commit c94391d3bfb18ed6ec0989fad1cdf66afd1292f7
author Hans Wennborg <hans@hanshq.net> Fri Jun 06 20:04:01 2014 +0000
committer Hans Wennborg <hans@hanshq.net> Fri Jun 06 20:04:01 2014 +0000
tree 79d3f58f5657986f0a5559f71854f6bc9e1c93b3
parent 0766ae08e58cb6358ed1ce407439bd3614380b2e

MS ABI: Update the thunk linkage computation

As suggested by Reid:

 - class has GVA_Internal linkage -> internal
 - thunk has return adjustment -> weak_odr, to handle evil corner case [1]
 - all other normal methods -> linkonce_odr

 1. Evil corner case:

  struct Incomplete;
  struct A { int a; virtual A *bar(); };
  struct B { int b; virtual B *foo(Incomplete); };
  struct C : A, B { int c; virtual C *foo(Incomplete); };
  C c;

Here, the thunk for C::foo() will be emitted when C::foo() is defined, which
might be in a different translation unit, so it needs to be weak_odr.

Differential Revision: http://reviews.llvm.org/D3992

llvm-svn: 210368

clang/lib/CodeGen/CGCXXABI.h

diff --git a/clang/lib/CodeGen/CGCXXABI.h b/clang/lib/CodeGen/CGCXXABI.h
index 615ec23..8268774 100644
--- a/clang/lib/CodeGen/CGCXXABI.h
+++ b/clang/lib/CodeGen/CGCXXABI.h
@@ -359,7 +359,8 @@
   /// base tables.
   virtual void emitVirtualInheritanceTables(const CXXRecordDecl *RD) = 0;
 
-  virtual void setThunkLinkage(llvm::Function *Thunk, bool ForVTable) = 0;
+  virtual void setThunkLinkage(llvm::Function *Thunk, bool ForVTable,
+                               GlobalDecl GD, bool ReturnAdjustment) = 0;
 
   virtual llvm::Value *performThisAdjustment(CodeGenFunction &CGF,
                                              llvm::Value *This,

clang/lib/CodeGen/CGVTables.cpp

diff --git a/clang/lib/CodeGen/CGVTables.cpp b/clang/lib/CodeGen/CGVTables.cpp
index 8984a70..91e6a18 100644
--- a/clang/lib/CodeGen/CGVTables.cpp
+++ b/clang/lib/CodeGen/CGVTables.cpp
@@ -382,12 +382,14 @@
     // FIXME: Do something better here; GenerateVarArgsThunk is extremely ugly.
     if (!UseAvailableExternallyLinkage) {
       CodeGenFunction(CGM).GenerateVarArgsThunk(ThunkFn, FnInfo, GD, Thunk);
-      CGM.getCXXABI().setThunkLinkage(ThunkFn, ForVTable);
+      CGM.getCXXABI().setThunkLinkage(ThunkFn, ForVTable, GD,
+                                      !Thunk.Return.isEmpty());
     }
   } else {
     // Normal thunk body generation.
     CodeGenFunction(CGM).GenerateThunk(ThunkFn, FnInfo, GD, Thunk);
-    CGM.getCXXABI().setThunkLinkage(ThunkFn, ForVTable);
+    CGM.getCXXABI().setThunkLinkage(ThunkFn, ForVTable, GD,
+                                    !Thunk.Return.isEmpty());
   }
 }
 

clang/lib/CodeGen/ItaniumCXXABI.cpp

diff --git a/clang/lib/CodeGen/ItaniumCXXABI.cpp b/clang/lib/CodeGen/ItaniumCXXABI.cpp
index 951174b..86eb36d 100644
--- a/clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -174,7 +174,8 @@
 
   void emitVirtualInheritanceTables(const CXXRecordDecl *RD) override;
 
-  void setThunkLinkage(llvm::Function *Thunk, bool ForVTable) override {
+  void setThunkLinkage(llvm::Function *Thunk, bool ForVTable, GlobalDecl GD,
+                       bool ReturnAdjustment) override {
     // Allow inlining of thunks by emitting them with available_externally
     // linkage together with vtables when needed.
     if (ForVTable)

clang/lib/CodeGen/MicrosoftCXXABI.cpp

diff --git a/clang/lib/CodeGen/MicrosoftCXXABI.cpp b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
index 5fd9e97..ffcf76e 100644
--- a/clang/lib/CodeGen/MicrosoftCXXABI.cpp
+++ b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
@@ -201,11 +201,20 @@
   void emitVBTableDefinition(const VPtrInfo &VBT, const CXXRecordDecl *RD,
                              llvm::GlobalVariable *GV) const;
 
-  void setThunkLinkage(llvm::Function *Thunk, bool ForVTable) override {
-    Thunk->setLinkage(llvm::GlobalValue::WeakAnyLinkage);
-
+  void setThunkLinkage(llvm::Function *Thunk, bool ForVTable,
+                       GlobalDecl GD, bool ReturnAdjustment) override {
     // Never dllimport/dllexport thunks.
     Thunk->setDLLStorageClass(llvm::GlobalValue::DefaultStorageClass);
+
+    GVALinkage Linkage =
+        getContext().GetGVALinkageForFunction(cast<FunctionDecl>(GD.getDecl()));
+
+    if (Linkage == GVA_Internal)
+      Thunk->setLinkage(llvm::GlobalValue::InternalLinkage);
+    else if (ReturnAdjustment)
+      Thunk->setLinkage(llvm::GlobalValue::WeakODRLinkage);
+    else
+      Thunk->setLinkage(llvm::GlobalValue::LinkOnceODRLinkage);
   }
 
   llvm::Value *performThisAdjustment(CodeGenFunction &CGF, llvm::Value *This,