Mark the special ABI primitive types as having stable layout #120802

tannergooding · 2025-10-16T14:59:23Z

This resolves #120367 and was tested using the following program:

using System.Numerics;
using System.Runtime.Intrinsics;

TestV();
TestV64();
TestV128();
TestV256();
TestV512();

static ushort[] TestV()
{
    Console.WriteLine(Vector<byte>.Count);
    ushort[] numbers = new ushort[32];
    Vector<ushort>.Zero.CopyTo(numbers);
    return numbers;
}

static ushort[] TestV64()
{
    Console.WriteLine(Vector64<byte>.Count);
    ushort[] numbers = new ushort[4];
    Vector64<ushort>.Zero.CopyTo(numbers);
    return numbers;
}

static ushort[] TestV128()
{
    Console.WriteLine(Vector128<byte>.Count);
    ushort[] numbers = new ushort[8];
    Vector128<ushort>.Zero.CopyTo(numbers);
    return numbers;
}

static ushort[] TestV256()
{
    Console.WriteLine(Vector256<byte>.Count);
    ushort[] numbers = new ushort[16];
    Vector256<ushort>.Zero.CopyTo(numbers);
    return numbers;
}

static ushort[] TestV512()
{
    Console.WriteLine(Vector512<byte>.Count);
    ushort[] numbers = new ushort[32];
    Vector512<ushort>.Zero.CopyTo(numbers);
    return numbers;
}

Results

Before

BEFORE
   1: JIT compiled Program:<Main>$(System.String[]) [Tier0, IL size=31, code size=51]
   2: JIT compiled Program:<<Main>$>g__TestV|0_0() [Tier0, IL size=34, code size=92]
   3: JIT compiled System.Threading.Thread:GetThreadStaticsBase() [Tier0, IL size=18, code size=34]
   4: JIT compiled System.Numerics.Vector`1[ushort]:CopyTo(ushort[]) [Tier0, IL size=39, code size=79]
   5: JIT compiled Program:<<Main>$>g__TestV64|0_1() [Tier0, IL size=30, code size=85]
   6: JIT compiled System.Runtime.Intrinsics.Vector64:CopyTo[ushort](System.Runtime.Intrinsics.Vector64`1[ushort],ushort[]) [Tier0, IL size=34, code size=71]
   7: JIT compiled Program:<<Main>$>g__TestV128|0_2() [Tier0, IL size=30, code size=84]
   8: JIT compiled Program:<<Main>$>g__TestV256|0_3() [Tier0, IL size=31, code size=84]
   9: JIT compiled System.Runtime.Intrinsics.Vector256:CopyTo[ushort](System.Runtime.Intrinsics.Vector256`1[ushort],ushort[]) [Tier0, IL size=34, code size=79]
  10: JIT compiled Program:<<Main>$>g__TestV512|0_4() [Tier0, IL size=31, code size=98]
  11: JIT compiled System.Runtime.Intrinsics.Vector512:CopyTo[ushort](System.Runtime.Intrinsics.Vector512`1[ushort],ushort[]) [Tier0, IL size=34, code size=83]

After - .NET 10

AVX512 Capable Machine

1: JIT compiled System.Threading.Thread:GetThreadStaticsBase() [Tier0, IL size=18, code size=34]
   2: JIT compiled System.Numerics.Vector`1[ushort]:CopyTo(ushort[]) [Tier0, IL size=39, code size=79]
   3: JIT compiled System.Runtime.Intrinsics.Vector64:CopyTo[ushort](System.Runtime.Intrinsics.Vector64`1[ushort],ushort[]) [Tier0, IL size=34, code size=71]
   4: JIT compiled System.Runtime.Intrinsics.Vector256:CopyTo[ushort](System.Runtime.Intrinsics.Vector256`1[ushort],ushort[]) [Tier0, IL size=34, code size=79]
   5: JIT compiled Program:<<Main>$>g__TestV512|0_4() [Tier0, IL size=31, code size=98]
   6: JIT compiled System.Runtime.Intrinsics.Vector512:CopyTo[ushort](System.Runtime.Intrinsics.Vector512`1[ushort],ushort[]) [Tier0, IL size=34, code size=83]

