Antoine Pitrou schrieb:
Hi,
Maciej Fijalkowski did an opcode analysis for PyPy,
it also shows the relative frequency of opcodes following a
specifc one:
http://codespeak.net/svn/user/fijal/opcodes.txt
Nice, but we have to be careful here: what is the tested workload?
For example, I find it hard to believe that CALL_FUNCTION_VAR_KW would
always (99%) be followed by STORE_FAST.
I'm sorry, I should have given a reference to the original message:
http://codespeak.net/pipermail/pypy-dev/2008q2/004666.html
I'm not even sure we're talking about the same VM/compiler. What are
CALL_LIKELY_BUILTIN and LOOKUP_METHOD? :-)
He used the PyPy compiler, of course.
Might it make sense to add more PREDICT()ions based
on this, e.g. for BUILD_SLICE -> BINARY_SUBSCR?
This particular one sounds fine, yes.
Another approach is to create opcodes which better reflect actual usage.
For example part of the following patch (*) was to create opcodes fusing
JUMP_IF_{TRUE,FALSE} and POP_TOP. This is because in most cases, you want
to pop the comparison result regardless of its value (true or false), which
nowadays produces the following kind of code:
JUMP_IF_FALSE <branch_for_false>
POP_TOP
[... do stuff and then ...]
JUMP_FORWARD <branch_for_false_after_pop_top>
branch_for_false:
POP_TOP
branch_for_false_after_pop_top:
[etc.]
With a JUMP_IF_FALSE which also pops the pop of the stack, this gives:
JUMP_IF_FALSE <branch_for_false>
[... do stuff and then ...]
branch_for_false:
[etc.]
Prediction doesn't help you in this case.
Agreed; is there a way for a JUMP to end up without popping the top
after jumping? It would have to do a DUP first then.
Georg
_______________________________________________
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
