1 files changed, 9 insertions, 0 deletions
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index f721017..2e96fff 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -3851,10 +3851,19 @@ CodeGenModule::isTriviallyRecursive(const FunctionDecl *FD) {
 bool CodeGenModule::shouldEmitFunction(GlobalDecl GD) {
   if (getFunctionLinkage(GD) != llvm::Function::AvailableExternallyLinkage)
     return true;
+
   const auto *F = cast<FunctionDecl>(GD.getDecl());
   if (CodeGenOpts.OptimizationLevel == 0 && !F->hasAttr<AlwaysInlineAttr>())
     return false;
 
+  // We don't import function bodies from other named module units since that
+  // behavior may break ABI compatibility of the current unit.
+  if (const Module *M = F->getOwningModule();
+      M && M->isModulePurview() &&
+      getContext().getCurrentNamedModule() != M->getTopLevelModule() &&
+      !F->hasAttr<AlwaysInlineAttr>())
+    return false;
+
   if (F->hasAttr<NoInlineAttr>())
     return false;