Add Swift compilation flags to enable Clang's validate-per-build-session module behavior

include/swift/AST/DiagnosticsFrontend.def

@@ -221,6 +221,10 @@ ERROR(error_mode_requires_one_sil_multi_sib,none,
       "this mode requires .sil for primary-file and only .sib for other inputs",
       ())
 
+ERROR(error_clang_validate_once_requires_session_file,none,
+      "'-validate-clang-modules-once' also requires a '-clang-build-session-file' argument",
+      ())
+
 ERROR(error_no_output_filename_specified,none,
       "an %0 filename was not specified for a mode which requires an "
       "%0 filename", (StringRef))

include/swift/Basic/LangOptions.h

@@ -783,6 +783,14 @@ namespace swift {
     /// Disable validating the persistent PCH.
     bool PCHDisableValidation = false;
 
+    /// Don't verify input files for Clang modules if the module has been
+    /// successfully validated or loaded during this build session.
+    bool ValidateModulesOnce = false;
+
+    /// Use the last modification time of this file as the underlying Clang
+    /// build session timestamp.
+    std::string BuildSessionFilePath;
+
     /// \see Mode
     enum class Modes : uint8_t {
       /// Set up Clang for importing modules into Swift and generating IR from

include/swift/Frontend/ModuleInterfaceLoader.h

@@ -550,6 +550,7 @@ struct InterfaceSubContextDelegateImpl: InterfaceSubContextDelegate {
   void
   inheritOptionsForBuildingInterface(const SearchPathOptions &SearchPathOpts,
                                      const LangOptions &LangOpts,
+                                     const ClangImporterOptions &clangImporterOpts,
                                      bool suppressRemarks,
                                      RequireOSSAModules_t requireOSSAModules);
   bool extractSwiftInterfaceVersionAndArgs(CompilerInvocation &subInvocation,

include/swift/Option/Options.td

@@ -178,6 +178,15 @@ def no_strict_implicit_module_context :
   Flags<[FrontendOption, HelpHidden]>,
   HelpText<"Disable the strict forwarding of compilation context to downstream implicit module dependencies">;
 
+def validate_clang_modules_once :
+  Flag<["-"], "validate-clang-modules-once">,
+  Flags<[FrontendOption]>,
+  HelpText<"Don't verify input files for Clang modules if the module has been successfully validated or loaded during this build session">;
+
+def clang_build_session_file : Separate<["-"], "clang-build-session-file">,
+  Flags<[FrontendOption, ArgumentIsPath]>,
+  HelpText<"Use the last modification time of <file> as the underlying Clang build session timestamp">;
+
 def disallow_forwarding_driver :
   Flag<["-"], "disallow-use-new-driver">, Flags<[]>,
   HelpText<"Disable using new swift-driver">;

lib/ClangImporter/ClangImporter.cpp

@@ -810,6 +810,11 @@ importer::addCommonInvocationArguments(
   invocationArgStrs.push_back("-Xclang");
   invocationArgStrs.push_back("-no-opaque-pointers");
 
+  if (importerOpts.ValidateModulesOnce) {
+    invocationArgStrs.push_back("-fmodules-validate-once-per-build-session");
+    invocationArgStrs.push_back("-fbuild-session-file=" + importerOpts.BuildSessionFilePath);
+  }
+
   for (auto extraArg : importerOpts.ExtraArgs) {
     invocationArgStrs.push_back(extraArg);
   }

lib/Frontend/CompilerInvocation.cpp

@@ -1220,6 +1220,15 @@ static bool ParseTypeCheckerArgs(TypeCheckerOptions &Opts, ArgList &Args,
   return HadError;
 }
 
+static bool ValidateModulesOnceOptions(const ClangImporterOptions &Opts,
+                                       DiagnosticEngine &Diags) {
+  if (Opts.ValidateModulesOnce && Opts.BuildSessionFilePath.empty()) {
+    Diags.diagnose(SourceLoc(), diag::error_clang_validate_once_requires_session_file);
+    return true;
+  }
+  return false;
+}
+
 static bool ParseClangImporterArgs(ClangImporterOptions &Opts,
                                    ArgList &Args,
                                    DiagnosticEngine &Diags,
@@ -1314,6 +1323,12 @@ static bool ParseClangImporterArgs(ClangImporterOptions &Opts,
     Opts.PCHDisableValidation |= Args.hasArg(OPT_pch_disable_validation);
   }
 
+  Opts.ValidateModulesOnce |= Args.hasArg(OPT_validate_clang_modules_once);
+  if (auto *A = Args.getLastArg(OPT_clang_build_session_file))
+    Opts.BuildSessionFilePath = A->getValue();
+  if (ValidateModulesOnceOptions(Opts, Diags))
+    return true;
+
   if (Args.hasFlag(options::OPT_warnings_as_errors,
                    options::OPT_no_warnings_as_errors, false))
     Opts.ExtraArgs.push_back("-Werror");

lib/Frontend/ModuleInterfaceLoader.cpp

@@ -1448,6 +1448,7 @@ void ModuleInterfaceLoader::collectVisibleTopLevelModuleNames(
 
