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AndyAyersMS merged 3 commits into from
Apr 24, 2025
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JIT: boost inlining for methods that may return small arrays #114806

AndyAyersMS merged 3 commits into from
Apr 24, 2025

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@AndyAyersMS AndyAyersMS commented Apr 17, 2025

Look for inlinees that may be allocating and returning small fixed sized arrays. When inlined, these array allocations may end up non-escaping and be stack allocated.

This analysis is approximate; we can't tell for sure in the IL scan what the array size is, and we can't easily tell if the allocated array is actually returned.

Contributes to #113236

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JIT: boost inlining for methods that may return small arrays
5d4a574 
Look for inlinees that may be allocating and returning small fixed sized arrays.
When inlined, these array allocations may end up non-escaping and be stack allocated.

This analysis is approximate; we can't tell for sure in the IL scan what the array
size is, and we can't easily tell if the allocated array is actually returned.

Contributes to dotnet#113236
@ghost ghost added the area-CodeGen-coreclr CLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI label Apr 17, 2025
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AndyAyersMS commented Apr 17, 2025

@EgorBo FYI

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dotnet-policy-service bot commented Apr 17, 2025

Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch
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AndyAyersMS commented Apr 17, 2025

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@AndyAyersMS AndyAyersMS marked this pull request as ready for review April 24, 2025 17:44
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AndyAyersMS commented Apr 24, 2025

@EgorBo PTAL
cc @dotnet/jit-contrib

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Pull Request Overview

This PR enhances the JIT inlining heuristics by adding a new observation for methods that may return small fixed-sized arrays, potentially enabling stack allocation of these arrays when inlined.

  • Introduces a new flag (m_MayReturnSmallArray) in the inline policy.
  • Marks inline observations based on array allocation in CEE_NEWARR cases to adjust the inlining multiplier.
  • Updates XML dumping and multiplier determination logic to include the new observation.

Reviewed Changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 1 comment.

File Description
src/coreclr/jit/inlinepolicy.h Added a new boolean flag for tracking small array returns.
src/coreclr/jit/inlinepolicy.cpp Implemented observation handling and updated multiplier.
src/coreclr/jit/fgbasic.cpp Integrated logic to detect array allocations in inline code.
Files not reviewed (1)
  • src/coreclr/jit/inline.def: Language not supported
Comments suppressed due to low confidence (1)

src/coreclr/jit/fgbasic.cpp:924

  • [nitpick] Consider renaming 'isReturnsArrayKnown' to 'arrayTypeDetermined' or a similarly descriptive name to more clearly convey its purpose.
bool        isReturnsArrayKnown = false;

src/coreclr/jit/inlinepolicy.cpp
}
}

if (m_MayReturnSmallArray)
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It might help maintainability to add a comment explaining why the multiplier is increased by 4.0 when a small array return is observed.

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@AndyAyersMS AndyAyersMS mentioned this pull request Apr 17, 2025
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AndyAyersMS commented Apr 24, 2025

Seeing quite a few failures with

Assert failure(PID 4332 [0x000010ec], Thread: 196 [0x00c4]): !"Did findClass() return a Byref?"

CORECLR! CEEInfo::getClassAttribsInternal + 0x34A (0x00007ff9`494486aa)
CORECLR! CEEInfo::getClassAttribs + 0xFA (0x00007ff9`494482da)
CLRJIT! Compiler::fgFindJumpTargets<1> + 0x1DF7 (0x00007ff9`4d34d7f7

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EgorBo commented Apr 24, 2025 •
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Seeing quite a few failures with

Assert failure(PID 4332 [0x000010ec], Thread: 196 [0x00c4]): !"Did findClass() return a Byref?"

CORECLR! CEEInfo::getClassAttribsInternal + 0x34A (0x00007ff9`494486aa)
CORECLR! CEEInfo::getClassAttribs + 0xFA (0x00007ff9`494482da)
CLRJIT! Compiler::fgFindJumpTargets<1> + 0x1DF7 (0x00007ff9`4d34d7f7

@AndyAyersMS I presume it fails on ref int[] Callee()

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AndyAyersMS commented Apr 24, 2025

Seeing quite a few failures with

Assert failure(PID 4332 [0x000010ec], Thread: 196 [0x00c4]): !"Did findClass() return a Byref?"

CORECLR! CEEInfo::getClassAttribsInternal + 0x34A (0x00007ff9`494486aa)
CORECLR! CEEInfo::getClassAttribs + 0xFA (0x00007ff9`494482da)
CLRJIT! Compiler::fgFindJumpTargets<1> + 0x1DF7 (0x00007ff9`4d34d7f7

@AndyAyersMS I presume it fails on ref int[] Callee()

Yeah likely....

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EgorBo commented Apr 24, 2025 •
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Yeah likely....

I wonder if you just can check info.compMethodInfo->args.retType and if it's byref - give up (or if you want to get underlying type - you can then call info.compCompHnd->getChildType on it and continue with getClassAttribs).

I'm actually not sure why getClassAttribs gives up on byref cls handles, but I remember I hit it somewhere else too once.

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LGTM assuming CI passes

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AndyAyersMS commented Apr 24, 2025

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@AndyAyersMS AndyAyersMS merged commit 006ad21 into dotnet:main Apr 24, 2025
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