[PATCH] [-cxx-abi microsoft] Emit linkonce_odr definitions for declarations of static data members with inline initializers (PR17689)

[Hans Wennborg]

  Address Reid's comments.

Hi rnk,

http://llvm-reviews.chandlerc.com/D2233

CHANGE SINCE LAST DIFF
  http://llvm-reviews.chandlerc.com/D2233?vs=5684&id=5687#toc

Files:
  lib/CodeGen/CGCXXABI.h
  lib/CodeGen/CodeGenModule.cpp
  lib/CodeGen/MicrosoftCXXABI.cpp
  test/CodeGenCXX/ms-integer-static-data-members.cpp

Index: lib/CodeGen/CGCXXABI.h
===================================================================
--- lib/CodeGen/CGCXXABI.h
+++ lib/CodeGen/CGCXXABI.h
@@ -373,6 +373,10 @@
   /// Gets the deleted virtual member call name.
   virtual StringRef GetDeletedVirtualCallName() = 0;
 
+  /// \brief Returns true iff static data members that are initialized in the
+  /// class definition should have linkonce linkage.
+  virtual bool isInlineInitializedStaticDataMemberLinkOnce() { return false; }
+
   /**************************** Array cookies ******************************/
 
   /// Returns the extra size required in order to store the array
Index: lib/CodeGen/CodeGenModule.cpp
===================================================================
--- lib/CodeGen/CodeGenModule.cpp
+++ lib/CodeGen/CodeGenModule.cpp
@@ -1607,6 +1607,13 @@
         CXXThreadLocals.push_back(std::make_pair(D, GV));
       setTLSMode(GV, *D);
     }
+
+    // In the MS ABI, treat declarations of static data members with inline
+    // initializers as definitions.
+    if (getCXXABI().isInlineInitializedStaticDataMemberLinkOnce() &&
+        D->isStaticDataMember() && D->hasInit() &&
+        !D->isThisDeclarationADefinition())
+      EmitGlobalVarDefinition(D); 
   }
 
   if (AddrSpace != Ty->getAddressSpace())
@@ -1860,6 +1867,14 @@
   llvm::GlobalValue::LinkageTypes Linkage = 
     GetLLVMLinkageVarDefinition(D, GV->isConstant());
   GV->setLinkage(Linkage);
+
+  // In the MS ABI, give definitions of static data members with inline
+  // initializers linkonce_odr linkage.
+  if (getCXXABI().isInlineInitializedStaticDataMemberLinkOnce() &&
+      D->isStaticDataMember() && InitExpr &&
+      !InitDecl->isThisDeclarationADefinition())
+    GV->setLinkage(llvm::GlobalVariable::LinkOnceODRLinkage);
+
   if (Linkage == llvm::GlobalVariable::CommonLinkage)
     // common vars aren't constant even if declared const.
     GV->setConstant(false);
Index: lib/CodeGen/MicrosoftCXXABI.cpp
===================================================================
--- lib/CodeGen/MicrosoftCXXABI.cpp
+++ lib/CodeGen/MicrosoftCXXABI.cpp
@@ -50,6 +50,8 @@
   // arbitrary.
   StringRef GetDeletedVirtualCallName() { return "_purecall"; }
 
+  bool isInlineInitializedStaticDataMemberLinkOnce() { return true; }
+
   llvm::Value *adjustToCompleteObject(CodeGenFunction &CGF,
                                       llvm::Value *ptr,
                                       QualType type);
Index: test/CodeGenCXX/ms-integer-static-data-members.cpp
===================================================================
--- /dev/null
+++ test/CodeGenCXX/ms-integer-static-data-members.cpp
@@ -0,0 +1,35 @@
+// RUN: %clang_cc1 -emit-llvm -cxx-abi microsoft -triple=i386-pc-win32 %s -o - | FileCheck %s
+// RUN: %clang_cc1 -DINLINE_INIT -emit-llvm -cxx-abi microsoft -triple=i386-pc-win32 %s -o - | FileCheck %s --check-prefix=CHECK-INLINE
+// RUN: %clang_cc1 -DREAL_DEFINITION -emit-llvm -cxx-abi microsoft -triple=i386-pc-win32 %s -o - | FileCheck %s --check-prefix=CHECK-OUTOFLINE
+// RUN: %clang_cc1 -DINLINE_INIT -DREAL_DEFINITION -emit-llvm -cxx-abi microsoft -triple=i386-pc-win32 %s -o - | FileCheck %s --check-prefix=CHECK-INLINE
+
+struct S {
+  // For MS ABI, we emit a linkonce_odr definition here, even though it's really just a declaration.
+#ifdef INLINE_INIT
+  static const int x = 5;
+#else
+  static const int x;
+#endif
+};
+
+const int *f() {
+  return &S::x;
+};
+
+#ifdef REAL_DEFINITION
+#ifdef INLINE_INIT
+const int S::x;
+#else
+const int S::x = 5;
+#endif
+#endif
+
+
+// Inline initialization.
+// CHECK-INLINE: @"\01?x at S@@2HB" = linkonce_odr constant i32 5, align 4 
+
+// Out-of-line initialization.
+// CHECK-OUTOFLINE: @"\01?x at S@@2HB" = constant i32 5, align 4 
+
+// No initialization.
+// CHECK: @"\01?x at S@@2HB" = external constant i32
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