Enable parallel compilation features for users of LangVersion=preview

FSharp.Profiles.props

@@ -18,8 +18,8 @@
     <NullCheckingSupportInLibrary>false</NullCheckingSupportInLibrary>
   </PropertyGroup>
 
-  <PropertyGroup Condition="'$(Configuration)' != 'Proto' and '$(BUILDING_USING_DOTNET)' != 'true'"> 
-    <OtherFlags>$(OtherFlags) /langversion:preview</OtherFlags>
+  <PropertyGroup Condition="'$(Configuration)' != 'Proto' and '$(BUILDING_USING_DOTNET)' != 'true' and '$(MSBuildProjectExtension)' == '.fsproj'"> <!-- VB.NET does not understand "preview". It only knows "old","older" and "boomer" :-)) (jk)-->
+    <LangVersion>preview</LangVersion>
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(BUILDING_USING_DOTNET)' == 'true'"> 

docs/release-notes/.FSharp.Compiler.Service/9.0.200.md

@@ -15,6 +15,7 @@
 * Deprecate places where `seq` can be omitted. ([Language suggestion #1033](https://github.com/fsharp/fslang-suggestions/issues/1033), [PR #17772](https://github.com/dotnet/fsharp/pull/17772))
 * Support literal attribute on decimals ([PR #17769](https://github.com/dotnet/fsharp/pull/17769))
 * Added type conversions cache, only enabled for compiler runs, guarded by language version preview ([PR#17668](https://github.com/dotnet/fsharp/pull/17668))
+* Added project property ParallelCompilation which turns on graph based type checking, parallel ILXGen and parallel optimization. By default on for users of langversion=preview ([PR#17948](https://github.com/dotnet/fsharp/pull/17948))
 
 ### Changed
 

src/Compiler/Driver/CompilerConfig.fs

@@ -566,7 +566,7 @@ type TcConfigBuilder =
         mutable optSettings: Optimizer.OptimizationSettings
         mutable emitTailcalls: bool
         mutable deterministic: bool
-        mutable concurrentBuild: bool
+        mutable parallelParsing: bool
         mutable parallelIlxGen: bool
         mutable emitMetadataAssembly: MetadataAssemblyGeneration
         mutable preferredUiLang: string option
@@ -817,7 +817,7 @@ type TcConfigBuilder =
                 }
             emitTailcalls = true
             deterministic = false
-            concurrentBuild = true
+            parallelParsing = true
             parallelIlxGen = FSharpExperimentalFeaturesEnabledAutomatically
             emitMetadataAssembly = MetadataAssemblyGeneration.None
             preferredUiLang = None
@@ -1380,7 +1380,7 @@ type TcConfig private (data: TcConfigBuilder, validate: bool) =
     member _.optSettings = data.optSettings
     member _.emitTailcalls = data.emitTailcalls
     member _.deterministic = data.deterministic
-    member _.concurrentBuild = data.concurrentBuild
+    member _.parallelParsing = data.parallelParsing
     member _.parallelIlxGen = data.parallelIlxGen
     member _.emitMetadataAssembly = data.emitMetadataAssembly
     member _.pathMap = data.pathMap

src/Compiler/Driver/CompilerConfig.fsi

@@ -435,7 +435,7 @@ type TcConfigBuilder =
 
         mutable deterministic: bool
 
-        mutable concurrentBuild: bool
+        mutable parallelParsing: bool
 
         mutable parallelIlxGen: bool
 
@@ -771,7 +771,7 @@ type TcConfig =
 
     member deterministic: bool
 
-    member concurrentBuild: bool
+    member parallelParsing: bool
 
     member parallelIlxGen: bool
 

src/Compiler/Driver/CompilerOptions.fs

@@ -622,6 +622,26 @@ let splittingSwitch (tcConfigB: TcConfigBuilder) switch =
 let callVirtSwitch (tcConfigB: TcConfigBuilder) switch =
     tcConfigB.alwaysCallVirt <- switch = OptionSwitch.On
 
+let callParallelCompilationSwitch (tcConfigB: TcConfigBuilder) switch =
+    tcConfigB.parallelIlxGen <- switch = OptionSwitch.On
+
+    let (graphCheckingMode, optMode) =
+        match switch with
+        | OptionSwitch.On -> TypeCheckingMode.Graph, OptimizationProcessingMode.Parallel
+        | OptionSwitch.Off -> TypeCheckingMode.Sequential, OptimizationProcessingMode.Sequential
+
+    if tcConfigB.typeCheckingConfig.Mode <> graphCheckingMode then
+        tcConfigB.typeCheckingConfig <-
+            { tcConfigB.typeCheckingConfig with
+                Mode = graphCheckingMode
+            }
+
+    if tcConfigB.optSettings.processingMode <> optMode then
+        tcConfigB.optSettings <-
+            { tcConfigB.optSettings with
+                processingMode = optMode
+            }
+
 let useHighEntropyVASwitch (tcConfigB: TcConfigBuilder) switch =
     tcConfigB.useHighEntropyVA <- switch = OptionSwitch.On
 
