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

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@241102 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/CGVTables.cpp b/lib/CodeGen/CGVTables.cpp
index 17db40138296b0c52c7e0cd8ae04c38a3812a424..ca0f7807772fc788ca3675d344cf388af00e357d 100644 (file)
--- a/lib/CodeGen/CGVTables.cpp
+++ b/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/test/CodeGenCXX/microsoft-abi-thunks.cpp b/test/CodeGenCXX/microsoft-abi-thunks.cpp
index 8cbea5c4deebe77bdc6e5abd78fd04970c12f54b..823033461612a52a801f7878ab970df40f89c0dd 100644 (file)
--- a/test/CodeGenCXX/microsoft-abi-thunks.cpp
+++ b/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