[clr-interp] Implement Managed Return Value support for the interpreter by kotlarmilos · Pull Request #127760 · dotnet/runtime

kotlarmilos · 2026-05-04T15:11:08Z

Description

This PR adds managed return value support for interpreted methods so the debugger can surface the value a method just returned when stepping over or out of a call. Building on the variable-home contract from #128479 where EmitCall flags each value-returning IL call/callvirt site. The interpreter stores every return value in that slot, so the generic DI consumer reads it like any other variable home with no interpreter-specific disassembly or ABI logic.

Testing

Ran the MRV debugger tests against a local Checked CoreCLR build with DOTNET_InterpMode=3 and all active MRV tests pass under the interpreter:

MRV.TestArrays
MRV.TestAsyncMethods
MRV.TestClasses
MRV.TestComplexGenerics
MRV.TestEnums
MRV.TestGenerics
MRV.TestMisc
MRV.TestNativeCalls
MRV.TestPointers
MRV.TestPrimitiveTypes
MRV.TestReflectionWithAbstractMethod
MRV.TestRefs
MRV.TestStructs

dotnet-policy-service · 2026-05-04T15:12:46Z

Tagging subscribers to this area: @JulieLeeMSFT, @BrzVlad, @janvorli, @kg
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Copilot

Pull request overview

This PR extends CoreCLR interpreter debug info so managed return values can be surfaced for interpreted calls, and broadens IL/native mapping beyond stack-empty offsets. It fits into the debugger/interpreter pipeline by teaching the interpreter to emit richer boundary data and teaching DI to decode interpreter callsites.

Changes:

Adds interpreter-side IL/native map capacity tracking and emits per-IL-offset mappings plus CALL_INSTRUCTION entries for interpreter call opcodes.
Adds DI-side interpreter opcode-length decoding and synthetic stack-home lookup for interpreter return values.
Wires CordbJITILFrame to read interpreted return values from FP-relative dvars instead of native return registers.

Review found a blocking correctness issue: the new CALL_INSTRUCTION tagging in compiler.cpp also marks compiler-inserted helper calls (for example the helper emitted by EmitPushLdvirtftn), so GetReturnValueLiveOffset can report extra offsets for a single IL callsite and one of those offsets corresponds to the helper’s function-pointer result rather than the user call’s return value.

Show a summary per file

File	Description
`src/coreclr/interpreter/compiler.h`	Adds native-map capacity tracking for interpreter-emitted debug boundaries.
`src/coreclr/interpreter/compiler.cpp`	Emits expanded IL/native mappings and interpreter callsite markers.
`src/coreclr/debug/di/rsthread.cpp`	Reads interpreted return values from synthetic FP-relative variable homes.
`src/coreclr/debug/di/rspriv.h`	Declares the new interpreter-specific DI helper.
`src/coreclr/debug/di/module.cpp`	Decodes interpreter callsite lengths and dvar offsets in DI.

Copilot's findings

Files reviewed: 5/5 changed files
Comments generated: 1

Copilot

Copilot's findings

Files reviewed: 5/5 changed files
Comments generated: 3

Copilot

Copilot's findings

Files reviewed: 5/5 changed files
Comments generated: 1

Copilot

Copilot's findings

Files reviewed: 8/8 changed files
Comments generated: 2

Caller uses IfFailRet which treats S_FALSE as success. With the IsInterpreted() gating in place, neither S_FALSE return path is reachable on the happy path, so propagate them as real errors. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Copilot's findings

Files reviewed: 8/8 changed files
Comments generated: 0 new

noahfalk

@kotlarmilos - If possible lets hold off on this one until we settle what data contract we want here overall. If getting this in is blocking making progress elsewhere let me know but I'm guessing its relatively isolated. If we do wind up embedding this interpreter info into the debugger code we'll probably want to define some new IDacDbiInterface APIs and put the logic that understands interpreter disassembly in the DAC instead.

Rework interpreter managed-return-value (MRV) support to use the CALL_RETURN_ILNUM native-variable contract introduced in dotnet#128479 instead of the obsolete CALL_INSTRUCTION source-map encoding. The interpreter now emits one ICorDebugInfo::CALL_RETURN_ILNUM NativeVarInfo entry per value-returning managed call site through the standard setVars path. Each entry describes the call's destination var (an FP-relative stack slot) as the return value home, with callReturnValueILOffset set to the call's IL offset and startOffset set to the post-call native offset. The generic DI consumer (GetReturnValueVariableHomes / GetNativeVariable) handles the VLT_STK location identically to ordinary interpreter locals, so all of the PR's former DI-side instruction-decoding additions are obsolete and dropped (reverted to main): module.cpp, rsthread.cpp, rspriv.h, dacdbiimpl.cpp, and the dacdbistructures isInterpreted plumbing. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Copilot's findings

Files reviewed: 2/2 changed files
Comments generated: 1

The debugger resolves managed return values only for IL call/callvirt opcodes (CordbNativeCode::GetCallSignature), so CALL_RETURN_ILNUM entries emitted for calli sites are never consumed and only grow the var table. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

kotlarmilos · 2026-06-11T09:40:19Z

@kotlarmilos - If possible lets hold off on this one until we settle what data contract we want here overall. If getting this in is blocking making progress elsewhere let me know but I'm guessing its relatively isolated. If we do wind up embedding this interpreter info into the debugger code we'll probably want to define some new IDacDbiInterface APIs and put the logic that understands interpreter disassembly in the DAC instead.

