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[cdac] x86 GCInfo decoder + PromoteCallerStack -> GCRefMap; enforce 0 known issues on windows-x86/x64 - #129858

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[cdac] x86 GCInfo decoder + PromoteCallerStack -> GCRefMap; enforce 0 known issues on windows-x86/x64#129858
max-charlamb merged 4 commits into
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max-charlamb:x86-gc-info-w-argiterator

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@max-charlambmax-charlamb commented Jun 25, 2026•
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This PR was authored with assistance from GitHub Copilot.

Summary

Fixes#126359.

Brings the cDAC IGCInfoDecoder x86 implementation (originally on the now-closed PR #129547) plus the GcScanner.PromoteCallerStack rewire (using ICallingConvention.TryComputeArgGCRefMapBlob from #129769) into a single change, and tightens the GCREFS stress assertion so any non-zero KnownIssues count on Windows x86 / x64 fails the test.

After this change, x86 cDAC stack walking is at full parity with the runtime for the cdacstress GCREFS suite (BasicAlloc local run: 4798 / 4798 pass, 0 known, 0 fail).

Three logical groupings

1. x86 IGCInfoDecoder implementation (28 commits, the bulk of the diff)

Implements EnumerateLiveSlots and GetInterruptibleRanges on x86 by walking the legacy InfoHdr byte-stream and the per-offset Transitions already decoded in GCInfo.cs / GCArgTable.cs. Includes a long tail of correctness fixes uncovered by the cdacstress harness: 0xFB huge-encoding code-delta is cumulative; partial-EBP this-pointer-tag bytes do not record a call entry; ESP-frame untracked / VarPtr slots need a pushedSize bias; ApplyPointerTransition honors IsPtr=false for non-pointer pushes; etc.

2. GcScanner.PromoteCallerStack rewire (1 commit + 1 supporting commit)

Replaces the RecordDeferredFrame stub with a real implementation that synthesizes a GCRefMap blob via ICallingConvention.TryComputeArgGCRefMapBlob and runs the same token-iteration loop as the R2R-backed PromoteCallerStackUsingGCRefMap. Falls back to RecordDeferredFrame on unsupported targets (non-Windows or non-x86/x64) and on any failure to synthesize a blob. The supporting commit adds the PInvokeCalliFrame data class used by the x86 HandleTransitionFrame override (PInvokeCalliFrame has no MethodDesc so it falls back to VASigCookie.SizeOfArgs).

Also adds:

  • GCRefMapDecoder(byte[]) second constructor so synthesized blobs can be decoded with the same bit-stream reader as TargetPointer-resident blobs.
  • X86FrameHandler.HandleTransitionFrame override -- decodes the leading ReadStackPop() of the synthesized blob to recover cbStackPop on x86.
  • EnumerateGCRefMapTokens helper, factored out so both the R2R-blob and synthesized-blob paths share the same token-iteration loop.

3. Stress framework hardening

  • CdacStressTests.GCRefStress_AllVerificationsPass: removed the if (arch == Architecture.X86) throw new SkipTestException block.
  • CdacStressTestBase.AssertAllPassed: on Windows x86 / x64, fail the test if results.KnownIssues > 0. Every transition Frame's caller-stack scan must succeed via ICallingConvention.TryComputeArgGCRefMapBlob.

Local validation (windows-x86 Checked)

BasicAlloc smoke test:

Total verifications: 4,798
Passed: 4,798
Failed: 0
Known issues: 0
Frames examined: 64,406 (all matched)

cDAC unit tests: 2611 / 2611 pass.

Full GCRefStress suite will be validated by CI.

Scope notes

CopilotAI review requested due to automatic review settings June 25, 2026 15:30
CopilotAI reviewed Jun 25, 2026
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Pull request overview

This PR expands the cDAC stack-walking and stress infrastructure by wiring Windows x86 transition-frame caller scanning to the shared ICallingConvention/GCRefMap machinery, and by extending the in-proc cdacstress harness to support multiple sub-checks (GCREFS + ARGITER) with richer test/debuggee coverage.

