[Mips] Fix debug information for __thread variable

[abeserminji]

Summary

This patch fixes debug information for __thread variable on Mips, using .dtprelword and .dtpreldword directives.

[sdardis]

This looks ok, do you have any comments @aprantl ?

include/llvm/CodeGen/AsmPrinter.h

549–553

Rename this EmitDebugValue and move it to the "Dwarf Emission Helper Routines" section.

[aprantl]

looks fine to me.

[abeserminji]

Comments resolved.

include/llvm/CodeGen/AsmPrinter.h

public:
   /// This callback can be used restore the original mode in case the
   /// inlineasm contains directives to switch modes.
   /// \p StartInfo - the original subtarget info before inline asm
   /// \p EndInfo   - the final subtarget info after parsing the inline asm,
   ///                or NULL if the value is unknown.
   virtual void emitInlineAsmEnd(const MCSubtargetInfo &StartInfo,
                                 const MCSubtargetInfo *EndInfo) const;
 
+  /// Emit the directive and value for debug thread local expression 
+  ///
+  /// \p Value - The value to emit.
+  /// \p Size - The size of the integer (in bytes) to emit.
+  virtual void EmitDebugThreadLocal(const MCExpr *Value, unsigned Size) const;
+
 private:
   /// Private state for PrintSpecial()
   // Assign a unique ID to this machine instruction.
   mutable const MachineInstr *LastMI;
   mutable unsigned LastFn;
   mutable unsigned Counter;
 
   /// This method emits the header for the current function.

lib/CodeGen/AsmPrinter/AsmPrinter.cpp

void AsmPrinter::EmitGlobalVariable(const GlobalVariable *GV) {
   if (MAI->hasDotTypeDotSizeDirective())
     // .size foo, 42
     OutStreamer->emitELFSize(EmittedInitSym,
                              MCConstantExpr::create(Size, OutContext));
 
   OutStreamer->AddBlankLine();
 }
 
+/// Emit the directive and value for debug thread local expression 
+///
+/// \p Value - The value to emit.
+/// \p Size - The size of the integer (in bytes) to emit.
+void AsmPrinter::EmitDebugThreadLocal(const MCExpr *Value,
+                                      unsigned Size) const {
+  OutStreamer->EmitValue(Value, Size);
+}
+
 /// EmitFunctionHeader - This method emits the header for the current
 /// function.
 void AsmPrinter::EmitFunctionHeader() {
   // Print out constants referenced by the function
   EmitConstantPool();
 
   // Print the 'header' of function.
   const Function *F = MF->getFunction();

lib/CodeGen/AsmPrinter/DIE.cpp

 
 //===----------------------------------------------------------------------===//
 // DIEExpr Implementation
 //===----------------------------------------------------------------------===//
 
 /// EmitValue - Emit expression value.
 ///
 void DIEExpr::EmitValue(const AsmPrinter *AP, dwarf::Form Form) const {
-  AP->OutStreamer->EmitValue(Expr, SizeOf(AP, Form));
+  AP->EmitDebugThreadLocal(Expr, SizeOf(AP, Form));
 }
 
 /// SizeOf - Determine size of expression value in bytes.
 ///
 unsigned DIEExpr::SizeOf(const AsmPrinter *AP, dwarf::Form Form) const {
   if (Form == dwarf::DW_FORM_data4) return 4;
   if (Form == dwarf::DW_FORM_sec_offset) return 4;
   if (Form == dwarf::DW_FORM_strp) return 4;

lib/Target/Mips/MipsAsmPrinter.h

public:
   void printMemOperand(const MachineInstr *MI, int opNum, raw_ostream &O);
   void printMemOperandEA(const MachineInstr *MI, int opNum, raw_ostream &O);
   void printFCCOperand(const MachineInstr *MI, int opNum, raw_ostream &O,
                        const char *Modifier = nullptr);
   void printRegisterList(const MachineInstr *MI, int opNum, raw_ostream &O);
   void EmitStartOfAsmFile(Module &M) override;
   void EmitEndOfAsmFile(Module &M) override;
   void PrintDebugValueComment(const MachineInstr *MI, raw_ostream &OS);
+  void EmitDebugThreadLocal(const MCExpr *Value, unsigned Size) const override;
 };
 }
 
