Don't treat .symver as a regular alias definition

[• espindola]

Summary

This patch starts simplifying the handling of .symver.

For now it just moves the responsibility for creating an alias down to the streamer. With that the asm streamer can pass a .symver unchanged, which is nice since gas cannot parse "foo@bar = zed".

In a followup I hope to move the handling down to the writer so that we don't need special hacks for avoiding breaking names with @@@ on windows.

[vitalybuka]

lib/MC/MCParser/ELFAsmParser.cpp

774

Can we still pass AliasName instead of created Alias ?

[pcc]

LGTM

lib/MC/MCParser/ELFAsmParser.cpp

774

Most clients will want to consume the MCSymbol, so it seems a little simpler to create it here.

[vitalybuka]

lib/MC/MCParser/ELFAsmParser.cpp

774

Then I am sure when to replace @@@ with @ or @@

[vitalybuka]

lib/MC/MCParser/ELFAsmParser.cpp

774

I can e.g. discard already created MCSymbol and replace with new one

[pcc]

lib/MC/MCParser/ELFAsmParser.cpp

774

Either that or see if we can avoid creating the new MCSymbol at all.

[• rafael]

Vitaly Buka via Phabricator via llvm-commits
<[e-mail]> writes:

vitalybuka added inline comments.

Comment at: lib/MC/MCParser/ELFAsmParser.cpp:774

MCSymbol *Sym = getContext().getOrCreateSymbol(Name);

• const MCExpr *Value = MCSymbolRefExpr::create(Sym, getContext()); -
• getStreamer().EmitAssignment(Alias, Value); getStreamer().emitELFSymverDirective(Alias, Sym); return false; ----------------

Can we still pass AliasName instead of created Alias ?

That is what I intend to do in a followup patch. That way we only create
the symbol once we know if @@@ should be a @@ or a @.

Cheers,
Rafael

[• espindola]

r327101

include/llvm/MC/MCELFStreamer.h

public:
   void EmitThumbFunc(MCSymbol *Func) override;
   void EmitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol) override;
   bool EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute) override;
   void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) override;
   void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                         unsigned ByteAlignment) override;
 
   void emitELFSize(MCSymbol *Symbol, const MCExpr *Value) override;
+  void emitELFSymverDirective(MCSymbol *Alias,
+                              const MCSymbol *Aliasee) override;
 
   void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                              unsigned ByteAlignment) override;
 
   void EmitZerofill(MCSection *Section, MCSymbol *Symbol = nullptr,
                     uint64_t Size = 0, unsigned ByteAlignment = 0) override;
   void EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol, uint64_t Size,
                       unsigned ByteAlignment = 0) override;

lib/MC/MCAsmStreamer.cpp

void AddBlankLine() override {
     EmitEOL();
   }
 
   /// @name MCStreamer Interface
   /// @{
 
   void ChangeSection(MCSection *Section, const MCExpr *Subsection) override;
 
+  void emitELFSymverDirective(MCSymbol *Alias,
+                              const MCSymbol *Aliasee) override;
+
   void EmitLOHDirective(MCLOHType Kind, const MCLOHArgs &Args) override;
   void EmitLabel(MCSymbol *Symbol, SMLoc Loc = SMLoc()) override;
 
   void EmitAssemblerFlag(MCAssemblerFlag Flag) override;
   void EmitLinkerOptions(ArrayRef<std::string> Options) override;
   void EmitDataRegion(MCDataRegionType Kind) override;
   void EmitVersionMin(MCVersionMinType Kind, unsigned Major, unsigned Minor,
                       unsigned Update) override;
if (MCTargetStreamer *TS = getTargetStreamer()) {
     TS->changeSection(getCurrentSectionOnly(), Section, Subsection, OS);
   } else {
     Section->PrintSwitchToSection(
         *MAI, getContext().getObjectFileInfo()->getTargetTriple(), OS,
         Subsection);
   }
 }
 
