From: Hans Wennborg <hans@hanshq.net>
Date: Fri, 6 Jun 2014 20:04:01 +0000 (+0000)
Subject: MS ABI: Update the thunk linkage computation
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=6c87b4a75691215d3b0a16083d9499d0ed869f81;p=clang

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

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@210368 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/CGCXXABI.h b/lib/CodeGen/CGCXXABI.h
index 615ec23aa7..82687746ed 100644
--- a/lib/CodeGen/CGCXXABI.h
+++ b/lib/CodeGen/CGCXXABI.h
@@ -359,7 +359,8 @@ public:
   /// 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,
diff --git a/lib/CodeGen/CGVTables.cpp b/lib/CodeGen/CGVTables.cpp
index 8984a707c4..91e6a18398 100644
--- a/lib/CodeGen/CGVTables.cpp
+++ b/lib/CodeGen/CGVTables.cpp
@@ -382,12 +382,14 @@ void CodeGenVTables::emitThunk(GlobalDecl GD, const ThunkInfo &Thunk,
     // 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());
   }
 }
 
diff --git a/lib/CodeGen/ItaniumCXXABI.cpp b/lib/CodeGen/ItaniumCXXABI.cpp
index 951174b485..86eb36d865 100644
--- a/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/lib/CodeGen/ItaniumCXXABI.cpp
@@ -174,7 +174,8 @@ public:
 
   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)
diff --git a/lib/CodeGen/MicrosoftCXXABI.cpp b/lib/CodeGen/MicrosoftCXXABI.cpp
index 5fd9e97948..ffcf76eb42 100644
--- a/lib/CodeGen/MicrosoftCXXABI.cpp
+++ b/lib/CodeGen/MicrosoftCXXABI.cpp
@@ -201,11 +201,20 @@ public:
   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,
diff --git a/test/CodeGenCXX/dllimport.cpp b/test/CodeGenCXX/dllimport.cpp
index 004c07e9f6..0295943fde 100644
--- a/test/CodeGenCXX/dllimport.cpp
+++ b/test/CodeGenCXX/dllimport.cpp
@@ -566,7 +566,7 @@ namespace DontUseDtorAlias {
 
 namespace Vtordisp {
   // Don't dllimport the vtordisp.
-  // MO1-DAG: define weak x86_thiscallcc void @"\01?f@?$C@D@Vtordisp@@$4PPPPPPPM@A@AEXXZ"
+  // MO1-DAG: define linkonce_odr x86_thiscallcc void @"\01?f@?$C@D@Vtordisp@@$4PPPPPPPM@A@AEXXZ"
 
   class Base {
     virtual void f() {}
diff --git a/test/CodeGenCXX/microsoft-abi-structors.cpp b/test/CodeGenCXX/microsoft-abi-structors.cpp
index b79da8d6cb..04227e311b 100644
--- a/test/CodeGenCXX/microsoft-abi-structors.cpp
+++ b/test/CodeGenCXX/microsoft-abi-structors.cpp
@@ -153,7 +153,7 @@ C::~C() {
 void foo() {
   C c;
 }
-// DTORS2-LABEL: define weak x86_thiscallcc void @"\01??_EC@dtor_in_second_nvbase@@W3AEPAXI@Z"
+// DTORS2-LABEL: define linkonce_odr x86_thiscallcc void @"\01??_EC@dtor_in_second_nvbase@@W3AEPAXI@Z"
 // DTORS2:       (%"struct.dtor_in_second_nvbase::C"* %this, i32 %should_call_delete)
 //      Do an adjustment from B* to C*.
 // DTORS2:   getelementptr i8* %{{.*}}, i32 -4
diff --git a/test/CodeGenCXX/microsoft-abi-thunks.cpp b/test/CodeGenCXX/microsoft-abi-thunks.cpp
index 2be642c47d..c755b30006 100644
--- a/test/CodeGenCXX/microsoft-abi-thunks.cpp
+++ b/test/CodeGenCXX/microsoft-abi-thunks.cpp
@@ -61,13 +61,13 @@ struct C : A, B {
 
 C::C() {}  // Emits vftable and forces thunk generation.
 
-// CODEGEN-LABEL: define weak x86_thiscallcc void @"\01??_EC@@W3AEPAXI@Z"(%struct.C* %this, i32 %should_call_delete)
+// CODEGEN-LABEL: define linkonce_odr x86_thiscallcc void @"\01??_EC@@W3AEPAXI@Z"(%struct.C* %this, i32 %should_call_delete)
 // CODEGEN:   getelementptr i8* {{.*}}, i32 -4
 // FIXME: should actually call _EC, not _GC.
 // CODEGEN:   call x86_thiscallcc void @"\01??_GC@@UAEPAXI@Z"
 // CODEGEN: ret
 
-// CODEGEN-LABEL: define weak x86_thiscallcc void @"\01?public_f@C@@W3AEXXZ"(%struct.C*
+// CODEGEN-LABEL: define linkonce_odr x86_thiscallcc void @"\01?public_f@C@@W3AEXXZ"(%struct.C*
 // CODEGEN:   getelementptr i8* {{.*}}, i32 -4
 // CODEGEN:   call x86_thiscallcc void @"\01?public_f@C@@UAEXXZ"(%struct.C*
 // CODEGEN: ret
@@ -91,7 +91,7 @@ struct E : D {
 
 E::E() {}  // Emits vftable and forces thunk generation.
 
