Increase number of assertions (GlobalAP) + VN cache by EgorBo · Pull Request #124132 · dotnet/runtime

EgorBo · 2026-02-07T19:53:18Z

This PR does two things:

Implements a quick O(1) check to answer: “Do we have any assertions for this VN?”
I initially tried to use this cache everywhere, but ended up keeping it only in a few places where it had a noticeable TP benefit. This change alone has zero size diffs and reduces the TP regression from change (2) by 2×.
Increases the maximum number of assertions (GlobalAP) using a heuristic.
With help from SPMI, I analyzed 1M methods and built a large table: | BB count | TrackedLocals count | assertions created |. I then fed it to an AI agent, which iterated for a while, generated some Python scripts, and proposed a heuristic (after several rounds of SPMI TP/size feedback). This is the best trade-off between improvements and TP regression that I was able to find. We could potentially incorporate more parameters (e.g., number of conditional blocks against null/constant, number of indirects), but I think the current version is good enough for now.

* I had 3 variants and ended up picking the 3rd one due to better TP results (obviously, less of =256 entities)

NOTE: If I unconditionally set optMaxAssertionCount to 256 the size diffs become ~8% better and TP regresses by 3x

The worst-case +0.3% TP regression should be more than covered by my earlier refactoring PRs that improved TP (the combined net effect should be around -0.5%).

Overall, TP-wise, the most expensive thing is the forward flow analysis

dotnet-policy-service · 2026-02-07T19:54:08Z

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Pull request overview

This PR increases Global Assertion Propagation capacity and adds a small VN-based cache to avoid unnecessary full-table assertion scans, benefiting range check/range analysis and assertion propagation throughput.

Changes:

Adjusts optMaxAssertionCount heuristics to allow tracking more assertions (especially for GlobalAP).
Introduces optAssertionVNsMap + optAssertionHasAssertionsForVN() to quickly determine if any assertions exist for a given VN (with lazy initialization).
Uses the VN cache to early-out in range-check assertion merges and GlobalAP local-var assertion propagation.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
`src/coreclr/jit/rangecheck.cpp`	Uses the new VN cache to skip assertion scanning when no assertions exist for the VN.
`src/coreclr/jit/compiler.h`	Adds `optAssertionVNsMap` and declares `optAssertionHasAssertionsForVN()`.
`src/coreclr/jit/assertionprop.cpp`	Updates assertion table sizing, populates/queries the VN cache, and applies new early-out paths in GlobalAP.

src/coreclr/jit/assertionprop.cpp

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

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Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

EgorBo · 2026-02-09T14:03:45Z

@AndyAyersMS @dotnet/jit-contrib PTAL. This is still a hacky way (I mean the heuristic) to deal with the TP regression, but it's better than nothing. Very few regressions, lots of improvements, small TP regression overall.

EgorBo · 2026-02-11T16:21:00Z

ping @AndyAyersMS

Bad merge of two PRs at once. #124132 - introduced a VN cache to find out if we have any assertions for a VN. And #124242 introduced a VN decomposition inside MergeEdgeAssertion loop where it tries to match VNF_ADD(X, CNS). So the fix is to register VNF_ADD's op1 VN as well. As the result, #124242 couldn't find the matching assertion and the FILECHECK test failed due to bounds check in the codegen.

…24132)" This reverts commit 92741be.

#124928) This reverts commit 92741be. This was causing excessive memory allocation during jitting (see dotnet/dotnet#4933).

This reverts commit 92741be.

@akoeplinger

…AP) + VN cache (#124132)" (#124955) Backport of #124928 to release/11.0-preview2 /cc @akoeplinger @AndyAyersMS ## Customer Impact - [ ] Customer reported - [x] Found internally This was causing excessive memory allocation during jitting (see dotnet/dotnet#4933). ## Regression - [X] Yes - [ ] No Caused by: 92741be ## Testing Manual testing. ## Risk Low. Reverts an earlier change. [High/Medium/Low. Justify the indication by mentioning how risks were measured and addressed.] **IMPORTANT**: If this backport is for a servicing release, please verify that: - For .NET 8 and .NET 9: The PR target branch is `release/X.0-staging`, not `release/X.0`. - For .NET 10+: The PR target branch is `release/X.0` (no `-staging` suffix). ## Package authoring no longer needed in .NET 9 **IMPORTANT**: Starting with .NET 9, you no longer need to edit a NuGet package's csproj to enable building and bump the version. Keep in mind that we still need package authoring in .NET 8 and older versions. Co-authored-by: Andy Ayers <andya@microsoft.com>

