[issue2499] Fold unary + and not on constants
Raymond Hettinger
report at bugs.python.org
Fri Mar 28 08:25:25 CET 2008
Raymond Hettinger <rhettinger at users.sourceforge.net> added the comment:
It would be helpful if we talked before going further on build-outs to
the peephole optimizer. IIRC, we chose to not do this one because it
interfered with other more important optimizations.
More importantly, we decided that the peepholer is the wrong place to
do much of this work. Most of the peepholer is going to be migrated
up the chain, after the AST is generated, but before the opcodes are
generated. That is a faster, more reliable, and more general
approach.
The constant folding anti-duplication patch should also not be done
for this same reason. That patch slows down compilation and makes it
more fragile but does not add speed (just like the dead code
elimination patches). When the peepholer is moved-up, the anti-
duplication code won't be needed (as you won't need its attendant
rescan/rewrite pass of the bytecode).
You're writing these faster than I have time to review and likely
reject them. Please show some moderation. The peepholer is
intentionally very conservative.
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nosy: +rhettinger
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