AVX512=0

   1: JIT compiled System.Threading.Thread:GetThreadStaticsBase() [Tier0, IL size=18, code size=34]
   2: JIT compiled System.Numerics.Vector`1[ushort]:CopyTo(ushort[]) [Tier0, IL size=39, code size=79]
   3: JIT compiled System.Runtime.Intrinsics.Vector64:CopyTo[ushort](System.Runtime.Intrinsics.Vector64`1[ushort],ushort[]) [Tier0, IL size=34, code size=71]
   4: JIT compiled System.Runtime.Intrinsics.Vector256:CopyTo[ushort](System.Runtime.Intrinsics.Vector256`1[ushort],ushort[]) [Tier0, IL size=34, code size=79]
   5: JIT compiled System.Runtime.Intrinsics.Vector512:CopyTo[ushort](System.Runtime.Intrinsics.Vector512`1[ushort],ushort[]) [Tier0, IL size=34, code size=100]

AVX2=0

   1: JIT compiled Program:<Main>$(System.String[]) [Tier0, IL size=31, code size=51]
   2: JIT compiled Program:<<Main>$>g__TestV|0_0() [Tier0, IL size=34, code size=87]
   3: JIT compiled System.Threading.Thread:GetThreadStaticsBase() [Tier0, IL size=18, code size=34]
   4: JIT compiled Program:<<Main>$>g__TestV64|0_1() [Tier0, IL size=30, code size=85]
   5: JIT compiled System.Runtime.Intrinsics.Vector64:CopyTo[ushort](System.Runtime.Intrinsics.Vector64`1[ushort],ushort[]) [Tier0, IL size=34, code size=71]
   6: JIT compiled Program:<<Main>$>g__TestV128|0_2() [Tier0, IL size=30, code size=84]
   7: JIT compiled Program:<<Main>$>g__TestV256|0_3() [Tier0, IL size=31, code size=84]
   8: JIT compiled System.Runtime.Intrinsics.Vector256:CopyTo[ushort](System.Runtime.Intrinsics.Vector256`1[ushort],ushort[]) [Tier0, IL size=34, code size=79]
   9: JIT compiled Program:<<Main>$>g__TestV512|0_4() [Tier0, IL size=31, code size=126]
  10: JIT compiled System.Runtime.Intrinsics.Vector512:CopyTo[ushort](System.Runtime.Intrinsics.Vector512`1[ushort],ushort[]) [Tier0, IL size=34, code size=100]

SSE42=0

   1: JIT compiled System.SpanHelpers:IndexOfNullCharacter(ptr) [Instrumented Tier0, IL size=1148, code size=926]
   2: JIT compiled System.SpanHelpers:GetCharVector128SpanLength(nint,nint) [Tier0, IL size=14, code size=26]
   3: JIT compiled System.SpanHelpers:NonPackedIndexOfValueType[short,System.SpanHelpers+DontNegate`1[short]](byref,short,int) [Instrumented Tier0, IL size=1204, code size=1761]
   4: JIT compiled System.Text.Unicode.Utf16Utility:GetPointerToFirstInvalidChar(ptr,int,byref,byref) [Instrumented Tier0, IL size=946, code size=1280]
   5: JIT compiled System.Text.Ascii:GetIndexOfFirstNonAsciiChar_Intrinsified(ptr,nuint) [Instrumented Tier0, IL size=473, code size=1390]
   6: JIT compiled System.Text.Ascii:VectorContainsNonAsciiChar(System.Runtime.Intrinsics.Vector128`1[ushort]) [Tier0, IL size=109, code size=63]
   7: JIT compiled System.Text.Unicode.Utf8Utility:TranscodeToUtf8(ptr,int,ptr,int,byref,byref) [Instrumented Tier0, IL size=1494, code size=2856]
   8: JIT compiled System.Text.Ascii:NarrowUtf16ToAscii(ptr,ptr,nuint) [Instrumented Tier0, IL size=380, code size=755]
   9: JIT compiled Program:<Main>$(System.String[]) [Tier0, IL size=31, code size=51]
  10: JIT compiled Program:<<Main>$>g__TestV|0_0() [Tier0, IL size=34, code size=87]
  11: JIT compiled System.Threading.Thread:GetThreadStaticsBase() [Tier0, IL size=18, code size=34]
  12: JIT compiled System.PackedSpanHelpers:IndexOfAnyInRange[System.SpanHelpers+DontNegate`1[short]](byref,short,short,int) [Instrumented Tier0, IL size=861, code size=1316]
  13: JIT compiled Program:<<Main>$>g__TestV64|0_1() [Tier0, IL size=30, code size=85]
  14: JIT compiled System.Runtime.Intrinsics.Vector64:CopyTo[ushort](System.Runtime.Intrinsics.Vector64`1[ushort],ushort[]) [Tier0, IL size=34, code size=71]
  15: JIT compiled Program:<<Main>$>g__TestV128|0_2() [Tier0, IL size=30, code size=82]
  16: JIT compiled Program:<<Main>$>g__TestV256|0_3() [Tier0, IL size=31, code size=104]
  17: JIT compiled System.Runtime.Intrinsics.Vector256:CopyTo[ushort](System.Runtime.Intrinsics.Vector256`1[ushort],ushort[]) [Tier0, IL size=34, code size=93]
  18: JIT compiled Program:<<Main>$>g__TestV512|0_4() [Tier0, IL size=31, code size=135]
  19: JIT compiled System.Runtime.Intrinsics.Vector512:CopyTo[ushort](System.Runtime.Intrinsics.Vector512`1[ushort],ushort[]) [Tier0, IL size=34, code size=109]

