Add a InitSections method to the streamer interface.

The ELF implementation now creates text, data and bss to match the gnu as
behavior.

The text streamer still has the old MachO specific behavior since
the testsuite checks that it will error when a directive is given
before a setting the current section for example.

A nice benefit is that -n is not required anymore when producing
ELF files.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@114027 91177308-0d34-0410-b5e6-96231b3b80d8

lib/MC/MCMachOStreamer.cpp

@@ -46,6 +46,7 @@ public:
   /// @name MCStreamer Interface
   /// @{
 
+  virtual void InitSections();
   virtual void EmitLabel(MCSymbol *Symbol);
   virtual void EmitAssemblerFlag(MCAssemblerFlag Flag);
   virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value);
@@ -110,6 +111,13 @@ public:
 
 } // end anonymous namespace.
 
+void MCMachOStreamer::InitSections() {
+  SwitchSection(getContext().getMachOSection("__TEXT", "__text",
+                                    MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
+                                    0, SectionKind::getText()));
+
+}
+
 void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
   // TODO: This is almost exactly the same as WinCOFFStreamer. Consider merging
   // into MCObjectStreamer.