[release/10.0] JIT: SpanHelpers.Fill may escape its last argument #122919
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EgorBo
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Jan 6, 2026
JulieLeeMSFT
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Jan 6, 2026
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For the arm64 failure, looks like we should port #120291 to the 10.0 branch. For OSX, "error : Helix queue osx.13.arm64.open was set for estimated removal date of 2026-01-01". So maybe we need to update the queues we use here? |
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/ba-g installer tests using deprecated OSX queue, arm64 tests using outdated harness |
rbhanda
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Backport of #122902 to release/10.0
/cc @AndyAyersMS
Customer Impact
Customer reported in #122879
Silent bad code in some cases involving calls to
SpanHelpers.Fillwhere the fill value is a GC ref coming from a locally allocated object.Regression
This is a bug in a new optimization in .NET 10.
Testing
Verified fix on customer reported case; also added this as regression test. Bug was an oversight; the first argument to
SpanHelpers.Filldoes not escape, but the other two might. The JIT was assuming none of the arguments escaped.Risk
Low, we now disable stack allocation in this case.