Changes:

  • Reworked caller-stack promotion to optionally synthesize and decode GCRefMap blobs via a new ICallingConvention.TryComputeArgGCRefMapBlob path and shared token enumeration.
  • Extended cdacstress configuration/telemetry (flag layout, [GC_STATS] / [ARG_STATS]) and updated managed stress harness parsing/assertions; added multiple new stress debuggees.
  • Refactored/shared calling convention code (ArgIterator/TransitionBlock/ITypeHandle) for reuse by cDAC and ReadyToRun tooling.

Reviewed changes

Copilot reviewed 60 out of 60 changed files in this pull request and generated 4 comments.

Show a summary per file
FileDescription
src/native/managed/cdac/tests/StressTests/RunStressTests.ps1Updates stress flag documentation/defaults to new WHERE/WHAT/MODIFIER layout.
src/native/managed/cdac/tests/StressTests/README.mdDocuments new flag regions, sub-check markers, and updated defaults.
src/native/managed/cdac/tests/StressTests/known-issues.mdUpdates defaults and adds documentation for an intermittent x86 flake.
src/native/managed/cdac/tests/StressTests/Debuggees/VarArgs/VarArgs.csprojAdds VarArgs debuggee project file.
src/native/managed/cdac/tests/StressTests/Debuggees/VarArgs/Program.csAdds varargs-focused ARGITER debuggee.
src/native/managed/cdac/tests/StressTests/Debuggees/StructScenarios/Program.csAdds nested-struct scenario to stress ArgIterator/GCDesc paths.
src/native/managed/cdac/tests/StressTests/Debuggees/CrossModule/Program.csAdds cross-module signature/type-resolution debuggee.
src/native/managed/cdac/tests/StressTests/Debuggees/CrossModule/Lib/Types.csAdds library types used by CrossModule debuggee to force cross-module resolution.
src/native/managed/cdac/tests/StressTests/Debuggees/CrossModule/Lib/CrossModuleLib.csprojAdds library project for CrossModule debuggee.
src/native/managed/cdac/tests/StressTests/Debuggees/CrossModule/CrossModule.csprojAdds main CrossModule debuggee project file + ProjectReference wiring.
src/native/managed/cdac/tests/StressTests/Debuggees/CallSignatures/Program.csAdds comprehensive ARGITER signature-shape coverage debuggee.
src/native/managed/cdac/tests/StressTests/Debuggees/CallSignatures/CallSignatures.csprojAdds CallSignatures debuggee project file and warning suppressions.
src/native/managed/cdac/tests/StressTests/CdacStressTests.csReplaces prior basic test entrypoint with expanded debuggee catalog and GCREFS/ARGITER theories.
src/native/managed/cdac/tests/StressTests/CdacStressTestBase.csAdds per-mode stress runner and stricter assertions/target detection.
src/native/managed/cdac/tests/StressTests/CdacStressResults.csAdds parsing of [GC_STATS] / [ARG_STATS] and captures ARGITER divergence lines.
src/native/managed/cdac/tests/StressTests/BasicCdacStressTests.csRemoves the older stress test harness class (superseded by CdacStressTests).
src/native/managed/cdac/tests/DumpTests/StackReferenceDumpTests.csRemoves x86 skip now that x86 GCInfo decoding is supported.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/StressTestApi/CdacStressApi.csAdds legacy DAC request handlers for cdacstress private opcodes, including ARGITER blob request.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/SOSDacImpl.IXCLRDataProcess.csRoutes stress private requests to the new CdacStressApi helper.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/RuntimeTypeSystemHelpers/MethodTableFlags_1.csExtends MethodTable flags helpers (shared instantiation + byreflike).
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Microsoft.Diagnostics.DataContractReader.Contracts.csprojLinks in shared CallingConvention/ArgIterator sources into Contracts build.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/DataType.csAdds PInvokeCalliFrame to the cDAC type discriminator enum.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Data/Frames/TransitionBlock.csAdds OffsetOfArgs field address to support correct x86 GCRefMap pos->addr mapping.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Data/Frames/PInvokeCalliFrame.csAdds cDAC data type to expose VASigCookiePtr for PInvokeCalliFrame.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/CoreCLRContracts.csRegisters the new ICallingConvention contract implementation.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/StackWalk_1.csSwallows NotImplementedException per-frame to allow partial stack-walk results.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/GC/GcScanner.csReworks caller-stack scanning to use synthesized GCRefMap blobs on Windows x86/x64; factors shared token iteration; fixes x86 DynamicHelperFrame arg-reg offsets; corrects x86 pos->addr mapping.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/GC/GCRefMapDecoder.csAdds a byte[]-backed decoder constructor for host-synthesized blobs.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/FrameHandling/X86FrameHandler.csComputes x86 transition-frame caller SP by decoding stack-pop prefix (or VASigCookie for PInvokeCalliFrame).