HWIntrinsics=0

   A LOT - Not actually going to list the several hundred APIs, this is expected since the "baseline" ISA is disabled

After - .NET 11

AVX512 Capable Machine

  1: JIT compiled System.Runtime.Intrinsics.Vector64:CopyTo[ushort](System.Runtime.Intrinsics.Vector64`1[ushort],ushort[]) [Tier0, IL size=34, code size=71]
  2: JIT compiled System.Runtime.Intrinsics.Vector256:CopyTo[ushort](System.Runtime.Intrinsics.Vector256`1[ushort],ushort[]) [Tier0, IL size=34, code size=79]
  3: JIT compiled Program:<<Main>$>g__TestV512|0_4() [Tier0, IL size=31, code size=98]
  4: JIT compiled System.Runtime.Intrinsics.Vector512:CopyTo[ushort](System.Runtime.Intrinsics.Vector512`1[ushort],ushort[]) [Tier0, IL size=34, code size=83]

AVX512=0

  1: JIT compiled System.Runtime.Intrinsics.Vector64:CopyTo[ushort](System.Runtime.Intrinsics.Vector64`1[ushort],ushort[]) [Tier0, IL size=34, code size=71]
  2: JIT compiled System.Runtime.Intrinsics.Vector256:CopyTo[ushort](System.Runtime.Intrinsics.Vector256`1[ushort],ushort[]) [Tier0, IL size=34, code size=79]
  3: JIT compiled System.Runtime.Intrinsics.Vector512:CopyTo[ushort](System.Runtime.Intrinsics.Vector512`1[ushort],ushort[]) [Tier0, IL size=34, code size=100]

AVX2=0

  A LOT - This is also expected since we bumped the R2R baseline to AVX2 for .NET 11

Copilot

Pull Request Overview

This PR marks special ABI primitive types (Vector types and Int128/UInt128) as having stable layout to improve R2R (ReadyToRun) performance. The change eliminates unnecessary JIT compilations for vector and Int128 operations when hardware capabilities support them.

Removes the vectorAbiIsStable parameter from VectorFieldLayoutAlgorithm constructors and always treats vector types as ABI stable
Updates Int128FieldLayoutAlgorithm to mark Int128/UInt128 types as having stable layout on all platforms including ARM
Simplifies VectorOfTFieldLayoutAlgorithm by removing conditional ABI stability logic

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
TestTypeSystemContext.cs	Removed second parameter from VectorFieldLayoutAlgorithm constructor call
ReadyToRunCompilerContext.cs	Removed conditional ABI stability logic and always marks vector types as stable
VectorFieldLayoutAlgorithm.cs	Removed vectorAbiIsStable parameter and field, hardcoded LayoutAbiStable to true
Int128FieldLayoutAlgorithm.cs	Changed LayoutAbiStable from false to true for Int128/UInt128 types

tannergooding · 2025-10-16T15:00:16Z

CC. @jkotas, @EgorBo

jkotas · 2025-10-16T15:22:17Z

Are these types still blocked for interop (re #120367 (comment) )?

tannergooding · 2025-10-16T15:29:01Z

Are these types still blocked for interop (re #120367 (comment) )?

