[Python-Dev] Wordcode: new regular bytecode using 16-bit units
ericfahlgren at gmail.com
Wed Apr 13 17:35:27 EDT 2016
The EXTENDED_ARG is included in the multibyte ops, I treat it just like any
other operator. Here's a snippet of my hacked-dis.dis output, which made
it clear to me that I could just count them as an "operator with word
Line 3000: x = x if x or not x and x is None else x
0001dc83 7c 00 00 LOAD_FAST x
0001dc86 91 01 00 EXTENDED_ARG 1
0001dc89 70 9f dc JUMP_IF_TRUE_OR_POP L1dc9f
0001dc8c 7c 00 00 LOAD_FAST x
0001dc8f 0c UNARY_NOT
0001dc90 91 01 00 EXTENDED_ARG 1
0001dc93 6f 9f dc JUMP_IF_FALSE_OR_POPL1dc9f
0001dc96 7c 00 00 LOAD_FAST x
0001dc99 74 01 00 LOAD_GLOBAL None
0001dc9c 6b 08 00 COMPARE_OP 'is'
0001dc9f 91 01 00 EXTENDED_ARG 1
0001dca2 72 ab dc POP_JUMP_IF_FALSE L1dcab
0001dca5 7c 00 00 LOAD_FAST x
0001dca8 6e 03 00 JUMP_FORWARD L1dcae (+3)
0001dcab 7c 00 00 LOAD_FAST x
0001dcae 7d 00 00 STORE_FAST x
On Wed, Apr 13, 2016 at 2:23 PM, Victor Stinner <victor.stinner at gmail.com>
> 2016-04-13 23:02 GMT+02:00 Eric Fahlgren <ericfahlgren at gmail.com>:
> > Percentage of 1-byte args = 96.80%
> Yeah, I expected such high ratio. Good news that you confirm it.
> > Non-argument ops = 53,719
> > One-byte args = 368,787
> > Multi-byte args = 12,191
> Again, only a very few arguments take multiple bytes. Good, the
> bytecode will be smaller.
> IMHO it's more a nice side effect than a real goal. The runtime
> performance matters more than the size of the bytecode, it's not like
> a bytecode take 4 MB. It's probably closer to 1 KB and so can probably
> benefit of the fatest CPU caches.
> > Just for the record, here's my arithmetic:
> > byteCodeSize = 1*nonArgumentOps + 3*oneByteArgs + 3*multiByteArgs
> > wordCodeSize = 2*nonArgumentOps + 2*oneByteArgs + 4*multiByteArgs
> If multiByteArgs means any size > 1 byte, the wordCodeSize formula is
> - no parameter: 2 bytes
> - 8-bit parameter: 2 bytes
> - 16-bit parameter: 4 bytes
> - 24-bit parameter: 6 bytes
> - 32-bit parameter: 8 bytes
> But you wrote that you didn't see EXTEND_ARG, so I guess that
> multibyte means 16-bit in your case, and so your formula is correct.
> Hopefully, I don't expect 32-bit parameters in the wild, only 24-bit
> parameter for function with annotation.
> > (It is interesting to note that I have never encountered an EXTENDED_ARG
> operator in the wild, only in my own synthetic examples.)
> As I wrote, EXTENDED_ARG can be seen when MAKE_FUNCTION is used with
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the Python-Dev