JIT: Fix invalid zero-init suppression for untracked variables #91580
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optRemoveRedundantZeroInits has logic to remove unnecessary zero inits if we can determine that the local will be zeroed in the prolog. In addition, it also has logic to suppress the prolog zero init if there is a dominating initialization already. The latter logic was trying to reason about liveness for untracked locals, which does not make sense. Fix dotnet#91576
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Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch Issue DetailsoptRemoveRedundantZeroInits has logic to remove unnecessary zero inits if we can determine that the local will be zeroed in the prolog. In addition, it also has logic to suppress the prolog zero init if there is a dominating initialization already. The latter logic was trying to reason about liveness for untracked locals, which does not make sense. Fix #91576
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jakobbotsch
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This sadly has some quite significant regressions, will see if I can address some of these. |
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cc @dotnet/jit-contrib PTAL @AndyAyersMS Diffs where we now need to zero init in some cases again. |
Yep, for example in https://github.com/dotnet/runtime/blob/cf65ea21bfcb4f53a416506d43d79900413e5b1b/src/tests/JIT/Regression/JitBlue/Runtime_85892/Runtime_85892.cs It seems like we could be even more precise by tracking the set of locals that are actually live to handlers we have seen and only disqualifying those in this optimization, though I doubt it would be significantly better than what we have with this PR. |
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/azp run runtime-coreclr superpmi-diffs |
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Azure Pipelines successfully started running 1 pipeline(s). |
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/azp run runtime-coreclr superpmi-diffs |
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Azure Pipelines successfully started running 1 pipeline(s). |
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/azp run runtime-coreclr jitstress, runtime-coreclr libraries-jitstress, Fuzzlyn |
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Azure Pipelines successfully started running 3 pipeline(s). |
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/backport to release/8.0 |
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Started backporting to release/8.0: https://github.com/dotnet/runtime/actions/runs/6131654931 |
optRemoveRedundantZeroInits has logic to remove unnecessary zero inits if we can determine that the local will be zeroed in the prolog. In addition, it also has logic to suppress the prolog zero init if there is a dominating initialization already. The latter logic was trying to reason about liveness for untracked locals, which does not make sense.
Fix #91576
Also makes the handling for potential implicit control flow more precise, to counteract regressions.