[Diffs](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1284439&view=ms.vss-build-web.run-extensions-tab) This PR does two things: 1. Implements a quick O(1) check to answer: “Do we have any assertions for this VN?” I initially tried to use this cache everywhere, but ended up keeping it only in a few places where it had a noticeable TP benefit. This change alone has zero size diffs and reduces the TP regression from change (2) by 2×. 2. Increases the maximum number of assertions (GlobalAP) using a heuristic. With help from SPMI, I analyzed 1M methods and built a large table: `| BB count | TrackedLocals count | assertions created |`. I then fed it to an AI agent, which iterated for a while, generated some Python scripts, and proposed a heuristic (after several rounds of SPMI TP/size feedback). This is the best trade-off between improvements and TP regression that I was able to find. We could potentially incorporate more parameters (e.g., number of conditional blocks against null/constant, number of indirects), but I think the current version is good enough for now. <img width="914" height="351" alt="{3217F8D3-BE47-4C82-AA12-0281D51D519C}" src="https://github.com/user-attachments/assets/e76eb379-bfda-4792-9c5b-d918b29a6a62" /> _* I had 3 variants and ended up picking the 3rd one due to better TP results_ (obviously, less of =256 entities) NOTE: If I unconditionally set `optMaxAssertionCount` to **256** the size diffs become ~8% better and TP regresses by 3x The worst-case +0.3% TP regression should be more than covered by my earlier refactoring PRs that improved TP (the combined net effect should be around -0.5%). <img width="1161" height="587" alt="image" src="https://github.com/user-attachments/assets/46cd5c6d-c2ac-4341-9d0f-0cf7a92c8164" /> Overall, TP-wise, the most expensive thing is the forward flow analysis --------- Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Bad merge of two PRs at once. dotnet#124132 - introduced a VN cache to find out if we have any assertions for a VN. And dotnet#124242 introduced a VN decomposition inside MergeEdgeAssertion loop where it tries to match VNF_ADD(X, CNS). So the fix is to register VNF_ADD's op1 VN as well. As the result, dotnet#124242 couldn't find the matching assertion and the FILECHECK test failed due to bounds check in the codegen.

Copilot AI review requested due to automatic review settings February 7, 2026 19:53

github-actions bot added the area-CodeGen-coreclr CLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI label Feb 7, 2026

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MSBuild crashing in the build #92290

Open

Test failure: baseservices/exceptions/stackoverflow/stackoverflowtester/stackoverflowtester.cmd #110173

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impl

732a71e

EgorBo force-pushed the cache-vn-2 branch from 782abc8 to 732a71e Compare February 8, 2026 01:31

Apply suggestions from code review

3e2dcfc

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Copilot AI review requested due to automatic review settings February 8, 2026 03:01

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build-analysis bot mentioned this pull request Feb 8, 2026

Crossgen2 coreroot_determinism test failure (exit code 134) #124052

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EgorBo marked this pull request as ready for review February 9, 2026 14:03

EgorBo requested a review from AndyAyersMS February 9, 2026 14:04

This was referenced Feb 9, 2026

Checkout failure: "Git fetch failed with exit code 128" dotnet/arcade#9009

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Unable to checkout dotnet/dnceng#4115

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AndyAyersMS approved these changes Feb 11, 2026

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EgorBo merged commit 92741be into dotnet:main Feb 11, 2026
136 checks passed

EgorBo deleted the cache-vn-2 branch February 11, 2026 18:41

EgorBo mentioned this pull request Feb 11, 2026

Fix failed ElidedBoundsChecks test #124306

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dotnet-maestro bot mentioned this pull request Feb 12, 2026

[main] Source code updates from dotnet/runtime dotnet/dotnet#4810

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AndyAyersMS added a commit to AndyAyersMS/runtime that referenced this pull request Feb 26, 2026

Revert "Increase number of assertions (GlobalAP) + VN cache (dotnet#1…

b63b9f4

…24132)" This reverts commit 92741be.

janvorli mentioned this pull request Feb 27, 2026

Memory blowing up during dotnet/dotnet repo build #124931

Open

AndyAyersMS added a commit that referenced this pull request Feb 27, 2026

Revert "Increase number of assertions (GlobalAP) + VN cache (#124132)" (

71ffd70

#124928) This reverts commit 92741be. This was causing excessive memory allocation during jitting (see dotnet/dotnet#4933).

github-actions bot pushed a commit that referenced this pull request Feb 27, 2026

Revert "Increase number of assertions (GlobalAP) + VN cache (#124132)"

4d369f2

This reverts commit 92741be.

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Increase number of assertions (GlobalAP) + VN cache#124132

Increase number of assertions (GlobalAP) + VN cache#124132
EgorBo merged 2 commits intodotnet:mainfrom
EgorBo:cache-vn-2

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