@@ -1365,9 +1385,9 @@ let testFlag tcConfigB =
             | "DumpDebugInfo" -> tcConfigB.dumpDebugInfo <- true
             | "ShowLoadedAssemblies" -> tcConfigB.showLoadedAssemblies <- true
             | "ContinueAfterParseFailure" -> tcConfigB.continueAfterParseFailure <- true
-            | "ParallelOff" -> tcConfigB.concurrentBuild <- false
-            | "ParallelIlxGen" -> tcConfigB.parallelIlxGen <- true
-            | "GraphBasedChecking" ->
+            | "ParallelOff" -> tcConfigB.parallelParsing <- false
+            | "ParallelIlxGen" -> tcConfigB.parallelIlxGen <- true // Kept as --test:.. flag for temporary backwards compatibility during .NET10 period.
+            | "GraphBasedChecking" -> // Kept as --test:.. flag for temporary backwards compatibility during .NET10 period.
                 tcConfigB.typeCheckingConfig <-
                     { tcConfigB.typeCheckingConfig with
                         Mode = TypeCheckingMode.Graph
@@ -1378,7 +1398,7 @@ let testFlag tcConfigB =
                         DumpGraph = true
                     }
             | "DumpSignatureData" -> tcConfigB.dumpSignatureData <- true
-            | "ParallelOptimization" ->
+            | "ParallelOptimization" -> // Kept as --test:.. flag for temporary backwards compatibility during .NET10 period.
                 tcConfigB.optSettings <-
                     { tcConfigB.optSettings with
                         processingMode = OptimizationProcessingMode.Parallel
@@ -1692,6 +1712,14 @@ let internalFlags (tcConfigB: TcConfigBuilder) =
             None
         )
 
+        CompilerOption(
+            "parallelcompilation",
+            tagNone,
+            OptionSwitch(callParallelCompilationSwitch tcConfigB),
+            Some(InternalCommandLineOption("--parallelcompilation", rangeCmdArgs)),
+            None
+        )
+
         testFlag tcConfigB
     ]
     @

src/Compiler/Driver/ParseAndCheckInputs.fs

@@ -853,7 +853,7 @@ let ParseInputFilesSequential (tcConfig: TcConfig, lexResourceManager, sourceFil
 /// Parse multiple input files from disk
 let ParseInputFiles (tcConfig: TcConfig, lexResourceManager, sourceFiles, diagnosticsLogger: DiagnosticsLogger, retryLocked) =
     try
-        if tcConfig.concurrentBuild then
+        if tcConfig.parallelParsing then
             ParseInputFilesInParallel(tcConfig, lexResourceManager, sourceFiles, diagnosticsLogger, retryLocked)
         else
             ParseInputFilesSequential(tcConfig, lexResourceManager, sourceFiles, diagnosticsLogger, retryLocked)

src/FSharp.Build/Fsc.fs

@@ -49,6 +49,7 @@ type public Fsc() as this =
     let mutable otherFlags: string MaybeNull = null
     let mutable outputAssembly: string MaybeNull = null
     let mutable outputRefAssembly: string MaybeNull = null
+    let mutable parallelCompilation: bool option = None
     let mutable pathMap: string MaybeNull = null
     let mutable pdbFile: string MaybeNull = null
     let mutable platform: string MaybeNull = null
@@ -202,6 +203,7 @@ type public Fsc() as this =
         if not tailcalls then
             builder.AppendSwitch("--tailcalls-")
 
+        // Nullables
         match nullable with
         | Some true ->
             builder.AppendSwitch("--checknulls+")
@@ -345,6 +347,8 @@ type public Fsc() as this =
         if deterministic then
             builder.AppendSwitch("--deterministic+")
 
+        builder.AppendOptionalSwitch("--parallelcompilation", parallelCompilation)
+
         // OtherFlags - must be second-to-last
         builder.AppendSwitchUnquotedIfNotNull("", otherFlags)
         capturedArguments <- builder.CapturedArguments()
@@ -504,6 +508,10 @@ type public Fsc() as this =
         with get () = outputRefAssembly
         and set (s) = outputRefAssembly <- s
 
+    member _.ParallelCompilation
+        with get () = parallelCompilation |> Option.defaultValue false
+        and set (p) = parallelCompilation <- Some p
+
     // --pathmap <string>: Paths to rewrite when producing deterministic builds
     member _.PathMap
         with get () = pathMap

src/FSharp.Build/Microsoft.FSharp.NetSdk.props

@@ -50,6 +50,7 @@ WARNING:  DO NOT MODIFY this file unless you are knowledgeable about MSBuild and
     <UseStandardResourceNames Condition=" '$(UseStandardResourceNames)' == '' ">true</UseStandardResourceNames>
     <FsiExec Condition=" '$(FsiExec)' == '' ">true</FsiExec>
     <ReflectionFree Condition=" '$(ReflectionFree)' == '' ">false</ReflectionFree>
+    <ParallelCompilation Condition=" '$(ParallelCompilation)' == '' and '$(LangVersion)' == 'preview' "></ParallelCompilation>                       <!-- Default to parallel compilation for preview language users before it is rolled out to everyone -->
   </PropertyGroup>
 
   <!-- BinaryFormatter is disabled (warning is treated as error) by default in .NET8+, this mirroring the change in SDK (https://github.com/dotnet/sdk/pull/31591) -->

src/FSharp.Build/Microsoft.FSharp.Targets

@@ -380,6 +380,7 @@ this file.
               OtherFlags="$(FscOtherFlags)"
               OutputAssembly="@(IntermediateAssembly)"
               OutputRefAssembly="@(IntermediateRefAssembly)"
+    	      ParallelCompilation="@(ParallelCompilation)"
               PathMap="$(PathMap)"
               PdbFile="$(PdbFile)"
               Platform="$(PlatformTarget)"