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

2 files changed, 115 insertions, 29 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 8a0854628a6..bf1b628aff8 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -343,8 +343,58 @@ MCSymbol *AsmPrinter::getSymbol(const GlobalValue *GV) const {
   return TM.getSymbol(GV, *Mang);
 }
 
+static MCSymbol *getOrCreateEmuTLSControlSym(MCSymbol *GVSym, MCContext &C) {
+  return C.getOrCreateSymbol(Twine("__emutls_v.") + GVSym->getName());
+}
+
+static MCSymbol *getOrCreateEmuTLSInitSym(MCSymbol *GVSym, MCContext &C) {
+  return C.getOrCreateSymbol(Twine("__emutls_t.") + GVSym->getName());
+}
+
+/// EmitEmulatedTLSControlVariable - Emit the control variable for an emulated TLS variable.
+void AsmPrinter::EmitEmulatedTLSControlVariable(const GlobalVariable *GV,
+                                                MCSymbol *EmittedSym,
+                                                bool AllZeroInitValue) {
+  // If there is init value, use .data.rel.local section;
+  // otherwise use the .data section.
+  MCSection *TLSVarSection = const_cast<MCSection*>(
+      (GV->hasInitializer() && !AllZeroInitValue)
+      ? getObjFileLowering().getDataRelLocalSection()
+      : getObjFileLowering().getDataSection());
+  OutStreamer->SwitchSection(TLSVarSection);
+  MCSymbol *GVSym = getSymbol(GV);
+  EmitLinkage(GV, EmittedSym);  // same linkage as GV
+  const DataLayout &DL = GV->getParent()->getDataLayout();
+  uint64_t Size = DL.getTypeAllocSize(GV->getType()->getElementType());
+  unsigned AlignLog = getGVAlignmentLog2(GV, DL);
+  unsigned WordSize = DL.getPointerSize();
+  unsigned Alignment = DL.getPointerABIAlignment();
+  EmitAlignment(Log2_32(Alignment));
+  OutStreamer->EmitLabel(EmittedSym);
+  OutStreamer->EmitIntValue(Size, WordSize);
+  OutStreamer->EmitIntValue((1 << AlignLog), WordSize);
+  OutStreamer->EmitIntValue(0, WordSize);
+  if (GV->hasInitializer() && !AllZeroInitValue) {
+    OutStreamer->EmitSymbolValue(
+        getOrCreateEmuTLSInitSym(GVSym, OutContext), WordSize);
+  } else
+    OutStreamer->EmitIntValue(0, WordSize);
+  if (MAI->hasDotTypeDotSizeDirective())
+    OutStreamer->emitELFSize(cast<MCSymbolELF>(EmittedSym),
+                             MCConstantExpr::create(4 * WordSize, OutContext));
+  OutStreamer->AddBlankLine();  // End of the __emutls_v.* variable.
+}
+
 /// EmitGlobalVariable - Emit the specified global variable to the .s file.
 void AsmPrinter::EmitGlobalVariable(const GlobalVariable *GV) {
+  bool IsEmuTLSVar =
+      GV->getThreadLocalMode() != llvm::GlobalVariable::NotThreadLocal &&
+      TM.Options.EmulatedTLS;
+  assert((!IsEmuTLSVar || getObjFileLowering().getDataRelLocalSection()) &&
+         "Need relocatable local section for emulated TLS variables");
+  assert(!(IsEmuTLSVar && GV->hasCommonLinkage()) &&
+         "No emulated TLS variables in the common section");
+
   if (GV->hasInitializer()) {
     // Check to see if this is a special global used by LLVM, if so, emit it.
     if (EmitSpecialLLVMGlobal(GV))
@@ -355,7 +405,9 @@ void AsmPrinter::EmitGlobalVariable(const GlobalVariable *GV) {
     if (GlobalGOTEquivs.count(getSymbol(GV)))
       return;
 
-    if (isVerbose()) {
+    if (isVerbose() && !IsEmuTLSVar) {
+      // When printing the control variable __emutls_v.*,
+      // we don't need to print the original TLS variable name.
       GV->printAsOperand(OutStreamer->GetCommentOS(),
                      /*PrintType=*/false, GV->getParent());
       OutStreamer->GetCommentOS() << '\n';
@@ -363,7 +415,12 @@ void AsmPrinter::EmitGlobalVariable(const GlobalVariable *GV) {
   }
 
   MCSymbol *GVSym = getSymbol(GV);
-  EmitVisibility(GVSym, GV->getVisibility(), !GV->isDeclaration());
+  MCSymbol *EmittedSym = IsEmuTLSVar ?
+      getOrCreateEmuTLSControlSym(GVSym, OutContext) : GVSym;
+  // getOrCreateEmuTLSControlSym only creates the symbol with name and default attributes.
+  // GV's or GVSym's attributes will be used for the EmittedSym.
+
+  EmitVisibility(EmittedSym, GV->getVisibility(), !GV->isDeclaration());
 
   if (!GV->hasInitializer())   // External globals require no extra code.
     return;
@@ -374,7 +431,7 @@ void AsmPrinter::EmitGlobalVariable(const GlobalVariable *GV) {
                        "' is already defined");
 
   if (MAI->hasDotTypeDotSizeDirective())
-    OutStreamer->EmitSymbolAttribute(GVSym, MCSA_ELF_TypeObject);
+    OutStreamer->EmitSymbolAttribute(EmittedSym, MCSA_ELF_TypeObject);
 
