JIT: recompute exit weight in loop inversion#131362
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Avoids amplifying pre-existing small profile inconsistencies once the loop-exit flow is scaled down. Fixes dotnet#131329. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Pull request overview
This PR adjusts how loop inversion updates profile weights in optTryInvertWhileLoop to avoid profile self-consistency failures after the transformation.
Changes:
- Stops adjusting the loop-exit block weight via subtraction of the newly introduced edge weight.
- Recomputes the loop-exit block weight from its incoming edges after the duplicated blocks’ weights are updated.
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| // Recompute exit's weight from its (now updated) incoming edges. | ||
| // Using computeIncomingWeight here (rather than decreasing by the newly | ||
| // introduced preheader-to-exit edge weight) avoids amplifying small | ||
| // pre-existing inconsistencies once the loop-exit flow is scaled down. | ||
| exit->setBBProfileWeight(exit->computeIncomingWeight()); |
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Avoids amplifying pre-existing small profile inconsistencies once the loop-exit flow is scaled down.
Fixes #131329.