[MC] Replace hasAltEntry() with isMachO()

All Mach-O targets have this property, so just remove this variable,
which could lure contributors to add unneeded object file format
specific properties.

Author: MaskRay

llvm/include/llvm/MC/MCAsmInfo.h

@@ -382,10 +382,6 @@ class MCAsmInfo {
   /// to false.
   bool HasNoDeadStrip = false;
 
-  /// True if this target supports the MachO .alt_entry directive.  Defaults to
-  /// false.
-  bool HasAltEntry = false;
-
   /// Used to declare a global as being a weak symbol. Defaults to ".weak".
   const char *WeakDirective;
 
@@ -714,7 +710,6 @@ class MCAsmInfo {
   bool hasFourStringsDotFile() const { return HasFourStringsDotFile; }
   bool hasIdentDirective() const { return HasIdentDirective; }
   bool hasNoDeadStrip() const { return HasNoDeadStrip; }
-  bool hasAltEntry() const { return HasAltEntry; }
   const char *getWeakDirective() const { return WeakDirective; }
   const char *getWeakRefDirective() const { return WeakRefDirective; }
 

llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -2147,7 +2147,7 @@ void AsmPrinter::emitGlobalAlias(const Module &M, const GlobalAlias &GA) {
 
   const MCExpr *Expr = lowerConstant(GA.getAliasee());
 
-  if (MAI->hasAltEntry() && isa<MCBinaryExpr>(Expr))
+  if (MAI->isMachO() && isa<MCBinaryExpr>(Expr))
     OutStreamer->emitSymbolAttribute(Name, MCSA_AltEntry);
 
   // Emit the directives as assignments aka .set:

llvm/lib/MC/MCAsmInfoDarwin.cpp

@@ -81,7 +81,6 @@ MCAsmInfoDarwin::MCAsmInfoDarwin() {
 
   HasDotTypeDotSizeDirective = false;
   HasNoDeadStrip = true;
-  HasAltEntry = true;
 
   DwarfUsesRelocationsAcrossSections = false;
   SetDirectiveSuppressesReloc = true;