From 7c6b7ba5f5410d4b552ee53c60d0690522c99959 Mon Sep 17 00:00:00 2001
From: Bill Wendling <isanbard@gmail.com>
Date: Mon, 29 Apr 2013 22:27:16 +0000
Subject: [PATCH] Emit the TLS intialization functions into a list.

Add the TLS initialization functions to a list of initialization functions. The
back-end takes this list and places the function pointers into the correct
section. This way they're called before `main().'

<rdar://problem/13733006>


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@180739 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/CGDeclCXX.cpp          |  1 +
 lib/CodeGen/CodeGenModule.cpp      | 26 ++++++++++++++++++++++++++
 lib/CodeGen/CodeGenModule.h        | 11 +++++++++++
 test/CodeGenCXX/tls-init-funcs.cpp | 21 +++++++++++++++++++++
 4 files changed, 59 insertions(+)
 create mode 100644 test/CodeGenCXX/tls-init-funcs.cpp

diff --git a/lib/CodeGen/CGDeclCXX.cpp b/lib/CodeGen/CGDeclCXX.cpp
index 9ffcff2766..4d78ea8f3a 100644
--- a/lib/CodeGen/CGDeclCXX.cpp
+++ b/lib/CodeGen/CGDeclCXX.cpp
@@ -304,6 +304,7 @@ void CodeGenModule::EmitCXXThreadLocalInitFunc() {
     Guard->setThreadLocal(true);
     CodeGenFunction(*this)
         .GenerateCXXGlobalInitFunc(InitFn, CXXThreadLocalInits, Guard);
+    AddTLSInitFunc(InitFn);
   }
 
   getCXXABI().EmitThreadLocalInitFuncs(CXXThreadLocals, InitFn);
diff --git a/lib/CodeGen/CodeGenModule.cpp b/lib/CodeGen/CodeGenModule.cpp
index bf67bd1007..6247b15ce9 100644
--- a/lib/CodeGen/CodeGenModule.cpp
+++ b/lib/CodeGen/CodeGenModule.cpp
@@ -182,6 +182,7 @@ void CodeGenModule::Release() {
       AddGlobalCtor(ObjCInitFunction);
   EmitCtorList(GlobalCtors, "llvm.global_ctors");
   EmitCtorList(GlobalDtors, "llvm.global_dtors");
+  EmitTLSList(TLSInitFuncs);
   EmitGlobalAnnotations();
   EmitStaticExternCAliases();
   EmitLLVMUsed();
@@ -479,6 +480,12 @@ void CodeGenModule::AddGlobalDtor(llvm::Function * Dtor, int Priority) {
   GlobalDtors.push_back(std::make_pair(Dtor, Priority));
 }
 
+/// AddTLSInitFunc - Add a function to the list that will initialize TLS
+/// variables before main() runs.
+void CodeGenModule::AddTLSInitFunc(llvm::Function *Init) {
+  TLSInitFuncs.push_back(Init);
+}
+
 void CodeGenModule::EmitCtorList(const CtorList &Fns, const char *GlobalName) {
   // Ctor function type is void()*.
   llvm::FunctionType* CtorFTy = llvm::FunctionType::get(VoidTy, false);
@@ -507,6 +514,25 @@ void CodeGenModule::EmitCtorList(const CtorList &Fns, const char *GlobalName) {
   }
 }
 
+void CodeGenModule::EmitTLSList(ArrayRef<llvm::Constant*> Fns) {
+  if (Fns.empty()) return;
+
+  // TLS init function types are void()*.
+  llvm::FunctionType* TLSFTy = llvm::FunctionType::get(VoidTy, false);
+  llvm::Type *TLSPFTy = llvm::PointerType::getUnqual(TLSFTy);
+
+  SmallVector<llvm::Constant*, 8> Inits;
+  for (ArrayRef<llvm::Constant*>::iterator I = Fns.begin(),
+         E = Fns.end(); I != E; ++I)
+    Inits.push_back(llvm::ConstantExpr::getBitCast(*I, TLSPFTy));
+
+  llvm::ArrayType *AT = llvm::ArrayType::get(TLSPFTy, Inits.size());
+  new llvm::GlobalVariable(TheModule, AT, false,
+                           llvm::GlobalValue::AppendingLinkage,
+                           llvm::ConstantArray::get(AT, Inits),
+                           "llvm.tls_init_funcs");
+}
+
 llvm::GlobalValue::LinkageTypes
 CodeGenModule::getFunctionLinkage(const FunctionDecl *D) {
   GVALinkage Linkage = getContext().GetGVALinkageForFunction(D);
diff --git a/lib/CodeGen/CodeGenModule.h b/lib/CodeGen/CodeGenModule.h
index 0f4fe8ae51..ca30096dcb 100644
--- a/lib/CodeGen/CodeGenModule.h
+++ b/lib/CodeGen/CodeGenModule.h
@@ -293,6 +293,10 @@ class CodeGenModule : public CodeGenTypeCache {
   /// priorities to be emitted when the translation unit is complete.
   CtorList GlobalDtors;
 
+  /// TLSInitFuncs - Store the list of TLS initialization functions toe be
+  /// emitted with the translation unit is complete.
+  std::vector<llvm::Constant*> TLSInitFuncs;
+
   /// MangledDeclNames - A map of canonical GlobalDecls to their mangled names.
   llvm::DenseMap<GlobalDecl, StringRef> MangledDeclNames;
   llvm::BumpPtrAllocator MangledNamesAllocator;
@@ -1053,11 +1057,18 @@ private:
   void AddGlobalCtor(llvm::Function *Ctor, int Priority=65535);
   void AddGlobalDtor(llvm::Function *Dtor, int Priority=65535);
 
+  void AddTLSInitFunc(llvm::Function *Init);
+
   /// EmitCtorList - Generates a global array of functions and priorities using
   /// the given list and name. This array will have appending linkage and is
   /// suitable for use as a LLVM constructor or destructor array.
   void EmitCtorList(const CtorList &Fns, const char *GlobalName);
 
+  /// EmitTLSList - Generates a global array of functions with the name
+  /// `llvm.tls_init_funcs'. This array will have appending linkage and is meant
+  /// to hold initialization functions for TLS variables.
+  void EmitTLSList(ArrayRef<llvm::Constant*> Fns);
+
   /// EmitFundamentalRTTIDescriptor - Emit the RTTI descriptors for the
   /// given type.
   void EmitFundamentalRTTIDescriptor(QualType Type);
diff --git a/test/CodeGenCXX/tls-init-funcs.cpp b/test/CodeGenCXX/tls-init-funcs.cpp
new file mode 100644
index 0000000000..79b0ea4319
--- /dev/null
+++ b/test/CodeGenCXX/tls-init-funcs.cpp
@@ -0,0 +1,21 @@
+// RUN: %clang_cc1 -triple x86_64-apple-darwin11 -std=c++11 -S -emit-llvm %s -o - | FileCheck -check-prefix=BITCODE %s
+// RUN: %clang_cc1 -triple x86_64-apple-darwin11 -std=c++11 -S %s -o - | FileCheck -check-prefix=ASM %s
+
+// BITCODE: @llvm.tls_init_funcs = appending global [1 x void ()*] [void ()* @__tls_init]
+
+struct A {
+  A();
+};
+
+struct B {
+  int i;
+  B(int i);
+};
+
+thread_local int i = 37;
+thread_local A a;
+thread_local B b(927);
+
+// ASM: .section __DATA,__thread_init,thread_local_init_function_pointers
+// ASM: .align 3
+// ASM: .quad ___tls_init
-- 
2.40.0