This PR is rebased on #128479, in which EmitCall flags each IL call/callvirt site that returns a value.

Copilot

Copilot's findings

Files reviewed: 2/2 changed files
Comments generated: 0 new

Copilot AI review requested due to automatic review settings May 4, 2026 15:11

Copilot started reviewing on behalf of kotlarmilos May 4, 2026 15:11 View session

github-actions Bot added the area-CodeGen-Interpreter-coreclr label May 4, 2026

dotnet-policy-service Bot assigned kotlarmilos May 4, 2026

kotlarmilos changed the title ~~[interp] Implement Managed Return Value support for the interpreter~~ [clr-interp] Implement managed return value support for the interpreter May 4, 2026

kotlarmilos changed the title ~~[clr-interp] Implement managed return value support for the interpreter~~ [clr-interp] Implement Managed Return Value support for the interpreter May 4, 2026

kotlarmilos added this to the 11.0.0 milestone May 4, 2026

Copilot AI reviewed May 4, 2026

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Comment thread src/coreclr/interpreter/compiler.cpp Outdated

kotlarmilos closed this May 4, 2026

kotlarmilos reopened this May 5, 2026

kotlarmilos force-pushed the interp-mrv-return-value branch from fe82178 to 3c1ac90 Compare May 5, 2026 09:27

kotlarmilos marked this pull request as ready for review May 5, 2026 12:51

kotlarmilos requested a review from BrzVlad as a code owner May 5, 2026 12:51

Copilot AI review requested due to automatic review settings May 5, 2026 12:51

kotlarmilos requested review from janvorli and kg as code owners May 5, 2026 12:51

Copilot started reviewing on behalf of kotlarmilos May 5, 2026 12:51 View session

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Comment thread src/coreclr/interpreter/compiler.cpp Outdated

Comment thread src/coreclr/interpreter/compiler.cpp Outdated

Comment thread src/coreclr/interpreter/compiler.cpp Outdated

kotlarmilos force-pushed the interp-mrv-return-value branch from 3c1ac90 to 9f2787a Compare May 5, 2026 14:09

Copilot AI review requested due to automatic review settings May 5, 2026 14:15

kotlarmilos force-pushed the interp-mrv-return-value branch from 9f2787a to 946174b Compare May 5, 2026 14:15

Copilot started reviewing on behalf of kotlarmilos May 5, 2026 14:15 View session

kotlarmilos force-pushed the interp-mrv-return-value branch from 946174b to 9bffeb9 Compare May 5, 2026 14:15

Copilot AI reviewed May 5, 2026

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Comment thread src/coreclr/interpreter/compiler.cpp Outdated

Copilot AI reviewed May 6, 2026

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Comment thread src/coreclr/debug/di/rsthread.cpp Outdated

Comment thread src/coreclr/debug/di/module.cpp Outdated

kotlarmilos force-pushed the interp-mrv-return-value branch from 8afd1eb to a1932f7 Compare May 6, 2026 11:53

kotlarmilos force-pushed the interp-mrv-return-value branch from a1932f7 to 23409b8 Compare May 6, 2026 11:55

Merge branch 'main' into interp-mrv-return-value

74836a7

Copilot AI review requested due to automatic review settings May 7, 2026 11:53

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This was referenced May 7, 2026

[clr-ios] Enable debugging on CoreCLR mobile platforms #124744

Closed

[clr-interp] Implement interpreter debugging support in CoreCLR #120842

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BrzVlad approved these changes May 8, 2026

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noahfalk reviewed May 12, 2026

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Comment thread src/coreclr/debug/di/module.cpp Outdated

kotlarmilos marked this pull request as draft May 12, 2026 13:57

noahfalk mentioned this pull request May 20, 2026

Add return value variable homes #128397

Closed

kotlarmilos and others added 2 commits June 11, 2026 10:34

Drop redundant comment on m_callReturnInfos

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Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot AI review requested due to automatic review settings June 11, 2026 08:41

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Comment thread src/coreclr/interpreter/compiler.cpp Outdated

kotlarmilos and others added 2 commits June 11, 2026 11:28

Drop explanatory comments on MRV emission

45cbe47

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot AI review requested due to automatic review settings June 11, 2026 09:36

Copilot started reviewing on behalf of kotlarmilos June 11, 2026 09:36 View session

kotlarmilos requested review from BrzVlad, janvorli and noahfalk June 11, 2026 09:36

kotlarmilos marked this pull request as ready for review June 11, 2026 09:37

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build-analysis Bot mentioned this pull request Jun 11, 2026

[browser][coreCLR] Wasm.Console.Node.Sample - undefined symbol: SystemInteropJS_GetManagedStackTrace #129229

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

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kotlarmilos commented May 4, 2026 •

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