8 files changed, 18 insertions, 4 deletions
diff --git a/llvm/lib/MC/MCAsmStreamer.cpp b/llvm/lib/MC/MCAsmStreamer.cpp
index c11d28b..6f21566 100644
--- a/llvm/lib/MC/MCAsmStreamer.cpp
+++ b/llvm/lib/MC/MCAsmStreamer.cpp
@@ -772,6 +772,9 @@ bool MCAsmStreamer::emitSymbolAttribute(MCSymbol *Symbol,
   case MCSA_Memtag:
     OS << "\t.memtag\t";
     break;
+  case MCSA_WeakAntiDep:
+    OS << "\t.weak_anti_dep\t";
+    break;
   }
 
   Symbol->print(OS, MAI);
diff --git a/llvm/lib/MC/MCELFStreamer.cpp b/llvm/lib/MC/MCELFStreamer.cpp
index 8dd002f..303eb16 100644
--- a/llvm/lib/MC/MCELFStreamer.cpp
+++ b/llvm/lib/MC/MCELFStreamer.cpp
@@ -216,6 +216,7 @@ bool MCELFStreamer::emitSymbolAttribute(MCSymbol *S, MCSymbolAttr Attribute) {
   case MCSA_Invalid:
   case MCSA_IndirectSymbol:
   case MCSA_Exported:
+  case MCSA_WeakAntiDep:
     return false;
 
   case MCSA_NoDeadStrip:
diff --git a/llvm/lib/MC/MCExpr.cpp b/llvm/lib/MC/MCExpr.cpp
index 04682fd..68cd88f 100644
--- a/llvm/lib/MC/MCExpr.cpp
+++ b/llvm/lib/MC/MCExpr.cpp
@@ -761,6 +761,9 @@ bool MCExpr::evaluateAsValue(MCValue &Res, const MCAsmLayout &Layout) const {
 }
 
 static bool canExpand(const MCSymbol &Sym, bool InSet) {
+  if (Sym.isWeakExternal())
+    return false;
+
   const MCExpr *Expr = Sym.getVariableValue();
   const auto *Inner = dyn_cast<MCSymbolRefExpr>(Expr);
   if (Inner) {
diff --git a/llvm/lib/MC/MCMachOStreamer.cpp b/llvm/lib/MC/MCMachOStreamer.cpp
index 986c0c2c..6711ff9 100644
--- a/llvm/lib/MC/MCMachOStreamer.cpp
+++ b/llvm/lib/MC/MCMachOStreamer.cpp
@@ -358,6 +358,7 @@ bool MCMachOStreamer::emitSymbolAttribute(MCSymbol *Sym,
   case MCSA_LGlobal:
   case MCSA_Exported:
   case MCSA_Memtag:
+  case MCSA_WeakAntiDep:
     return false;
 
   case MCSA_Global:
diff --git a/llvm/lib/MC/MCParser/AsmParser.cpp b/llvm/lib/MC/MCParser/AsmParser.cpp
index c49e513..254c747 100644
--- a/llvm/lib/MC/MCParser/AsmParser.cpp
+++ b/llvm/lib/MC/MCParser/AsmParser.cpp
@@ -6371,7 +6371,7 @@ static bool isSymbolUsedInExpression(const MCSymbol *Sym, const MCExpr *Value) {
   case MCExpr::SymbolRef: {
     const MCSymbol &S =
         static_cast<const MCSymbolRefExpr *>(Value)->getSymbol();
-    if (S.isVariable())
+    if (S.isVariable() && !S.isWeakExternal())
       return isSymbolUsedInExpression(Sym, S.getVariableValue());
     return &S == Sym;
   }
diff --git a/llvm/lib/MC/MCParser/COFFAsmParser.cpp b/llvm/lib/MC/MCParser/COFFAsmParser.cpp
index fc3d1e9..3f88257 100644
--- a/llvm/lib/MC/MCParser/COFFAsmParser.cpp
+++ b/llvm/lib/MC/MCParser/COFFAsmParser.cpp
@@ -67,6 +67,7 @@ class COFFAsmParser : public MCAsmParserExtension {
     addDirectiveHandler<&COFFAsmParser::ParseDirectiveLinkOnce>(".linkonce");
     addDirectiveHandler<&COFFAsmParser::ParseDirectiveRVA>(".rva");
     addDirectiveHandler<&COFFAsmParser::ParseDirectiveSymbolAttribute>(".weak");
+    addDirectiveHandler<&COFFAsmParser::ParseDirectiveSymbolAttribute>(".weak_anti_dep");
     addDirectiveHandler<&COFFAsmParser::ParseDirectiveCGProfile>(".cg_profile");
 
     // Win64 EH directives.
@@ -281,6 +282,7 @@ bool COFFAsmParser::ParseSectionFlags(StringRef SectionName,
 bool COFFAsmParser::ParseDirectiveSymbolAttribute(StringRef Directive, SMLoc) {
   MCSymbolAttr Attr = StringSwitch<MCSymbolAttr>(Directive)
     .Case(".weak", MCSA_Weak)
+    .Case(".weak_anti_dep", MCSA_WeakAntiDep)
     .Default(MCSA_Invalid);
   assert(Attr != MCSA_Invalid && "unexpected symbol attribute directive!");
   if (getLexer().isNot(AsmToken::EndOfStatement)) {
diff --git a/llvm/lib/MC/MCWinCOFFStreamer.cpp b/llvm/lib/MC/MCWinCOFFStreamer.cpp
index c9a9681..ad0b1c1 100644
--- a/llvm/lib/MC/MCWinCOFFStreamer.cpp
+++ b/llvm/lib/MC/MCWinCOFFStreamer.cpp
@@ -115,7 +115,11 @@ bool MCWinCOFFStreamer::emitSymbolAttribute(MCSymbol *S,
   default: return false;
   case MCSA_WeakReference:
   case MCSA_Weak:
-    Symbol->setIsWeakExternal();
+    Symbol->setIsWeakExternal(COFF::IMAGE_WEAK_EXTERN_SEARCH_ALIAS);
+    Symbol->setExternal(true);
+    break;
+  case MCSA_WeakAntiDep:
+    Symbol->setIsWeakExternal(COFF::IMAGE_WEAK_EXTERN_ANTI_DEPENDENCY);
     Symbol->setExternal(true);
     break;
   case MCSA_Global:
diff --git a/llvm/lib/MC/WinCOFFObjectWriter.cpp b/llvm/lib/MC/WinCOFFObjectWriter.cpp
index 4927ea6..6687fd6 100644
--- a/llvm/lib/MC/WinCOFFObjectWriter.cpp
+++ b/llvm/lib/MC/WinCOFFObjectWriter.cpp
@@ -414,9 +414,9 @@ void WinCOFFObjectWriter::DefineSymbol(const MCSymbol &MCSym,
     Sym->Aux.resize(1);
     memset(&Sym->Aux[0], 0, sizeof(Sym->Aux[0]));
     Sym->Aux[0].AuxType = ATWeakExternal;
-    Sym->Aux[0].Aux.WeakExternal.TagIndex = 0;
+    Sym->Aux[0].Aux.WeakExternal.TagIndex = 0; // Filled in later
     Sym->Aux[0].Aux.WeakExternal.Characteristics =
-        COFF::IMAGE_WEAK_EXTERN_SEARCH_ALIAS;
+        cast<MCSymbolCOFF>(MCSym).getWeakExternalCharacteristics();
   } else {
     if (!Base)
       Sym->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;