[PATCH] MS ABI: Implement thread_local for global variables

[Reid Kleckner]

================
Comment at: lib/CodeGen/CGCXXABI.h:449-450
@@ -448,1 +448,4 @@
 
+  /// Return whether the __tls_init function require a guard variable.
+  virtual bool requiresTLSGuard() const = 0;
+
----------------
This method appears dead now.

================
Comment at: lib/CodeGen/CGCXXABI.h:493
@@ -489,3 +492,3 @@
   virtual void registerGlobalDtor(CodeGenFunction &CGF, const VarDecl &D,
                                   llvm::Constant *dtor, llvm::Constant *addr);
 
----------------
Make this pure and delete the generic CGCXXABI implementation now?

================
Comment at: lib/CodeGen/CGCXXABI.h:500-501
@@ -496,4 +499,4 @@
   ///
   /// \param Decls The thread_local declarations in this translation unit.
   /// \param InitFunc If this translation unit contains any non-constant
   ///        initialization or non-trivial destruction for thread_local
----------------
Can you update or delete the doxygen? IIRC there are clang warnings that detect parameter name mismatches like this.

================
Comment at: lib/CodeGen/ItaniumCXXABI.cpp:237-238
@@ -236,2 +236,4 @@
 
+  virtual bool requiresTLSGuard() const override { return true; }
+
   llvm::Function *getOrCreateThreadLocalWrapper(const VarDecl *VD,
----------------
dead

================
Comment at: lib/CodeGen/MicrosoftCXXABI.cpp:274
@@ -261,1 +273,3 @@
+
+  virtual bool requiresTLSGuard() const override { return false; }
 
----------------
dead

================
Comment at: lib/CodeGen/MicrosoftCXXABI.cpp:1780
@@ +1779,3 @@
+
+  std::vector<llvm::Function *> NondiscardableInits;
+  for (size_t I = 0, E = CXXThreadLocalInitVars.size(); I != E; ++I) {
----------------
"Nondiscardable" seems like the wrong name. Perhaps "NonComdatInits" or "TUOrderedInits"?

================
Comment at: lib/CodeGen/MicrosoftCXXABI.cpp:1801-1803
@@ +1800,5 @@
+  if (!NondiscardableInits.empty()) {
+    llvm::Function *InitFunc =
+        CGM.CreateGlobalInitOrDestructFunction(FTy, "__tls_init",
+                                               /*TLS=*/true);
+    CodeGenFunction(CGM)
----------------
One possible alternative is to build a single global in the .CRT$XDU section that is an ordered array of all the thread local initializers that need to be run. I guess you considered and rejected this, because the single function allows for more optimization?

================
Comment at: test/CodeGenCXX/ms-thread_local.cpp:21
@@ +20,2 @@
+  (void)b;
+}
----------------
Maybe add some code CHECKs like:
  // CHECK-LABEL: define internal void @__tls_init()
  // CHECK: call void @"\01??__E?b@@3UA@@A"()

http://reviews.llvm.org/D5597