[MicroPerf] Cache IL method parameter attributes during overload resolution - #20353
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MethInfo.GetParamAttribs rebuilt the full per-parameter attribute list (custom-attr decoding, well-known-attr probes, OptionalArgInfo) from IL metadata on every call and was never cached. On an overload-heavy compile it was called 2.17M times against only 137 distinct underlying methods. Memoize the decode with the existing MemoizationTable, held per compilation via WeakMap.getOrCreate keyed on the ImportMap. The key is the method's physical ILMethodDef plus extension-member use (the C#-style extension view drops the object argument from ParamMetadata, so the two views must not share an entry); canMemoize restricts caching to monomorphic declaring types (an optional arg's default can otherwise depend on the instantiation), matching InfoReader's monomorphic-only caches. Add a regression test covering an IL extension method used with both instance and static call syntax, which shares one ILMethodDef across both views. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
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| let xs : System.Collections.Generic.IEnumerable<int> = Seq.ofList [ 1; 2; 3 ] | ||
| let a = xs.Select(fun x -> x + 1) |> Seq.length | ||
| let b = System.Linq.Enumerable.Select(xs, (fun x -> x + 1)) |> Seq.length | ||
| if a <> b then failwith "unexpected" |
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This is a runtime check, but the test only asserts that compilation should succeed.
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| "ilMethodParamAttribs", | ||
| (fun (struct (ilMethInfo: ILMethInfo, m)) -> ComputeILMethodParamAttribs amap.g ilMethInfo amap m), | ||
| keyComparer = | ||
| { new IEqualityComparer<struct (ILMethInfo * range)> with |
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Does dropping the range in the methods below create a risk of reporting a diagnostic with a wrong range later on?
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I'm wondering if it also improves the time 🙂 |
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MethInfo.GetParamAttribsdecoded a method's per-parameter attributes from IL metadata on every call and was never cached — on an overload-heavy compile that's 2.17M calls for 137 distinct methods.Memoized via the existing
MemoizationTable, held per compilation throughWeakMap.getOrCreate, keyed by the physicalILMethodDef(plus an extension-member flag, since the C#-style extension view drops the object argument). Cache stats fromfsc --times:Allocation on the workload:
ComputeILMethodParamAttribs477 MB → 0 (~810 MB total). Output byte-identical vs HEAD.