+void MCAsmStreamer::emitELFSymverDirective(MCSymbol *Alias,
+                                           const MCSymbol *Aliasee) {
+  OS << ".symver ";
+  Aliasee->print(OS, MAI);
+  OS << ", ";
+  Alias->print(OS, MAI);
+  EmitEOL();
+}
+
 void MCAsmStreamer::EmitLabel(MCSymbol *Symbol, SMLoc Loc) {
   MCStreamer::EmitLabel(Symbol, Loc);
 
   Symbol->print(OS, MAI);
   OS << MAI->getLabelSuffix();
 
   EmitEOL();
 }

lib/MC/MCELFStreamer.cpp

void MCELFStreamer::EmitCommonSymbol(MCSymbol *S, uint64_t Size,
   cast<MCSymbolELF>(Symbol)
       ->setSize(MCConstantExpr::create(Size, getContext()));
 }
 
 void MCELFStreamer::emitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
   cast<MCSymbolELF>(Symbol)->setSize(Value);
 }
 
+void MCELFStreamer::emitELFSymverDirective(MCSymbol *Alias,
+                                           const MCSymbol *Aliasee) {
+  const MCExpr *Value = MCSymbolRefExpr::create(Aliasee, getContext());
+  EmitAssignment(Alias, Value);
+}
+
 void MCELFStreamer::EmitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
                                           unsigned ByteAlignment) {
   auto *Symbol = cast<MCSymbolELF>(S);
   // FIXME: Should this be caught and done earlier?
   getAssembler().registerSymbol(*Symbol);
   Symbol->setBinding(ELF::STB_LOCAL);
   Symbol->setExternal(false);
   EmitCommonSymbol(Symbol, Size, ByteAlignment);

lib/MC/MCParser/ELFAsmParser.cpp

bool ELFAsmParser::ParseDirectiveSymver(StringRef, SMLoc) {
   if (getParser().parseIdentifier(AliasName))
     return TokError("expected identifier in directive");
 
   if (AliasName.find('@') == StringRef::npos)
     return TokError("expected a '@' in the name");
 
   MCSymbol *Alias = getContext().getOrCreateSymbol(AliasName);
   MCSymbol *Sym = getContext().getOrCreateSymbol(Name);
-  const MCExpr *Value = MCSymbolRefExpr::create(Sym, getContext());
-
-  getStreamer().EmitAssignment(Alias, Value);
   getStreamer().emitELFSymverDirective(Alias, Sym);
   return false;
 }
 
 /// ParseDirectiveVersion
 ///  ::= .version string
 bool ELFAsmParser::ParseDirectiveVersion(StringRef, SMLoc) {
   if (getLexer().isNot(AsmToken::String))
     return TokError("unexpected token in '.version' directive");

lib/Object/RecordStreamer.cpp

 
 void RecordStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                                       unsigned ByteAlignment) {
   markDefined(*Symbol);
 }
 
 void RecordStreamer::emitELFSymverDirective(MCSymbol *Alias,
                                             const MCSymbol *Aliasee) {
+  const MCExpr *Value = MCSymbolRefExpr::create(Aliasee, getContext());
+  EmitAssignment(Alias, Value);
   SymverAliasMap[Aliasee].push_back(Alias);
 }

test/MC/ARM/comment.s

 @CHECK: .long bar
 @CHECK-NOT: @
 @CHECK: .long baz
 @CHECK-NOT: @
 @CHECK: add r0, r0
 @CHECK-NOT: @
 
 @CHECK-LABEL: bar:
-@CHECK: bar1@zed = defined1
-@CHECK: bar3@@zed = defined2
-@CHECK: bar5@@@zed = defined3
+@CHECK: .symver defined1, bar1@zed
+@CHECK: .symver defined2, bar3@@zed
+@CHECK: .symver defined3, bar5@@@zed
 
 @ Make sure we did not mess up the parser state and it still lexes
 @ comments correctly by excluding the @ in normal symbols
 @CHECK-LABEL: far:
 @CHECK:  .long baz
 @CHECK-NOT: @
 
 @ERROR-NOT: error: