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/rpython/translator/backendopt/tailrecursion.py

https://bitbucket.org/pypy/pypy/
Python | 33 lines | 29 code | 3 blank | 1 comment | 4 complexity | ca2918a06ba06f5342209d6a5374cbe1 MD5 | raw file
Possible License(s): AGPL-3.0, BSD-3-Clause, Apache-2.0 
    

  1. from rpython.flowspace.model import mkentrymap, checkgraph
    2. 

  2. 

  3. # this transformation is very academical -- I had too much time
    4. 

  4. 

  5. def _remove_tail_call(translator, graph, block):
    6. 

  6.     print "removing tail call"
    7. 

  7.     assert len(block.exits) == 1
    8. 

  8.     assert block.exits[0].target is graph.returnblock
    9. 

  9.     assert block.operations[-1].result == block.exits[0].args[0]
    10. 

  10.     op = block.operations[-1]
    11. 

  11.     block.operations = block.operations[:-1]
    12. 

  12.     block.exits[0].args = op.args[1:]
    13. 

  13.     block.exits[0].target = graph.startblock
    14. 

  14. 

  15. def remove_tail_calls_to_self(translator, graph):
    16. 

  16.     entrymap = mkentrymap(graph)
    17. 

  17.     changed = False
    18. 

  18.     for link in entrymap[graph.returnblock]:
    19. 

  19.         block = link.prevblock
    20. 

  20.         if (len(block.exits) == 1 and
    21. 

  21.             len(block.operations) > 0 and
    22. 

  22.             block.operations[-1].opname == 'direct_call' and
    23. 

  23.             block.operations[-1].result == link.args[0]):
    24. 

  24.             print "getgraph", graph
    25. 

  25.             if graph is graph:
    26. 

  26.                 _remove_tail_call(translator, graph, block)
    27. 

  27.                 changed = True
    28. 

  28.     if changed:
    29. 

  29.         from rpython.translator import simplify
    30. 

  30.         checkgraph(graph)
    31. 

  31.         simplify.remove_identical_vars(graph)
    32. 

  32.         simplify.eliminate_empty_blocks(graph)
    33. 

  33.         simplify.join_blocks(graph)
    34. 

  34.