Represent managed-return-values as native vars by jakobbotsch · Pull Request #128479 · dotnet/runtime

jakobbotsch · 2026-05-22T12:01:34Z

Update representation of managed return values to follow #128397.

dotnet-policy-service · 2026-05-22T12:03:21Z

Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch
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Copilot

Pull request overview

This PR updates CoreCLR JIT/VM debug-info plumbing to represent managed call return values as explicit ICorDebugInfo::NativeVarInfo entries (via a new CALL_RETURN_ILNUM sentinel plus a callReturnValueILOffset field), instead of relying on CALL_INSTRUCTION IP mapping entries. It also updates the compression/writer paths to encode this new data.

Changes:

Extended NativeVarInfo (and the shared JIT interface model) with callReturnValueILOffset, and added CALL_RETURN_ILNUM / updated MAX_ILNUM.
Updated debug info encoding/compression to treat CALL_RETURN_ILNUM specially (encode call IL offset; implicit native end offset).
Updated the JIT to collect per-call return-value location info and removed call-site CALL_INSTRUCTION mapping emission in multiple emitters.

Reviewed changes

Copilot reviewed 22 out of 22 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/coreclr/vm/debuginfostore.cpp	Adds special-case encoding/decoding for `CALL_RETURN_ILNUM` and implicit fields.
src/coreclr/tools/Common/JitInterface/CorInfoTypes.VarInfo.cs	Extends `NativeVarInfo` model with `callReturnValueILOffset`.
src/coreclr/tools/Common/JitInterface/CorInfoTypes.cs	Adds `CALL_RETURN_ILNUM` and updates `MAX_ILNUM`.
src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRun/DebugInfoTableNode.cs	Updates R2R var blob writer to encode call-return entries differently.
src/coreclr/jit/scopeinfo.cpp	Adds emission of call-return var entries; updates `getSiVarLoc` signature/use.
src/coreclr/jit/emitxarch.cpp	Removes call-site mapping emission previously used for return value reporting.
src/coreclr/jit/emitwasm.cpp	Removes call-site mapping emission previously used for return value reporting.
src/coreclr/jit/emitriscv64.cpp	Removes call-site mapping emission previously used for return value reporting.
src/coreclr/jit/emitloongarch64.cpp	Removes call-site mapping emission previously used for return value reporting.
src/coreclr/jit/emitarm64.cpp	Removes call-site mapping emission previously used for return value reporting.
src/coreclr/jit/emitarm.cpp	Removes call-site mapping emission previously used for return value reporting.
src/coreclr/jit/emit.h	Replaces `EmitCallParams.debugInfo` with `returnValueCall`.
src/coreclr/jit/ee_il_dll.cpp	Updates var reporting storage to carry call IL offset; improves display of call-return entries.
src/coreclr/jit/compiler.h	Extends `VarResultInfo` and updates `eeSetLVinfo` signature for call return metadata.
src/coreclr/jit/codegenxarch.cpp	Switches call emission plumbing to pass `returnValueCall`.
src/coreclr/jit/codegenwasm.cpp	Switches call emission plumbing to pass `returnValueCall`.
src/coreclr/jit/codegenlinear.cpp	Initializes storage for emitted call-return info.
src/coreclr/jit/codegeninterface.h	Adds `EmittedCallReturnInfo` container and updates `getSiVarLoc` signature.
src/coreclr/jit/codegencommon.cpp	Captures return-value location after emitting a call and records it for scope info.
src/coreclr/jit/codegenarmarch.cpp	Switches call emission plumbing to pass `returnValueCall`.
src/coreclr/inc/cordebuginfo.h	Adds `CALL_RETURN_ILNUM` and extends `NativeVarInfo` with `callReturnValueILOffset`.

Comments suppressed due to low confidence (2)

src/coreclr/jit/scopeinfo.cpp:516

getSiVarLoc now takes unsigned offset and then adds varDsc->GetStackOffset() (a signed stack offset that can be negative). This can underflow/wrap for typical frame-pointer locals (negative offsets), and then gets converted to int when constructing siVarLoc, producing incorrect stack locations in debug info.

