Implement target independent TLS compatible with glibc's emutls.c.

The 'common' section TLS is not implemented.
Current C/C++ TLS variables are not placed in common section.
DWARF debug info to get the address of TLS variables is not generated yet.

clang and driver changes in http://reviews.llvm.org/D10524

  Added -femulated-tls flag to select the emulated TLS model,
  which will be used for old targets like Android that do not
  support ELF TLS models.

Added TargetLowering::LowerToTLSEmulatedModel as a target-independent
function to convert a SDNode of TLS variable address to a function call
to __emutls_get_address.

Added into lib/Target/*/*ISelLowering.cpp to call LowerToTLSEmulatedModel
for TLSModel::Emulated. Although all targets supporting ELF TLS models are
enhanced, emulated TLS model has been tested only for Android ELF targets.
Modified AsmPrinter.cpp to print the emutls_v.* and emutls_t.* variables for
emulated TLS variables.
Modified DwarfCompileUnit.cpp to skip some DIE for emulated TLS variabls.

TODO: Add proper DIE for emulated TLS variables.
      Added new unit tests with emulated TLS.

Differential Revision: http://reviews.llvm.org/D10522

llvm-svn: 243438

1 files changed, 24 insertions, 20 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index fc54a2925be..f29ad65129c 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -151,28 +151,32 @@ DIE *DwarfCompileUnit::getOrCreateGlobalVariableDIE(
     DIELoc *Loc = new (DIEValueAllocator) DIELoc;
     const MCSymbol *Sym = Asm->getSymbol(Global);
     if (Global->isThreadLocal()) {
-      // FIXME: Make this work with -gsplit-dwarf.
-      unsigned PointerSize = Asm->getDataLayout().getPointerSize();
-      assert((PointerSize == 4 || PointerSize == 8) &&
-             "Add support for other sizes if necessary");
-      // Based on GCC's support for TLS:
-      if (!DD->useSplitDwarf()) {
-        // 1) Start with a constNu of the appropriate pointer size
-        addUInt(*Loc, dwarf::DW_FORM_data1,
-                PointerSize == 4 ? dwarf::DW_OP_const4u : dwarf::DW_OP_const8u);
-        // 2) containing the (relocated) offset of the TLS variable
-        //    within the module's TLS block.
-        addExpr(*Loc, dwarf::DW_FORM_udata,
-                Asm->getObjFileLowering().getDebugThreadLocalSymbol(Sym));
+      if (Asm->TM.Options.EmulatedTLS) {
+        // TODO: add debug info for emulated thread local mode.
       } else {
-        addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_GNU_const_index);
-        addUInt(*Loc, dwarf::DW_FORM_udata,
-                DD->getAddressPool().getIndex(Sym, /* TLS */ true));
+        // FIXME: Make this work with -gsplit-dwarf.
+        unsigned PointerSize = Asm->getDataLayout().getPointerSize();
+        assert((PointerSize == 4 || PointerSize == 8) &&
+               "Add support for other sizes if necessary");
+        // Based on GCC's support for TLS:
+        if (!DD->useSplitDwarf()) {
+          // 1) Start with a constNu of the appropriate pointer size
+          addUInt(*Loc, dwarf::DW_FORM_data1,
+                  PointerSize == 4 ? dwarf::DW_OP_const4u : dwarf::DW_OP_const8u);
+          // 2) containing the (relocated) offset of the TLS variable
+          //    within the module's TLS block.
+          addExpr(*Loc, dwarf::DW_FORM_udata,
+                  Asm->getObjFileLowering().getDebugThreadLocalSymbol(Sym));
+        } else {
+          addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_GNU_const_index);
+          addUInt(*Loc, dwarf::DW_FORM_udata,
+                  DD->getAddressPool().getIndex(Sym, /* TLS */ true));
+        }
+        // 3) followed by an OP to make the debugger do a TLS lookup.
+        addUInt(*Loc, dwarf::DW_FORM_data1,
+                DD->useGNUTLSOpcode() ? dwarf::DW_OP_GNU_push_tls_address
+                                      : dwarf::DW_OP_form_tls_address);
       }
-      // 3) followed by an OP to make the debugger do a TLS lookup.
-      addUInt(*Loc, dwarf::DW_FORM_data1,
-              DD->useGNUTLSOpcode() ? dwarf::DW_OP_GNU_push_tls_address
-                                    : dwarf::DW_OP_form_tls_address);
     } else {
       DD->addArangeLabel(SymbolCU(this, Sym));
       addOpAddress(*Loc, Sym);