diff --git a/docs/release-notes/.FSharp.Compiler.Service/11.0.100.md b/docs/release-notes/.FSharp.Compiler.Service/11.0.100.md
index ed1e382d6c7..87cf3f3db02 100644
--- a/docs/release-notes/.FSharp.Compiler.Service/11.0.100.md
+++ b/docs/release-notes/.FSharp.Compiler.Service/11.0.100.md
@@ -194,6 +194,7 @@
 * Make Entity's adhoc members list lazy ([PR #20286](https://github.com/dotnet/fsharp/pull/20286/changes))
 * Constraint solver: `TryD` is now `inline` with `[<InlineIfLambda>]` on its always-run continuation, so the argument closures are no longer allocated at the (very hot) constraint-solver call sites; `IgnoreFailedMemberConstraintResolution` is `inline` so its forwarded continuation stays a literal. ([PR #20367](https://github.com/dotnet/fsharp/pull/20367))
 * `DelayedILModuleReader` no longer boxes its cached `ILModuleReader` on every read: the field is typed `ILModuleReader | null` and matched directly. ([PR #20413](https://github.com/dotnet/fsharp/pull/20413))
+* IlxGen: `HashRangeSorted` returns immediately for an empty dictionary and otherwise sorts one exact-size array in place, rather than building three intermediate lists. Most type definitions carry no properties, so this takes the whole pipeline off the common path. ([PR #20456](https://github.com/dotnet/fsharp/pull/20456))
 
 ### Changed
 * The `--warnaserror` option now ignores unrecognized diagnostic identifiers in warning lists while still applying recognized F# warning codes. ([PR #20246](https://github.com/dotnet/fsharp/pull/20246))
diff --git a/src/Compiler/CodeGen/IlxGen.fs b/src/Compiler/CodeGen/IlxGen.fs
index ceeec0a69ec..b582b524e09 100644
--- a/src/Compiler/CodeGen/IlxGen.fs
+++ b/src/Compiler/CodeGen/IlxGen.fs
@@ -1971,8 +1971,21 @@ let GenPossibleILDebugRange (cenv: cenv) m =
 // Helpers for merging property definitions
 //--------------------------------------------------------------------------
 
+/// <summary>
+/// Returns the merged property definitions ordered by the index they were added with.
+/// </summary>
+/// <remarks>
+/// Most type definitions carry no properties at all, so the empty case is the one worth being cheap.
+/// The sort keys are the indices <see cref="AddPropertyDefToHash"/> hands out, which are never
+/// duplicated, so an unstable sort orders these exactly as the stable one did.
+/// </remarks>
 let HashRangeSorted (ht: IDictionary<_, int * _>) =
-    [ for KeyValue(_k, v) in ht -> v ] |> List.sortBy fst |> List.map snd
+    if ht.Count = 0 then
+        []
+    else
+        let entries = Array.ofSeq ht.Values
+        Array.sortInPlaceBy fst entries
+        [ for _, v in entries -> v ]
 
