CodeGen: Don't drop thread_local when emitting __thread aliases

CodeGen wouldn't mark the aliasee as thread_local if the aliasee was a
tentative definition.

Even if the definition was already emitted, it would never mark the
alias as thread_local.

This fixes PR21288.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@219859 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/CodeGenModule.cpp

@@ -523,11 +523,10 @@ static llvm::GlobalVariable::ThreadLocalMode GetLLVMTLSModel(
   llvm_unreachable("Invalid TLS model!");
 }
 
-void CodeGenModule::setTLSMode(llvm::GlobalVariable *GV,
-                               const VarDecl &D) const {
+void CodeGenModule::setTLSMode(llvm::GlobalValue *GV, const VarDecl &D) const {
   assert(D.getTLSKind() && "setting TLS mode on non-TLS var!");
 
-  llvm::GlobalVariable::ThreadLocalMode TLM;
+  llvm::GlobalValue::ThreadLocalMode TLM;
   TLM = GetLLVMTLSModel(CodeGenOpts.getDefaultTLSModel());
 
   // Override the TLS model if it is explicitly specified.
@@ -1942,10 +1941,9 @@ void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D) {
   // has internal linkage; all accesses should just be calls to the
   // Itanium-specified entry point, which has the normal linkage of the
   // variable.
-  if (const auto *VD = dyn_cast<VarDecl>(D))
-    if (!VD->isStaticLocal() && VD->getTLSKind() == VarDecl::TLS_Dynamic &&
-        Context.getTargetInfo().getTriple().isMacOSX())
-      Linkage = llvm::GlobalValue::InternalLinkage;
+  if (!D->isStaticLocal() && D->getTLSKind() == VarDecl::TLS_Dynamic &&
+      Context.getTargetInfo().getTriple().isMacOSX())
+    Linkage = llvm::GlobalValue::InternalLinkage;
 
   GV->setLinkage(Linkage);
   if (D->hasAttr<DLLImportAttr>())
@@ -1959,6 +1957,12 @@ void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D) {
 
   setNonAliasAttributes(D, GV);
 
+  if (D->getTLSKind() && !GV->isThreadLocal()) {
+    if (D->getTLSKind() == VarDecl::TLS_Dynamic)
+      CXXThreadLocals.push_back(std::make_pair(D, GV));
+    setTLSMode(GV, *D);
+  }
+
   // Emit the initializer function if necessary.
   if (NeedsGlobalCtor || NeedsGlobalDtor)
     EmitCXXGlobalVarDeclInitFunc(D, GV, NeedsGlobalCtor);
@@ -2326,7 +2330,7 @@ void CodeGenModule::EmitAliasDefinition(GlobalDecl GD) {
   else
     Aliasee = GetOrCreateLLVMGlobal(AA->getAliasee(),
                                     llvm::PointerType::getUnqual(DeclTy),
-                                    nullptr);
+                                    /*D=*/nullptr);
 
   // Create the new alias itself, but don't set a name yet.
   auto *GA = llvm::GlobalAlias::create(
@@ -2365,6 +2369,10 @@ void CodeGenModule::EmitAliasDefinition(GlobalDecl GD) {
     GA->setLinkage(llvm::Function::WeakAnyLinkage);
   }
 
+  if (const auto *VD = dyn_cast<VarDecl>(D))
+    if (VD->getTLSKind())
+      setTLSMode(GA, *VD);
+
   setAliasAttributes(D, GA);
 }
 

lib/CodeGen/CodeGenModule.h

@@ -652,9 +652,9 @@ public:
   /// Set the visibility for the given LLVM GlobalValue.
   void setGlobalVisibility(llvm::GlobalValue *GV, const NamedDecl *D) const;
 
-  /// Set the TLS mode for the given LLVM GlobalVariable for the thread-local
+  /// Set the TLS mode for the given LLVM GlobalValue for the thread-local
   /// variable declaration D.
-  void setTLSMode(llvm::GlobalVariable *GV, const VarDecl &D) const;
+  void setTLSMode(llvm::GlobalValue *GV, const VarDecl &D) const;
 
   static llvm::GlobalValue::VisibilityTypes GetLLVMVisibility(Visibility V) {
     switch (V) {

test/CodeGen/alias.c

@@ -3,6 +3,8 @@
 
 int g0;
 // CHECKBASIC: @g0 = common global i32 0
+__thread int TL_WITH_ALIAS;
+// CHECKBASIC-DAG: @TL_WITH_ALIAS = thread_local global i32 0, align 4
 static int bar1 = 42;
 // CHECKBASIC: @bar1 = internal global i32 42
 
@@ -10,6 +12,9 @@ extern int g1;
 extern int g1 __attribute((alias("g0")));
 // CHECKBASIC-DAG: @g1 = alias i32* @g0
 
+extern __thread int __libc_errno __attribute__ ((alias ("TL_WITH_ALIAS")));
+// CHECKBASIC-DAG: @__libc_errno = thread_local alias i32* @TL_WITH_ALIAS
+
 void f0(void) { }
 extern void f1(void);
 extern void f1(void) __attribute((alias("f0")));