[release/6.0] Disable poisoning for large structs #61601
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For very large structs (> 64K in size) poisoning could end up generating instructions requiring larger local var offsets than we can handle. This hits IMPL_LIMIT that throws InvalidProgramException. Turn off poisoning for larger structs that require more than 16 movs to also avoid the significant code bloat by the singular movs. This is a less risky version of #61521 for backporting to .NET 6. Fix #60852
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Tagging subscribers to this area: @JulieLeeMSFT Issue DetailsBackport of #61589 to release/6.0 /cc @jakobbotsch Customer ImpactTestingRisk
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AndyAyersMS
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Nov 15, 2021
Co-authored-by: Andy Ayers <[email protected]>
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CC @jeffschwMSFT please consider this for .NET6 servicing. |
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Backport of #61589 to release/6.0
/cc @jakobbotsch
Customer Impact
Code that uses large (> 64 KB) stack allocated structs without the .zeroinit bit may hit InvalidProgramException in debug mode in .NET 6. This is particularly the case for large stack allocated arrays in C++/CLI when the program is compiled without optimizations. Reported by a customer in #60852.
Regression
Yes, this is a .NET 6 regression introduced with the poisoning feature in #54685. The poisoning is a debug aid that puts a recognizable value into uninitialized variables so that developers will more easily notice uninitialized uses of these.
Testing
There is a regression test included.
Risk
Low, this disables the poisoning feature in cases that would hit the problem.