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/RuntimeTypeSystem_1.csImplements new RTS helpers (byreflike, unboxing stub, approx field type handle).
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/GCInfo/X86/GCTransition.csFixes ctor assignments for IsThis/Iptr fields.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/GCInfo/X86/GCArgTable.csFixes several x86 arg table decoding issues and removes debug prints; adjusts stack-depth transition deltas.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/CallingConvention/CdacTypeHandle.csAdds cDAC-backed ITypeHandle implementation for shared ArgIterator.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/CallingConvention/ArgumentLocation.csAdds internal argument-location record for encoder bookkeeping.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/Contracts/IRuntimeTypeSystem.csAdds new contract APIs (byreflike, unboxing stub, approx field type handle).
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/Contracts/ICallingConvention.csIntroduces new calling-convention contract + public surface.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/ContractRegistry.csExposes CallingConvention contract property on registry.
src/coreclr/vm/frames.hExposes PInvokeCalliFrame::m_pVASigCookie via cdac_data specialization.
src/coreclr/vm/datadescriptor/datadescriptor.incAdds PInvokeCalliFrame descriptor and registers CallingConvention global contract.
src/coreclr/vm/cdacstress.cppAdds WHAT/WHERE/MODIFIER flag regions, ARGITER sub-check (runtime-vs-cDAC blob comparison), and emits [GC_STATS]/[ARG_STATS].
src/coreclr/tools/Common/CallingConvention/TransitionBlock.csMoves TransitionBlock into Internal.CallingConvention and refactors to use ITypeHandle.
src/coreclr/tools/Common/CallingConvention/SystemVAmd64PassingDescriptor.csAdds extracted SystemV descriptor types for shared use.
src/coreclr/tools/Common/CallingConvention/ITypeHandle.csAdds shared type abstraction for calling convention computation.
src/coreclr/tools/Common/CallingConvention/FpStructInRegistersInfo.csAdds extracted RISC-V/LoongArch FP struct classification types for shared use.
src/coreclr/tools/Common/CallingConvention/ArgIterator.csRefactors ArgIterator into Internal.CallingConvention and reworks it to use ITypeHandle + shared TransitionBlock.
src/coreclr/tools/aot/ILCompiler.ReadyToRun/JitInterface/WasmLowering.ReadyToRun.csUpdates Wasm lowering code to use new ITypeHandle shape.
src/coreclr/tools/aot/ILCompiler.ReadyToRun/ILCompiler.ReadyToRun.csprojLinks in shared CallingConvention sources and adjusts ReadyToRun file list.
src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRun/WasmR2RToInterpreterThunkNode.csUpdates using/aliasing for new ArgIterator namespace.
src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRun/WasmInterpreterToR2RThunkNode.csUpdates using/aliasing for new ArgIterator namespace.
src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRun/WasmImportThunk.csUpdates using/aliasing for new ArgIterator namespace.
src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRun/TypeHandle.csAdds crossgen2-backed ITypeHandle implementation.
src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRun/GCRefMapBuilder.csUpdates builder to use shared TransitionBlock/ArgIterator/ITypeHandle.
src/coreclr/inc/dacprivate.hAdds new private request opcode and request struct for ARGITER blob retrieval (CDAC_STRESS).
src/coreclr/inc/clrconfigvalues.hSimplifies CdacStress config description now that layout is more complex.
eng/pipelines/runtime-diagnostics.ymlAdds windows_x86 to runtime-diagnostics pipeline parameter default list.
docs/design/datacontracts/RuntimeTypeSystem.mdDocuments new RTS APIs and flags.
docs/design/datacontracts/GCInfo.mdUpdates x86 behavior documentation and adds x86 specifics section.
docs/design/datacontracts/CallingConvention.mdAdds new CallingConvention contract design doc.

