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Detect ByRefLike types using attribute #15745

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jkotas
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@jkotas jkotas commented Jan 5, 2018

Detect ByRefLike types using attribute and improve error messages for their invalid use

Fixes #11371 and #15458

@mikedn
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mikedn commented Jan 5, 2018

Hmm, I wonder if there are sufficient guarantees that by ref like types only live on the stack for the JIT to be able to eliminate GC write barriers when writing to fields of such types.

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Looks good apart from the minor comments.

@@ -4085,8 +4089,10 @@ VOID MethodTableBuilder::InitializeFieldDescs(FieldDesc *pFieldDescList,
// Non-value-classes cannot contain by-ref-like instance fields
BuildMethodTableThrowException(IDS_CLASSLOAD_BYREFLIKE_NOTVALUECLASSFIELD);
}

bmtFP->fIsByRefLikeType = true;
if (!bmtFP->fIsByRefLikeType)
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Maybe update the comment above (// Inherit IsByRefLike characteristic from fields) since we're not inheriting it anymore, but merely checking?

.maxstack 1
ldc.i4.1
newarr valuetype MyByRefLikeType
ret
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Non-empty stack but returns void?

.method private hidebysig static void ByRefLikeGenericInstantiation() cil managed
{
.maxstack 1
newobj instance void class [System.Runtime]System.Collections.Generic.List`1<valuetype MyByRefLikeType>::.ctor()
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Non-empty stack but returns void?

@jkotas
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jkotas commented Jan 5, 2018

Hmm, I wonder if there are sufficient guarantees that by ref like types only live on the stack for the JIT to be able to eliminate GC write barriers when writing to fields of such types.

Yes, there are. It would be nice optimization to have.

Opened https://github.com/dotnet/coreclr/issues/15755

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jkotas commented Jan 5, 2018

@dotnet-bot test OSX10.12 x64 Checked Innerloop Build and Test please

@kouvel
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kouvel commented Jan 5, 2018

LGTM

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jkotas commented Jan 5, 2018

@dotnet-bot test Tizen armel Cross Checked Innerloop Build and Test please
@dotnet-bot test Windows_NT arm64 Cross Checked Innerloop Build and Test please

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