2011/3/12 Benjamin Peterson <benja...@python.org> > 2011/3/11 Raymond Hettinger <raymond.hettin...@gmail.com>: > > Today, there was a significant check-in to the peephole optimizer that I > > think should be reverted: > > http://hg.python.org/cpython/rev/14205d0fee45/ > > The peephole optimizer pre-dated the introduction of the abstract syntax > > tree. Now that we have an AST, the preferred way to implement additional > > optimizations is with AST manipulation, upstream from code generation. > This > > approach is faster and much more reliable than the more brittle approach > > of disassembling, analyzing, and rewriting the bytecode created by the > > compiler. > > The problem is no such AST optimizer exists. It's one thing avoid > changing old code because an improved version is in the works or > available (say argparse in lieu of getopt) and quite another when no > replacement code exists. At the moment, there is little reason not to > accept progressive improvements (with sights on overall design as > usual) to the code. > > IMO, Ast or not ast statically optimizing python in any meaningful way > is a impossible task anyway. So, a better solution would be to just > rip the thing out. > > -- > Regards, > Benjamin
It's not true. I already moved almost all peephole optimizations (introducing others, as well) from peephole.c to ast.c<http://code.google.com/p/wpython2/source/browse/Python/ast.c?repo=wpython11>and compiler.c<http://code.google.com/p/wpython2/source/browse/Python/compile.c?repo=wpython11>in WPython 1.1. Take a look at pages 21-23 of this<http://wpython2.googlecode.com/files/Cleanup%20and%20new%20optimizations%20in%20WPython%201.1.pdf> . Also, optimizations can be done not only for numbers, but even for tuples, lists, dictionaries, and... slices (pag. 22). See pages 21-24 of this<http://wpython2.googlecode.com/files/Beyond%20Bytecode%20-%20A%20Wordcode-based%20Python.pdf> . Cesare
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