On 04/06/16 10:02, Eric Snow wrote:

You should get in touch with Mark Shannon, while you're working on ceval. He has some definite improvements that can be made to the eval loop.

See http://bugs.python.org/issue17611 for my suggested improvements. I've made a new comment there. Cheers, Mark.

-eric

On Sat, Jun 4, 2016 at 2:08 AM, Serhiy Storchaka wrote:

...

Following the converting 8-bit bytecode to 16-bit bytecode (wordcode), there are other issues for improving the bytecode.

1. http://bugs.python.org/issue27129 Make the bytecode more 16-bit oriented.

2. http://bugs.python.org/issue27140 Add new opcode BUILD_CONST_KEY_MAP for building a dict with constant keys. This optimize the common case and especially helpful for two following issues (creating and calling functions).

3. http://bugs.python.org/issue27095 Simplify MAKE_FUNCTION/MAKE_CLOSURE. Instead packing three numbers in oparg the new MAKE_FUNCTION takes built tuples and dicts from the stack. MAKE_FUNCTION and MAKE_CLOSURE are merged in the single opcode.

4. http://bugs.python.org/issue27213 Rework CALL_FUNCTION* opcodes. Replace four existing opcodes with three simpler and more efficient opcodes.

5. http://bugs.python.org/issue27127 Rework the for loop implementation.

6. http://bugs.python.org/issue17611 Move unwinding of stack for "pseudo exceptions" from interpreter to compiler.

_______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/ericsnowcurrently%40gmail...

On 05.06.16 21:24, Raymond Hettinger wrote:

...

On Jun 4, 2016, at 1:08 AM, Serhiy Storchaka wrote: 1. http://bugs.python.org/issue27129 Make the bytecode more 16-bit oriented.

I don' think this should be done. Adding the /2 and *2 just complicates the code and messes with my ability to reason about jumps.

With VM opcodes, there is always a tension between being close to implementation (what byte address are we jumping to) and being high level (what is the word offset). In this case, I think we should stay with the former because they are primarily used in ceval.c and peephole.c which are close to the implementation. At the higher level, there isn't any real benefit either (because dis.py already does a nice job of translating the jump targets).

Here is one example of the parts of the diff that cause concern that future maintenance will be made more difficult by the change:

- j = blocks[j + i + 2] - blocks[i] - 2; + j = (blocks[j * 2 + i + 2] - blocks[i] - 2) / 2;

Reviewing the original line only gives me a mild headache while the second one really makes me want to avert my eyes ;-)

The /2 and *2 are added just because Victor wants to keep f_lineno counting bytes. Please look at my first patch. It doesn't contain /2 and *2. It even contains much less +2 and -2. For example the above change looks as: - j = blocks[j + i + 2] - blocks[i] - 2; + j = blocks[j + i + 1] - blocks[i] - 1; Doesn't this give you less headache?

...

2. http://bugs.python.org/issue27140 Add new opcode BUILD_CONST_KEY_MAP for building a dict with constant keys. This optimize the common case and especially helpful for two following issues (creating and calling functions).

This shows promise.

The proposed name BUILD_CONST_KEY_MAP is much more clear than BUILD_MAP_EX.

If you accept this patch, I'll commit it. At least two other issues wait this.

...

5. http://bugs.python.org/issue27127 Rework the for loop implementation.

I'm unclear what problem is being solved by requiring that GET_ITER always followed immediately by FOR_ITER.

As I understand, the purpose was to decrease the number of executed opcodes. It looks to me that existing patch is not acceptable, because there is a reason for using two opcodes in the for loop start. But I think that we can use other optimization here. I'll try to write a patch.