Description

markshannon

opened on Mar 20, 2025

Issue body actions

Top-of-stack caching is technique where one or more values on the top of the stack are kept in local variables, with the assumption that the C compiler will put them in registers.

We should implement this for the interpreter (tier 1).
We cannot afford to increase the number of instructions by much, so we'll have to use a fixed size cache of 1.
This will likely only produce a modest speedup, as the total memory traffic is unlikely to decrease. There should be some ILP improvements.

The main benefit of TOS caching is likely to be in the JIT where we can use a variable sized cache.
We want to do it in the interpreter first though, as it will be simpler and requires a subset of the changes needed for the JIT.

Linked PRs

• GH-131498: Remove conditional stack effects #131499
• GH-131498: Another refactoring of the code generator #131827
• GH-131498: Cases generator: Parse down to C statement level. #131948
• GH-131498: manage stacks automatically #132074
• GH-131498: Allow 'peek' variables to be modified #132506
• GH-131498: Replace single-element arrays with scalars in bytecodes.c #132615
• gh-131498: Remove commented-out dead code in cases_generator/analyzer.py #141168
• [3.15] gh-131498: Remove commented-out dead code in cases_generator/analyzer.py (GH-141168) #160461

Activity

1. markshannon

   added a commit that references this issue on Mar 20, 2025

   GH-131498: Remove conditional stack effects (GH-131499)

   7ebd71e
2. picnixz

   added

   type-featureA feature request or enhancementA feature request or enhancement

   interpreter-core(Objects, Python, Grammar, and Parser dirs)(Objects, Python, Grammar, and Parser dirs)

   performancePerformance or resource usagePerformance or resource usage

   on Mar 22, 2025
3. markshannon

   added a commit that references this issue on Mar 31, 2025

   GH-131498: Another refactoring of the code generator (GH-131827)

   c535a13
4. python

   deleted a comment from hasanisaeed on Mar 31, 2025
5. markshannon

   added 2 commits that reference this issue on Apr 2, 2025

   GH-131498: Cases generator: Parse down to C statement level. (GH-131948)

   ad053d8

   GH-131498: Cases generator: manage stacks automatically (GH-132074)

   7099c75
6. picnixz

   added a commit that references this issue on Apr 5, 2025

   pythonGH-131498: Cases generator: manage stacks automatically (python…

   0b437c4
7. markshannon

   added a commit that references this issue on Apr 14, 2025

   GH-131498: Cases generator: Allow input and 'peek' variables to be mo…

   844596c
8. brandtbucher

   added a commit that references this issue on Apr 18, 2025

   GH-131498: Replace single-element arrays with scalars in bytecodes.c (G…

   40ae889
9. markshannon commented on Jun 11, 2025

   

   markshannon

   on Jun 11, 2025

   MemberAuthor

   More actions

   It turns out that caching a single value in the interpreter has no positive effect on performance. Probably what is happening is that any speedup from improved IPC is being undone by increased overhead of spilling around escapes.

   However, all the work done is necessary for #135379 which will improve performance.
10. markshannon

    closed this as completedon Jun 11, 2025
11. ambv

    added 2 commits that reference this issue on Oct 23, 2026

    gh-131498: Remove commented-out dead code in cases_generator/analyzer…

    1c75034

    [3.15] gh-131498: Remove commented-out dead code in cases_generator/a…

    c4f6007

Issue actions