Convert async context helpers from getAsyncInfo method handles to JIT helpers by jtschuster · Pull Request #125079 · dotnet/runtime

jtschuster · 2026-03-02T21:46:28Z

Splits off work from #124203

Replace the method handle fields in CORINFO_ASYNC_INFO for async context helpers (CaptureContexts, RestoreContexts, CaptureExecutionContext, RestoreExecutionContext, RestoreContextsOnSuspension, CaptureContinuationContext) with proper CORINFO_HELP_* JIT helpers.

The previous approach passed method handles via getAsyncInfo and used gtNewCallNode(CT_USER_FUNC, ...) with getFunctionEntryPoint/setEntryPoint in crossgen2. This created MethodEntrypoint nodes in the R2R dependency graph, which made previously-uncompilable methods compilable and exposed a bug where IL 'jmp' instructions generate R2R indirect jumps that the delay-load thunk cannot resolve.

Using JIT helpers avoids this — helpers go through the ReadyToRun helper fixup table and don't add method entry points to the dependency graph.

Changes:

Add 6 new CORINFO_HELP_ASYNC_* helpers and DYNAMICJITHELPER entries
Add corresponding ReadyToRun helper IDs (0x123-0x128) and renumber AllocContinuation helpers to 0x120-0x122 for sequential layout
Convert JIT async.cpp to use gtNewHelperCallNode
Convert interpreter to use INTOP_CALL_HELPER_V_SS/SSS for CaptureContexts/RestoreContexts, and resolve suspend data method handles at compile time via getHelperFtn to avoid GC-unsafe CoreLibBinder lookups at runtime
Add helper mappings in crossgen2, NativeAOT, and R2RDump
Remove method handle fields from CORINFO_ASYNC_INFO and all places that populate/serialize them (VM, managed JitInterface, SuperPMI)

… helpers Replace the method handle fields in CORINFO_ASYNC_INFO for async context helpers (CaptureContexts, RestoreContexts, CaptureExecutionContext, RestoreExecutionContext, RestoreContextsOnSuspension, CaptureContinuationContext) with proper CORINFO_HELP_* JIT helpers. The previous approach passed method handles via getAsyncInfo and used gtNewCallNode(CT_USER_FUNC, ...) with getFunctionEntryPoint/setEntryPoint in crossgen2. This created MethodEntrypoint nodes in the R2R dependency graph, which made previously-uncompilable methods compilable and exposed a bug where IL 'jmp' instructions generate R2R indirect jumps that the delay-load thunk cannot resolve. Using JIT helpers avoids this — helpers go through the ReadyToRun helper fixup table and don't add method entry points to the dependency graph. Changes: - Add 6 new CORINFO_HELP_ASYNC_* helpers and DYNAMICJITHELPER entries - Add corresponding ReadyToRun helper IDs (0x123-0x128) and renumber AllocContinuation helpers to 0x120-0x122 for sequential layout - Convert JIT async.cpp to use gtNewHelperCallNode - Convert interpreter to use INTOP_CALL_HELPER_V_SS/SSS for CaptureContexts/RestoreContexts, and resolve suspend data method handles at compile time via getHelperFtn to avoid GC-unsafe CoreLibBinder lookups at runtime - Add helper mappings in crossgen2, NativeAOT, and R2RDump - Remove method handle fields from CORINFO_ASYNC_INFO and all places that populate/serialize them (VM, managed JitInterface, SuperPMI) Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

This PR converts the JIT’s async context save/restore plumbing from passing AsyncHelpers.* method handles via getAsyncInfo to using dedicated CORINFO_HELP_ASYNC_* JIT helpers, avoiding unwanted MethodEntrypoint R2R dependencies and the associated jmp/delay-load thunk resolution issue described in the PR.

Changes:

Introduces six new async-related CORINFO_HELP_ASYNC_* helpers and wires them through ReadyToRun helper IDs and DynamicJitHelper mappings.
Updates CoreCLR JIT (async.cpp) and the interpreter to emit helper calls instead of user-function calls through method handles.
Removes async helper method-handle fields from CORINFO_ASYNC_INFO and updates VM, tooling, and SuperPMI serialization accordingly.