Comment thread...d/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/Contracts/ICallingConvention.cs
Comment thread.../managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/StressTestApi/CdacStressApi.cs Outdated
Comment threadsrc/native/managed/cdac/tests/StressTests/Debuggees/CallSignatures/CallSignatures.csproj
Comment thread...osoft.Diagnostics.DataContractReader.Contracts/Contracts/CallingConvention/CdacTypeHandle.cs
@max-charlamb
max-charlambforce-pushed the x86-gc-info-w-argiterator branch from 7648cd9 to 8bed0e2CompareJune 25, 2026 15:51
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@max-charlamb
max-charlambforce-pushed the x86-gc-info-w-argiterator branch from 8bed0e2 to 2869d31CompareJune 27, 2026 17:03
@max-charlambmax-charlamb changed the title [cdac] x86: rewire stack-walker to shared CallingConvention / GCRefMap[cdac] Wire PromoteCallerStack to ICallingConvention; enforce 0 known issues on windows-x64Jun 27, 2026
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Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

Comment threadsrc/native/managed/cdac/tests/StressTests/CdacStressTestBase.cs Outdated
Comment thread.../cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/GC/GcScanner.cs
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@max-charlamb
max-charlambforce-pushed the x86-gc-info-w-argiterator branch from 2869d31 to 2c648d9CompareJune 27, 2026 21:29
@max-charlambmax-charlamb changed the title [cdac] Wire PromoteCallerStack to ICallingConvention; enforce 0 known issues on windows-x64[cdac] x86 GCInfo decoder + PromoteCallerStack -> GCRefMap; enforce 0 known issues on windows-x86/x64Jun 27, 2026
Max Charlamb
[cDAC] x86 GCInfo decoder + PromoteCallerStack rewire
e335d6a
- Add x86 IGCInfoDecoder (EnumerateLiveSlots, GetInterruptibleRanges)
- Rewire GcScanner.PromoteCallerStack to use ICallingConvention.TryComputeArgGCRefMapBlob
- Centralize x86 cbStackPop handling inside EnumerateGCRefMapTokens
- Encapsulate x86 ENUM_ARGUMENT_REGISTERS_BACKWARD layout in ArgSlotAddress helper
- GCRefMapDecoder: add byte[] ctor for synthesized blobs + MemberNotNullWhen attrs
- TransitionBlock.OffsetOfArgs uses [InstanceDataStart] (drop redundant datadescriptor field)
- Add PInvokeCalliFrame data class + datadescriptor wiring for X86FrameHandler fallback
- Stress tests: enforce KnownIssues == 0 on Windows x86/x64, remove x86 skip from GCRefStress
Verified: x86 + x64 GCRefStress 11/11 pass, 0 known issues.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
CopilotAI review requested due to automatic review settings June 28, 2026 20:12
@max-charlamb
max-charlambforce-pushed the x86-gc-info-w-argiterator branch from 2c648d9 to e335d6aCompareJune 28, 2026 20:12
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Pull request overview

Copilot reviewed 15 out of 15 changed files in this pull request and generated 6 comments.

