[NFC] clean up the AsmPrinter::emitLinkage for AIX part

[DiggerLin]

Summary

Since we deal with aix emitLinkage in the PPCAIXAsmPrinter::emitLinkage() in the patch https://reviews.llvm.org/D75866. It do not go to AsmPrinter::emitLinkage() any more, we clean up some aix related code in the AsmPrinter::emitLinkage()

[jasonliu]

LGTM with minor nit.

llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

423–424

nit: remove this return.

llvm/include/llvm/MC/MCAsmInfo.h

protected:
   /// True if this target supports the MachO .no_dead_strip directive.  Defaults
   /// to false.
   bool HasNoDeadStrip = false;
 
   /// True if this target supports the MachO .alt_entry directive.  Defaults to
   /// false.
   bool HasAltEntry = false;
 
-  /// True if this target supports the XCOFF .extern directive.  Defaults to
-  /// false.
-  bool HasDotExternDirective = false;
-
   /// Used to declare a global as being a weak symbol. Defaults to ".weak".
   const char *WeakDirective;
 
   /// This directive, if non-null, is used to declare a global as being a weak
   /// undefined symbol.  Defaults to nullptr.
   const char *WeakRefDirective = nullptr;
 
   /// True if we have a directive to declare a global as being a weak defined
   /// symbol.  Defaults to false.
   bool HasWeakDefDirective = false;
 
   /// True if we have a directive to declare a global as being a weak defined
   /// symbol that can be hidden (unexported).  Defaults to false.
   bool HasWeakDefCanBeHiddenDirective = false;
 
   /// True if we should mark symbols as global instead of weak, for
   /// weak*/linkonce*, if the symbol has a comdat.
   /// Defaults to false.
   bool AvoidWeakIfComdat = false;
 
-  /// True if we have a .lglobl directive, which is used to emit the information
-  /// of a static symbol into the symbol table. Defaults to false.
-  bool HasDotLGloblDirective = false;
-
   /// This attribute, if not MCSA_Invalid, is used to declare a symbol as having
   /// hidden visibility.  Defaults to MCSA_Hidden.
   MCSymbolAttr HiddenVisibilityAttr = MCSA_Hidden;
 
   /// This attribute, if not MCSA_Invalid, is used to declare an undefined
   /// symbol as having hidden visibility. Defaults to MCSA_Hidden.
   MCSymbolAttr HiddenDeclarationVisibilityAttr = MCSA_Hidden;
 
public:
   }
 
   bool hasFunctionAlignment() const { return HasFunctionAlignment; }
   bool hasDotTypeDotSizeDirective() const { return HasDotTypeDotSizeDirective; }
   bool hasSingleParameterDotFile() const { return HasSingleParameterDotFile; }
   bool hasIdentDirective() const { return HasIdentDirective; }
   bool hasNoDeadStrip() const { return HasNoDeadStrip; }
   bool hasAltEntry() const { return HasAltEntry; }
-  bool hasDotExternDirective() const { return HasDotExternDirective; }
   const char *getWeakDirective() const { return WeakDirective; }
   const char *getWeakRefDirective() const { return WeakRefDirective; }
   bool hasWeakDefDirective() const { return HasWeakDefDirective; }
 
   bool hasWeakDefCanBeHiddenDirective() const {
     return HasWeakDefCanBeHiddenDirective;
   }
 
   bool avoidWeakIfComdat() const { return AvoidWeakIfComdat; }
 
-  bool hasDotLGloblDirective() const { return HasDotLGloblDirective; }
-
   MCSymbolAttr getHiddenVisibilityAttr() const { return HiddenVisibilityAttr; }
 
   MCSymbolAttr getHiddenDeclarationVisibilityAttr() const {
     return HiddenDeclarationVisibilityAttr;
   }
 
   MCSymbolAttr getProtectedVisibilityAttr() const {
     return ProtectedVisibilityAttr;

llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

static bool canBeHidden(const GlobalValue *GV, const MCAsmInfo &MAI) {
 
   return GV->canBeOmittedFromSymbolTable();
 }
 
 void AsmPrinter::emitLinkage(const GlobalValue *GV, MCSymbol *GVSym) const {
   GlobalValue::LinkageTypes Linkage = GV->getLinkage();
   switch (Linkage) {
   case GlobalValue::CommonLinkage:
-    assert(!TM.getTargetTriple().isOSBinFormatXCOFF() &&
-           "CommonLinkage of XCOFF should not come to this path.");
-    LLVM_FALLTHROUGH;
   case GlobalValue::LinkOnceAnyLinkage:
   case GlobalValue::LinkOnceODRLinkage:
   case GlobalValue::WeakAnyLinkage:
   case GlobalValue::WeakODRLinkage:
     if (MAI->hasWeakDefDirective()) {
       // .globl _foo
       OutStreamer->emitSymbolAttribute(GVSym, MCSA_Global);
 