 #endif
 

lib/Target/Mips/MipsAsmPrinter.cpp

void MipsAsmPrinter::EmitEndOfAsmFile(Module &M) {
   OutStreamer->SwitchSection(OutContext.getObjectFileInfo()->getTextSection());
 }
 
 void MipsAsmPrinter::PrintDebugValueComment(const MachineInstr *MI,
                                            raw_ostream &OS) {
   // TODO: implement
 }
 
+// Emit directive .dtprelword or .dtpreldword directive
+// and value for debug thread local expression.
+void MipsAsmPrinter::EmitDebugThreadLocal(const MCExpr *Value,
+                                          unsigned Size) const {
+  switch (Size) {
+  case 4:
+    OutStreamer->EmitDTPRel32Value(Value);
+    break;
+  case 8:
+    OutStreamer->EmitDTPRel64Value(Value);
+    break;
+  default:
+    llvm_unreachable("Unexpected size of expression value.");
+  }
+}
+
 // Align all targets of indirect branches on bundle size.  Used only if target
 // is NaCl.
 void MipsAsmPrinter::NaClAlignIndirectJumpTargets(MachineFunction &MF) {
   // Align all blocks that are jumped to through jump table.
   if (MachineJumpTableInfo *JtInfo = MF.getJumpTableInfo()) {
     const std::vector<MachineJumpTableEntry> &JT = JtInfo->getJumpTables();
     for (unsigned I = 0; I < JT.size(); ++I) {
       const std::vector<MachineBasicBlock*> &MBBs = JT[I].MBBs;

lib/Target/Mips/MipsTargetObjectFile.h

public:
 
     /// Return true if this constant should be placed into small data section.
     bool IsConstantInSmallSection(const DataLayout &DL, const Constant *CN,
                                   const TargetMachine &TM) const;
 
     MCSection *getSectionForConstant(const DataLayout &DL, SectionKind Kind,
                                      const Constant *C,
                                      unsigned &Align) const override;
+    /// Describe a TLS variable address within debug info.
+    const MCExpr *getDebugThreadLocalSymbol(const MCSymbol *Sym) const override;
   };
 } // end namespace llvm
 
 #endif

lib/Target/Mips/MipsTargetObjectFile.cpp

MCSection *MipsTargetObjectFile::getSectionForConstant(const DataLayout &DL,
                                                        const Constant *C,
                                                        unsigned &Align) const {
   if (IsConstantInSmallSection(DL, C, *TM))
     return SmallDataSection;
 
   // Otherwise, we work the same as ELF.
   return TargetLoweringObjectFileELF::getSectionForConstant(DL, Kind, C, Align);
 }
+
+const MCExpr *
+MipsTargetObjectFile::getDebugThreadLocalSymbol(const MCSymbol *Sym) const {
+  const MCExpr *Expr =
+      MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_None, getContext());
+  return MCBinaryExpr::createAdd(
+      Expr, MCConstantExpr::create(0x8000, getContext()), getContext());
+}

test/DebugInfo/Mips/tls.ll

+; RUN: llc -O0 -march=mips -mcpu=mips32r2 -filetype=asm < %s | FileCheck %s -check-prefix=CHECK-WORD
+; RUN: llc -O0 -march=mips64 -mcpu=mips64r2 -filetype=asm < %s | FileCheck %s -check-prefix=CHECK-DWORD
+
+@x = thread_local global i32 5, align 4, !dbg !0
+
+; CHECK-WORD: .dtprelword x+32768
+; CHECK-DWORD: .dtpreldword x+32768
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!7, !8}
+!llvm.ident = !{!9}
+
+!0 = !DIGlobalVariableExpression(var: !1)
+!1 = distinct !DIGlobalVariable(name: "x", scope: !2, file: !3, line: 1, type: !6, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 4.0.0", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5)
+!3 = !DIFile(filename: "tls.c", directory: "/tmp")
+!4 = !{}
+!5 = !{!0}
+!6 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!7 = !{i32 2, !"Dwarf Version", i32 4}
+!8 = !{i32 2, !"Debug Info Version", i32 3}
+!9 = !{!"clang version 4.0.0"}