Comment threadsrc/native/managed/cdac/tests/StressTests/CdacStressTests.cs
Comment threadsrc/native/managed/cdac/tests/StressTests/CdacStressTests.cs
Comment threadsrc/native/managed/cdac/tests/StressTests/CdacStressTestBase.cs Outdated
Comment thread...d/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/GCInfo/X86/GCArgTable.cs
Comment thread...naged/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/GCInfo/X86/GCInfo.cs
Comment threadsrc/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/DataType.cs
@build-analysisbuild-analysisBot mentioned this pull request Jun 28, 2026
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3 tasks
Max Charlamb
Address Copilot review: reword KnownIssues failure message, discard u…
8761677
…nused arch
- CdacStressTestBase: reword the Windows-x86/x64 KnownIssues failure
message to a generic explanation (the prior wording was PR-scope
specific and pinned a single root cause).
- CdacStressTests: discard the unused 'arch' out parameter in
GCRefStress_AllVerificationsPass; the x86 skip has been removed so
only 'os' is consulted now.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@max-charlamb
max-charlamb marked this pull request as ready for review June 29, 2026 20:09
CopilotAI review requested due to automatic review settings June 29, 2026 20:09
Max Charlamb
Revert known-issues.md changes (no longer relevant)
3670fec
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Pull request overview

Copilot reviewed 14 out of 14 changed files in this pull request and generated 2 comments.