       if (!canBeHidden(GV, *MAI))
         // .weak_definition _foo
         OutStreamer->emitSymbolAttribute(GVSym, MCSA_WeakDefinition);
       else
         OutStreamer->emitSymbolAttribute(GVSym, MCSA_WeakDefAutoPrivate);
     } else if (MAI->avoidWeakIfComdat() && GV->hasComdat()) {
       // .globl _foo
       OutStreamer->emitSymbolAttribute(GVSym, MCSA_Global);
       //NOTE: linkonce is handled by the section the symbol was assigned to.
     } else {
       // .weak _foo
       OutStreamer->emitSymbolAttribute(GVSym, MCSA_Weak);
     }
     return;
   case GlobalValue::ExternalLinkage:
-    if (MAI->hasDotExternDirective() && GV->isDeclaration())
-      OutStreamer->emitSymbolAttribute(GVSym, MCSA_Extern);
-    else
-      OutStreamer->emitSymbolAttribute(GVSym, MCSA_Global);
     return;
   case GlobalValue::PrivateLinkage:
-    return;
   case GlobalValue::InternalLinkage:
-    if (MAI->hasDotLGloblDirective())
-      OutStreamer->emitSymbolAttribute(GVSym, MCSA_LGlobal);
     return;
   case GlobalValue::ExternalWeakLinkage:
-    if (TM.getTargetTriple().isOSBinFormatXCOFF()) {
-      OutStreamer->emitSymbolAttribute(GVSym, MCSA_Weak);
-      return;
-    }
-    LLVM_FALLTHROUGH;
   case GlobalValue::AvailableExternallyLinkage:
-    if (MAI->hasDotExternDirective()) {
-      OutStreamer->emitSymbolAttribute(GVSym, MCSA_Extern);
-      return;
-    }
-    LLVM_FALLTHROUGH;
   case GlobalValue::AppendingLinkage:
     llvm_unreachable("Should never emit this");
   }
   llvm_unreachable("Unknown linkage type!");
 }
 
 void AsmPrinter::getNameWithPrefix(SmallVectorImpl<char> &Name,
                                    const GlobalValue *GV) const {

llvm/lib/MC/MCAsmInfoXCOFF.cpp

MCAsmInfoXCOFF::MCAsmInfoXCOFF() {
   // Use .vbyte for data definition to avoid directives that apply an implicit
   // alignment.
   Data16bitsDirective = "\t.vbyte\t2, ";
   Data32bitsDirective = "\t.vbyte\t4, ";
 
   COMMDirectiveAlignmentIsInBytes = false;
   LCOMMDirectiveAlignmentType = LCOMM::Log2Alignment;
   HasDotTypeDotSizeDirective = false;
-  HasDotExternDirective = true;
-  HasDotLGloblDirective = true;
   SymbolsHaveSMC = true;
   UseIntegratedAssembler = false;
   NeedsFunctionDescriptors = true;
 }
 
 bool MCAsmInfoXCOFF::isAcceptableChar(char C) const {
   // QualName is allowed for a MCSymbolXCOFF, and
   // QualName contains '[' and ']'.
   if (C == '[' || C == ']')
     return true;
 
   return MCAsmInfo::isAcceptableChar(C);
 }

llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp

case GlobalValue::ExternalWeakLinkage:
     LinkageAttr = MCSA_Weak;
     break;
   case GlobalValue::AvailableExternallyLinkage:
     LinkageAttr = MCSA_Extern;
     break;
   case GlobalValue::PrivateLinkage:
     return;
   case GlobalValue::InternalLinkage:
-    assert(MAI->hasDotLGloblDirective() &&
-           "Expecting .lglobl to be supported for AIX.");
     OutStreamer->emitSymbolAttribute(GVSym, MCSA_LGlobal);
     return;
   case GlobalValue::AppendingLinkage:
     llvm_unreachable("Should never emit this");
   case GlobalValue::CommonLinkage:
     llvm_unreachable("CommonLinkage of XCOFF should not come to this path");
   }