 let MergeOptions m o1 o2 =
     match o1, o2 with
diff --git a/tests/ILVerify/ilverify_FSharp.Compiler.Service_Release_netcoreapp.bsl b/tests/ILVerify/ilverify_FSharp.Compiler.Service_Release_netcoreapp.bsl
index 75176d28029..984349b58e0 100644
--- a/tests/ILVerify/ilverify_FSharp.Compiler.Service_Release_netcoreapp.bsl
+++ b/tests/ILVerify/ilverify_FSharp.Compiler.Service_Release_netcoreapp.bsl
@@ -8,5 +8,3 @@
 [IL]: Error [ReturnPtrToStack]: : FSharp.Compiler.CodeAnalysis.ItemKeyStore::ReadFirstKeyString()][offset 0x00000064] Return type is ByRef, TypedReference, ArgHandle, or ArgIterator.
 [IL]: Error [StackUnexpected]: : FSharp.Compiler.CodeAnalysis.ItemKeyStoreBuilder::writeRange([FSharp.Compiler.Service]FSharp.Compiler.Text.Range)][offset 0x00000019][found address of '[FSharp.Compiler.Service]FSharp.Compiler.Text.Range'][expected Native Int] Unexpected type on the stack.
 [IL]: Error [ExpectedNumericType]: : FSharp.Compiler.EditorServices.SemanticClassificationKeyStoreBuilder::WriteAll([FSharp.Compiler.Service]FSharp.Compiler.EditorServices.SemanticClassificationItem[])][offset 0x0000001A][found address of '[FSharp.Compiler.Service]FSharp.Compiler.EditorServices.SemanticClassificationItem'] Expected numeric type on the stack.
-[IL]: Error [StackUnexpected]: : FSharp.Compiler.IlxGen::HashRangeSorted([S.P.CoreLib]System.Collections.Generic.IDictionary`2<!!0,System.Tuple`2<int32,!!1>>)][offset 0x0000000A][found ref '[FSharp.Compiler.Service]FSharp.Compiler.IlxGen+HashRangeSorted<T1>'][expected ref '[FSharp.Core]Microsoft.FSharp.Core.FSharpFunc`2<System.Tuple`2<int32,T0>,int32>'] Unexpected type on the stack.
-[IL]: Error [StackUnexpected]: : FSharp.Compiler.IlxGen::HashRangeSorted([S.P.CoreLib]System.Collections.Generic.IDictionary`2<!!0,System.Tuple`2<int32,!!1>>)][offset 0x0000000B][found ref '[FSharp.Compiler.Service]FSharp.Compiler.IlxGen+HashRangeSorted<T1>'][expected ref '[FSharp.Core]Microsoft.FSharp.Core.FSharpFunc`2<System.Tuple`2<int32,T0>,T0>'] Unexpected type on the stack.
diff --git a/tests/ILVerify/ilverify_FSharp.Compiler.Service_Release_netstandard2.0.bsl b/tests/ILVerify/ilverify_FSharp.Compiler.Service_Release_netstandard2.0.bsl
index 75176d28029..984349b58e0 100644
--- a/tests/ILVerify/ilverify_FSharp.Compiler.Service_Release_netstandard2.0.bsl
+++ b/tests/ILVerify/ilverify_FSharp.Compiler.Service_Release_netstandard2.0.bsl
@@ -8,5 +8,3 @@
 [IL]: Error [ReturnPtrToStack]: : FSharp.Compiler.CodeAnalysis.ItemKeyStore::ReadFirstKeyString()][offset 0x00000064] Return type is ByRef, TypedReference, ArgHandle, or ArgIterator.
 [IL]: Error [StackUnexpected]: : FSharp.Compiler.CodeAnalysis.ItemKeyStoreBuilder::writeRange([FSharp.Compiler.Service]FSharp.Compiler.Text.Range)][offset 0x00000019][found address of '[FSharp.Compiler.Service]FSharp.Compiler.Text.Range'][expected Native Int] Unexpected type on the stack.
 [IL]: Error [ExpectedNumericType]: : FSharp.Compiler.EditorServices.SemanticClassificationKeyStoreBuilder::WriteAll([FSharp.Compiler.Service]FSharp.Compiler.EditorServices.SemanticClassificationItem[])][offset 0x0000001A][found address of '[FSharp.Compiler.Service]FSharp.Compiler.EditorServices.SemanticClassificationItem'] Expected numeric type on the stack.
-[IL]: Error [StackUnexpected]: : FSharp.Compiler.IlxGen::HashRangeSorted([S.P.CoreLib]System.Collections.Generic.IDictionary`2<!!0,System.Tuple`2<int32,!!1>>)][offset 0x0000000A][found ref '[FSharp.Compiler.Service]FSharp.Compiler.IlxGen+HashRangeSorted<T1>'][expected ref '[FSharp.Core]Microsoft.FSharp.Core.FSharpFunc`2<System.Tuple`2<int32,T0>,int32>'] Unexpected type on the stack.
-[IL]: Error [StackUnexpected]: : FSharp.Compiler.IlxGen::HashRangeSorted([S.P.CoreLib]System.Collections.Generic.IDictionary`2<!!0,System.Tuple`2<int32,!!1>>)][offset 0x0000000B][found ref '[FSharp.Compiler.Service]FSharp.Compiler.IlxGen+HashRangeSorted<T1>'][expected ref '[FSharp.Core]Microsoft.FSharp.Core.FSharpFunc`2<System.Tuple`2<int32,T0>,T0>'] Unexpected type on the stack.