Frontend: Add language mode and enabled features to .SWIFT_TRACE.

To allow tooling to analyze use of language mode and experimental/upcoming
features, add that information to the `.SWIFT_TRACE` file.

Resolves rdar://152673681.

lib/FrontendTool/LoadedModuleTrace.cpp

@@ -65,6 +65,8 @@ struct LoadedModuleTraceFormat {
   unsigned Version;
   Identifier Name;
   std::string Arch;
+  std::string LanguageMode;
+  std::vector<StringRef> EnabledLanguageFeatures;
   bool StrictMemorySafety;
   std::vector<SwiftModuleTraceInfo> SwiftModules;
   std::vector<SwiftMacroTraceInfo> SwiftMacros;
@@ -107,6 +109,11 @@ template <> struct ObjectTraits<LoadedModuleTraceFormat> {
 
     out.mapRequired("arch", contents.Arch);
 
+    out.mapRequired("languageMode", contents.LanguageMode);
+
+    out.mapRequired("enabledLanguageFeatures",
+                    contents.EnabledLanguageFeatures);
+
     out.mapRequired("strictMemorySafety", contents.StrictMemorySafety);
 
     // The 'swiftmodules' key is kept for backwards compatibility.
@@ -723,6 +730,38 @@ computeSwiftMacroTraceInfo(ASTContext &ctx, const DependencyTracker &depTracker,
       });
 }
 
+static void computeEnabledFeatures(ASTContext &ctx,
+                                   std::vector<StringRef> &enabledFeatures) {
+  struct FeatureAndName {
+    Feature feature;
+    StringRef name;
+  };
+
+  static const FeatureAndName features[] = {
+#define FEATURE_ENTRY(FeatureName) {Feature::FeatureName, #FeatureName},
+#define LANGUAGE_FEATURE(FeatureName, SENumber, Version)
+#define EXPERIMENTAL_FEATURE(FeatureName, AvailableInProd)                     \
+  FEATURE_ENTRY(FeatureName)
+#define UPCOMING_FEATURE(FeatureName, SENumber, Version)                       \
+  FEATURE_ENTRY(FeatureName)
+#define OPTIONAL_LANGUAGE_FEATURE(FeatureName, SENumber, Version)              \
+  FEATURE_ENTRY(FeatureName)
+#include "swift/Basic/Features.def"
+  };
+
+  for (auto &featureAndName : features) {
+    if (ctx.LangOpts.hasFeature(featureAndName.feature))
+      enabledFeatures.push_back(featureAndName.name);
+  }
+
+  // FIXME: It would be nice if the features were added in sorted order instead.
+  // However, std::sort is not constexpr until C++20.
+  std::sort(enabledFeatures.begin(), enabledFeatures.end(),
+            [](const StringRef &lhs, const StringRef &rhs) -> bool {
+              return lhs.compare(rhs) < 0;
+            });
+}
+
 // [NOTE: Bailing-vs-crashing-in-trace-emission] There are certain edge cases
 // in trace emission where an invariant that you think should hold does not hold
 // in practice. For example, sometimes we have seen modules without any
@@ -785,12 +824,18 @@ bool swift::emitLoadedModuleTraceIfNeeded(ModuleDecl *mainModule,
   std::vector<SwiftMacroTraceInfo> swiftMacros;
   computeSwiftMacroTraceInfo(ctxt, *depTracker, swiftMacros);
 
+  std::vector<StringRef> enabledFeatures;
+  computeEnabledFeatures(ctxt, enabledFeatures);
+
   LoadedModuleTraceFormat trace = {
       /*version=*/LoadedModuleTraceFormat::CurrentVersion,
       /*name=*/mainModule->getName(),
       /*arch=*/ctxt.LangOpts.Target.getArchName().str(),
+      ctxt.LangOpts.EffectiveLanguageVersion.asAPINotesVersionString(),
+      enabledFeatures,
       mainModule ? mainModule->strictMemorySafety() : false,
-      swiftModules, swiftMacros};
+      swiftModules,
+      swiftMacros};
 
   // raw_fd_ostream is unbuffered, and we may have multiple processes writing,
   // so first write to memory and then dump the buffer to the trace file.

test/Driver/loaded_module_trace.swift

@@ -12,6 +12,7 @@
 // CHECK: "version":2
 // CHECK: "name":"loaded_module_trace"
 // CHECK: "arch":"{{[^"]*}}"
+// CHECK: "languageMode":"4"
 // CHECK: "strictMemorySafety":false
 // CHECK: "swiftmodules":[
 // CHECK-DAG: "{{[^"]*\\[/\\]}}Module2.swiftmodule"

