JIT: Refine post-dominance check in strength reduction #104687
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When strength reduction has to find an insertion point for the new primary IV update it needs to find a block that post-dominates all the users of the IV. This was using `optReachable` before, but that is conservative since it finds paths that may exit the loop. This implements a more precise check.
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Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch |
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/azp run runtime-coreclr jitstress, runtime-coreclr libraries-jitstress |
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Azure Pipelines successfully started running 2 pipeline(s). |
This was referenced Jul 10, 2024
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/azp run runtime-coreclr libraries-jitstress, runtime, dotnet-linker-tests |
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Azure Pipelines successfully started running 3 pipeline(s). |
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cc @dotnet/jit-contrib PTAL @AndyAyersMS Diffs with strength reduction enabled show a lot of new cases where strength reduction is now considered legal. |
AndyAyersMS
approved these changes
Jul 11, 2024
Hmm, that could very well be. We could also check all of the users simultaneously instead of just checking them one at a time. I'll keep this in mind for when I start looking at TP. |
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When strength reduction has to find an insertion point for the new primary IV update it needs to find a block that post-dominates all the users of the IV. This was using
optReachablebefore, but that is conservative since it finds paths that may exit the loop. This implements a more precise check.