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ARM64: Fix AllocFast large object size check #8292
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After allocation objects in the large object heap needs to be published for some cleanups related to the background gc. The constant value for this limit (RH_LARGE_OBJECT_SIZE) was not loaded correctly in the register. This caused that the upper 32 bits of the register were in an undefined state. Therefore the check for large objects did practically always fail and the objects were never published. Therefore the cleanup never happened and the background GC did fail.
ARM64: Fix AllocFast large object size check
| @@ -81,7 +81,7 @@ RhpNewFast_RarePath | |||
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| ;; If the object is bigger than RH_LARGE_OBJECT_SIZE, we must publish it to the BGC | |||
| ldr w1, [x19, #OFFSETOF__EEType__m_uBaseSize] | |||
| movk x2, #(RH_LARGE_OBJECT_SIZE & 0xFFFF) | |||
| movz x2, #(RH_LARGE_OBJECT_SIZE & 0xFFFF) | |||
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Cc @AntonLapounov who tends to troubleshoot weird ARM bugs on .NET Native - we have this bug in ProjectNRel.
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This is just a information for someone else. Nothing to do for me?
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Yep - this code originates from .NET Native but there's no backflow of fixes from this repo to .NET Native so if we want to fix anything there, it needs to be done separately. It's good to be at least aware that an issue exists.
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Nice catch. I guess in .NET Native RhpGcAlloc does not modify x2, which is why we have never hit this issue.
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After allocation objects in the large object heap needs to be published for some cleanups related to the background gc. The constant value for this limit (RH_LARGE_OBJECT_SIZE) was not loaded correctly in the register. This caused that the upper 32 bits of the register were in an undefined state. Therefore the check for large objects did practically always fail and the objects were never published. Therefore the cleanup never happened and the background GC did fail.