Expose an InitToTextSection through MCStreamer.

The aim of this patch is to fix the following piece of code in the
platform-independent AsmParser:

void AsmParser::CheckForValidSection() {
  if (!ParsingInlineAsm && !getStreamer().getCurrentSection()) {
    TokError("expected section directive before assembly directive");
    Out.SwitchSection(Ctx.getMachOSection(
                        "__TEXT", "__text",
                        MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
                        0, SectionKind::getText()));
  }
}

This was added for the "-n" option of llvm-mc.

The proposed fix adds another virtual method to MCStreamer, called
InitToTextSection. Conceptually, it's similar to the existing
InitSections which initializes all common sections and switches to
text. The new method is implemented by each platform streamer in a way
that it sees fit. So AsmParser can now do this:

void AsmParser::CheckForValidSection() {
  if (!ParsingInlineAsm && !getStreamer().getCurrentSection()) {
    TokError("expected section directive before assembly directive");
    Out.InitToTextSection();
  }
}

Which is much more reasonable.

llvm-svn: 172450

llvm/include/llvm/MC/MCELFStreamer.h

@@ -44,6 +44,7 @@ public:
   /// @{
 
   virtual void InitSections();
+  virtual void InitToTextSection();
   virtual void ChangeSection(const MCSection *Section);
   virtual void EmitLabel(MCSymbol *Symbol);
   virtual void EmitDebugLabel(MCSymbol *Symbol);

llvm/include/llvm/MC/MCStreamer.h

@@ -234,6 +234,9 @@ namespace llvm {
     /// InitSections - Create the default sections and set the initial one.
     virtual void InitSections() = 0;
 
+    /// InitToTextSection - Create a text section and switch the streamer to it.
+    virtual void InitToTextSection() = 0;
+
     /// EmitLabel - Emit a label for @p Symbol into the current section.
     ///
     /// This corresponds to an assembler statement such as:

llvm/lib/MC/MCAsmStreamer.cpp

@@ -127,9 +127,14 @@ public:
   virtual void ChangeSection(const MCSection *Section);
 
   virtual void InitSections() {
+    InitToTextSection();
+  }
+
+  virtual void InitToTextSection() {
     // FIXME, this is MachO specific, but the testsuite
     // expects this.
-    SwitchSection(getContext().getMachOSection("__TEXT", "__text",
+    SwitchSection(getContext().getMachOSection(
+                                      "__TEXT", "__text",
                                       MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
                                       0, SectionKind::getText()));
   }

llvm/lib/MC/MCELFStreamer.cpp

@@ -65,6 +65,10 @@ inline void MCELFStreamer::SetSectionBss() {
 MCELFStreamer::~MCELFStreamer() {
 }
 
+void MCELFStreamer::InitToTextSection() {
+  SetSectionText();
+}
+
 void MCELFStreamer::InitSections() {
   // This emulates the same behavior of GNU as. This makes it easier
   // to compare the output as the major sections are in the same order.

llvm/lib/MC/MCMachOStreamer.cpp

@@ -42,6 +42,7 @@ public:
   /// @{
 
   virtual void InitSections();
+  virtual void InitToTextSection();
   virtual void EmitLabel(MCSymbol *Symbol);
   virtual void EmitDebugLabel(MCSymbol *Symbol);
   virtual void EmitEHSymAttributes(const MCSymbol *Symbol,
@@ -90,10 +91,14 @@ public:
 } // end anonymous namespace.
 
 void MCMachOStreamer::InitSections() {
-  SwitchSection(getContext().getMachOSection("__TEXT", "__text",
-                                    MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
-                                    0, SectionKind::getText()));
+  InitToTextSection();
+}
 
+void MCMachOStreamer::InitToTextSection() {
+  SwitchSection(getContext().getMachOSection(
+                                    "__TEXT", "__text",
+                                    MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS, 0,
+                                    SectionKind::getText()));
 }
 
 void MCMachOStreamer::EmitEHSymAttributes(const MCSymbol *Symbol,

llvm/lib/MC/MCNullStreamer.cpp

@@ -24,6 +24,9 @@ namespace {
     /// @name MCStreamer Interface
     /// @{
 
+    virtual void InitToTextSection() {
+    }
+
     virtual void InitSections() {
     }
 

llvm/lib/MC/MCParser/AsmParser.cpp

@@ -708,10 +708,7 @@ bool AsmParser::Run(bool NoInitialTextSection, bool NoFinalize) {
 void AsmParser::CheckForValidSection() {
   if (!ParsingInlineAsm && !getStreamer().getCurrentSection()) {
     TokError("expected section directive before assembly directive");
-    Out.SwitchSection(Ctx.getMachOSection(
-                        "__TEXT", "__text",
-                        MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
-                        0, SectionKind::getText()));
+    Out.InitToTextSection();
   }
 }
 

llvm/lib/MC/MCPureStreamer.cpp

@@ -36,6 +36,7 @@ public:
   /// @{
 
   virtual void InitSections();
+  virtual void InitToTextSection();
   virtual void EmitLabel(MCSymbol *Symbol);
   virtual void EmitDebugLabel(MCSymbol *Symbol);
   virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
@@ -104,11 +105,14 @@ public:
 } // end anonymous namespace.
 
 void MCPureStreamer::InitSections() {
+  InitToTextSection();
+}
+
+void MCPureStreamer::InitToTextSection() {
   // FIMXE: To what!?
   SwitchSection(getContext().getMachOSection("__TEXT", "__text",
                                     MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
                                     0, SectionKind::getText()));
-
 }
 
 void MCPureStreamer::EmitLabel(MCSymbol *Symbol) {

llvm/lib/MC/WinCOFFStreamer.cpp

@@ -50,6 +50,7 @@ public:
   // MCStreamer interface
 
   virtual void InitSections();
+  virtual void InitToTextSection();
   virtual void EmitLabel(MCSymbol *Symbol);
   virtual void EmitDebugLabel(MCSymbol *Symbol);
   virtual void EmitAssemblerFlag(MCAssemblerFlag Flag);
@@ -173,6 +174,10 @@ void WinCOFFStreamer::AddCommonSymbol(MCSymbol *Symbol, uint64_t Size,
 
 // MCStreamer interface
 
+void WinCOFFStreamer::InitToTextSection() {
+  SetSectionText();
+}
+
 void WinCOFFStreamer::InitSections() {
   SetSectionText();
   SetSectionData();

llvm/tools/lto/LTOModule.cpp

@@ -771,6 +771,7 @@ namespace {
 
     // Noop calls.
     virtual void ChangeSection(const MCSection *Section) {}
+    virtual void InitToTextSection() {}
     virtual void InitSections() {}
     virtual void EmitAssemblerFlag(MCAssemblerFlag Flag) {}
     virtual void EmitThumbFunc(MCSymbol *Func) {}