[frontend] Fix TBD validation almost always done for modules

lib/FrontendTool/FrontendTool.cpp

@@ -1390,10 +1390,14 @@ static bool validateTBDIfNeeded(const CompilerInvocation &Invocation,
     // may have serialized hand-crafted SIL definitions that are invisible to
     // TBDGen as it is an AST-only traversal.
     if (auto *mod = MSF.dyn_cast<ModuleDecl *>()) {
-      return llvm::none_of(mod->getFiles(), [](const FileUnit *File) -> bool {
+      bool hasSIB = llvm::any_of(mod->getFiles(), [](const FileUnit *File) -> bool {
         auto SASTF = dyn_cast<SerializedASTFile>(File);
         return SASTF && SASTF->isSIB();
       });
+
+      if (hasSIB) {
+        return false;
+      }
     }
 
     // "Default" mode's behavior varies if using a debug compiler.

test/TBD/sib-module.swift

@@ -0,0 +1,25 @@
+// RUN: %empty-directory(%t)
+
+// RUN: %target-swiftc_driver -emit-sib -module-name mysibmodule %s -o - | %target-swiftc_driver -emit-module -module-name mysibmodule -o %t/mysibmodule.swiftmodule -
+
+/// Since -validate-tbd-against-ir=default, TBD validation is not done since the module has a SIB file
+// RUN: %target-swift-frontend -emit-sil %t/mysibmodule.swiftmodule | %FileCheck %s
+
+// RUN: %target-swiftc_driver -emit-module -module-name mynonsibmodule -o %t/mynonsibmodule.swiftmodule %s
+
+/// Since -validate-tbd-against-ir=default, TBD validation is done or not depending on the build configuration
+// RUN: %target-swift-frontend -emit-sil %t/mynonsibmodule.swiftmodule | %FileCheck %s
+
+public class MyClass {
+  var x : Int
+
+  public init(input : Int) {
+    x = 2 * input
+  }
+
+  public func do_something(input : Int) -> Int {
+    return x * input
+  }
+}
+
+// CHECK: class MyClass