Reviewed changes

Copilot reviewed 20 out of 20 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/coreclr/vm/jitinterface.cpp	Stops populating removed async helper method handles in `getAsyncInfo`.
src/coreclr/tools/superpmi/superpmi-shared/methodcontext.cpp	Removes recording/replay of async helper method handles.
src/coreclr/tools/superpmi/superpmi-shared/agnostic.h	Updates SuperPMI agnostic async info struct to match new layout.
src/coreclr/tools/aot/ILCompiler.RyuJit/JitInterface/CorInfoImpl.RyuJit.cs	Maps new `CorInfoHelpFunc` values to R2R helper IDs.
src/coreclr/tools/aot/ILCompiler.Reflection.ReadyToRun/ReadyToRunSignature.cs	Adds textual decoding for new async R2R helper IDs.
src/coreclr/tools/aot/ILCompiler.ReadyToRun/JitInterface/CorInfoImpl.ReadyToRun.cs	Maps new `CorInfoHelpFunc` values to R2R helper IDs for crossgen2.
src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/ReadyToRunCodegenCompilation.cs	Removes unnecessary AsyncHelpers metadata rooting previously needed for `getAsyncInfo` method handles.
src/coreclr/tools/aot/ILCompiler.Compiler/IL/ILImporter.Scanner.cs	Switches async infra dependency rooting from method entrypoints to helper entrypoints.
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/JitHelper.cs	Adds ReadyToRun helper -> CoreLib entrypoint mapping for new async helpers.
src/coreclr/tools/Common/JitInterface/CorInfoTypes.cs	Removes async helper method-handle fields from managed `CORINFO_ASYNC_INFO`.
src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs	Stops filling removed async helper method-handle fields in managed `getAsyncInfo`.
src/coreclr/tools/Common/JitInterface/CorInfoHelpFunc.cs	Adds six new `CORINFO_HELP_ASYNC_*` values.
src/coreclr/tools/Common/Internal/Runtime/ReadyToRunConstants.cs	Adds new async R2R helper IDs and renumbers continuation alloc helpers.
src/coreclr/jit/utils.cpp	Defines helper call properties for the new async helpers.
src/coreclr/jit/async.cpp	Uses `gtNewHelperCallNode` for async context capture/restore instead of user-func calls.
src/coreclr/interpreter/compiler.cpp	Uses interpreter “call helper” opcodes for context capture/restore; resolves helper method handles at compile time for suspend/resume paths.
src/coreclr/inc/readytorunhelpers.h	Registers new async helpers in the ReadyToRun helper mapping list.
src/coreclr/inc/readytorun.h	Adds new async ReadyToRun helper IDs and renumbers existing continuation alloc helper IDs.
src/coreclr/inc/jithelpers.h	Adds `DYNAMICJITHELPER` entries for the new async helpers.
src/coreclr/inc/corinfo.h	Adds new helper enums and removes async helper method-handle fields from `CORINFO_ASYNC_INFO`.

Copilot · 2026-03-02T21:54:43Z

src/coreclr/inc/readytorun.h

+    READYTORUN_HELPER_AllocContinuation         = 0x120,
+    READYTORUN_HELPER_AllocContinuationClass    = 0x121,
+    READYTORUN_HELPER_AllocContinuationMethod   = 0x122,
+    READYTORUN_HELPER_AsyncCaptureContexts      = 0x123,
+    READYTORUN_HELPER_AsyncRestoreContexts      = 0x124,
+    READYTORUN_HELPER_AsyncCaptureExecCtx       = 0x125,
+    READYTORUN_HELPER_AsyncRestoreExecCtx       = 0x126,
+    READYTORUN_HELPER_AsyncRestoreCtxOnSusp     = 0x127,
+    READYTORUN_HELPER_AsyncCaptureContinCtx     = 0x128,


Renumbering existing ReadyToRunHelper values (AllocContinuation* moved from 0x113–0x115 to 0x120–0x122) is a ReadyToRun file-format compatibility break: older R2R images containing helper fixups with the previous IDs will no longer map in MapReadyToRunHelper() and can fail at runtime. Keep existing numeric IDs stable and only append new helper IDs (or add explicit backward-compat handling for the old values) instead of renumbering.

src/coreclr/tools/Common/Internal/Runtime/ReadyToRunConstants.cs

src/coreclr/tools/aot/ILCompiler.Compiler/IL/ILImporter.Scanner.cs

src/coreclr/interpreter/compiler.cpp

src/coreclr/inc/corinfo.h

src/coreclr/inc/readytorunhelpers.h

jakobbotsch · 2026-03-02T23:44:42Z

src/coreclr/jit/async.cpp

-        CORINFO_CALL_INFO callInfo = {};
-        callInfo.hMethod           = captureCall->gtCallMethHnd;
-        callInfo.methodFlags       = info.compCompHnd->getMethodAttribs(callInfo.hMethod);
-        impMarkInlineCandidate(captureCall, MAKE_METHODCONTEXT(callInfo.hMethod), false, &callInfo, compInlineContext);


Can you please open a follow-up issue about reallowing these helpers to be inlined?

jkotas · 2026-03-03T02:06:02Z

exposed a bug where IL 'jmp' instructions generate R2R indirect jumps that the delay-load thunk cannot resolve.

