Test JsonEncodedText.GetHashCode code shape for ARM64 regression

[eiriktsarpalis]

Tests whether restoring the pre-#130976 ternary code shape for JsonEncodedText.GetHashCode() removes #131600.

Utf8JsonReader.GetUInt64, TryGetUInt64, and TryGetUInt64Core have identical IL before and after #130976. The current evidence points to an ARM64 tiering or code-layout interaction rather than a semantic reader change. This draft retains #130976's original commit history only so EgorBot can compare its internal stages. It is not ready to merge until the Ampere measurements identify the first bad stage and validate this candidate.

Note

This pull request was prepared by GitHub Copilot.

[eiriktsarpalis]

@EgorBot -ubuntu24_azure_ampere -pr 132399 -commits af85196,66b30d95f08c6dafb73a5006ccbf1faccfc41f01,43560bc79db55b49722afff9eeeac9704803315d,a271e683ebac9ab3d3cc2d24ffec341a558a6f86,7c12816f5c1ddd67b23ec8f0f42513b693736c29,6ca403a8a24576553af420df7e5ce0dc94671c06 --filter "System.Text.Json.Tests.Perf_Get.GetUInt64"

Note

This benchmark request was prepared by GitHub Copilot.

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[Copilot]

Pull request overview

This change adjusts the IL/code shape of JsonEncodedText.GetHashCode() in System.Text.Json to help investigate an ARM64 tiering/code-layout performance regression (#131600) by restoring the pre-#130976 ternary-based null check pattern.

Changes:

• Replaces the null-conditional/?? GetHashCode implementation with an equivalent ternary (is null ? 0 : ...) to produce the desired code shape on ARM64.

[eiriktsarpalis]

Rerunning after restoring the private-libunwind linker fallback needed to build current main on the benchmark image.

@EgorBot -ubuntu24_azure_ampere -pr 132399 -commits af85196,66b30d95f08c6dafb73a5006ccbf1faccfc41f01,43560bc79db55b49722afff9eeeac9704803315d,a271e683ebac9ab3d3cc2d24ffec341a558a6f86,7c12816f5c1ddd67b23ec8f0f42513b693736c29,a3dd4f855a512477197fece0a8d05d56ce724188 --filter "System.Text.Json.Tests.Perf_Get.GetUInt64"

Note

This benchmark request was prepared by GitHub Copilot.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

Suppressed comments (1)

src/coreclr/nativeaot/Runtime/Full/CMakeLists.txt:39

• This PR’s title/description focuses on testing the JsonEncodedText.GetHashCode() code shape for an ARM64 perf regression, but this hunk also changes NativeAOT’s libunwind privatization linker selection logic. Since it affects the NativeAOT build pipeline on Unix, it looks like a separate concern; consider splitting it into a dedicated PR or explicitly documenting why it’s needed for the perf investigation so reviewers can evaluate the build impact in context.

  set(NATIVEAOT_PRIVATE_LIBUNWIND_LINKER "${CMAKE_LINKER}")
  get_filename_component(NATIVEAOT_PRIVATE_LIBUNWIND_LINKER_NAME "${NATIVEAOT_PRIVATE_LIBUNWIND_LINKER}" NAME)
  if(NATIVEAOT_PRIVATE_LIBUNWIND_LINKER_NAME MATCHES "^llvm-link(-[0-9.]+)?(\\.exe)?$")
    set(NATIVEAOT_PRIVATE_LIBUNWIND_LINKER_VERSION "${CMAKE_MATCH_1}")
    set(NATIVEAOT_PRIVATE_LIBUNWIND_LINKER_EXTENSION "${CMAKE_MATCH_2}")

[eiriktsarpalis]

Focused stage matrix 1/2: field-backed properties, pattern rewrites, and the Deprecated property follow-up.

@EgorBot -ubuntu24_azure_ampere -pr 132399 -commits 66b30d9,43560bc79db55b49722afff9eeeac9704803315d,a271e683ebac9ab3d3cc2d24ffec341a558a6f86 --filter "System.Text.Json.Tests.Perf_Get.GetUInt64"

Note

This benchmark request was prepared by GitHub Copilot.

[eiriktsarpalis]

Focused stage matrix 2/2: the Deprecated property follow-up, final #130976 head, and the GetHashCode() code-shape candidate.

@EgorBot -ubuntu24_azure_ampere -pr 132399 -commits a271e68,7c12816f5c1ddd67b23ec8f0f42513b693736c29,a3dd4f855a512477197fece0a8d05d56ce724188 --filter "System.Text.Json.Tests.Perf_Get.GetUInt64"

Note

This benchmark request was prepared by GitHub Copilot.