Comment threadsrc/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/DataType.cs
Comment thread...d/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/GCInfo/X86/GCArgTable.cs
davidwrighton
davidwrighton reviewed Jun 29, 2026
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Comment thread...d/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/GCInfo/X86/GCArgTable.cs Outdated
Comment thread.../cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/GC/GcScanner.cs
Comment threadsrc/native/managed/cdac/tests/StressTests/CdacStressTests.cs
@max-charlambmax-charlamb mentioned this pull request Jun 29, 2026
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Max Charlamb
Address David's review: drop pre-PR commentary, add TODO links
ab9a6d1
- GCArgTable (0xFB huge encoding): remove "pre-PR cDAC port" commentary;
keep only the description of current behavior.
- GcScanner.PromoteCallerStack: add TODO referencing dotnet#130008 for extending
ICallingConvention.TryComputeArgGCRefMapBlob coverage beyond Windows x86/x64.
- CdacStressTests.GCRefStress: add TODO referencing dotnet#130008 for extending
GCREFS stress coverage to non-Windows / ARM targets.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@max-charlamb
max-charlamb merged commit 3ae0f12 into dotnet:mainJun 30, 2026
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max-charlamb added a commit that referenced this pull request Jul 2, 2026
@max-charlambMax Charlamb
[cdac] HFA / HVA support: enable ARGITER + zero-known-issues on Windo…
4f6a0ae
…ws ARM64 + Linux ARM/ARM64 (#130090)
Fills in the HFA / HVA classification paths in the cDAC's shared
ArgIterator port so `ICallingConvention.TryComputeArgGCRefMapBlob`
produces correct output on FEATURE_HFA targets, then lights up **Windows
ARM64**, **Linux ARM**, and **Linux ARM64** for both the ARGITER stress
sub-check and the zero-known-issues GCREFS assertion.
Follow-up to #129769 and #129858. Advances the platform matrix tracked
in #130008.
## What lights up in CI
| Platform | ARGITER stress | GCREFS 0-known-issues |
|---|---|---|
| Windows x64 | ✅ pre-existing | ✅ pre-existing |
| Windows x86 | ✅ pre-existing | ✅ pre-existing |
| **Windows ARM64** | ✅ **new** | ✅ **new** |
| **Linux ARM** | ✅ **new** | ✅ **new** |
| **Linux ARM64** | ✅ **new** | ✅ **new** |
| Linux / macOS x64 | ⏭ still deferred (SystemV-AMD64 eightbyte
classifier) | ⏭ tolerated |
| RISC-V, LoongArch, WASM | ⏭ still deferred | ⏭ tolerated |
The Helix stress matrix in `runtime-diagnostics.yml` already covers all
six platforms; this PR is purely lifting the xunit-level and
contract-level gates.
## Contract addition
Single new API on `IRuntimeTypeSystem`:
```csharp
bool TryGetHFAElementSize(TypeHandle typeHandle, out int elementSize);
```
Returns `4` / `8` / `16` for HFA / HVA types, `false` otherwise.
Self-gates on target architecture (FEATURE_HFA = ARM/ARM64) so callers
don't need to. Mirrors `MethodTable::GetHFAType`
(src/coreclr/vm/class.cpp:1867):
- At each recursion level, first checks `GetVectorHFAElementSize` for an
intrinsic Vector shape (`Vector64<T>` / `Vector128<T>` /
`System.Numerics.Vector<T>`)
- Then walks the first non-static instance field. `R4` -> 4, `R8` -> 8,
`ValueType` -> recurse via the existing `GetFieldDescApproxTypeHandle`
- HVA detection uses `enum_flag_IsIntrinsicType`
(`WFLAGS2_ENUM.IsIntrinsicType = 0x0020`) plus TypeDef name+namespace
match, with T-must-be-numerical verification (`CorIsNumericalType`:
`I1..R8 || I || U`)
`MethodTable` flag `WFLAGS_LOW.IsHFA = 0x00000800` is added to
`MethodTableFlags_1.cs`. That bit is repurposed on `UNIX_AMD64_ABI` as
`enum_flag_IsRegStructPassed`, hence the arch self-gate baked into the
API.
## `CdacTypeHandle` (thin adapter)
```csharp
public bool IsHomogeneousAggregate()
=> !_typeHandle.IsNull && Rts.TryGetHFAElementSize(_typeHandle, out _);
public int GetHomogeneousAggregateElementSize()
{
if (Arch == RuntimeInfoArchitecture.Arm)
return RequiresAlign8() ? 8 : 4; // ARM has no HVA; shortcut avoids the field walk
return _typeHandle.IsNull ? 0
: (Rts.TryGetHFAElementSize(_typeHandle, out int size) ? size : 0);
}
```
