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Avoid stripping IL of non-async Task-returning methods - #129884

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jakobbotsch:fix-129813
Jun 27, 2026
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Avoid stripping IL of non-async Task-returning methods#129884
jakobbotsch merged 1 commit into
dotnet:mainfrom
jakobbotsch:fix-129813

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@jakobbotschjakobbotsch commented Jun 26, 2026•
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The IL of these may be needed at runtime to compile async versions.

Fix#129813

@jakobbotsch
Avoid stripping IL of non-async Task-returning methods
6e40d2b
The IL of these may be needed at runtime to compile async versions.
CopilotAI review requested due to automatic review settings June 26, 2026 07:52
@github-actionsgithub-actionsBot added the area-crossgen2-coreclr only use for closed issues label Jun 26, 2026
@jakobbotschjakobbotsch mentioned this pull request Jun 26, 2026
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Pull request overview

This change updates ReadyToRun IL body stripping so the compiler retains real IL for methods whose IL may be needed at runtime (notably synchronous Task/ValueTask-returning methods that can have async variants), instead of replacing their bodies with the minimal throwing stub when --strip-il-bodies is enabled.

Changes:

  • Replaces the previous “non-generic only” strip condition with a helper (MayNeedILAtRuntime) that centralizes the decision.
  • Preserves IL for generic methods/types (existing behavior) and additionally for non-async Task/ValueTask-returning methods.

Comment thread...tools/aot/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRun/CopiedMethodILNode.cs
Comment thread...tools/aot/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRun/CopiedMethodILNode.cs
@jakobbotsch

jakobbotsch commented Jun 26, 2026

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Once the crossgen2 support makes it in we could also consider being a bit more precise -- we can strip the IL body if we have compiled both the async and non-async variants.

@jkotasjkotas added runtime-async area-ReadyToRun and removed area-crossgen2-coreclr only use for closed issues labels Jun 26, 2026
@jkotas
jkotas marked this pull request as ready for review June 26, 2026 18:01
@jakobbotsch
jakobbotsch merged commit ac17f52 into dotnet:mainJun 27, 2026
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jakobbotsch deleted the fix-129813 branch June 27, 2026 04:35
@dotnet-maestrodotnet-maestroBot mentioned this pull request Jun 28, 2026
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@dotnet-milestone-botdotnet-milestone-botBot added this to the 11.0-preview7 milestone Jun 28, 2026
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jakobbotsch commented Jun 29, 2026

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/backport to release/11.0-preview6

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Started backporting to release/11.0-preview6 (link to workflow run)

