations (cold) Initial state built Building state 1 Loading registers values Propagating registers Forking on input signal I Building branch where I is present

32. SCOC automaton compilation new informations (hot) propagated informations (cold) Initial state built Building state 1 Loading registers values Propagating registers Forking on input signal I Building branch where I is present

33. SCOC automaton compilation new informations (hot) propagated informations (cold) Initial state built Building state 1 Loading registers values Propagating registers Forking on input signal I Building branch where I is present

34. SCOC automaton compilation new informations (hot) propagated informations (cold) Initial state built Building state 1 Loading registers values Propagating registers Forking on input signal I Building branch where I is present

35. SCOC automaton compilation new informations (hot) propagated informations (cold) Initial state built Building state 1 Loading registers values Propagating registers Forking on input signal I Building branch where I is present

36. SCOC automaton compilation new informations (hot) propagated informations (cold) Initial state built Building state 1 Loading registers values Propagating registers Forking on input signal I Building branch where I is present

37. SCOC automaton compilation new informations (hot) propagated informations (cold) Initial state built Building state 1 Loading registers values Propagating registers Forking on input signal I Final state reached Building branch where I is present

38. SCOC automaton compilation new informations (hot) propagated informations (cold) Initial state built Building state 1 Loading registers values Propagating registers Forking on input signal I Building branch where I is present Building branch where I is absent

39. SCOC automaton compilation new informations (hot) propagated informations (cold) Initial state built Building state 1 Loading registers values Propagating registers Forking on input signal I Building branch where I is present Building branch where I is absent

40. SCOC automaton compilation new informations (hot) propagated informations (cold) Initial state built Building state 1 Loading registers values Propagating registers Forking on input signal I Building branch where I is present Building branch where I is absent

41. SCOC automaton compilation new informations (hot) propagated informations (cold) Initial state built Building state 1 Loading registers values Propagating registers Forking on input signal I Building branch where I is present Building branch where I is absent

42. SCOC automaton compilation new informations (hot) propagated informations (cold) Initial state built Building state 1 Loading registers values Propagating registers Forking on input signal I Building branch where I is present Building branch where I is absent

43. SCOC automaton compilation new informations (hot) propagated informations (cold) Initial state built Building state 1 Loading registers values Propagating registers Forking on input signal I Building branch where I is present Building branch where I is absent

44. SCOC automaton compilation new informations (hot) propagated informations (cold) Initial state built Building state 1 Loading registers values Propagating registers Forking on input signal I Building branch where I is present Building branch where I is absent

45. SCOC automaton compilation new informations (hot) propagated informations (cold) Initial state built Building state 1 Loading registers values Propagating registers Forking on input signal I Building branch where I is present Building branch where I is absent

46. SCOC automaton compilation new informations (hot) propagated informations (cold) Initial state built Building state 1 Loading registers values Propagating registers Forking on input signal I Building branch where I is present Building branch where I is absent State 1 reached again

47. Circuit saving and restoring To avoid saving the whole circuit at each step of automata building : Restoration data are stored in a stack of stacks

48. Circuit saving and restoring To avoid saving the whole circuit at each step of automata building : Restoration data are stored in a stack of stacks

49. Circuit saving and restoring To avoid saving the whole circuit at each step of automata building : Restoration data are stored in a stack of stacks

50. Circuit saving and restoring To avoid saving the whole circuit at each step of automata building : Restoration data are stored in a stack of stacks

51. Circuit saving and restoring To avoid saving the whole circuit at each step of automata building : Restoration data are stored in a stack of stacks

52. Circuit saving and restoring To avoid saving the whole circuit at each step of automata building : Restoration data are stored in a stack of stacks

53. Circuit saving and restoring To avoid saving the whole circuit at each step of automata building : Restoration data are stored in a stack of stacks

54. Circuit saving and restoring To avoid saving the whole circuit at each step of automata building : Restoration data are stored in a stack of stacks

55. Signal relations processing Stored in a directed graph Example : 3  2 2  1 1 # 4 # 5 :present  absent absent  present :present  present :absent  absent

56. Signal relations processing Stored in a directed graph Example : 3  2 2  1 1 # 4 # 5 :present  absent absent  present :present  present :absent  absent

57. Signal relations processing Stored in a directed graph Example : 3  2 2  1 1 # 4 # 5 :present  absent absent  present :present  present :absent  absent

58. Signal relations processing Stored in a directed graph Example : 3  2 2  1 1 # 4 # 5 :present  absent absent  present :present  present :absent  absent

59. Signal relations processing Stored in a directed graph Example : 3  2 2  1 1 # 4 # 5 :present  absent absent  present :present  present :absent  absent

60. Signal relations processing Stored in a directed graph Example : 3  2 2  1 1 # 4 # 5 :present  absent absent  present :present  present :absent  absent

61. Signal relations processing Stored in a directed graph Example : 3  2 2  1 1 # 4 # 5 :present  absent absent  present :present  present :absent  absent

62. Signal relations processing Stored in a directed graph Example : 3  2 2  1 1 # 4 # 5 :present  absent absent  present :present  present :absent  absent

63. Smart circuit evaluation Circuit evaluation algorithm stops as soon as all required nets are stabilized : Registers (determine next state) K0/K1 (determine whether automaton has terminated) Output signals Action nets (side-effects operating on values)

64. Input partitionning After registers propagation : Inputs reachable from required nets will be processed first Other inputs will probably not be processed at all Depending on current state, parts of the circuit are disabled

65. Input sorting Example : bus arbiter Set of cells requesting the access to a data bus Cells have rotating priorities

66. Input sorting Inputs are sorted upon the number of reachable registers This turns transitions from full trees (2 n -sized) to combs (n-sized):

67. DAG sharing present A emit A' end present || present B emit B' end present Goals : Saving memory Emphazing semantic aspects

68. Performance comparison