Remove more write-barriers by EgorBo · Pull Request #128238 · dotnet/runtime

EgorBo · 2026-05-15T00:17:50Z

GT_STORE_BLK now uses the same address analysis as GT_STOREIND

For block stores that contain GC pointers, attempt to prove via VN/assertion analysis that the destination address is not on the GC heap, and if so set GTF_IND_TGT_NOT_HEAP. This enables fast non-barrier codegen for CpObj (genCodeForCpObj's dstOnStack path replacing per-slot CORINFO_HELP_ASSIGN_BYREF with movsp) and SIMD-based zeroing for InitBlk (via IsOnHeapAndContainsReferences). Also update IsOnHeapAndContainsReferences() to honor GTF_IND_TGT_NOT_HEAP. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

dotnet-policy-service · 2026-05-15T00:19:20Z

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Pull request overview

Extends the JIT's write-barrier elimination (previously only for STOREIND) to STORE_BLK nodes. When VN/assertion analysis can prove that a block-store destination is not on the GC heap, the new helper sets GTF_IND_TGT_NOT_HEAP, which lets codegen take the fast non-barrier CpObj/SIMD InitBlk paths. Also strengthens GetWriteBarrierForm's GT_ADD analysis so it can recurse on the TYP_BYREF/TYP_REF operand even when the offset is non-constant, mirroring GCInfo::gcWriteBarrierFormFromTargetAddress.

Changes:

Add optWriteBarrierAssertionProp_StoreBlk and dispatch it from optAssertionProp_BlockStore.
Teach GetWriteBarrierForm's GT_ADD case to identify the BYREF/REF base operand by VN type when neither operand is a constant; switch the func compare to VNF_ADD and route the StoreInd calls through optConservativeNormalVN (also normalizes the VN before VNVisitReachingVNs).
Update GenTreeBlk::IsOnHeapAndContainsReferences to honor GTF_IND_TGT_NOT_HEAP.

Reviewed changes

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

File	Description
src/coreclr/jit/gentree.h	`IsOnHeapAndContainsReferences` now also returns false when `GTF_IND_TGT_NOT_HEAP` is set, so the new assertion-prop result feeds CpObj/InitBlk decisions.
src/coreclr/jit/compiler.h	Declares the new `optWriteBarrierAssertionProp_StoreBlk`; widens `optConservativeNormalVN` to take `const GenTree*`.
src/coreclr/jit/assertionprop.cpp	Adds the BYREF-base recursion in `GetWriteBarrierForm`, switches to `VNF_ADD`, normalizes VNs through `optConservativeNormalVN`, and implements the new `STORE_BLK` write-barrier removal helper.

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

Copilot

Pull request overview

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

Copilot

Pull request overview

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

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

Copilot

Pull request overview

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

EgorBo · 2026-05-15T13:11:47Z

@MihuBot

EgorBo · 2026-05-15T13:15:02Z

@MihuBot -nuget

MihaZupan · 2026-05-15T14:28:42Z

@MihuBot -nuget

Copilot

Pull request overview

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

Copilot

Pull request overview

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

github-actions · 2026-05-17T00:54:07Z

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🤖 Copilot Code Review — PR #128238

Holistic Assessment

Motivation: Justified. GT_STORE_BLK nodes containing GC pointers already benefit from write-barrier elimination when the address is a GT_LCL_ADDR, but CSE can hide that behind a local, making this optimization unreachable. Extending the same VN-based analysis from STOREIND to STORE_BLK is a natural next step.

Approach: Sound. The new optWriteBarrierAssertionProp_StoreBlk mirrors the address-analysis portion of the existing STOREIND path, and the IsOnHeapAndContainsReferences change propagates the flag so downstream lowering/codegen respects it. The const qualification and VNF_ADD fix are good cleanups.

Summary: ✅ LGTM. The change is small, consistent with established patterns, and the previous review concerns (type mismatch bug, missing WBF_BarrierUnchecked handling) have been addressed in subsequent commits.

Detailed Findings

✅ Correctness — Address analysis reuse is safe

GetWriteBarrierForm is a pure function over VNs and is already validated by the STOREIND path. Reusing it for STORE_BLK addresses is correct. The early-out conditions (local assertion prop, no GC pointers, flag already set) match the STOREIND guard logic.

✅ `IsOnHeapAndContainsReferences` change is consistent

Adding (gtFlags & GTF_IND_TGT_NOT_HEAP) == 0 means callers in lowering and codegen (lowerxarch, codegenxarch, lsraxarch) that use this predicate to decide whether SIMD moves are safe will now correctly account for the new assertion-derived flag — a block proven not-on-heap won't be forced into per-pointer stores.

💡 JITDUMP messages end with trailing ": "

The JITDUMP strings in the new function ("Add GTF_IND_TGT_NOT_HEAP to STORE_BLK [%06d]: ") end with a colon-space but nothing follows before the return. The STOREIND counterpart prints a descriptive suffix ("is not needed at all.\n"). This is cosmetic and doesn't affect correctness, but adding a \n or a brief suffix would improve diagnostic readability.

✅ VNF_ADD fix and const qualification

The VNFunc(GT_ADD) → VNF_ADD change aligns with how VN funcs are referenced elsewhere in the file (e.g., line 5440). The const GenTree* change to optConservativeNormalVN is safe since the function only reads gtVNPair.

Generated by Code Review for issue #128238 · ● 1.9M · ◷

EgorBo and others added 2 commits May 15, 2026 01:44

remove more wb

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github-actions Bot added the area-CodeGen-coreclr CLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI label May 15, 2026

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Potential fix for pull request finding

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Update assertionprop.cpp

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Potential fix for pull request finding

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fix format

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EgorBo marked this pull request as ready for review May 15, 2026 02:14

Merge branch 'main' into improve-wb

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MihuBot mentioned this pull request May 15, 2026

[JitDiff X64] [EgorBo] Remove more write-barriers MihuBot/runtime-utils#1906

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MihuBot mentioned this pull request May 15, 2026

[JitDiff X64] [EgorBo] Remove more write-barriers MihuBot/runtime-utils#1907

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MihuBot mentioned this pull request May 15, 2026

[JitDiff X64] [EgorBo] Remove more write-barriers MihuBot/runtime-utils#1909

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Merge branch 'main' into improve-wb

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Update assertionprop.cpp

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Merge branch 'main' into improve-wb

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build-analysis Bot mentioned this pull request May 17, 2026

[wasm] Tests failing with DirectoryNotFoundException trying to load test data #128293

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github-actions Bot commented May 17, 2026

🤖 Copilot Code Review — PR #128238

Holistic Assessment

Detailed Findings

✅ Correctness — Address analysis reuse is safe

✅ IsOnHeapAndContainsReferences change is consistent

💡 JITDUMP messages end with trailing ": "

✅ VNF_ADD fix and const qualification

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EgorBo commented May 15, 2026 •

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✅ `IsOnHeapAndContainsReferences` change is consistent