CodeGen: Assign an appropriate comdat to thunks.

Previously we were not assigning a comdat to thunks in the Microsoft ABI,
which would have required us to emit these functions outside of a comdat.
(Due to an inconsistency in how we were emitting objects, we were getting this
right most of the time, but only when compiling with function sections.) This
code generator change causes us to create a comdat for each thunk.

Differential Revision: http://reviews.llvm.org/D10829

llvm-svn: 241102

diff --git a/clang/lib/CodeGen/CGVTables.cpp b/clang/lib/CodeGen/CGVTables.cpp
index 17db401..ca0f780 100644 (file)
--- a/clang/lib/CodeGen/CGVTables.cpp
+++ b/clang/lib/CodeGen/CGVTables.cpp
@@ -378,9 +378,6 @@ void CodeGenFunction::GenerateThunk(llvm::Function *Fn,
   // Set the right linkage.
   CGM.setFunctionLinkage(GD, Fn);
 
-  if (CGM.supportsCOMDAT() && Fn->isWeakForLinker())
-    Fn->setComdat(CGM.getModule().getOrInsertComdat(Fn->getName()));
-
   // Set the right visibility.
   const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
   setThunkVisibility(CGM, MD, Thunk, Fn);
@@ -450,17 +447,18 @@ void CodeGenVTables::emitThunk(GlobalDecl GD, const ThunkInfo &Thunk,
     // expensive/sucky at the moment, so don't generate the thunk unless
     // we have to.
     // FIXME: Do something better here; GenerateVarArgsThunk is extremely ugly.
-    if (!UseAvailableExternallyLinkage) {
-      CodeGenFunction(CGM).GenerateVarArgsThunk(ThunkFn, FnInfo, GD, Thunk);
-      CGM.getCXXABI().setThunkLinkage(ThunkFn, ForVTable, GD,
-                                      !Thunk.Return.isEmpty());
-    }
+    if (UseAvailableExternallyLinkage)
+      return;
+    CodeGenFunction(CGM).GenerateVarArgsThunk(ThunkFn, FnInfo, GD, Thunk);
   } else {
     // Normal thunk body generation.
     CodeGenFunction(CGM).GenerateThunk(ThunkFn, FnInfo, GD, Thunk);
-    CGM.getCXXABI().setThunkLinkage(ThunkFn, ForVTable, GD,
-                                    !Thunk.Return.isEmpty());
   }
+
+  CGM.getCXXABI().setThunkLinkage(ThunkFn, ForVTable, GD,
+                                  !Thunk.Return.isEmpty());
+  if (CGM.supportsCOMDAT() && ThunkFn->isWeakForLinker())
+    ThunkFn->setComdat(CGM.getModule().getOrInsertComdat(ThunkFn->getName()));
 }
 
 void CodeGenVTables::maybeEmitThunkForVTable(GlobalDecl GD,

diff --git a/clang/test/CodeGenCXX/microsoft-abi-thunks.cpp b/clang/test/CodeGenCXX/microsoft-abi-thunks.cpp
index 8cbea5c..8230334 100644 (file)
--- a/clang/test/CodeGenCXX/microsoft-abi-thunks.cpp
+++ b/clang/test/CodeGenCXX/microsoft-abi-thunks.cpp
@@ -91,7 +91,7 @@ struct E : D {
 
 E::E() {}  // Emits vftable and forces thunk generation.
 
-// CODEGEN-LABEL: define weak_odr x86_thiscallcc %struct.C* @"\01?goo@E@@QAEPAUB@@XZ"
+// CODEGEN-LABEL: define weak_odr x86_thiscallcc %struct.C* @"\01?goo@E@@QAEPAUB@@XZ"{{.*}} comdat
 // CODEGEN:   call x86_thiscallcc %struct.C* @"\01?goo@E@@UAEPAUC@@XZ"
 // CODEGEN:   getelementptr inbounds i8, i8* {{.*}}, i32 4
 // CODEGEN: ret
@@ -124,7 +124,7 @@ struct I : D {
 
 I::I() {}  // Emits vftable and forces thunk generation.
 
-// CODEGEN-LABEL: define weak_odr x86_thiscallcc %struct.{{[BF]}}* @"\01?goo@I@@QAEPAUB@@XZ"
+// CODEGEN-LABEL: define weak_odr x86_thiscallcc %struct.{{[BF]}}* @"\01?goo@I@@QAEPAUB@@XZ"{{.*}} comdat
 // 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, i8* %[[ORIG_RET_i8]], i32 4