[gcc compatibility]Add support for ".stabs" directive

[myatsina]

Summary

The ".stabs" has the following format:
.stabs "string",type,other,desc,value
where type, other, desc and value are numbers.

The ".stabs" directive should be emitted as is to the generated assembly. This is in compatibility with GCC.

[• rafael]

This needs a testcase.

What is the longer term objective? Do you intent to add support to the object streamer? What is still using stabs?

lib/MC/MCObjectStreamer.cpp

314

Why call an empty function?

include/llvm/MC/MCObjectStreamer.h

void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
                             unsigned MaxBytesToEmit = 0) override;
   void EmitCodeAlignment(unsigned ByteAlignment,
                          unsigned MaxBytesToEmit = 0) override;
   void emitValueToOffset(const MCExpr *Offset, unsigned char Value) override;
   void EmitDwarfLocDirective(unsigned FileNo, unsigned Line,
                              unsigned Column, unsigned Flags,
                              unsigned Isa, unsigned Discriminator,
                              StringRef FileName) override;
+  void EmitStabs(StringRef Str, unsigned Type, unsigned Other, unsigned Desc,
+                 unsigned Value) override;
   void EmitDwarfAdvanceLineAddr(int64_t LineDelta, const MCSymbol *LastLabel,
                                 const MCSymbol *Label,
                                 unsigned PointerSize);
   void EmitDwarfAdvanceFrameAddr(const MCSymbol *LastLabel,
                                  const MCSymbol *Label);
   void EmitCVLocDirective(unsigned FunctionId, unsigned FileNo, unsigned Line,
                           unsigned Column, bool PrologueEnd, bool IsStmt,
                           StringRef FileName) override;

include/llvm/MC/MCStreamer.h

public:
 
   /// \brief This implements the DWARF2 '.loc fileno lineno ...' assembler
   /// directive.
   virtual void EmitDwarfLocDirective(unsigned FileNo, unsigned Line,
                                      unsigned Column, unsigned Flags,
                                      unsigned Isa, unsigned Discriminator,
                                      StringRef FileName);
 
+  /// \brief This implements the '.stabs' assembler directive.
+  virtual void EmitStabs(StringRef Str, unsigned Type, unsigned Other,
+                         unsigned Desc, unsigned Value);
+
   /// \brief Associate a filename with a specified logical file number.  This
   /// implements the '.cv_file 4 "foo.c"' assembler directive.
   virtual unsigned EmitCVFileDirective(unsigned FileNo, StringRef Filename);
 
   /// \brief This implements the CodeView '.cv_loc' assembler directive.
   virtual void EmitCVLocDirective(unsigned FunctionId, unsigned FileNo,
                                   unsigned Line, unsigned Column,
                                   bool PrologueEnd, bool IsStmt,

lib/MC/MCAsmStreamer.cpp

public:
   void EmitFileDirective(StringRef Filename) override;
   unsigned EmitDwarfFileDirective(unsigned FileNo, StringRef Directory,
                                   StringRef Filename,
                                   unsigned CUID = 0) override;
   void EmitDwarfLocDirective(unsigned FileNo, unsigned Line,
                              unsigned Column, unsigned Flags,
                              unsigned Isa, unsigned Discriminator,
                              StringRef FileName) override;
+  void EmitStabs(StringRef Str, unsigned Type, unsigned Other, unsigned Desc,
+                 unsigned Value) override;
   MCSymbol *getDwarfLineTableSymbol(unsigned CUID) override;
 
   unsigned EmitCVFileDirective(unsigned FileNo, StringRef Filename) override;
   void EmitCVLocDirective(unsigned FunctionId, unsigned FileNo, unsigned Line,
                           unsigned Column, bool PrologueEnd, bool IsStmt,
                           StringRef FileName) override;
   void EmitCVLinetableDirective(unsigned FunctionId, const MCSymbol *FnStart,
                                 const MCSymbol *FnEnd) override;
if (IsVerboseAsm) {
     OS << MAI->getCommentString() << ' ' << FileName << ':'
        << Line << ':' << Column;
   }
   EmitEOL();
   this->MCStreamer::EmitDwarfLocDirective(FileNo, Line, Column, Flags,
                                           Isa, Discriminator, FileName);
 }
 