The ARM shortcut avoids a field walk: on ARM there's no HVA, and
`RequiresAlign8` mirrors `CheckForHFA`'s element-type-driven alignment
choice.
## Test coverage additions
`CallSignatures` debuggee gains an `HfaCategory` (~100 LOC) exercising:
- **Scalar HFAs**: `Float2/3/4`, `Double2/3/4` (all legal HFA arities)
- **Nested HFAs**: `NestedFloat3`, `NestedDouble4` (first-field
recursion)
- **Mixed args**: `HfaThenRef` / `RefThenHfa` / `TwoFloatHfas` — FP-reg
+ int-reg interaction; validates GCRefMap tokens for trailing ref args
after FP-reg consumption
- **HFA returns**: `ReturnFloat3`, `ReturnDouble2` (FP-register return
path, no `HasRetBufArg`)
- **HVA args**: `Vector64<float>`, `Vector128<float>`,
`System.Numerics.Vector<float>` (ARM64-only classification; benign on
other targets)
- **Negative shapes**: `Float5` (>4 fields), `MixedR4R8` (mixed FP) —
runtime correctly declines to flag as HFA, cDAC matches
Same debuggee compiles/passes everywhere; only exercises the new HFA
walker on ARM/ARM64.
## Gate expansions
Three gates now all match: **Windows {x86, x64, ARM64} + Linux {ARM,
ARM64}**
1. **`CdacStressTests.ArgIterStress_AllVerificationsPass`**: admits the
new ARM/ARM64 platforms.
2. **`CdacStressTestBase.AssertAllPassed.requiresZeroKnownIssues`**:
extended from Windows x86/x64 to include the same set. Any deferred
Frame on these platforms is now a hard failure.
3. **`GcScanner.PromoteCallerStack.supportedByCallingConvention`**:
lifted to match, so on ARM/ARM64 caller-stack refs are enumerated via
`TryComputeArgGCRefMapBlob` instead of falling through to
`RecordDeferredFrame`.
## Local validation
- `dotnet build src/native/managed/cdac/cdac.slnx -c Release` -- clean
- `dotnet test
.../UnitTests/Microsoft.Diagnostics.DataContractReader.Tests.csproj` --
2611 pass / 0 fail / 16 skipped
- No local ARM hardware; the ARM/ARM64 paths are validated by CI. If any
HFA/HVA shape produces a divergence, the ARGITER assertion will surface
the exact `MethodDesc` + slot mismatch.
## Known gaps (follow-ups, tracked in #130008)
- Linux / macOS x64: SystemV-AMD64 eightbyte struct classifier not
ported (`CdacTypeHandle.GetSystemVAmd64PassStructInRegisterDescriptor`
throws)
- RISC-V64 / LoongArch64: FP struct classifier not ported
(`GetFpStructInRegistersInfo` throws)
- WASM32: `GetFieldAlignment` not ported
> [!NOTE]
> This change was authored with assistance from GitHub Copilot.
---------
Co-authored-by: Max Charlamb <maxcharlamb@microsoft.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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eiriktsarpalis pushed a commit that referenced this pull request Jul 15, 2026
@max-charlamb@eiriktsarpalis
[cdac] x86 GCInfo decoder + PromoteCallerStack -> GCRefMap; enforce 0…
063fb77
… known issues on windows-x86/x64 (#129858)
eiriktsarpalis pushed a commit that referenced this pull request Jul 15, 2026
@max-charlambMax Charlamb
@eiriktsarpalis
[cdac] HFA / HVA support: enable ARGITER + zero-known-issues on Windo…
fbe35e6
…ws ARM64 + Linux ARM/ARM64 (#130090)
Fills in the HFA / HVA classification paths in the cDAC's shared
ArgIterator port so `ICallingConvention.TryComputeArgGCRefMapBlob`
produces correct output on FEATURE_HFA targets, then lights up **Windows
ARM64**, **Linux ARM**, and **Linux ARM64** for both the ARGITER stress
sub-check and the zero-known-issues GCREFS assertion.
Follow-up to #129769 and #129858. Advances the platform matrix tracked
in #130008.
## What lights up in CI
| Platform | ARGITER stress | GCREFS 0-known-issues |
|---|---|---|
| Windows x64 | ✅ pre-existing | ✅ pre-existing |
| Windows x86 | ✅ pre-existing | ✅ pre-existing |
| **Windows ARM64** | ✅ **new** | ✅ **new** |
| **Linux ARM** | ✅ **new** | ✅ **new** |
| **Linux ARM64** | ✅ **new** | ✅ **new** |
| Linux / macOS x64 | ⏭ still deferred (SystemV-AMD64 eightbyte
classifier) | ⏭ tolerated |
| RISC-V, LoongArch, WASM | ⏭ still deferred | ⏭ tolerated |
The Helix stress matrix in `runtime-diagnostics.yml` already covers all
six platforms; this PR is purely lifting the xunit-level and
contract-level gates.
## Contract addition
Single new API on `IRuntimeTypeSystem`:
