I'm not sure I understand the problem exactly. If we have one pass converting the concrete syntax to the AST, we can mark functions as generators as part of that pass. In a later pass, you can remove the unreachable code.
Jeremy On Sat, May 3, 2008 at 12:51 AM, Thomas Lee <[EMAIL PROTECTED]> wrote: > The next problem that cropped up during the implementation of the AST code > optimizer is related to branch elimination and the elimination of any code > after a return. > > Within a FunctionDef node, we would (ideally) like to blow away If nodes > with a constant - but false - test expression. e.g.: > > def foo(): > if False: > # ... stuff ... > > For most functions, this will cause no problems and the code will behave as > expected. However, if the eliminated branch contains a "yield" expression, > the function is actually a generator function - even if the yield expression > can never be reached: > > def foo(): > if False: > yield 5 > > In addition to this, the following should also be treated as a generator > even though we'd like to be able to get rid of all the code following the > "return" statement: > > def foo(): > return > yield 5 > > Again, blowing away the yield results in a normal function instead of a > generator. Not what we want: we need to preserve the generator semantics. > > Upon revisiting this, it's actually made me reconsider the use of a Const > node for the earlier problem relating to arbitrary constants. We may be > better off with annotations after all ... then we could mark FunctionDef > nodes as being generators at the AST level to force the compiler to produce > code for a generator, but eliminate the branches anyway. > > The other alternative I can think of is injecting a yield node somewhere > unreachable and ensuring it doesn't get optimized away, but this seems > pretty hacky in comparison. > > Any other ideas? > > Cheers, > Tom > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > http://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: > http://mail.python.org/mailman/options/python-dev/jeremy%40alum.mit.edu > _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
