JIT: Relax cost improvement assert in 3-opt layout #109835
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cc @dotnet/jit-contrib, @AndyAyersMS PTAL. |
AndyAyersMS
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Nov 18, 2024
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Follow-up to #109741. Fixes #109831. Fixes #109905. Fixes #109903.
Tolerate some floating point imprecision when comparing the cost of a new layout produced by 3-opt to the previous layout's cost. The JitStress failures I looked all stressed JitOptRepeat, which can produce absurdly large loop block weights by rerunning
optSetBlockWeights. Manually inspecting the layout decisions made for these methods shows 3-opt making reasonable transformations, but the assertionnewLayoutCost < currLayoutCostfails due to imprecision from summing large block weights. Having a backup check that the layout costs are within some epsilon seems like a reasonable fix.