[mono] Skip exact interface matches when an interface has variance

[kg]

Issue #103365 appears to be caused by us preferring an 'exact match' for interfaces even when variance means an inexact match may be what we should actually use, because the exact match is on a base class and the inexact one is on a derived class.

This PR changes mono's variance interface lookup to more closely match the spec, by doing two scans per class and walking up the class hierarchy. To reduce the performance cost of this more complex scan, a new 'variance search table' is maintained (created on demand) for each type, which only contains generically variant interfaces so that we're not checking against all interfaces.

I also noticed our list of interfaces implemented by Array was incomplete, so this PR updates it.

[lambdageek]

Question: how is this variance search table different from the interfaces_packed table? Do we really need both? if the variance search table is more correct, can we get rid of the interfaces_packed table?

[kg]

The variance search table should be smaller. I can try to figure out whether we can get rid of interfaces_packed

[kg]

Two examples of what I was thinking in action:

 System.IBinaryFloatParseAndFormatInfo`1 vst_size=1 io_count=39
System.Single vst_size=1 io_count=40

[kg]

Issue #103365 appears to be caused by us preferring an 'exact match' for interfaces even when variance means an inexact match may be what we should actually use, because the exact match is on a base class and the inexact one is on a derived class.

This PR changes mono's variance interface lookup to more closely match the spec, by doing two scans per class and walking up the class hierarchy. To reduce the performance cost of this more complex scan, a new 'variance search table' is maintained (created on demand) for each type, which only contains generically variant interfaces so that we're not checking against all interfaces.

I also noticed our list of interfaces implemented by Array was incomplete, so this PR updates it.

[lambdageek]

Question: how is this variance search table different from the interfaces_packed table? Do we really need both? if the variance search table is more correct, can we get rid of the interfaces_packed table?

[kg]

The variance search table should be smaller. I can try to figure out whether we can get rid of interfaces_packed

[kg]

Two examples of what I was thinking in action:

 System.IBinaryFloatParseAndFormatInfo`1 vst_size=1 io_count=39
System.Single vst_size=1 io_count=40

[kg]

Issue #103365 appears to be caused by us preferring an 'exact match' for interfaces even when variance means an inexact match may be what we should actually use, because the exact match is on a base class and the inexact one is on a derived class.

This PR changes mono's variance interface lookup to more closely match the spec, by doing two scans per class and walking up the class hierarchy. To reduce the performance cost of this more complex scan, a new 'variance search table' is maintained (created on demand) for each type, which only contains generically variant interfaces so that we're not checking against all interfaces.

I also noticed our list of interfaces implemented by Array was incomplete, so this PR updates it.

[lambdageek]

Question: how is this variance search table different from the interfaces_packed table? Do we really need both? if the variance search table is more correct, can we get rid of the interfaces_packed table?

[kg]

The variance search table should be smaller. I can try to figure out whether we can get rid of interfaces_packed

[kg]

Two examples of what I was thinking in action:

 System.IBinaryFloatParseAndFormatInfo`1 vst_size=1 io_count=39
System.Single vst_size=1 io_count=40

[kg]

Issue #103365 appears to be caused by us preferring an 'exact match' for interfaces even when variance means an inexact match may be what we should actually use, because the exact match is on a base class and the inexact one is on a derived class.

This PR changes mono's variance interface lookup to more closely match the spec, by doing two scans per class and walking up the class hierarchy. To reduce the performance cost of this more complex scan, a new 'variance search table' is maintained (created on demand) for each type, which only contains generically variant interfaces so that we're not checking against all interfaces.

I also noticed our list of interfaces implemented by Array was incomplete, so this PR updates it.

[lambdageek]

Question: how is this variance search table different from the interfaces_packed table? Do we really need both? if the variance search table is more correct, can we get rid of the interfaces_packed table?

[kg]

The variance search table should be smaller. I can try to figure out whether we can get rid of interfaces_packed

[kg]

Two examples of what I was thinking in action:

 System.IBinaryFloatParseAndFormatInfo`1 vst_size=1 io_count=39
System.Single vst_size=1 io_count=40

[kg]

Issue #103365 appears to be caused by us preferring an 'exact match' for interfaces even when variance means an inexact match may be what we should actually use, because the exact match is on a base class and the inexact one is on a derived class.

