[do-not-merge] Verify Release determinism CI catches optimizer Val race

azure-pipelines-PR.yml

@@ -100,7 +100,7 @@ stages:
         helixRepo: dotnet/fsharp
         jobs:
           # Determinism, we want to run it only in PR builds
-        - job: Determinism_Debug
+        - job: Determinism_Release
           condition: eq(variables['Build.Reason'], 'PullRequest')
           variables:
           - name: _SignType
@@ -129,15 +129,15 @@ stages:
               workingDirectory: $(Build.SourcesDirectory)
               installationPath: $(Build.SourcesDirectory)/.dotnet
           - script: .\eng\common\dotnet.cmd
-          - script: .\eng\test-determinism.cmd -configuration Debug
+          - script: .\eng\test-determinism.cmd -configuration Release
             env:
               FSHARP_EXPERIMENTAL_FEATURES: $(_experimental_flag)
-            displayName: Determinism tests with Debug configuration
+            displayName: Determinism tests with Release configuration
           - task: PublishPipelineArtifact@1
             displayName: Publish Determinism Logs
             inputs:
-              targetPath: '$(Build.SourcesDirectory)/artifacts/log/Debug'
-              artifactName: 'Determinism_Debug Attempt $(System.JobAttempt) Logs'
+              targetPath: '$(Build.SourcesDirectory)/artifacts/log/Release'
+              artifactName: 'Determinism_Release Attempt $(System.JobAttempt) Logs'
             continueOnError: true
             condition: not(succeeded())
 

docs/release-notes/.FSharp.Compiler.Service/11.0.100.md

@@ -1,5 +1,6 @@
 ### Fixed
 
+* Improve determinism under parallel optimization: `Optimize/DetupleArgs` and `Optimize/InnerLambdasToTopLevelFuncs` now walk their `Val` sets in stable source-position order before calling into `NiceNameGenerator`, so compiler-generated names no longer vary across builds due to `Val.Stamp` assignment races during parallel type-check. ([Issue #19732](https://github.com/dotnet/fsharp/issues/19732), [PR #19810](https://github.com/dotnet/fsharp/pull/19810))
 * Honor `--nowarn` and `--warnaserror` for warnings emitted during command-line option parsing ([Issue #19576](https://github.com/dotnet/fsharp/issues/19576), [PR #19776](https://github.com/dotnet/fsharp/pull/19776))
 * Fix `[<return: X>]` prefix attributes being silently dropped on class members, and fix false-positive `AllowMultiple=false` errors when `[<X>]` and `[<return: X>]` are applied to the same binding. ([Issue #17904](https://github.com/dotnet/fsharp/issues/17904), [Issue #19020](https://github.com/dotnet/fsharp/issues/19020), [PR #19738](https://github.com/dotnet/fsharp/pull/19738))
 * Fix attributes on return type of unparenthesized tuple methods being silently dropped from IL. ([Issue #462](https://github.com/dotnet/fsharp/issues/462), [PR #19714](https://github.com/dotnet/fsharp/pull/19714))

src/Compiler/Driver/OptimizeInputs.fs

@@ -511,8 +511,12 @@ let ApplyAllOptimizations
 
     let results, optEnvFirstLoop =
         match tcConfig.optSettings.processingMode with
-        // Parallel optimization breaks determinism - turn it off in deterministic builds.
         | Optimizer.OptimizationProcessingMode.Parallel ->
+            // Determinism under Parallel mode relies on the per-pass sorts in
+            // DetupleArgs.determineTransforms and InnerLambdasToTopLevelFuncs.CreateNewValuesForTLR
+            // (via valSourceOrderKey). Any new pass calling NiceNameGenerator from a
+            // parallel optimizer phase must sort its Val collection the same way.
+            // See https://github.com/dotnet/fsharp/issues/19732.
             let results, optEnvFirstPhase =
                 ParallelOptimization.optimizeFilesInParallel optEnv phases implFiles
 

src/Compiler/Optimize/DetupleArgs.fs

@@ -704,7 +704,8 @@ let determineTransforms g (z: Results) =
                     let callPatterns = sitesCPs sites // callPatterns from sites
                     decideTransform g z f callPatterns (m, tps, vss, retTy) // make transform (if required)
 
-    let vtransforms = Zmap.chooseL selectTransform z.Uses
+    let vtransforms =
+        Zmap.chooseL selectTransform z.Uses
     let vtransforms = Zmap.ofList valOrder vtransforms
     vtransforms
 

src/Compiler/TypedTree/TypedTreeOps.ExprConstruction.fs

@@ -44,6 +44,15 @@ module internal ExprConstruction =
             member _.Compare(v1, v2) = compareBy v1 v2 _.Stamp
         }
 
+    // Source-position-derived order key for Vals. Used to walk Val collections
+    // in a stable, build-independent order before calling NiceNameGenerator
+    // from parallel optimizer passes. Stamp is the final tiebreaker for
+    // synthetic Vals at the same location; stamps are fixed within a single
+    // process so the order is total. See https://github.com/dotnet/fsharp/issues/19732.
+    let valSourceOrderKey (v: Val) =
+        let r = v.Range
+        struct (r.FileIndex, r.StartLine, r.StartColumn, v.LogicalName, v.Stamp)
+
     let tyconOrder =
         { new IComparer<Tycon> with
             member _.Compare(tycon1, tycon2) = compareBy tycon1 tycon2 _.Stamp

src/Compiler/TypedTree/TypedTreeOps.ExprConstruction.fsi

@@ -22,6 +22,12 @@ module internal ExprConstruction =
     /// An ordering for value definitions, based on stamp
     val valOrder: IComparer<Val>
 
+    /// Stable, source-position-derived key for ordering Vals.
+    /// Use this before calling NiceNameGenerator from parallel optimizer passes
+    /// so the generated names do not depend on Val.Stamp assignment race.
+    /// See https://github.com/dotnet/fsharp/issues/19732.
+    val valSourceOrderKey: Val -> struct (int * int * int * string * int64)
+
     /// An ordering for type definitions, based on stamp
     val tyconOrder: IComparer<Tycon>