```csharp
bool TryGetHFAElementSize(TypeHandle typeHandle, out int elementSize);
```
Returns `4` / `8` / `16` for HFA / HVA types, `false` otherwise.
Self-gates on target architecture (FEATURE_HFA = ARM/ARM64) so callers
don't need to. Mirrors `MethodTable::GetHFAType`
(src/coreclr/vm/class.cpp:1867):
- At each recursion level, first checks `GetVectorHFAElementSize` for an
intrinsic Vector shape (`Vector64<T>` / `Vector128<T>` /
`System.Numerics.Vector<T>`)
- Then walks the first non-static instance field. `R4` -> 4, `R8` -> 8,
`ValueType` -> recurse via the existing `GetFieldDescApproxTypeHandle`
- HVA detection uses `enum_flag_IsIntrinsicType`
(`WFLAGS2_ENUM.IsIntrinsicType = 0x0020`) plus TypeDef name+namespace
match, with T-must-be-numerical verification (`CorIsNumericalType`:
`I1..R8 || I || U`)
`MethodTable` flag `WFLAGS_LOW.IsHFA = 0x00000800` is added to
`MethodTableFlags_1.cs`. That bit is repurposed on `UNIX_AMD64_ABI` as
`enum_flag_IsRegStructPassed`, hence the arch self-gate baked into the
API.
## `CdacTypeHandle` (thin adapter)
```csharp
public bool IsHomogeneousAggregate()
=> !_typeHandle.IsNull && Rts.TryGetHFAElementSize(_typeHandle, out _);
public int GetHomogeneousAggregateElementSize()
{
if (Arch == RuntimeInfoArchitecture.Arm)
return RequiresAlign8() ? 8 : 4; // ARM has no HVA; shortcut avoids the field walk
return _typeHandle.IsNull ? 0
: (Rts.TryGetHFAElementSize(_typeHandle, out int size) ? size : 0);
}
```
The ARM shortcut avoids a field walk: on ARM there's no HVA, and
`RequiresAlign8` mirrors `CheckForHFA`'s element-type-driven alignment
choice.
## Test coverage additions
`CallSignatures` debuggee gains an `HfaCategory` (~100 LOC) exercising:
- **Scalar HFAs**: `Float2/3/4`, `Double2/3/4` (all legal HFA arities)
- **Nested HFAs**: `NestedFloat3`, `NestedDouble4` (first-field
recursion)
- **Mixed args**: `HfaThenRef` / `RefThenHfa` / `TwoFloatHfas` — FP-reg
+ int-reg interaction; validates GCRefMap tokens for trailing ref args
after FP-reg consumption
- **HFA returns**: `ReturnFloat3`, `ReturnDouble2` (FP-register return
path, no `HasRetBufArg`)
- **HVA args**: `Vector64<float>`, `Vector128<float>`,
`System.Numerics.Vector<float>` (ARM64-only classification; benign on
other targets)
- **Negative shapes**: `Float5` (>4 fields), `MixedR4R8` (mixed FP) —
runtime correctly declines to flag as HFA, cDAC matches
Same debuggee compiles/passes everywhere; only exercises the new HFA
walker on ARM/ARM64.
## Gate expansions
Three gates now all match: **Windows {x86, x64, ARM64} + Linux {ARM,
ARM64}**
1. **`CdacStressTests.ArgIterStress_AllVerificationsPass`**: admits the
new ARM/ARM64 platforms.
2. **`CdacStressTestBase.AssertAllPassed.requiresZeroKnownIssues`**:
extended from Windows x86/x64 to include the same set. Any deferred
Frame on these platforms is now a hard failure.
3. **`GcScanner.PromoteCallerStack.supportedByCallingConvention`**:
lifted to match, so on ARM/ARM64 caller-stack refs are enumerated via
`TryComputeArgGCRefMapBlob` instead of falling through to
`RecordDeferredFrame`.
## Local validation
- `dotnet build src/native/managed/cdac/cdac.slnx -c Release` -- clean
- `dotnet test
.../UnitTests/Microsoft.Diagnostics.DataContractReader.Tests.csproj` --
2611 pass / 0 fail / 16 skipped
- No local ARM hardware; the ARM/ARM64 paths are validated by CI. If any
HFA/HVA shape produces a divergence, the ARGITER assertion will surface
the exact `MethodDesc` + slot mismatch.
## Known gaps (follow-ups, tracked in #130008)
- Linux / macOS x64: SystemV-AMD64 eightbyte struct classifier not
ported (`CdacTypeHandle.GetSystemVAmd64PassStructInRegisterDescriptor`
throws)
- RISC-V64 / LoongArch64: FP struct classifier not ported
(`GetFpStructInRegistersInfo` throws)
- WASM32: `GetFieldAlignment` not ported
> [!NOTE]
> This change was authored with assistance from GitHub Copilot.
---------
Co-authored-by: Max Charlamb <maxcharlamb@microsoft.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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cDAC: GCInfo decoder does not support x86

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