   SectionKind GVKind = TargetLoweringObjectFile::getKindForGlobal(GV, TM);
 
@@ -386,6 +443,18 @@ void AsmPrinter::EmitGlobalVariable(const GlobalVariable *GV) {
   // sections and expected to be contiguous (e.g. ObjC metadata).
   unsigned AlignLog = getGVAlignmentLog2(GV, DL);
 
+  bool AllZeroInitValue = false;
+  const Constant *InitValue = GV->getInitializer();
+  if (isa<ConstantAggregateZero>(InitValue))
+    AllZeroInitValue = true;
+  else {
+    const ConstantInt *InitIntValue = dyn_cast<ConstantInt>(InitValue);
+    if (InitIntValue && InitIntValue->isZero())
+      AllZeroInitValue = true;
+  }
+  if (IsEmuTLSVar)
+    EmitEmulatedTLSControlVariable(GV, EmittedSym, AllZeroInitValue);
+
   for (const HandlerInfo &HI : Handlers) {
     NamedRegionTimer T(HI.TimerName, HI.TimerGroupName, TimePassesIsEnabled);
     HI.Handler->setSymbolSize(GVSym, Size);
@@ -393,6 +462,8 @@ void AsmPrinter::EmitGlobalVariable(const GlobalVariable *GV) {
 
   // Handle common and BSS local symbols (.lcomm).
   if (GVKind.isCommon() || GVKind.isBSSLocal()) {
+    assert(!(IsEmuTLSVar && GVKind.isCommon()) &&
+           "No emulated TLS variables in the common section");
     if (Size == 0) Size = 1;   // .comm Foo, 0 is undefined, avoid it.
     unsigned Align = 1 << AlignLog;
 
@@ -437,12 +508,21 @@ void AsmPrinter::EmitGlobalVariable(const GlobalVariable *GV) {
     return;
   }
 
-  MCSection *TheSection =
+  if (IsEmuTLSVar && AllZeroInitValue)
+    return;  // No need of initialization values.
+
+  MCSymbol *EmittedInitSym = IsEmuTLSVar ?
+      getOrCreateEmuTLSInitSym(GVSym, OutContext) : GVSym;
+  // getOrCreateEmuTLSInitSym only creates the symbol with name and default attributes.
+  // GV's or GVSym's attributes will be used for the EmittedInitSym.
+
+  MCSection *TheSection = IsEmuTLSVar ?
+      getObjFileLowering().getReadOnlySection() :
       getObjFileLowering().SectionForGlobal(GV, GVKind, *Mang, TM);
 
   // Handle the zerofill directive on darwin, which is a special form of BSS
   // emission.
-  if (GVKind.isBSSExtern() && MAI->hasMachoZeroFillDirective()) {
+  if (GVKind.isBSSExtern() && MAI->hasMachoZeroFillDirective() && !IsEmuTLSVar) {
     if (Size == 0) Size = 1;  // zerofill of 0 bytes is undefined.
 
     // .globl _foo
@@ -462,7 +542,7 @@ void AsmPrinter::EmitGlobalVariable(const GlobalVariable *GV) {
   // TLOF class.  This will also make it more obvious that stuff like
   // MCStreamer::EmitTBSSSymbol is macho specific and only called from macho
   // specific code.
-  if (GVKind.isThreadLocal() && MAI->hasMachoTBSSDirective()) {
+  if (GVKind.isThreadLocal() && MAI->hasMachoTBSSDirective() && !IsEmuTLSVar) {
     // Emit the .tbss symbol
     MCSymbol *MangSym =
       OutContext.getOrCreateSymbol(GVSym->getName() + Twine("$tlv$init"));
@@ -506,16 +586,18 @@ void AsmPrinter::EmitGlobalVariable(const GlobalVariable *GV) {
 
   OutStreamer->SwitchSection(TheSection);
 
-  EmitLinkage(GV, GVSym);
+  // emutls_t.* symbols are only used in the current compilation unit.
+  if (!IsEmuTLSVar)
+    EmitLinkage(GV, EmittedInitSym);
   EmitAlignment(AlignLog, GV);
 
-  OutStreamer->EmitLabel(GVSym);
+  OutStreamer->EmitLabel(EmittedInitSym);
 
   EmitGlobalConstant(GV->getParent()->getDataLayout(), GV->getInitializer());
 
   if (MAI->hasDotTypeDotSizeDirective())
     // .size foo, 42
-    OutStreamer->emitELFSize(cast<MCSymbolELF>(GVSym),
+    OutStreamer->emitELFSize(cast<MCSymbolELF>(EmittedInitSym),
                              MCConstantExpr::create(Size, OutContext));
 
   OutStreamer->AddBlankLine();
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);