8 files changed, 37 insertions, 5 deletions
diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 28d793155ce..67153d1d20f 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -1165,8 +1165,13 @@ bool AsmPrinter::doFinalization(Module &M) {
 
     EmitVisibility(Name, Alias.getVisibility());
 
+    const MCExpr *Expr = lowerConstant(Alias.getAliasee());
+
+    if (MAI->hasAltEntry() && isa<MCBinaryExpr>(Expr))
+      OutStreamer->EmitSymbolAttribute(Name, MCSA_AltEntry);
+
     // Emit the directives as assignments aka .set:
-    OutStreamer->EmitAssignment(Name, lowerConstant(Alias.getAliasee()));
+    OutStreamer->EmitAssignment(Name, Expr);
 
     // If the aliasee does not correspond to a symbol in the output, i.e. the
     // alias is not of an object or the aliased object is private, then set the
diff --git a/llvm/lib/MC/MCAsmInfo.cpp b/llvm/lib/MC/MCAsmInfo.cpp
index 36e10b3c6a0..fa7d438d159 100644
--- a/llvm/lib/MC/MCAsmInfo.cpp
+++ b/llvm/lib/MC/MCAsmInfo.cpp
@@ -75,6 +75,7 @@ MCAsmInfo::MCAsmInfo() {
   HasSingleParameterDotFile = true;
   HasIdentDirective = false;
   HasNoDeadStrip = false;
+  HasAltEntry = false;
   WeakDirective = "\t.weak\t";
   WeakRefDirective = nullptr;
   HasWeakDefDirective = false;
diff --git a/llvm/lib/MC/MCAsmInfoDarwin.cpp b/llvm/lib/MC/MCAsmInfoDarwin.cpp
index ae9486d3db4..dff5dd0d63d 100644
--- a/llvm/lib/MC/MCAsmInfoDarwin.cpp
+++ b/llvm/lib/MC/MCAsmInfoDarwin.cpp
@@ -88,6 +88,7 @@ MCAsmInfoDarwin::MCAsmInfoDarwin() {
 
   HasDotTypeDotSizeDirective = false;
   HasNoDeadStrip = true;
+  HasAltEntry = true;
 
   DwarfUsesRelocationsAcrossSections = false;
 
diff --git a/llvm/lib/MC/MCAsmStreamer.cpp b/llvm/lib/MC/MCAsmStreamer.cpp
index c615752808c..be264496fa4 100644
--- a/llvm/lib/MC/MCAsmStreamer.cpp
+++ b/llvm/lib/MC/MCAsmStreamer.cpp
@@ -472,6 +472,7 @@ bool MCAsmStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
     OS << "\t.no_dead_strip\t";
     break;
   case MCSA_SymbolResolver: OS << "\t.symbol_resolver\t"; break;
+  case MCSA_AltEntry:       OS << "\t.alt_entry\t";       break;
   case MCSA_PrivateExtern:
     OS << "\t.private_extern\t";
     break;
diff --git a/llvm/lib/MC/MCELFStreamer.cpp b/llvm/lib/MC/MCELFStreamer.cpp
index eebdc9b7083..9249d9c49b6 100644
--- a/llvm/lib/MC/MCELFStreamer.cpp
+++ b/llvm/lib/MC/MCELFStreamer.cpp
@@ -283,6 +283,9 @@ bool MCELFStreamer::EmitSymbolAttribute(MCSymbol *S, MCSymbolAttr Attribute) {
   case MCSA_Internal:
     Symbol->setVisibility(ELF::STV_INTERNAL);
     break;
+
+  case MCSA_AltEntry:
+    llvm_unreachable("ELF doesn't support this attribute");
   }
 
   return true;
diff --git a/llvm/lib/MC/MCMachOStreamer.cpp b/llvm/lib/MC/MCMachOStreamer.cpp
index f59fa1d5169..a72516375a7 100644
--- a/llvm/lib/MC/MCMachOStreamer.cpp
+++ b/llvm/lib/MC/MCMachOStreamer.cpp
@@ -23,6 +23,7 @@
 #include "llvm/MC/MCSection.h"
 #include "llvm/MC/MCSectionMachO.h"
 #include "llvm/MC/MCSymbolMachO.h"
+#include "llvm/MC/MCValue.h"
 #include "llvm/Support/Dwarf.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/TargetRegistry.h"
@@ -70,6 +71,7 @@ public:
 
   void ChangeSection(MCSection *Sect, const MCExpr *Subsect) override;
   void EmitLabel(MCSymbol *Symbol) override;
+  void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) override;
   void EmitEHSymAttributes(const MCSymbol *Symbol, MCSymbol *EHSymbol) override;
   void EmitAssemblerFlag(MCAssemblerFlag Flag) override;
   void EmitLinkerOptions(ArrayRef<std::string> Options) override;
@@ -198,6 +200,16 @@ void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
   cast<MCSymbolMachO>(Symbol)->clearReferenceType();
 }
 
