[release/8.0] JIT: Fix invalid zero-init suppression for untracked variables #91840
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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 #91576
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Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch Issue DetailsBackport of #91580 to release/8.0 /cc @jakobbotsch Customer ImpactTestingRiskIMPORTANT: If this backport is for a servicing release, please verify that:
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AndyAyersMS
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Sep 9, 2023
jeffschwMSFT
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Sep 11, 2023
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Backport of #91580 to release/8.0
/cc @jakobbotsch
Customer Impact
The JIT may incorrectly remove zero-initialization of some local variables used in finally blocks, resulting in silent bad codegen through use of an uninitialized value. The bug occurs when:
In these cases the JIT may mistakenly remove the initialization before the
try. If an exception is then thrown inside thetrybefore the definition there, thefinallyblock can observe an uninitialized value for the local.Testing
Regression test included.
Risk
Low.