r241102 - CodeGen: Assign an appropriate comdat to thunks.

[Peter Collingbourne]

Author: pcc
Date: Tue Jun 30 14:07:26 2015
New Revision: 241102

URL: http://llvm.org/viewvc/llvm-project?rev=241102&view=rev
Log:
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

Modified:
    cfe/trunk/lib/CodeGen/CGVTables.cpp
    cfe/trunk/test/CodeGenCXX/microsoft-abi-thunks.cpp

Modified: cfe/trunk/lib/CodeGen/CGVTables.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGVTables.cpp?rev=241102&r1=241101&r2=241102&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CGVTables.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGVTables.cpp Tue Jun 30 14:07:26 2015
@@ -378,9 +378,6 @@ void CodeGenFunction::GenerateThunk(llvm
   // 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(GlobalDec
     // 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,

Modified: cfe/trunk/test/CodeGenCXX/microsoft-abi-thunks.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/microsoft-abi-thunks.cpp?rev=241102&r1=241101&r2=241102&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCXX/microsoft-abi-thunks.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/microsoft-abi-thunks.cpp Tue Jun 30 14:07:26 2015
@@ -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 at E@@QAEPAUB@@XZ"
+// CODEGEN-LABEL: define weak_odr x86_thiscallcc %struct.C* @"\01?goo at E@@QAEPAUB@@XZ"{{.*}} comdat
 // CODEGEN:   call x86_thiscallcc %struct.C* @"\01?goo at 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 at I@@QAEPAUB@@XZ"
+// CODEGEN-LABEL: define weak_odr x86_thiscallcc %struct.{{[BF]}}* @"\01?goo at I@@QAEPAUB@@XZ"{{.*}} comdat
 // CODEGEN: %[[ORIG_RET:.*]] = call x86_thiscallcc %struct.F* @"\01?goo at 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