[Python-Dev] Bytecode analysis (original) (raw)

Skip Montanaro skip@pobox.com
Tue, 25 Feb 2003 16:59:03 -0600 

Damien> Ive done a static analysis of the bytecodes from compiling the
Damien> python standard library:

...

Nice input, but I think you should deal with dynamic opcode frequencies. See the #define's in the ceval.c source for how to enable that and the recent thread in c.l.py. In short, it doesn't really matter how many LOAD_CONST instructions appear in the bytecode stream, only how many of them are executed. While LOAD_CONST is a relatively frequently executed opcode, if I recall correctly, LOAD_FAST is much more frequently executed, and LOAD_CONST is already pretty fast, so adding special opcodes probably won't buy you much and runs the risk of disturbing what locality of reference exists.

The LOAD_IF_FALSE issue was discussed recently (here I think). The problem is that chained operations like

if a < b < c:
    ...

require the value be retained. You could get rid of the separate POP_TOP instruction but it would require some work in the compiler.

as-always-patches-are-welcome-ly, y'rs,

Skip