CodeGenInterface::siVarLoc CodeGenInterface::getSiVarLoc(const LclVarDsc* varDsc, unsigned offset, unsigned stackLevel) const
{
    // For stack vars, find the base register, and offset

    regNumber baseReg;
    offset += varDsc->GetStackOffset();

    if (!varDsc->lvFramePointerBased)
    {
        baseReg = REG_SPBASE;
        offset += stackLevel;
    }
    else
    {
        baseReg = REG_FPBASE;
    }

    return CodeGenInterface::siVarLoc(varDsc, baseReg, offset, isFramePointerUsed());
}

src/coreclr/jit/emit.h:496

EmitCallParams removed the debugInfo field, but there are still target-specific codegen paths assigning params.debugInfo (e.g., in codegenloongarch64.cpp and codegenriscv64.cpp). This will break builds for those targets unless they are updated to the new returnValueCall mechanism.

struct EmitCallParams
{
    EmitCallType          callType = EC_COUNT;
    CORINFO_METHOD_HANDLE methHnd  = NO_METHOD_HANDLE;
#ifdef DEBUG
    // Used to report call sites to the EE
    CORINFO_SIG_INFO* sigInfo = nullptr;
#endif
    void*    addr    = nullptr;
    ssize_t  argSize = 0;
    emitAttr retSize = EA_PTRSIZE;
    // For multi-reg args with GC returns in the second arg
    emitAttr  secondRetSize = EA_UNKNOWN;
    bool      hasAsyncRet   = false;
    BitVec    ptrVars       = BitVecOps::UninitVal();
    regMaskTP gcrefRegs     = RBM_NONE;
    regMaskTP byrefRegs     = RBM_NONE;
    regNumber ireg        = REG_NA;
    regNumber xreg        = REG_NA;
    unsigned  xmul        = 0;
    ssize_t   disp        = 0;
    bool      isJump      = false;
    bool      noSafePoint = false;
    // If this call should have managed return value debug info associated with it, this is the call to associate it with.
    GenTreeCall* returnValueCall = nullptr;
#ifdef TARGET_WASM
    CORINFO_WASM_TYPE_SYMBOL_HANDLE wasmSignature = nullptr;
#endif
};

noahfalk

Thanks @jakobbotsch! I don't have the background knowledge to usefully review the JIT code but overall this looked like what I was hoping for. Since the debug info reader and ICorDebug code will need to stay synced with the writer let me see if I can get someone on my team to handle the remainder so we could put the whole thing in as one atomic commit.

tommcdon · 2026-06-01T17:22:00Z

I believe MRV is only used in live debugging scenarios, which requires consuming these changes in the DBI. I think we could consume the change in CordbNativeCode::GetReturnValueLiveOffsetImpl, and then we can delete CordbNativeCode::GetCallInstructionLength as it would be dead code. Should we do the DBI change as well (I think it is relatively small, noting that we would be deleting a long, unused function as part of it :) ).

Copilot

Pull request overview

Copilot reviewed 32 out of 32 changed files in this pull request and generated 6 comments.

Comments suppressed due to low confidence (1)

src/coreclr/jit/emit.h:496

EmitCallParams dropped the DebugInfo debugInfo field, but there are still backend codegen paths assigning to params.debugInfo (e.g., codegenriscv64.cpp / codegenloongarch64.cpp). As-is this will fail to compile for those targets; they likely need to be updated to use returnValueCall (or to stop emitting managed return value info on those backends).

struct EmitCallParams
{
    EmitCallType          callType = EC_COUNT;
    CORINFO_METHOD_HANDLE methHnd  = NO_METHOD_HANDLE;
#ifdef DEBUG
    // Used to report call sites to the EE
    CORINFO_SIG_INFO* sigInfo = nullptr;
#endif
    void*    addr    = nullptr;
    ssize_t  argSize = 0;
    emitAttr retSize = EA_PTRSIZE;
    // For multi-reg args with GC returns in the second arg
    emitAttr  secondRetSize = EA_UNKNOWN;
    bool      hasAsyncRet   = false;
    BitVec    ptrVars       = BitVecOps::UninitVal();
    regMaskTP gcrefRegs     = RBM_NONE;
    regMaskTP byrefRegs     = RBM_NONE;
    regNumber ireg        = REG_NA;
    regNumber xreg        = REG_NA;
    unsigned  xmul        = 0;
    ssize_t   disp        = 0;
    bool      isJump      = false;
    bool      noSafePoint = false;
    // If this call should have managed return value debug info associated with it, this is the call to associate it with.
    GenTreeCall* returnValueCall = nullptr;
#ifdef TARGET_WASM
    CORINFO_WASM_TYPE_SYMBOL_HANDLE wasmSignature = nullptr;
#endif
};

AndyAyersMS

JIT changes look good.

tommcdon

LGTM, thank you!

rcj1 · 2026-06-04T20:49:51Z

Added the debugger and cDAC support :)

Copilot

Copilot's findings

Files reviewed: 38/38 changed files
Comments generated: 3

rcj1 · 2026-06-04T23:20:47Z

@jakobbotsch fyi

jakobbotsch · 2026-06-08T09:48:38Z

Added the debugger and cDAC support :)

Thanks for doing that! I thought this would need change to the interface.