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@jakobbotschjakobbotsch linked an issue Jun 29, 2026 that may be closed by this pull request
Runtime-async miscompiles Stream.ReadAsync(Memory<byte>) tail-call forwarder into NullReferenceException (regression, likely from #128384) #129813
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svick pushed a commit that referenced this pull request Jun 30, 2026
@github-actions@jakobbotsch
[release/11.0-preview6] Avoid stripping IL of non-async Task-returnin…
3e2ff44
…g methods (#129975)
Backport of #129884 to release/11.0-preview6
/cc @jakobbotsch
## Customer Impact
- [X] Customer reported
- [ ] Found internally
Crossgen2 may strip IL of Task-returning methods that will be needed at
runtime if runtime async is enabled. This results in
`NullReferenceException` at runtime. Reported in #129813.
## Regression
- [X] Yes
- [ ] No
Introduced in #128384 that started depending on user IL when compiling
async variants of non-async Task/ValueTask-returning methods.
## Testing
Verified that customer's test case progresses further when IL stripping
is disabled.
## Risk
Low. Disable stripping of IL for non-async Task-returning methods.
Co-authored-by: Jakob Botsch Nielsen <jakob.botsch.nielsen@gmail.com>
@kotlarmiloskotlarmilos mentioned this pull request Jul 1, 2026
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kotlarmilos added a commit to kotlarmilos/runtime that referenced this pull request Jul 1, 2026
@kotlarmilos
Add crossgen2 --strip-il-bodies runtime-async regression test
c61119e
Adds an ILCompiler.ReadyToRun.Tests case that crossgen2-composites a small
runtime-async assembly with --strip-il-bodies and inspects the emitted
component MSIL to assert every branch of the strip decision, covering the
regression from dotnet#129813 fixed by dotnet#129884.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
kotlarmilos added a commit to kotlarmilos/runtime that referenced this pull request Jul 1, 2026
@kotlarmilos
Add crossgen2 --strip-il-bodies runtime-async regression test
50c77f3
Adds an ILCompiler.ReadyToRun.Tests case that crossgen2-composites a small
runtime-async assembly with --strip-il-bodies and inspects the emitted
component MSIL to assert every branch of the strip decision, covering the
regression from dotnet#129813 fixed by dotnet#129884.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
kotlarmilos added a commit that referenced this pull request Jul 2, 2026
@kotlarmilos
Add crossgen2 --strip-il-bodies runtime-async regression test (#130075)
aeac9fb
## Description
The `--strip-il-bodies` optimization in crossgen2 is applied when
building the composite ReadyToRun images that ship in the Apple mobile
runtime packs, and in #129813 it regressed by stripping the IL of
non-async `Task`/`ValueTask`-returning methods. That IL is still needed,
because with runtime-async enabled the runtime compiles a runtime-async
variant of such a method from its IL, so replacing it with a `ldnull`
throw stub threw `NullReferenceException` on the mobile packs until
#129884 narrowed the pass via `MayNeedILAtRuntime`.
This PR adds a deterministic `ILCompiler.ReadyToRun.Tests` tests that
inspect the emitted component MSIL to assert every branch of the strip
logic. Non-async `Task<T>`/`ValueTask<T>`/`Task`/`ValueTask`-returning
methods, a generic method, and a method on a generic type keep their IL,
while plain methods and async `Task<T>`/`ValueTask` methods are still
stripped.
TODO: This PR should be aligned with
#130025
---------
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@kotlarmiloskotlarmilos mentioned this pull request Jul 3, 2026
Closed
eiriktsarpalis pushed a commit that referenced this pull request Jul 15, 2026
@jakobbotsch@eiriktsarpalis
Avoid stripping IL of non-async Task-returning methods (#129884)
cd410a0
The IL of these may be needed at runtime to compile async versions.
eiriktsarpalis pushed a commit that referenced this pull request Jul 15, 2026
@kotlarmilos@eiriktsarpalis
Add crossgen2 --strip-il-bodies runtime-async regression test (#130075)
ae2f859
## Description
The `--strip-il-bodies` optimization in crossgen2 is applied when
building the composite ReadyToRun images that ship in the Apple mobile
runtime packs, and in #129813 it regressed by stripping the IL of
non-async `Task`/`ValueTask`-returning methods. That IL is still needed,
because with runtime-async enabled the runtime compiles a runtime-async
variant of such a method from its IL, so replacing it with a `ldnull`
throw stub threw `NullReferenceException` on the mobile packs until
#129884 narrowed the pass via `MayNeedILAtRuntime`.
This PR adds a deterministic `ILCompiler.ReadyToRun.Tests` tests that
inspect the emitted component MSIL to assert every branch of the strip
logic. Non-async `Task<T>`/`ValueTask<T>`/`Task`/`ValueTask`-returning
methods, a generic method, and a method on a generic type keep their IL,
while plain methods and async `Task<T>`/`ValueTask` methods are still
stripped.
TODO: This PR should be aligned with
#130025
---------
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@github-actionsgithub-actionsBot locked and limited conversation to collaborators Jul 30, 2026
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Runtime-async miscompiles Stream.ReadAsync(Memory<byte>) tail-call forwarder into NullReferenceException (regression, likely from #128384)

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