JIT: Potentially quadratic behavior in EH clause handling

[jakobbotsch]

https://github.com/dotnet/runtime/blob/5565135d21024ac2820e08d0a7aca3f2cb9d2b55/src/tests/JIT/Regression/VS-ia64-JIT/V1.2-M02/b28158/test.il

This is a very large test with 16731 EH clauses., On my 5950x the JIT spends around 14 seconds jitting this in tier 0. We should investigate if there is some unnecessary quadratic handling here in tier 0.

Some more context: #77465 (comment)

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Issue Details

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https://github.com/dotnet/runtime/blob/5565135d21024ac2820e08d0a7aca3f2cb9d2b55/src/tests/JIT/Regression/VS-ia64-JIT/V1.2-M02/b28158/test.il

This is a very large test with 16731 EH clauses., On my 5950x the JIT spends around 14 seconds jitting this in tier 0. We should investigate if there is some unnecessary quadratic handling here in tier 0.

Author:	jakobbotsch
Assignees:	-
Labels:	area-CodeGen-coreclr, untriaged
Milestone:	-

[jakobbotsch]

Profile:

[jakobbotsch]

We call fgVerifyHandlerTab from impImportLeave, so that ends up being quadratic in checked builds. Likely we can just do that once after we are done importing.

In release builds this function only takes 2.5 seconds to JIT on my machine. The profile looks like:

Looking at impImportLeave it's still quadratic in release builds since impImportLeave does a linear scan through the EH clauses.