test/Driver/loaded_module_trace_enabled_features.swift

@@ -0,0 +1,83 @@
+// RUN: %empty-directory(%t)
+
+// RUN: %target-swift-frontend %s -emit-module -o /dev/null -swift-version 4 \
+// RUN:   -emit-loaded-module-trace-path %t/swift4.trace.json
+// RUN: %FileCheck -check-prefix=CHECK-SWIFT4 %s < %t/swift4.trace.json
+
+// RUN: %target-swift-frontend %s -emit-module -o /dev/null -swift-version 5 \
+// RUN:   -emit-loaded-module-trace-path %t/swift5.trace.json
+// RUN: %FileCheck -check-prefix=CHECK-SWIFT5 %s < %t/swift5.trace.json
+
+// RUN: %target-swift-frontend %s -emit-module -o /dev/null -swift-version 5 \
+// RUN:   -emit-loaded-module-trace-path %t/swift5_and_features.trace.json \
+// RUN:   -enable-experimental-feature ParserValidation \
+// RUN:   -enable-upcoming-feature RegionBasedIsolation \
+// RUN:   -strict-memory-safety
+// RUN: %FileCheck -check-prefix=CHECK-SWIFT5-PLUS %s < %t/swift5_and_features.trace.json
+
+// RUN: %target-swift-frontend %s -emit-module -o /dev/null -swift-version 6 \
+// RUN:   -emit-loaded-module-trace-path %t/swift6.trace.json
+// RUN: %FileCheck -check-prefix=CHECK-SWIFT6 %s < %t/swift6.trace.json
+
+// NOTE: The matching of the enabledLanguageFeatures lists below is
+// intentionally inexact. There are few experimental features (ParserRoundTrip,
+// ParserValidation) that are enabled by default in asserts compilers but
+// otherwise disabled, so the enabled feature lists will sometimes contain
+// additional entries.
+
+// REQUIRES: swift_feature_ParserValidation
+// REQUIRES: swift_feature_RegionBasedIsolation
+
+// CHECK-SWIFT4: {
+// CHECK-SWIFT4: "version":2
+// CHECK-SWIFT4: "arch":"{{[^"]*}}"
+// CHECK-SWIFT4: "languageMode":"4"
+// CHECK-SWIFT4: "enabledLanguageFeatures":[
+// CHECK-SWIFT4: ]
+// CHECK-SWIFT4: "strictMemorySafety":false
+
+// CHECK-SWIFT5: {
+// CHECK-SWIFT5: "version":2
+// CHECK-SWIFT5: "arch":"{{[^"]*}}"
+// CHECK-SWIFT5: "languageMode":"5"
+// CHECK-SWIFT5: "enabledLanguageFeatures":[
+// CHECK-SWIFT5: "NonfrozenEnumExhaustivity"
+// CHECK-SWIFT5: ]
+// CHECK-SWIFT5: "strictMemorySafety":false
+
+// CHECK-SWIFT5-PLUS: {
+// CHECK-SWIFT5-PLUS: "version":2
+// CHECK-SWIFT5-PLUS: "arch":"{{[^"]*}}"
+// CHECK-SWIFT5-PLUS: "languageMode":"5"
+// CHECK-SWIFT5-PLUS: "enabledLanguageFeatures":[
+// CHECK-SWIFT5-PLUS: "NonfrozenEnumExhaustivity",
+// CHECK-SWIFT5-PLUS: "ParserValidation",
+// CHECK-SWIFT5-PLUS: "RegionBasedIsolation",
+// CHECK-SWIFT5-PLUS: "StrictMemorySafety"
+// CHECK-SWIFT5-PLUS: ]
+// CHECK-SWIFT5-PLUS: "strictMemorySafety":true
+
+// CHECK-SWIFT6: {
+// CHECK-SWIFT6: "version":2
+// CHECK-SWIFT6: "arch":"{{[^"]*}}"
+// CHECK-SWIFT6: "languageMode":"6"
+// CHECK-SWIFT6: "enabledLanguageFeatures":[
+// CHECK-SWIFT6: "BareSlashRegexLiterals",
+// CHECK-SWIFT6: "ConciseMagicFile",
+// CHECK-SWIFT6: "DeprecateApplicationMain",
+// CHECK-SWIFT6: "DisableOutwardActorInference",
+// CHECK-SWIFT6: "DynamicActorIsolation",
+// CHECK-SWIFT6: "ForwardTrailingClosures",
+// CHECK-SWIFT6: "GlobalActorIsolatedTypesUsability",
+// CHECK-SWIFT6: "GlobalConcurrency",
+// CHECK-SWIFT6: "ImplicitOpenExistentials",
+// CHECK-SWIFT6: "ImportObjcForwardDeclarations",
+// CHECK-SWIFT6: "InferSendableFromCaptures",
+// CHECK-SWIFT6: "IsolatedDefaultValues",
+// CHECK-SWIFT6: "NonfrozenEnumExhaustivity",
+// CHECK-SWIFT6: "RegionBasedIsolation",
+// CHECK-SWIFT6: "StrictConcurrency"
+// CHECK-SWIFT6: ]
+// CHECK-SWIFT6: "strictMemorySafety":false
+
+import Swift

test/Driver/loaded_module_trace_multifile.swift

@@ -14,6 +14,9 @@
 // CHECK: "version":2
 // CHECK: "name":"loaded_module_trace_multifile"
 // CHECK: "arch":"{{[^"]*}}"
+// CHECK: "languageMode":"4"
+// CHECK: "enabledLanguageFeatures":[
+// CHECK: ]
 // CHECK: "swiftmodules":[
 // CHECK-DAG: "{{[^"]*\\[/\\]}}Module2.swiftmodule"
 // CHECK-DAG: "{{[^"]*\\[/\\]}}Swift.swiftmodule{{(\\[/\\][^"]+[.]swiftmodule)?}}"