Extend the IL for selecting TLS models (PR9788)

This allows the user/front-end to specify a model that is better
than what LLVM would choose by default. For example, a variable
might be declared as

  @x = thread_local(initialexec) global i32 42

if it will not be used in a shared library that is dlopen'ed.

If the specified model isn't supported by the target, or if LLVM can
make a better choice, a different model may be used.

llvm-svn: 159077

1 files changed, 15 insertions, 4 deletions

diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 83756daa7ae..4a20b1c9d6e 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -102,6 +102,17 @@ static GlobalValue::VisibilityTypes GetDecodedVisibility(unsigned Val) {
   }
 }
 
+static GlobalVariable::ThreadLocalMode GetDecodedThreadLocalMode(unsigned Val) {
+  switch (Val) {
+    case 0: return GlobalVariable::NotThreadLocal;
+    default: // Map unknown non-zero value to general dynamic.
+    case 1: return GlobalVariable::GeneralDynamicTLSModel;
+    case 2: return GlobalVariable::LocalDynamicTLSModel;
+    case 3: return GlobalVariable::InitialExecTLSModel;
+    case 4: return GlobalVariable::LocalExecTLSModel;
+  }
+}
+
 static int GetDecodedCastOpcode(unsigned Val) {
   switch (Val) {
   default: return -1;
@@ -1544,9 +1555,10 @@ bool BitcodeReader::ParseModule(bool Resume) {
       GlobalValue::VisibilityTypes Visibility = GlobalValue::DefaultVisibility;
       if (Record.size() > 6)
         Visibility = GetDecodedVisibility(Record[6]);
-      bool isThreadLocal = false;
+
+      GlobalVariable::ThreadLocalMode TLM = GlobalVariable::NotThreadLocal;
       if (Record.size() > 7)
-        isThreadLocal = Record[7];
+        TLM = GetDecodedThreadLocalMode(Record[7]);
 
       bool UnnamedAddr = false;
       if (Record.size() > 8)
@@ -1554,12 +1566,11 @@ bool BitcodeReader::ParseModule(bool Resume) {
 
       GlobalVariable *NewGV =
         new GlobalVariable(*TheModule, Ty, isConstant, Linkage, 0, "", 0,
-                           isThreadLocal, AddressSpace);
+                           TLM, AddressSpace);
       NewGV->setAlignment(Alignment);
       if (!Section.empty())
         NewGV->setSection(Section);
       NewGV->setVisibility(Visibility);
-      NewGV->setThreadLocal(isThreadLocal);
       NewGV->setUnnamedAddr(UnnamedAddr);
 
       ValueList.push_back(NewGV);