JIT: Fix edge likelihoods in fgOptimizeBranch
#113235
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cc @dotnet/jit-contrib, @AndyAyersMS PTAL. Diffs show plenty of churn, as expected. Thanks! |
AndyAyersMS
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Mar 7, 2025
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Part of #113108. When converting an unconditional jump to a test block into a duplicate test block,
fgOptimizeBranchflips the condition (unnecessarily -- I plan to fix this someday), which means we need to derive the new true edge's likelihood from the cloned false edge, and vice versa. Now that late profile repair is enabled, if we get this wrong, the flipped edge likelihoods will flatten loop weights, and inflate non-loop weights. I suspect fixing this will also revert some of the regressions from late profile repair.