Remove Wrapper delegate kind; switch ARM32 VSD hidden arg to R12 and fix ARM32 fail-path register preservation by Copilot · Pull Request #129403 · dotnet/runtime

Copilot · 2026-06-15T03:44:24Z

CoreCLR’s Wrapper delegate kind was retained only to satisfy an ARM32 VSD ABI quirk (r4 hidden cell). This change removes that special delegate path by moving ARM32 VSD hidden-parameter passing to r12 and deleting wrapper-delegate infrastructure across VM/JIT/AOT/contracts and System.Private.CoreLib.

ARM32 VSD calling-convention alignment
- Updates ARM32 stub-dispatch plumbing to carry IndirectionCellAndFlags in r12 and token in r4.
- Aligns JIT virtual-stub parameter selection on ARM32 to REG_R12.
Wrapper delegate infrastructure removal
- Removes wrapper-delegate creation/detection/runtime paths from COMDelegate.
- Removes remaining wrapper handling from MulticastDelegate.CoreCLR.cs.
- Removes wrapper-specific IL stub kind/plumbing and associated metadata fields.
- Removes wrapper-specific JIT call flags and late-arg handling.
Cross-layer contract cleanup
- Deletes obsolete wrapperDelegateInvoke and offsetOfWrapperDelegateIndirectCell from EE/JIT interfaces and SuperPMI agnostic records.
- Keeps VM/JIT/AOT call-info structures consistent after field removal.
- Revs the JIT/EE interface GUID in jiteeversionguid.h to match the interface change.
IL stub enum cleanup
- Deletes the unused wrapper IL stub value and renumbers subsequent IL stub values in VM (method.hpp, dllimport.h) and corresponding cDAC contract mapping.
ARM32 ResolveStub correctness fix
- Fixes ResolveStub::_failEntryPoint to avoid clobbering r12 (which now carries IndirectionCellAndFlags).
- Uses r4 as decrement scratch for _pCounter update and preserves callee-saved r4 via stack save/restore in the fail path.
R2R compatibility boundary
- Bumps ReadyToRun major/minimum version to 23 for the ARM32 VSD register contract change.
- Syncs version constants across native and managed header definitions.
Documentation update
- Updates docs/design/coreclr/botr/clr-abi.md hidden-parameter section: ARM32 VSD hidden parameter is now R12.

// src/coreclr/jit/compiler.h (ARM32)
#elif defined(TARGET_ARM)
    reg     = REG_R12;
    regMask = RBM_R12;

Co-authored-by: jkotas <6668460+jkotas@users.noreply.github.com>

MichalPetryka · 2026-06-15T04:38:06Z

@copilot Remove all wrapper handling code from MulticastDelegate.CoreCLR.cs too.

jkotas · 2026-06-15T04:38:25Z


    CORINFO_CONST_LOOKUP    instParamLookup;
-
-    bool                    wrapperDelegateInvoke;


@copilot This is JIT/EE interface change. You need to rev the JIT/EE interface GUID.

Updated in commit cdd573d by revving JITEEVersionIdentifier in src/coreclr/inc/jiteeversionguid.h to match the JIT/EE interface change.

jkotas · 2026-06-15T04:38:59Z

@@ -1701,7 +1701,6 @@ private void getCallInfo(ref CORINFO_RESOLVED_TOKEN pResolvedToken, CORINFO_RESO
                pResult->sig.flags |= CorInfoSigInfoFlags.CORINFO_SIGFLAG_FAT_CALL;
            }



@copilot Nit: extra blank line

Fixed in 4611ce1 by removing the extra blank line.

jkotas · 2026-06-15T04:40:22Z

        StubArrayOp = 9,
        StubMulticastDelegate = 10,
-        StubWrapperDelegate = 11,
+        // 11 was StubWrapperDelegate


@copilot The cDAC contract is not stable yet. You can delete the unused value from here and cDAC.

Done in 4611ce1. Removed the unused ILStubType value and renumbered the remaining values in the runtime-side contract enum.

MichalPetryka · 2026-06-15T04:41:42Z

@copilot Remove all wrapper handling code from MulticastDelegate.CoreCLR.cs too.

@jkotas Can you repost this since only maintainers can interact with copilot?

jkotas · 2026-06-15T04:41:49Z

    ILSTUB_UNBOXINGILSTUB                = 0x80000005,
    ILSTUB_INSTANTIATINGSTUB             = 0x80000006,
-    ILSTUB_WRAPPERDELEGATE_INVOKE        = 0x80000007,
+    // 0x80000007 was ILSTUB_WRAPPERDELEGATE_INVOKE


@copilot Delete the unused value and renumber the rest.

