[MicroPerf] Make List.vMapFold inline to drop the nullness-import closure - #20415
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[MicroPerf] Make List.vMapFold inline to drop the nullness-import closure#20415T-Gro wants to merge 1 commit into
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vMapFold's only caller (ImportILTypeWithNullness in import.fs) passes a lambda; making the combinator inline + InlineIfLambda folds that lambda so no per-call closure is allocated per imported IL type. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
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List.vMapFold's only caller (ImportILTypeWithNullness) passes a lambda, so making the combinatorinline+[<InlineIfLambda>]beta-reduces that lambda into the call site and no closure is allocated per imported IL generic argument. No call-site change.Sampled closure allocation (
gc-verbose, fsc self-compilingsrc/Compileron the net11 perf bundle):ImportILTypeWithNullness@359(viaList.vMapFold)Deterministic proof: the
ImportILTypeWithNullness@359closure class is present inFSharp.Compiler.Service.dllonmainand absent after this change. Cost is +512 bytes of IL (+0.0024%). Behavior is unchanged — result order, state threading, and the empty / singleton / multi-element cases are byte-identical, and the innerlet rec gocompiles to awhileloop (verified stack-safe on a 5M-element list).