Why are not regular method calls exposed to this bug? Should we fix this bug instead?

jtschuster · 2026-03-03T05:02:52Z

Why are not regular method calls exposed to this bug? Should we fix this bug instead?

I believe it's due to the expectations that getFunctionEntryPoint returns a callable entrypoint of the method, but crossgen returns a DelayLoad method call. Calling the codegen a bug probably isn't right, I think the real issue was crossgen trying to implement getFunctionEntryPoint when it doesn't make sense. But am I wrong and crossgen should be able to implement it?

jkotas · 2026-03-03T05:09:21Z

It sounds like the problem solved by updateEntryPointForTailCall.

janvorli

Interpreter compiler changes LGTM.

janvorli · 2026-03-03T12:46:08Z

src/coreclr/inc/readytorun.h

    READYTORUN_HELPER_InitClass                 = 0x116,
    READYTORUN_HELPER_InitInstClass             = 0x117,
+
+    READYTORUN_HELPER_AllocContinuation         = 0x120,


Is there any reason for skipping some values of the enum?

Pre-existing scheme - it gives us a chance to keep one-off additions logically together.

jtschuster · 2026-03-04T00:26:08Z

It sounds like the problem solved by updateEntryPointForTailCall.

Setting isJumpableImportRequired=true for MethodEntrypoint doesn't work without additional changes to the JIT. We might be able to make some changes similar to #56669 to make getFunctionEntrypoint work, but I'm not familiar enough with the JIT to know for sure.

jtschuster · 2026-03-04T18:50:11Z

I created a couple alternatives to explore if we want to avoid using JIT helpers.

Use getAsyncInfo to get handles for the asynchelpers, and only implement getFunctionEntrypoint for those:
- Remove JIT helpers, only allow getFunctionEntrypoint on AsyncHelper jtschuster/runtime#8
Try to implement getFunctionEntrypoint for all methods (with some help from Copilot for the JIT changes):
- Implement getFunctionEntryPoint for runtime-async R2R compilation jtschuster/runtime#7

jtschuster · 2026-03-04T22:01:02Z

I'm also exploring if it be viable to have getAsyncInfo return mdTokens for the AsyncHelper methods and having the JIT to call getCallInfo which works fine in crossgen. Is there any reason I should avoid trying that?

jakobbotsch · 2026-03-04T22:14:04Z

I would probably suggest going with jtschuster#7 and then fixing JMP in the backend (can be done as a separate change). Alternatively we can abort R2R when we see CEE_JMP via implReadyToRunUnsupported, I think it would be fine too -- this IL instruction is rare.

Another option if the getFunctionEntryPoint implementation is questionable could be to return the lookup for the helpers from getAsyncInfo too.

I would not suggest returning tokens from getAsyncInfo. It is not going to be straightforward to handle what getCallInfo can return at the points where we need the helpers, and we cannot easily call into our usual helpers to create calls from these places.

Copilot AI review requested due to automatic review settings March 2, 2026 21:46

jtschuster requested review from BrzVlad, MichalStrehovsky, janvorli and kg as code owners March 2, 2026 21:46

github-actions bot added the area-crossgen2-coreclr label Mar 2, 2026

dotnet-policy-service bot assigned jtschuster Mar 2, 2026

github-project-automation bot added this to AppModel Mar 2, 2026

Copilot started reviewing on behalf of jtschuster March 2, 2026 21:47 View session

Copilot AI reviewed Mar 2, 2026

View reviewed changes

jkotas reviewed Mar 2, 2026

View reviewed changes

src/coreclr/inc/readytorunhelpers.h Outdated Show resolved Hide resolved

jtschuster added 2 commits March 2, 2026 14:07

Don't use abbreviated named in enums

7c1850d

Update JIT interface guid

1e424fc

jakobbotsch reviewed Mar 2, 2026

View reviewed changes

janvorli reviewed Mar 3, 2026

View reviewed changes

Conversation

jtschuster commented Mar 2, 2026

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

Copilot AI Mar 2, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

jakobbotsch Mar 2, 2026

Choose a reason for hiding this comment

Uh oh!

jkotas commented Mar 3, 2026

Uh oh!

jtschuster commented Mar 3, 2026

Uh oh!

jkotas commented Mar 3, 2026

Uh oh!

janvorli left a comment

Choose a reason for hiding this comment

Uh oh!

janvorli Mar 3, 2026

Choose a reason for hiding this comment

Uh oh!

jkotas Mar 3, 2026

Choose a reason for hiding this comment

Uh oh!

jtschuster commented Mar 4, 2026

Uh oh!

jtschuster commented Mar 4, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

jtschuster commented Mar 4, 2026

Uh oh!

jakobbotsch commented Mar 4, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

5 participants

jtschuster commented Mar 4, 2026 •

edited

Loading