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Revert "Increase cost of ARR_LENGTH node to match IND(ADD(..,CNS)) #117531 #118707

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Merged
merged 1 commit into from
Aug 14, 2025

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@EgorBo EgorBo commented Aug 13, 2025

This reverts commit 5c17036.

Fixes #117938 regression

Despite having a large PerfScore improvements only 1 benchmark improved and 5 regressed.

@Copilot Copilot AI review requested due to automatic review settings August 13, 2025 23:13
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Pull Request Overview

This PR reverts a previous change that increased the cost of ARR_LENGTH nodes to match IND(ADD(..,CNS)) operations. The revert addresses a performance regression where despite PerfScore improvements, actual benchmark results showed more regressions than improvements.

Key Changes:

  • Reverts cost calculation for array metadata operations (ARR_LENGTH and MDARR_LOWER_BOUND)
  • Reduces costEx from IND_COST_EX + 1 back to IND_COST_EX - 1
  • Reduces costSz from 2 * 2 back to 2

@github-actions github-actions bot added the area-CodeGen-coreclr CLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI label Aug 13, 2025
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Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch
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EgorBo commented Aug 13, 2025

@dotnet/jit-contrib PTAL revert

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Successfully merging this pull request may close these issues.

[Perf] Linux/x64: 5 Regressions on 7/14/2025 11:26:56 PM +00:00
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