Description

markshannon

opened on Nov 20, 2025

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With the tracing front-end to the JIT we are producing longer traces than before.
This should be good, but results in very large chunks of machine code.
Large chunks of machine code are bad because:

• It takes longer and uses more memory
• It puts a lot of pressure on the icache, possibly evicting the interpreter
• It makes handling of inline data and branches less efficient as the targets are further away.

To be clear, the problem is not the number of uops per trace, but the amount of machine code per uop.

Things we can do to fix this:

• Move code into helper functions for the larger uops
• Move complex decref sequences for DECREF_INPUTS() into helper functions.

(We can also do more optimizations to remove more uops, but that's a separate issue and we're doing it anyway)

Linked PRs

• GH-141794: Limit size of generated machine code. #142228
• gh-141794: Reduce size of compiler stress tests to fix Android warnings #142263
• GH-141794: Fix reference leaks introduced in GH-142228 #142257
• [3.14] gh-141794: Reduce size of compiler stress tests to fix Android warnings (GH-142263) #142386
• [3.13] gh-141794: Reduce size of compiler stress tests to fix Android warnings (GH-142263) #142409

Activity

1. markshannon

   added

   performancePerformance or resource usagePerformance or resource usage

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

   topic-JIT

   3.15bugs and security fixesbugs and security fixes

   on Nov 20, 2025
2. picnixz

   added

   type-featureA feature request or enhancementA feature request or enhancement

   and removed

   3.15bugs and security fixesbugs and security fixes

   on Dec 3, 2025
3. markshannon

   added a commit that references this issue on Dec 3, 2025

   GH-141794: Limit size of generated machine code. (GH-142228)

   62423c9
4. StanFromIreland

   added a commit that references this issue on Dec 6, 2025

   pythonGH-141794: Limit size of generated machine code. (pythonGH-142228)

   9a30601
5. Eclips4

   added a commit that references this issue on Dec 7, 2025

   gh-141794: Reduce size of compiler stress tests to fix Android warnin…

   f193c8f
6. miss-islington

   added a commit that references this issue on Dec 7, 2025

   pythongh-141794: Reduce size of compiler stress tests to fix Android …

   234148a
7. Eclips4

   added a commit that references this issue on Dec 8, 2025

   [3.14] gh-141794: Reduce size of compiler stress tests to fix Android…

   d2f5a0e
8. mhsmith

   added a commit that references this issue on Dec 8, 2025

   [3.13] pythongh-141794: Reduce size of compiler stress tests to fix A…

   4032012
9. Eclips4

   added a commit that references this issue on Dec 8, 2025

   [3.13] gh-141794: Reduce size of compiler stress tests to fix Android…

   2ef7698

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