 void InterfaceSubContextDelegateImpl::inheritOptionsForBuildingInterface(
     const SearchPathOptions &SearchPathOpts, const LangOptions &LangOpts,
+    const ClangImporterOptions &clangImporterOpts,
     bool suppressRemarks, RequireOSSAModules_t RequireOSSAModules) {
   GenericArgs.push_back("-frontend");
   // Start with a genericSubInvocation that copies various state from our
@@ -1544,6 +1545,16 @@ void InterfaceSubContextDelegateImpl::inheritOptionsForBuildingInterface(
     genericSubInvocation.getLangOptions().Features.insert(
       Feature::LayoutPrespecialization);
   }
+
+  // Validate Clang modules once per-build session flags must be consistent
+  // across all module sub-invocations
+  if (clangImporterOpts.ValidateModulesOnce) {
+    genericSubInvocation.getClangImporterOptions().ValidateModulesOnce = true;
+    genericSubInvocation.getClangImporterOptions().BuildSessionFilePath = clangImporterOpts.BuildSessionFilePath;
+    GenericArgs.push_back("-validate-clang-modules-once");
+    GenericArgs.push_back("-clang-build-session-file");
+    GenericArgs.push_back(clangImporterOpts.BuildSessionFilePath);
+  }
 }
 
 bool InterfaceSubContextDelegateImpl::extractSwiftInterfaceVersionAndArgs(
@@ -1586,6 +1597,7 @@ InterfaceSubContextDelegateImpl::InterfaceSubContextDelegateImpl(
     : SM(SM), Diags(Diags), ArgSaver(Allocator) {
   genericSubInvocation.setMainExecutablePath(LoaderOpts.mainExecutablePath);
   inheritOptionsForBuildingInterface(searchPathOpts, langOpts,
+                                     clangImporterOpts,
                                      Diags->getSuppressRemarks(),
                                      requireOSSAModules);
   // Configure front-end input.
@@ -1621,6 +1633,7 @@ InterfaceSubContextDelegateImpl::InterfaceSubContextDelegateImpl(
     genericSubInvocation.getLangOptions().EnableAppExtensionRestrictions = true;
     GenericArgs.push_back("-application-extension");
   }
+
   // Save the parent invocation's Target Triple
   ParentInvocationTarget = langOpts.Target;
 

test/ClangImporter/validate-modules-once.swift

@@ -0,0 +1,8 @@
+// RUN: %empty-directory(%t)
+// RUN: touch %t/Build.session
+// RUN: %swift %s -typecheck -dump-clang-diagnostics -validate-clang-modules-once -clang-build-session-file %t/Build.session 2>&1 | %FileCheck %s
+
+public func foo() {}
+
+// CHECK: '-fmodules-validate-once-per-build-session'
+// CHECK: '-fbuild-session-file=

test/ModuleInterface/clang-session-transitive.swift

@@ -0,0 +1,41 @@
+// This test ensures that the parent invocation's '-validate-clang-modules-once' flag is inherited when building dependency modules
+// RUN: %empty-directory(%t)
+// RUN: touch %t/Build.session
+
+// RUN: %target-build-swift -module-name TestModule -module-link-name TestModule %S/Inputs/TestModule.swift -enable-library-evolution -emit-module-interface -o %t/TestModule.swiftmodule -swift-version 5 -Xfrontend -disable-implicit-concurrency-module-import -Xfrontend -disable-implicit-string-processing-module-import
+
+// RUN: %target-swift-frontend -scan-dependencies %s -o %t/deps.json -I%t -validate-clang-modules-once -clang-build-session-file %t/Build.session -disable-implicit-concurrency-module-import -disable-implicit-string-processing-module-import
+// RUN: %FileCheck %s < %t/deps.json
+
+import TestModule
+
+ // CHECK:      "directDependencies": [
+ // CHECK-NEXT:        {
+ // CHECK-DAG:          "swift": "TestModule"
+ // CHECK-DAG:          "swift": "Swift"
+ // CHECK-DAG:          "swift": "SwiftOnoneSupport"
+
+ // CHECK:      "swift": "TestModule"
+ // CHECK-NEXT:    },
+ // CHECK-NEXT:    {
+ // CHECK-NEXT:      "modulePath": "{{.*}}TestModule-{{.*}}.swiftmodule",
+ // CHECK-NEXT:      "sourceFiles": [
+ // CHECK-NEXT:      ],
+ // CHECK-NEXT:      "directDependencies": [
+ // CHECK-NEXT:        {
+ // CHECK-NEXT:          "swift": "Swift"
+ // CHECK-NEXT:        },
+ // CHECK-NEXT:        {
+ // CHECK-NEXT:          "swift": "SwiftOnoneSupport"
+ // CHECK-NEXT:        }
+ // CHECK-NEXT:      ],
+ // CHECK-NEXT:      "details": {
+ // CHECK-NEXT:        "swift": {
+ // CHECK-NEXT:          "moduleInterfacePath": 
+ // CHECK-NEXT:          "contextHash":
+ // CHECK-NEXT:          "commandLine": [
+ // CHECK-NEXT:            "-frontend",
+ // CHECK-NEXT:            "-compile-module-from-interface",
+ // CHECK:                 "-validate-clang-modules-once",
+ // CHECK-NEXT:            "-clang-build-session-file",
+ // CHECK-NEXT:            "{{.*}}Build.session"