Yep. We block those in the VM, it has nothing to do with ABI stability:

jkotas · 2025-10-16T15:54:21Z

AVX512=0
1: JIT compiled System.Runtime.Intrinsics.Vector64:CopyToushort [Tier0, IL size=34, code size=71]
2: JIT compiled System.Runtime.Intrinsics.Vector256:CopyToushort [Tier0, IL size=34, code size=79]
3: JIT compiled System.Runtime.Intrinsics.Vector512:CopyToushort [Tier0, IL size=34, code size=100]

Why are these still getting compiled?

tannergooding · 2025-10-16T16:04:33Z

Why are these still getting compiled?

Nothing triggers them in the S.P.Corelib R2R image, unlike V128<byte>/V128<ushort>, and they aren't [NonVersionable] so they don't cross the corelib boundary.

We only have the R2R entry for CopyTo<__Cannon> for these types. Where-as V128 is used for byte/ushort from within corelib code paths itself.

tannergooding · 2025-10-16T16:07:43Z

R2RDump on S.P.Corelib reports

	Line 52321: void System.Runtime.Intrinsics.Vector64.CopyTo<__Canon>(System.Runtime.Intrinsics.Vector64`1<__Canon>, __Canon[])
	Line 52329: void System.Runtime.Intrinsics.Vector64.CopyTo<__Canon>(System.Runtime.Intrinsics.Vector64`1<__Canon>, __Canon[])
	Line 52371: void System.Runtime.Intrinsics.Vector64.CopyTo<__Canon>(System.Runtime.Intrinsics.Vector64`1<__Canon>, __Canon[], int)
	Line 52379: void System.Runtime.Intrinsics.Vector64.CopyTo<__Canon>(System.Runtime.Intrinsics.Vector64`1<__Canon>, __Canon[], int)
	Line 52435: void System.Runtime.Intrinsics.Vector64.CopyTo<__Canon>(System.Runtime.Intrinsics.Vector64`1<__Canon>, System.Span`1<__Canon>)
	Line 52444: void System.Runtime.Intrinsics.Vector64.CopyTo<__Canon>(System.Runtime.Intrinsics.Vector64`1<__Canon>, System.Span`1<__Canon>)
	
	Line 13155: void System.Runtime.Intrinsics.Vector128.CopyTo<__Canon>(System.Runtime.Intrinsics.Vector128`1<__Canon>, __Canon[])
	Line 13163: void System.Runtime.Intrinsics.Vector128.CopyTo<__Canon>(System.Runtime.Intrinsics.Vector128`1<__Canon>, __Canon[])
	Line 13205: void System.Runtime.Intrinsics.Vector128.CopyTo<__Canon>(System.Runtime.Intrinsics.Vector128`1<__Canon>, __Canon[], int)
	Line 13213: void System.Runtime.Intrinsics.Vector128.CopyTo<__Canon>(System.Runtime.Intrinsics.Vector128`1<__Canon>, __Canon[], int)
	Line 13269: void System.Runtime.Intrinsics.Vector128.CopyTo<__Canon>(System.Runtime.Intrinsics.Vector128`1<__Canon>, System.Span`1<__Canon>)
	Line 13278: void System.Runtime.Intrinsics.Vector128.CopyTo<__Canon>(System.Runtime.Intrinsics.Vector128`1<__Canon>, System.Span`1<__Canon>)
	Line 15982: void System.Runtime.Intrinsics.Vector128.CopyTo<ushort>(System.Runtime.Intrinsics.Vector128`1<ushort>, ushort[])
	Line 15988: void System.Runtime.Intrinsics.Vector128.CopyTo<ushort>(System.Runtime.Intrinsics.Vector128`1<ushort>, ushort[])
	Line 36641: void System.Runtime.Intrinsics.Vector128.CopyTo<byte>(System.Runtime.Intrinsics.Vector128`1<byte>, System.Span`1<byte>)
	Line 36649: void System.Runtime.Intrinsics.Vector128.CopyTo<byte>(System.Runtime.Intrinsics.Vector128`1<byte>, System.Span`1<byte>)
	
