Delete ArrayEEClass - compute multidim array rank from BaseSize

[Copilot]

ArrayEEClass (ArrayClass) stored only m_rank — a single byte redundant with information already encoded in MethodTable::m_baseSize. This PR removes the class entirely and derives rank from BaseSize, matching NativeAOT's approach.

Changes

CoreCLR VM (C++)

• class.h: Remove ArrayClass entirely. Remove PTR_ArrayClass typedef (no longer needed). Add Module::CreateArrayMethodTable as friend of EEClass (its constructor is protected, and the function now calls ::new (pMemory) EEClass() directly).
• methodtable.inl: MethodTable::GetRank() now computes rank from BaseSize:

  // SZARRAY fast path unchanged; multidim:
  DWORD boundsSize = GetBaseSize() - ARRAYBASE_BASESIZE;
  return boundsSize / (sizeof(DWORD) * 2);

  This works because CreateArrayMethodTable sets BaseSize = ARRAYBASE_BASESIZE + Rank * sizeof(DWORD) * 2 for ELEMENT_TYPE_ARRAY. The DATA_ALIGNMENT > 4 padding path on 32-bit is dead code on all supported platforms.
• array.cpp: GenerateArrayAccessorCallSig and InitArrayMethodDesc become local static void functions (were ArrayClass members). Allocation uses sizeof(EEClass) and EEClass* directly; SetRank() call removed.
• object.inl: GetLowerBoundsOffset uses pMT->GetRank() directly.
• datadescriptor.inc: Remove ArrayClass type block; add CDAC_GLOBAL(ArrayBaseSize, uint32, ARRAYBASE_BASESIZE).
• methodtable.cpp: Remove redundant if (IsArray()) DAC memory enumeration block (now handled uniformly by EEClass::EnumMemoryRegions). Simplify array cast check to use !pTargetMT->IsMultiDimArray() instead of GetInternalCorElementType() == ELEMENT_TYPE_SZARRAY.
• methodtable.h, ceeload.h: Delete all friend class NativeImageDumper; declarations throughout the repo (4 occurrences).

Managed cDAC

• Remove DataType.ArrayClass, Data.ArrayClass.
• RuntimeTypeSystem_1.IsArray() computes rank from BaseSize using the new ArrayBaseSize global (Constants.Globals.ArrayBaseSize).

cDAC Tests

• Mock descriptors no longer allocate ArrayClass; multidim array MethodTable mock now sets BaseSize = ArrayBaseSize + rank * 2 * sizeof(int) (previously always used ArrayBaseSize, which was inconsistent with the real runtime).
• ObjectTests data-pointer assertions updated: for a rank-R multidim array, data starts at address + ArrayBaseSize + R * 2 * sizeof(int).
• Added ValidateMultidimArrayRank test as a [Theory] over all standard architectures, directly verifying IsArray() returns correct rank (4 and 1) from BaseSize.

Documentation

• docs/design/datacontracts/RuntimeTypeSystem.md: Removed the ArrayClass | Rank data descriptor row, added ArrayBaseSize to the globals table (with description: "The base size of an array object; used to compute multidimensional array rank from MethodTable::BaseSize"), and updated the IsArray pseudocode to derive multidimensional array rank from BaseSize instead of reading from ArrayClass.

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[jkotas]

@copilot

[jkotas]

@copilot More feedback above

[jkotas]

@max-charlamb PTLA - small data contract simplification that makes NativeAOT and CoreCLR more similar.

Also, could you please take look at the runtime-diagnostics failures? They do not appear related to my change.

[Copilot]

Pull request overview

Removes the redundant CoreCLR ArrayClass/ArrayEEClass (which only stored array rank) and derives multidimensional array rank from MethodTable::BaseSize, aligning CoreCLR with the existing NativeAOT approach. Updates cDAC (native + managed) and its tests to match the new layout/contract shape.

Changes:

• CoreCLR VM: delete ArrayClass, refactor array helper methods to file-local statics, and compute MethodTable::GetRank() from BaseSize.
• cDAC: remove ArrayClass data/type usage and compute array rank from BaseSize (plus a new exported global for ARRAYBASE_BASESIZE).
• Tests: adjust mock descriptors/object layout math and add coverage validating multidim rank derivation.

