JIT: initial support for stack allocating arrays of GC type #112250
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Add the ability to create a ClassLayout for arrays, and use this to unblock stack allocation for arrays with GC types. Replaces dotnet#111686.
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Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch |
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@jakobbotsch PTAL This unblocks GC arrays of final types, but for GC arrays of non-final types many stores will use the covariant store check helper which currently causes the array to escape. So only a handful of diffs ( We need both a "only do the covariant store check" variant and a "do the covariant store check and then a checked write barrier" variant. |
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| elementSize = genTypeSize(type); |
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I suppose if we really wanted to we could provide a constructor for a class layout for primitive types, which could be used to unify paths like these.
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Seems like that might have been the original intention since we bias the indexes.
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In any case we can just create them as custom layouts now, but I suppose it would be slightly less efficient than this approach.
| @@ -828,7 +828,7 @@ unsigned int ObjectAllocator::MorphNewArrNodeIntoStackAlloc(GenTreeCall* | |||
| blockSize = AlignUp(blockSize, 8); | |||
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| comp->lvaSetStruct(lclNum, comp->typGetBlkLayout(blockSize), /* unsafeValueClsCheck */ false); | |||
| comp->lvaSetStruct(lclNum, comp->typGetArrayLayout(clsHnd, length), /* unsafe */ false); | |||
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Would it make sense to propagate the layout through instead of blockSize? We could probably save a call to getChildType.
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Yeah, I should get rid of the redundant layout fetch.
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Only a small step from there to using layouts everywhere.
I think I should do that first (leaving GC arrays disabled) and verify zero diff, then come back to this and enable gc arrays.
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After poking at it some, I think it might be simpler to take this change first and then revise the entire thing to be more layout centric (getting rid of the special box type, etc).
Thoughts?
Add the ability to create a ClassLayout for arrays, and use this to unblock stack allocation for arrays with GC types.
Replaces #111686.