	Line 11088: void System.Runtime.Intrinsics.Vector256.CopyTo<__Canon>(System.Runtime.Intrinsics.Vector256`1<__Canon>, __Canon[])
	Line 11096: void System.Runtime.Intrinsics.Vector256.CopyTo<__Canon>(System.Runtime.Intrinsics.Vector256`1<__Canon>, __Canon[])
	Line 11138: void System.Runtime.Intrinsics.Vector256.CopyTo<__Canon>(System.Runtime.Intrinsics.Vector256`1<__Canon>, __Canon[], int)
	Line 11146: void System.Runtime.Intrinsics.Vector256.CopyTo<__Canon>(System.Runtime.Intrinsics.Vector256`1<__Canon>, __Canon[], int)
	Line 11202: void System.Runtime.Intrinsics.Vector256.CopyTo<__Canon>(System.Runtime.Intrinsics.Vector256`1<__Canon>, System.Span`1<__Canon>)
	Line 11211: void System.Runtime.Intrinsics.Vector256.CopyTo<__Canon>(System.Runtime.Intrinsics.Vector256`1<__Canon>, System.Span`1<__Canon>)

	Line 40862: void System.Runtime.Intrinsics.Vector512.CopyTo<__Canon>(System.Runtime.Intrinsics.Vector512`1<__Canon>, __Canon[])
	Line 40870: void System.Runtime.Intrinsics.Vector512.CopyTo<__Canon>(System.Runtime.Intrinsics.Vector512`1<__Canon>, __Canon[])
	Line 40912: void System.Runtime.Intrinsics.Vector512.CopyTo<__Canon>(System.Runtime.Intrinsics.Vector512`1<__Canon>, __Canon[], int)
	Line 40920: void System.Runtime.Intrinsics.Vector512.CopyTo<__Canon>(System.Runtime.Intrinsics.Vector512`1<__Canon>, __Canon[], int)
	Line 40976: void System.Runtime.Intrinsics.Vector512.CopyTo<__Canon>(System.Runtime.Intrinsics.Vector512`1<__Canon>, System.Span`1<__Canon>)
	Line 40985: void System.Runtime.Intrinsics.Vector512.CopyTo<__Canon>(System.Runtime.Intrinsics.Vector512`1<__Canon>, System.Span`1<__Canon>)

EgorBo · 2025-10-16T18:37:06Z

Nothing triggers them in the S.P.Corelib

Yeah, we don't use Vector_.Create(Span) and Vector_.CopyTo(Span) Vector APIs in the BCL yet since they come with the bounds checks JIT can't eliminate today when used inside loops and rely on unsafe instead. The actual issue was driven by, literally the first usage of CopyTo in the whole Libraries.

tannergooding · 2025-10-16T18:42:20Z

I'm going to log an issue for the void System.Runtime.Intrinsics.Vector512.CopyTo<__Canon> R2R entries existing

These seem like cases we can actually avoid since they will always fault and shouldn't appear in code. It'd be more useful to pick the "most common" T for the SIMD types or just not R2R them at all unless used instead.

tannergooding · 2025-10-16T19:16:43Z

@jkotas, any other questions/comments?

jkotas · 2025-10-16T19:55:34Z

I'm going to log an issue for the void System.Runtime.Intrinsics.Vector512.CopyTo<__Canon> R2R entries existing

Yes, there is more fine-tunning we should do here, but it does not need to block this PR.

jkotas

Thanks

tannergooding · 2025-10-16T20:07:02Z

Logged #120816

Mark the special ABI primitive types as having stable layout

c848d92

tannergooding requested a review from MichalStrehovsky as a code owner October 16, 2025 14:59

Copilot AI review requested due to automatic review settings October 16, 2025 14:59

Copilot AI reviewed Oct 16, 2025

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dotnet-policy-service bot assigned tannergooding Oct 16, 2025

EgorBo approved these changes Oct 16, 2025

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jkotas approved these changes Oct 16, 2025

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tannergooding mentioned this pull request Oct 16, 2025

R2R contains unnecessary compilations for certain generic types #120816

Open

tannergooding merged commit 3be0023 into dotnet:main Oct 16, 2025
97 checks passed

tannergooding deleted the fix-120367 branch October 16, 2025 20:07

dotnet-maestro bot mentioned this pull request Oct 21, 2025

[main] Source code updates from dotnet/runtime dotnet/dotnet#3024

Merged

LoopedBard3 mentioned this pull request Oct 23, 2025

[Perf] Windows/x64: 2 Regressions on 10/16/2025 6:30:56 PM +00:00 #121049

Open

Mark the special ABI primitive types as having stable layout #120802

Mark the special ABI primitive types as having stable layout #120802

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Results

Before

After - .NET 10

AVX512 Capable Machine

AVX512=0

AVX2=0

SSE42=0

HWIntrinsics=0

After - .NET 11

AVX512 Capable Machine

AVX512=0

AVX2=0

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Pull Request Overview

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