commit 35ab328e942259b6ebb75785f54abbfdf6f50d93
author David Majnemer <david.majnemer@gmail.com> Wed Jun 11 04:08:55 2014 +0000
committer David Majnemer <david.majnemer@gmail.com> Wed Jun 11 04:08:55 2014 +0000
tree cc50a07928a9a2b04cbbff3a9aae354bfc8eca6e
parent a813d608a943579804eb9f12c8ede2955bb3a777

CodeGen: Correct linkage of thread_local for OS X

The backing store of thread local variables is internal for OS X and all
accesses must go through the thread wrapper.

However, individual TUs may have inlined through the thread wrapper.
To fix this, give the thread wrapper functions WeakAnyLinkage.  This
prevents them from getting inlined into call-sites.

This fixes PR19989.

llvm-svn: 210632

clang/lib/CodeGen/ItaniumCXXABI.cpp

diff --git a/clang/lib/CodeGen/ItaniumCXXABI.cpp b/clang/lib/CodeGen/ItaniumCXXABI.cpp
index 86eb36d..be8dac1 100644
--- a/clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -1575,11 +1575,21 @@
 /// Get the appropriate linkage for the wrapper function. This is essentially
 /// the weak form of the variable's linkage; every translation unit which wneeds
 /// the wrapper emits a copy, and we want the linker to merge them.
-static llvm::GlobalValue::LinkageTypes getThreadLocalWrapperLinkage(
-    llvm::GlobalValue::LinkageTypes VarLinkage) {
+static llvm::GlobalValue::LinkageTypes
+getThreadLocalWrapperLinkage(const VarDecl *VD, CodeGen::CodeGenModule &CGM) {
+  llvm::GlobalValue::LinkageTypes VarLinkage =
+      CGM.getLLVMLinkageVarDefinition(VD, /*isConstant=*/false);
+
   // For internal linkage variables, we don't need an external or weak wrapper.
   if (llvm::GlobalValue::isLocalLinkage(VarLinkage))
     return VarLinkage;
+
+  // All accesses to the thread_local variable go through the thread wrapper.
+  // However, this means that we cannot allow the thread wrapper to get inlined
+  // into any functions.
+  if (VD->getTLSKind() == VarDecl::TLS_Dynamic &&
+      CGM.getTarget().getTriple().isMacOSX())
+    return llvm::GlobalValue::WeakAnyLinkage;
   return llvm::GlobalValue::WeakODRLinkage;
 }
 
@@ -1602,10 +1612,9 @@
     RetTy = RetTy->getPointerElementType();
 
   llvm::FunctionType *FnTy = llvm::FunctionType::get(RetTy, false);
-  llvm::Function *Wrapper = llvm::Function::Create(
-      FnTy, getThreadLocalWrapperLinkage(
-                CGM.getLLVMLinkageVarDefinition(VD, /*isConstant=*/false)),
-      WrapperName.str(), &CGM.getModule());
+  llvm::Function *Wrapper =
+      llvm::Function::Create(FnTy, getThreadLocalWrapperLinkage(VD, CGM),
+                             WrapperName.str(), &CGM.getModule());
   // Always resolve references to the wrapper at link time.
   if (!Wrapper->hasLocalLinkage())
     Wrapper->setVisibility(llvm::GlobalValue::HiddenVisibility);