Reviewed changes

Copilot reviewed 20 out of 20 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/coreclr/vm/array.cpp	Refactors former ArrayClass helpers to static functions; allocates EEClass directly for arrays.
src/coreclr/vm/class.h	Removes ArrayClass definition; adds Module::CreateArrayMethodTable friend to allow placement-new EEClass.
src/coreclr/vm/classcompat.h	Removes ArrayClass forward decl.
src/coreclr/vm/ceeload.h	Removes NativeImageDumper friend declarations.
src/coreclr/vm/datadescriptor/datadescriptor.inc	Removes ArrayClass type; adds ArrayBaseSize global exporting ARRAYBASE_BASESIZE.
src/coreclr/vm/methodtable.cpp	Simplifies array casting logic and DAC memory enumeration now that ArrayClass is gone.
src/coreclr/vm/methodtable.h	Removes ArrayClass forward decl and NativeImageDumper friends.
src/coreclr/vm/methodtable.inl	Implements MethodTable::GetRank() using BaseSize - ARRAYBASE_BASESIZE.
src/coreclr/vm/object.inl	Computes lower-bounds offset using pMT->GetRank() directly.
src/coreclr/vm/vars.hpp	Removes ArrayClass forward decl.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/DataType.cs	Removes DataType.ArrayClass.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Constants.cs	Adds Globals.ArrayBaseSize.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/RuntimeTypeSystem_1.cs	Computes multidim rank from BaseSize using Globals.ArrayBaseSize.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Data/EEClass.cs	Deletes managed ArrayClass data reader.
src/native/managed/cdac/tests/ContractDescriptor/TargetTests.SubDescriptors.cs	Removes ArrayClass size-only descriptor entry.
src/native/managed/cdac/tests/MethodTableTests.cs	Adds ValidateMultidimArrayRank coverage for rank derivation.
src/native/managed/cdac/tests/MockDescriptors/MockDescriptors.cs	Removes ArrayClassFields descriptor.
src/native/managed/cdac/tests/MockDescriptors/MockDescriptors.Object.cs	Updates mock array BaseSize to encode rank for multidim arrays; uses EEClass directly.
src/native/managed/cdac/tests/MockDescriptors/MockDescriptors.RuntimeTypeSystem.cs	Removes AddArrayClass; adds Globals.ArrayBaseSize to the mock target.
src/native/managed/cdac/tests/ObjectTests.cs	Updates expected multidim array data pointer to account for rank-encoded bounds in BaseSize.

[max-charlamb]

@copilot, please update RuntimeTypeSystem.md docs with the relevant changes.

[Copilot]

@copilot, please update RuntimeTypeSystem.md docs with the relevant changes.

Done in 6e4b409. Updated RuntimeTypeSystem.md to: remove the ArrayClass | Rank data descriptor row, add ArrayBaseSize to the globals table, and update the IsArray pseudocode to derive multidim rank from BaseSize instead of reading from ArrayClass.

[max-charlamb]

@copilot , please fix the build break in linux-x64 checked CLR_Tools_Tests caused by the modified cDAC unit tests

[max-charlamb]

lgtm from a cDAC perspective once the cDAC unit tests pass CI

[Copilot]

@copilot , please fix the build break in linux-x64 checked CLR_Tools_Tests caused by the modified cDAC unit tests

Fixed in 0e7648e. The ValidateMultidimArrayRank method was missing [Theory] and [ClassData(typeof(MockTarget.StdArch))] attributes, triggering xUnit1013. All 916 cDAC tests pass locally.

[jkotas]

@copilot use ci-analysis skill to analyze the CI results. Are the failures related to this change?

[Copilot]

@copilot use ci-analysis skill to analyze the CI results. Are the failures related to this change?

The CI analysis script can't reach Azure DevOps from this sandbox (no auth), but based on what's visible:

Runtime-diagnostics failures — Not related to this PR. These were caused by a known Azure Pipelines regression in the "Publish Test Results" task (upstream issue). The workaround was already merged to main as 7356734a and is included in this branch via the merge commit.

linux-x64 checked CLR_Tools_Tests failure — Was related to this PR. Fixed in 0e7648ee: the new ValidateMultidimArrayRank test was missing [Theory] and [ClassData(typeof(MockTarget.StdArch))] attributes (xUnit1013). All 916 cDAC tests pass locally after the fix.

No files changed by this PR overlap with the runtime-diagnostics pipeline.

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[jkotas]

/ba-g iOS timeout, cDAC failures are same as on other PRs