This PR changes mono's variance interface lookup to more closely match the spec, by doing two scans per class and walking up the class hierarchy. To reduce the performance cost of this more complex scan, a new 'variance search table' is maintained (created on demand) for each type, which only contains generically variant interfaces so that we're not checking against all interfaces.

I also noticed our list of interfaces implemented by Array was incomplete, so this PR updates it.

[lambdageek]

Question: how is this variance search table different from the interfaces_packed table? Do we really need both? if the variance search table is more correct, can we get rid of the interfaces_packed table?

[kg]

The variance search table should be smaller. I can try to figure out whether we can get rid of interfaces_packed

[kg]

Two examples of what I was thinking in action:

 System.IBinaryFloatParseAndFormatInfo`1 vst_size=1 io_count=39
System.Single vst_size=1 io_count=40

[kg]

Issue #103365 appears to be caused by us preferring an 'exact match' for interfaces even when variance means an inexact match may be what we should actually use, because the exact match is on a base class and the inexact one is on a derived class.

This PR changes mono's variance interface lookup to more closely match the spec, by doing two scans per class and walking up the class hierarchy. To reduce the performance cost of this more complex scan, a new 'variance search table' is maintained (created on demand) for each type, which only contains generically variant interfaces so that we're not checking against all interfaces.

I also noticed our list of interfaces implemented by Array was incomplete, so this PR updates it.

[lambdageek]

Question: how is this variance search table different from the interfaces_packed table? Do we really need both? if the variance search table is more correct, can we get rid of the interfaces_packed table?

[kg]

The variance search table should be smaller. I can try to figure out whether we can get rid of interfaces_packed

[kg]

Two examples of what I was thinking in action:

 System.IBinaryFloatParseAndFormatInfo`1 vst_size=1 io_count=39
System.Single vst_size=1 io_count=40

[kg]

Issue #103365 appears to be caused by us preferring an 'exact match' for interfaces even when variance means an inexact match may be what we should actually use, because the exact match is on a base class and the inexact one is on a derived class.

This PR changes mono's variance interface lookup to more closely match the spec, by doing two scans per class and walking up the class hierarchy. To reduce the performance cost of this more complex scan, a new 'variance search table' is maintained (created on demand) for each type, which only contains generically variant interfaces so that we're not checking against all interfaces.

I also noticed our list of interfaces implemented by Array was incomplete, so this PR updates it.

[lambdageek]

Question: how is this variance search table different from the interfaces_packed table? Do we really need both? if the variance search table is more correct, can we get rid of the interfaces_packed table?

[kg]

The variance search table should be smaller. I can try to figure out whether we can get rid of interfaces_packed

[kg]

Two examples of what I was thinking in action:

 System.IBinaryFloatParseAndFormatInfo`1 vst_size=1 io_count=39
System.Single vst_size=1 io_count=40

[kg]

Issue #103365 appears to be caused by us preferring an 'exact match' for interfaces even when variance means an inexact match may be what we should actually use, because the exact match is on a base class and the inexact one is on a derived class.

This PR changes mono's variance interface lookup to more closely match the spec, by doing two scans per class and walking up the class hierarchy. To reduce the performance cost of this more complex scan, a new 'variance search table' is maintained (created on demand) for each type, which only contains generically variant interfaces so that we're not checking against all interfaces.

I also noticed our list of interfaces implemented by Array was incomplete, so this PR updates it.

[lambdageek]

Question: how is this variance search table different from the interfaces_packed table? Do we really need both? if the variance search table is more correct, can we get rid of the interfaces_packed table?

[kg]

The variance search table should be smaller. I can try to figure out whether we can get rid of interfaces_packed

[kg]

Two examples of what I was thinking in action:

 System.IBinaryFloatParseAndFormatInfo`1 vst_size=1 io_count=39
System.Single vst_size=1 io_count=40