[release/8.0-staging] Fix hwintrinsicChild->isContained() assert

[github-actions]

Backport of #90556 to release/8.0-staging

/cc @EgorBo

Customer Impact

Certain SIMD patterns may produce garbage values on CPUs with AVX-512 (mostly for unoptimized code). This is regression introduced in .NET 8 by AVX512 work.

There were two issues #96381 (customer reported) and #90508

Minimal repro:

double cns = 1.0;
var vec = Vector128.Create(42.0) + 
    Sse3.MoveAndDuplicate(Vector128.CreateScalarUnsafe(cns));
Console.WriteLine(vec);

Prints <42, 43> while <42, 42> is expected.

Testing

A test is added

Risk

Low. It is a simple fix, and the problem reproduces only on machines with AVX512 and with very specific patterns in Tier 0.

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Issue Details

---

Backport of #90556 to release/8.0-staging

/cc @EgorBo

Customer Impact

Testing

Risk

IMPORTANT: If this backport is for a servicing release, please verify that:

• The PR target branch is release/X.0-staging, not release/X.0.

• If the change touches code that ships in a NuGet package, you have added the necessary package authoring and gotten it explicitly reviewed.

Author:	github-actions[bot]
Assignees:	-
Labels:	area-CodeGen-coreclr
Milestone:	-

[kunalspathak]

LGTM

[carlossanlop]

@EgorBo Friendly reminder that Tuesday January 16th 4pm is the Code Complete deadline for the February Release. If all requirements are met, please merge your PR before that date and time to ensure this fix gets included in that Release.

[JulieLeeMSFT]

@jeffschwMSFT, please consider this for approval.

[jeffschwMSFT]

approved. we will take for consideration in 8.0.x