Done in 4611ce1. Deleted the unused ILSTUB value and renumbered the remaining ILSTUB_* constants.

jkotas · 2026-06-15T04:44:08Z

@copilot Remove all wrapper handling code from MulticastDelegate.CoreCLR.cs too.

dotnet-policy-service · 2026-06-15T04:44:19Z

Tagging subscribers to this area: @agocke
See info in area-owners.md if you want to be subscribed.

jkotas · 2026-06-15T04:48:59Z


 // ------------------------------------------------------------------
-// void ResolveWorkerAsmStub(r0, r1, r2, r3, r4:IndirectionCellAndFlags, r12:DispatchToken)
+// void ResolveWorkerAsmStub(r0, r1, r2, r3, r12:IndirectionCellAndFlags, r4:DispatchToken)


@copilot r4 won't work here. It is callee saved register. This will need to use stack instead.

Updated in 4611ce1. The fail path now preserves callee-saved r4 by saving/restoring it on the stack while using it as scratch.

Co-authored-by: jkotas <6668460+jkotas@users.noreply.github.com>

Copilot · 2026-06-15T06:10:11Z

@copilot Remove all wrapper handling code from MulticastDelegate.CoreCLR.cs too.

Done in 4611ce1. Removed remaining wrapper-handling paths from MulticastDelegate.CoreCLR.cs.

MichalPetryka · 2026-06-15T06:17:42Z

-    // The delegate may be put into a wrapper delegate if our target method requires it. This local
-    // will always hold the real (un-wrapped) delegate.
-    DELEGATEREF refRealDelegate = NULL;
+    DELEGATEREF refRealDelegate = *pRefThis;


Rename the local since *pRefThis is always the real one now.

@copilot Address this feedback

MichalPetryka · 2026-06-15T10:09:18Z

There seem to be tons of test failures on arm32 currently.

Initial plan

c7c6b25

Copilot AI assigned Copilot and jkotas Jun 15, 2026

Copilot AI requested review from Copilot and removed request for Copilot June 15, 2026 03:44

Copilot started work on behalf of jkotas June 15, 2026 03:44 View session

github-actions Bot added the area-Infrastructure label Jun 15, 2026

github-project-automation Bot added this to Runtime Infra Jun 15, 2026

Remove Wrapper delegate kind and switch ARM32 VSD hidden arg to r12

877724a

Co-authored-by: jkotas <6668460+jkotas@users.noreply.github.com>

Copilot AI requested review from Copilot and removed request for Copilot June 15, 2026 04:32

Copilot AI changed the title ~~[WIP] Remove need for the special Wrapper delegate kind~~ Remove Wrapper delegate kind; switch ARM32 VSD hidden arg to R12 Jun 15, 2026

Copilot finished work on behalf of jkotas June 15, 2026 04:33

Copilot AI requested a review from jkotas June 15, 2026 04:33

jkotas reviewed Jun 15, 2026

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Copilot started work on behalf of jkotas June 15, 2026 04:39 View session

jkotas reviewed Jun 15, 2026

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jkotas added arch-arm32 area-VM-coreclr and removed area-Infrastructure labels Jun 15, 2026

jkotas reviewed Jun 15, 2026

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Rev JIT/EE interface GUID for interface change

cdd573d

Co-authored-by: jkotas <6668460+jkotas@users.noreply.github.com>

Copilot AI requested review from Copilot and removed request for Copilot June 15, 2026 05:03

Preserve ARM32 VSD hidden arg in ResolveStub fail path

55da881

Co-authored-by: jkotas <6668460+jkotas@users.noreply.github.com>

Copilot AI requested review from Copilot and removed request for Copilot June 15, 2026 05:18

Copilot AI changed the title ~~Remove Wrapper delegate kind; switch ARM32 VSD hidden arg to R12~~ Remove Wrapper delegate kind; switch ARM32 VSD hidden arg to R12 and fix ARM32 fail-path clobber Jun 15, 2026

Copilot finished work on behalf of jkotas June 15, 2026 05:19

Copilot AI requested a review from jkotas June 15, 2026 05:19

Copilot started work on behalf of jkotas June 15, 2026 05:20 View session

Address PR feedback for wrapper removal and ARM32 stub fixups

4611ce1

Co-authored-by: jkotas <6668460+jkotas@users.noreply.github.com>

Copilot AI requested review from Copilot and removed request for Copilot June 15, 2026 06:09

Copilot AI changed the title ~~Remove Wrapper delegate kind; switch ARM32 VSD hidden arg to R12 and fix ARM32 fail-path clobber~~ Remove Wrapper delegate kind; switch ARM32 VSD hidden arg to R12 and fix ARM32 fail-path register preservation Jun 15, 2026

Copilot finished work on behalf of jkotas June 15, 2026 06:11

MichalPetryka reviewed Jun 15, 2026

View reviewed changes

Copilot started work on behalf of jkotas June 15, 2026 06:20 View session

Copilot finished work on behalf of jkotas June 15, 2026 06:23


		CORINFO_CONST_LOOKUP instParamLookup;

		bool wrapperDelegateInvoke;

		@@ -1701,7 +1701,6 @@ private void getCallInfo(ref CORINFO_RESOLVED_TOKEN pResolvedToken, CORINFO_RESO
		pResult->sig.flags \|= CorInfoSigInfoFlags.CORINFO_SIGFLAG_FAT_CALL;
		}

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