+void MCMachOStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
+  MCValue Res;
+
+  if (Value->evaluateAsRelocatable(Res, nullptr, nullptr))
+    if (Res.getSymA() && !Res.getSymB() && Res.getConstant() != 0)
+      cast<MCSymbolMachO>(Symbol)->setAltEntry();
+
+  MCObjectStreamer::EmitAssignment(Symbol, Value);
+}
+
 void MCMachOStreamer::EmitDataRegion(DataRegionData::KindTy Kind) {
   if (!getAssembler().getBackend().hasDataInCodeSupport())
     return;
@@ -346,6 +358,10 @@ bool MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Sym,
     Symbol->setSymbolResolver();
     break;
 
+  case MCSA_AltEntry:
+    Symbol->setAltEntry();
+    break;
+
   case MCSA_PrivateExtern:
     Symbol->setExternal(true);
     Symbol->setPrivateExtern(true);
diff --git a/llvm/lib/MC/MCParser/AsmParser.cpp b/llvm/lib/MC/MCParser/AsmParser.cpp
index b962d9f9b2c..fef6bb6b641 100644
--- a/llvm/lib/MC/MCParser/AsmParser.cpp
+++ b/llvm/lib/MC/MCParser/AsmParser.cpp
@@ -350,8 +350,8 @@ private:
     DK_BALIGNL, DK_P2ALIGN, DK_P2ALIGNW, DK_P2ALIGNL, DK_ORG, DK_FILL, DK_ENDR,
     DK_BUNDLE_ALIGN_MODE, DK_BUNDLE_LOCK, DK_BUNDLE_UNLOCK,
     DK_ZERO, DK_EXTERN, DK_GLOBL, DK_GLOBAL,
-    DK_LAZY_REFERENCE, DK_NO_DEAD_STRIP, DK_SYMBOL_RESOLVER, DK_PRIVATE_EXTERN,
-    DK_REFERENCE, DK_WEAK_DEFINITION, DK_WEAK_REFERENCE,
+    DK_LAZY_REFERENCE, DK_NO_DEAD_STRIP, DK_SYMBOL_RESOLVER, DK_ALT_ENTRY,
+    DK_PRIVATE_EXTERN, DK_REFERENCE, DK_WEAK_DEFINITION, DK_WEAK_REFERENCE,
     DK_WEAK_DEF_CAN_BE_HIDDEN, DK_COMM, DK_COMMON, DK_LCOMM, DK_ABORT,
     DK_INCLUDE, DK_INCBIN, DK_CODE16, DK_CODE16GCC, DK_REPT, DK_IRP, DK_IRPC,
     DK_IF, DK_IFEQ, DK_IFGE, DK_IFGT, DK_IFLE, DK_IFLT, DK_IFNE, DK_IFB,
@@ -1598,6 +1598,8 @@ bool AsmParser::parseStatement(ParseStatementInfo &Info,
       return parseDirectiveSymbolAttribute(MCSA_NoDeadStrip);
     case DK_SYMBOL_RESOLVER:
       return parseDirectiveSymbolAttribute(MCSA_SymbolResolver);
+    case DK_ALT_ENTRY:
+      return parseDirectiveSymbolAttribute(MCSA_AltEntry);
     case DK_PRIVATE_EXTERN:
       return parseDirectiveSymbolAttribute(MCSA_PrivateExtern);
     case DK_REFERENCE:
@@ -4625,6 +4627,7 @@ void AsmParser::initializeDirectiveKindMap() {
   DirectiveKindMap[".lazy_reference"] = DK_LAZY_REFERENCE;
   DirectiveKindMap[".no_dead_strip"] = DK_NO_DEAD_STRIP;
   DirectiveKindMap[".symbol_resolver"] = DK_SYMBOL_RESOLVER;
+  DirectiveKindMap[".alt_entry"] = DK_ALT_ENTRY;
   DirectiveKindMap[".private_extern"] = DK_PRIVATE_EXTERN;
   DirectiveKindMap[".reference"] = DK_REFERENCE;
   DirectiveKindMap[".weak_definition"] = DK_WEAK_DEFINITION;
diff --git a/llvm/lib/MC/MachObjectWriter.cpp b/llvm/lib/MC/MachObjectWriter.cpp
index 8ebd7031c65..2013c253d2d 100644
--- a/llvm/lib/MC/MachObjectWriter.cpp
+++ b/llvm/lib/MC/MachObjectWriter.cpp
@@ -334,7 +334,7 @@ void MachObjectWriter::writeNlist(MachSymbolData &MSD,
     if (AliaseeInfo)
       SectionIndex = AliaseeInfo->SectionIndex;
     Symbol = AliasedSymbol;
-    // FIXME: Should this update Data as well?  Do we need OrigSymbol at all?
+    // FIXME: Should this update Data as well?
   }
 
   // Set the N_TYPE bits. See <mach-o/nlist.h>.
@@ -377,7 +377,9 @@ void MachObjectWriter::writeNlist(MachSymbolData &MSD,
 
   // The Mach-O streamer uses the lowest 16-bits of the flags for the 'desc'
   // value.
-  write16(cast<MCSymbolMachO>(Symbol)->getEncodedFlags());
+  bool EncodeAsAltEntry =
+    IsAlias && cast<MCSymbolMachO>(OrigSymbol).isAltEntry();
+  write16(cast<MCSymbolMachO>(Symbol)->getEncodedFlags(EncodeAsAltEntry));
   if (is64Bit())
     write64(Address);
   else