-// CODEGEN-LABEL: define weak x86_thiscallcc %struct.C* @"\01?goo@E@@QAEPAUB@@XZ"
+// CODEGEN-LABEL: define weak_odr x86_thiscallcc %struct.C* @"\01?goo@E@@QAEPAUB@@XZ"
 // CODEGEN:   call x86_thiscallcc %struct.C* @"\01?goo@E@@UAEPAUC@@XZ"
 // CODEGEN:   getelementptr inbounds i8* {{.*}}, i32 4
 // CODEGEN: ret
@@ -124,7 +124,7 @@ struct I : D {
 
 I::I() {}  // Emits vftable and forces thunk generation.
 
-// CODEGEN-LABEL: define weak x86_thiscallcc %struct.{{[BF]}}* @"\01?goo@I@@QAEPAUB@@XZ"
+// CODEGEN-LABEL: define weak_odr x86_thiscallcc %struct.{{[BF]}}* @"\01?goo@I@@QAEPAUB@@XZ"
 // CODEGEN: %[[ORIG_RET:.*]] = call x86_thiscallcc %struct.F* @"\01?goo@I@@UAEPAUF@@XZ"
 // CODEGEN: %[[ORIG_RET_i8:.*]] = bitcast %struct.F* %[[ORIG_RET]] to i8*
 // CODEGEN: %[[VBPTR_i8:.*]] = getelementptr inbounds i8* %[[ORIG_RET_i8]], i32 4
@@ -152,3 +152,14 @@ struct C : A, B {
 };
 C c;
 }
+
+namespace {
+struct E : D {
+  E();
+  virtual C* goo();
+};
+E::E() {}
+E e;
+// Class with internal linkage has internal linkage thunks.
+// CODEGEN: define internal x86_thiscallcc %struct.C* @"\01?goo@E@?A@@QAEPAUB@@XZ"
+}
diff --git a/test/CodeGenCXX/microsoft-abi-virtual-inheritance-vtordisps.cpp b/test/CodeGenCXX/microsoft-abi-virtual-inheritance-vtordisps.cpp
index 5d11896247..a6fcdea749 100644
--- a/test/CodeGenCXX/microsoft-abi-virtual-inheritance-vtordisps.cpp
+++ b/test/CodeGenCXX/microsoft-abi-virtual-inheritance-vtordisps.cpp
@@ -23,7 +23,7 @@ struct D : virtual C {
 
 D::D() {}  // Forces vftable emission.
 
-// CHECK-LABEL: define weak x86_thiscallcc void @"\01?f@D@@$4PPPPPPPM@A@AEXXZ"
+// CHECK-LABEL: define linkonce_odr x86_thiscallcc void @"\01?f@D@@$4PPPPPPPM@A@AEXXZ"
 // CHECK: %[[ECX:.*]] = load %struct.D** %{{.*}}
 // CHECK: %[[ECX_i8:.*]] = bitcast %struct.D* %[[ECX]] to i8*
 // CHECK: %[[VTORDISP_PTR_i8:.*]] = getelementptr i8* %[[ECX_i8]], i32 -4
@@ -34,7 +34,7 @@ D::D() {}  // Forces vftable emission.
 // CHECK: call x86_thiscallcc void @"\01?f@D@@UAEXXZ"(i8* %[[ADJUSTED_i8]])
 // CHECK: ret void
 
-// CHECK-LABEL: define weak x86_thiscallcc void @"\01?f@D@@$4PPPPPPPI@3AEXXZ"
+// CHECK-LABEL: define linkonce_odr x86_thiscallcc void @"\01?f@D@@$4PPPPPPPI@3AEXXZ"
 // CHECK: %[[ECX:.*]] = load %struct.D** %{{.*}}
 // CHECK: %[[ECX_i8:.*]] = bitcast %struct.D* %[[ECX]] to i8*
 // CHECK: %[[VTORDISP_PTR_i8:.*]] = getelementptr i8* %[[ECX_i8]], i32 -8
@@ -63,7 +63,7 @@ struct G : virtual F, virtual E {
 
 G::G() {}  // Forces vftable emission.
 
-// CHECK-LABEL: define weak x86_thiscallcc void @"\01?f@E@@$R4BA@M@PPPPPPPM@7AEXXZ"(i8*)
+// CHECK-LABEL: define linkonce_odr x86_thiscallcc void @"\01?f@E@@$R4BA@M@PPPPPPPM@7AEXXZ"(i8*)
 // CHECK: %[[ECX:.*]] = load %struct.E** %{{.*}}
 // CHECK: %[[ECX_i8:.*]] = bitcast %struct.E* %[[ECX]] to i8*
 // CHECK: %[[VTORDISP_PTR_i8:.*]] = getelementptr i8* %[[ECX_i8]], i32 -4
diff --git a/test/CodeGenCXX/microsoft-abi-vtables-virtual-inheritance.cpp b/test/CodeGenCXX/microsoft-abi-vtables-virtual-inheritance.cpp
index 6ef3176935..4ce4e9c2e1 100644
--- a/test/CodeGenCXX/microsoft-abi-vtables-virtual-inheritance.cpp
+++ b/test/CodeGenCXX/microsoft-abi-vtables-virtual-inheritance.cpp
@@ -145,7 +145,7 @@ struct X: virtual C {
   // MANGLING-DAG: @"\01??_7X@Test4@@6B@"
 
   // Also check the mangling of the thunk.
-  // MANGLING-DAG: define weak x86_thiscallcc void @"\01?f@C@@WPPPPPPPI@AEXXZ"
+  // MANGLING-DAG: define linkonce_odr x86_thiscallcc void @"\01?f@C@@WPPPPPPPI@AEXXZ"
 };
 
 X::X() {}