CodeGen: fix runtime function dll storage

Properly attribute DLL storage to runtime functions.  When generating the
runtime function, scan for an existing declaration which may provide an explicit
declaration (local storage) or a DLL import or export storage from the user.
Honour that if available.  Otherwise, if building with a local visibility of the
public or standard namespaces (-flto-visibility-public-std), give the symbols
local storage (it indicates a /MT[d] link, so static runtime).  Otherwise,
assume that the link is dynamic, and give the runtime function dllimport
storage.

This allows for implementations to get the correct storage as long as they are
properly declared, the user to override the import storage, and in case no
explicit storage is given, use of the import storage.

llvm-svn: 289776

1 files changed, 58 insertions, 6 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 78f43bdef99..404cbae1d83 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -2038,18 +2038,70 @@ llvm::Constant *CodeGenModule::GetAddrOfFunction(GlobalDecl GD,
                                  IsForDefinition);
 }
 
+static const FunctionDecl *
+GetRuntimeFunctionDecl(ASTContext &C, StringRef Name) {
+  TranslationUnitDecl *TUDecl = C.getTranslationUnitDecl();
+  DeclContext *DC = TranslationUnitDecl::castToDeclContext(TUDecl);
+
+  IdentifierInfo &CII = C.Idents.get(Name);
+  for (const auto &Result : DC->lookup(&CII))
+    if (const auto FD = dyn_cast<FunctionDecl>(Result))
+      return FD;
+
+  if (!C.getLangOpts().CPlusPlus)
+    return nullptr;
+
+  // Demangle the premangled name from getTerminateFn()
+  IdentifierInfo &CXXII =
+      (Name == "_ZSt9terminatev" || Name == "\01?terminate@@YAXXZ")
+          ? C.Idents.get("terminate")
+          : C.Idents.get(Name);
+
+  for (const auto &N : {"__cxxabiv1", "std"}) {
+    IdentifierInfo &NS = C.Idents.get(N);
+    for (const auto &Result : DC->lookup(&NS)) {
+      NamespaceDecl *ND = dyn_cast<NamespaceDecl>(Result);
+      if (auto LSD = dyn_cast<LinkageSpecDecl>(Result))
+        for (const auto &Result : LSD->lookup(&NS))
+          if ((ND = dyn_cast<NamespaceDecl>(Result)))
+            break;
+
+      if (ND)
+        for (const auto &Result : ND->lookup(&CXXII))
+          if (const auto *FD = dyn_cast<FunctionDecl>(Result))
+            return FD;
+    }
+  }
+
+  return nullptr;
+}
+
 /// CreateRuntimeFunction - Create a new runtime function with the specified
 /// type and name.
 llvm::Constant *
-CodeGenModule::CreateRuntimeFunction(llvm::FunctionType *FTy,
-                                     StringRef Name,
-                                     llvm::AttributeSet ExtraAttrs) {
+CodeGenModule::CreateRuntimeFunction(llvm::FunctionType *FTy, StringRef Name,
+                                     llvm::AttributeSet ExtraAttrs,
+                                     bool Local) {
   llvm::Constant *C =
       GetOrCreateLLVMFunction(Name, FTy, GlobalDecl(), /*ForVTable=*/false,
-                              /*DontDefer=*/false, /*IsThunk=*/false, ExtraAttrs);
-  if (auto *F = dyn_cast<llvm::Function>(C))
-    if (F->empty())
+                              /*DontDefer=*/false, /*IsThunk=*/false,
+                              ExtraAttrs);
+
+  if (auto *F = dyn_cast<llvm::Function>(C)) {
+    if (F->empty()) {
       F->setCallingConv(getRuntimeCC());
+
+      if (!Local && getTriple().isOSBinFormatCOFF() &&
+          !getCodeGenOpts().LTOVisibilityPublicStd) {
+        const FunctionDecl *FD = GetRuntimeFunctionDecl(Context, Name);
+        if (!FD || FD->hasAttr<DLLImportAttr>()) {
+          F->setDLLStorageClass(llvm::GlobalValue::DLLImportStorageClass);
+          F->setLinkage(llvm::GlobalValue::ExternalLinkage);
+        }
+      }
+    }
+  }
+
   return C;
 }