Copilot

Pull request overview

Copilot reviewed 38 out of 38 changed files in this pull request and generated 2 comments.

Copilot

Pull request overview

Copilot reviewed 38 out of 38 changed files in this pull request and generated 3 comments.

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>

PR dotnet#128479 introduced emitting managed return values as native vars but used storeVariableInRegisters(REG_FLOATRET, REG_NA) for float returns, which sets vlType=VLT_REG (integer register). The DBI then fails to read the return value because it looks in an integer register instead of XMM0. Fix by using VLT_REG_FP with a 0-based FP register index, which is what the DBI's VLT_REG_FP handler expects (it adds REGISTER_AMD64_XMM0 to convert to CorDebugRegister). Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

JIT: Report managed-return-values as a native var

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Copilot AI review requested due to automatic review settings May 22, 2026 12:01

github-actions Bot added the area-CodeGen-coreclr CLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI label May 22, 2026

Copilot started reviewing on behalf of jakobbotsch May 22, 2026 12:02 View session

dotnet-policy-service Bot assigned jakobbotsch May 22, 2026

Bump JIT-EE GUID

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Copilot AI reviewed May 22, 2026

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Comment thread src/coreclr/jit/codegencommon.cpp

Comment thread src/coreclr/jit/codegencommon.cpp Outdated

Comment thread src/coreclr/jit/ee_il_dll.cpp

Comment thread src/coreclr/vm/debuginfostore.cpp

Comment thread src/coreclr/jit/codegenlinear.cpp

Fix theoretical issue

2fcf4c1

jakobbotsch mentioned this pull request May 25, 2026

Add return value variable homes #128397

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noahfalk reviewed May 27, 2026

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Comment thread ...tools/aot/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRun/DebugInfoTableNode.cs

jakobbotsch added 6 commits June 2, 2026 13:46

Merge branch 'main' of github.com:dotnet/runtime into mrv-return-vars

72afb1a

Add a blurb about version 22

66a87fe

Bump R2R version

556e026

Fix R2R reading for version 20 and 22

bc05e7b

Fix build

33b9b8f

Update debugger

1a96758

Copilot AI review requested due to automatic review settings June 2, 2026 12:43

jakobbotsch changed the title ~~JIT: Report managed-return-values as a native var~~ Represent managed-return-values as native vars Jun 2, 2026

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jakobbotsch added 3 commits June 2, 2026 14:57

Feedback

1fde692

Run jit-format

92d77ae

Fix GCC build

00078d1

Copilot AI review requested due to automatic review settings June 2, 2026 14:10

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AndyAyersMS approved these changes Jun 4, 2026

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tommcdon approved these changes Jun 4, 2026

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Comment thread src/coreclr/jit/emitxarch.cpp

add debugger support

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Copilot AI review requested due to automatic review settings June 4, 2026 20:49

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Comment thread src/coreclr/vm/debuginfostore.cpp

Comment thread src/coreclr/jit/codegencommon.cpp

Comment thread ...e/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/Contracts/IDebugInfo.cs

noahfalk reviewed Jun 5, 2026

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Comment thread src/coreclr/debug/di/rspriv.h Outdated

name

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Merge branch 'main' into mrv-return-vars

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

Comment thread src/coreclr/vm/debuginfostore.cpp

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db70c33

build-analysis Bot mentioned this pull request Jun 8, 2026

[ci-scan] Build break: crosscomp.h CONTEXT_UNWOUND_TO_CALL macro redefinition in runtime-diagnostics #129111

Closed

Merge branch 'main' into mrv-return-vars

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Comment thread ...e/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/Contracts/IDebugInfo.cs

Comment thread src/coreclr/jit/codegenlinear.cpp

Comment thread src/coreclr/vm/debuginfostore.cpp

jakobbotsch merged commit 70e7750 into dotnet:main Jun 10, 2026
144 of 146 checks passed

jakobbotsch deleted the mrv-return-vars branch June 10, 2026 12:19

build-analysis Bot mentioned this pull request Jun 10, 2026

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

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dotnet-maestro Bot mentioned this pull request Jun 11, 2026

[main] Source code updates from dotnet/runtime dotnet/dotnet#7160

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kotlarmilos mentioned this pull request Jun 11, 2026

[clr-interp] Implement Managed Return Value support for the interpreter #127760

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dotnet-maestro Bot mentioned this pull request Jun 11, 2026

[main] Source code updates from dotnet/runtime dotnet/dotnet#7196

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tommcdon mentioned this pull request Jun 12, 2026

JIT: Fix managed return value debug info for floating-point returns #129321

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jakobbotsch commented May 22, 2026 •

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