New submission from Mark Shannon <[email protected]>:
While the impact of making `if 0` and `while True` appear when tracing can be
mitigated, the impact of `continue` is more of a concern.
The following loop:
while True:
if test:
continue
rest
PEP 626 requires that the `continue` is traced, and continue can occur once per
iteration. So inserting a NOP for a continue will have a measurable impact on
performance.
In some cases the NOP can be folded into the preceding or following bytecode,
but often it cannot because the code is both branchy and spread across several
lines.
If PEP 626 allowed zero-width entries in the line number table, then any
remaining NOPs could be eliminated in the assembler, at the cost of a little
additional complexity in `maybe_call_line_trace()`
----------
assignee: Mark.Shannon
components: Interpreter Core
messages: 383585
nosy: Mark.Shannon, pablogsal, rhettinger, serhiy.storchaka
priority: normal
severity: normal
stage: needs patch
status: open
title: Allow zero-width entries in code.co_lines()
type: performance
versions: Python 3.10
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Python tracker <[email protected]>
<https://bugs.python.org/issue42718>
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