+void MCAsmStreamer::EmitStabs(StringRef Str, unsigned Type, unsigned Other,
+                              unsigned Desc, unsigned Value) {
+  OS << "\t.stabs\t"
+     << "\"" << Str << "\""
+     << "," << Type << "," << Other << "," << Desc << "," << Value;
+}
+
 MCSymbol *MCAsmStreamer::getDwarfLineTableSymbol(unsigned CUID) {
   // Always use the zeroth line table, since asm syntax only supports one line
   // table for now.
   return MCStreamer::getDwarfLineTableSymbol(0);
 }
 
 unsigned MCAsmStreamer::EmitCVFileDirective(unsigned FileNo,
                                             StringRef Filename) {

lib/MC/MCObjectStreamer.cpp

void MCObjectStreamer::EmitDwarfLocDirective(unsigned FileNo, unsigned Line,
   // In case we see two .loc directives in a row, make sure the
   // first one gets a line entry.
   MCDwarfLineEntry::Make(this, getCurrentSection().first);
 
   this->MCStreamer::EmitDwarfLocDirective(FileNo, Line, Column, Flags,
                                           Isa, Discriminator, FileName);
 }
 
+void MCObjectStreamer::EmitStabs(StringRef Str, unsigned Type, unsigned Other,
+                                 unsigned Desc, unsigned Value) {
+  this->MCStreamer::EmitStabs(Str, Type, Other, Desc, Value);
+}
+
 static const MCExpr *buildSymbolDiff(MCObjectStreamer &OS, const MCSymbol *A,
                                      const MCSymbol *B) {
   MCContext &Context = OS.getContext();
   MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
   const MCExpr *ARef = MCSymbolRefExpr::create(A, Variant, Context);
   const MCExpr *BRef = MCSymbolRefExpr::create(B, Variant, Context);
   const MCExpr *AddrDelta =
       MCBinaryExpr::create(MCBinaryExpr::Sub, ARef, BRef, Context);

lib/MC/MCParser/AsmParser.cpp

getStreamer().EmitDwarfLocDirective(FileNumber, LineNumber, ColumnPos, Flags,
                                       Isa, Discriminator, StringRef());
 
   return false;
 }
 
 /// parseDirectiveStabs
 /// ::= .stabs string, number, number, number
 bool AsmParser::parseDirectiveStabs() {
-  return TokError("unsupported directive '.stabs'");
+  std::string ErrorMsg = "Unexpexted format, expected format is: .stabs "
+                         "string, number, number, number";
+
+  if (getLexer().is(AsmToken::EndOfStatement))
+    return TokError(ErrorMsg);
+
+  if (getLexer().isNot(AsmToken::String))
+    return TokError(ErrorMsg);
+  StringRef Str = Lexer.getTok().getStringContents();
+  Lex(); // Eat string
+
+  unsigned Number[4];
+  for (int i = 0; i < 4; ++i) {
+    if (getLexer().isNot(AsmToken::Comma))
+      return TokError(ErrorMsg);
+    Lex(); // Eat comma
+
+    if (getLexer().isNot(AsmToken::Integer))
+      return TokError(ErrorMsg);
+    Number[i] = getLexer().getTok().getIntVal();
+    Lex(); // Eat integer number
+  }
+  if (getLexer().isNot(AsmToken::EndOfStatement))
+    return TokError(ErrorMsg);
+
+  getStreamer().EmitStabs(Str, Number[0], Number[1], Number[2], Number[3]);
+
+  return false;
 }
 
 /// parseDirectiveCVFile
 /// ::= .cv_file number filename
 bool AsmParser::parseDirectiveCVFile() {
   SMLoc FileNumberLoc = getLexer().getLoc();
   if (getLexer().isNot(AsmToken::Integer))
     return TokError("expected file number in '.cv_file' directive");

lib/MC/MCStreamer.cpp

void MCStreamer::EmitDwarfLocDirective(unsigned FileNo, unsigned Line,
                                        unsigned Column, unsigned Flags,
                                        unsigned Isa,
                                        unsigned Discriminator,
                                        StringRef FileName) {
   getContext().setCurrentDwarfLoc(FileNo, Line, Column, Flags, Isa,
                                   Discriminator);
 }
 
+void MCStreamer::EmitStabs(StringRef Str, unsigned Type, unsigned Other,
+                           unsigned Desc, unsigned Value) {}
+
 MCSymbol *MCStreamer::getDwarfLineTableSymbol(unsigned CUID) {
   MCDwarfLineTable &Table = getContext().getMCDwarfLineTable(CUID);
   if (!Table.getLabel()) {
     StringRef Prefix = Context.getAsmInfo()->getPrivateGlobalPrefix();
     Table.setLabel(
         Context.getOrCreateSymbol(Prefix + "line_table_start" + Twine(CUID)));
   }
   return Table.getLabel();