[MC][ARM] Delete MCSection::HasData and move SHF_ARM_PURECODE logic t…

…o ARMELFObjectWriter::addTargetSectionFlags

This simplifies the generic interface and also makes SHF_ARM_PURECODE
more robust (fixes a TODO). Inspecting MCDataFragment contents covers
more cases than MCObjectStreamer::EmitBytes.

llvm/include/llvm/MC/MCSection.h

@@ -78,10 +78,6 @@ class MCSection {
   /// Whether this section has had instructions emitted into it.
   bool HasInstructions : 1;
 
-  /// Whether this section has had data emitted into it.
-  /// Right now this is only used by the ARM backend.
-  bool HasData : 1;
-
   bool IsRegistered : 1;
 
   MCDummyFragment DummyFragment;
@@ -150,9 +146,6 @@ class MCSection {
   bool hasInstructions() const { return HasInstructions; }
   void setHasInstructions(bool Value) { HasInstructions = Value; }
 
-  bool hasData() const { return HasData; }
-  void setHasData(bool Value) { HasData = Value; }
-
   bool isRegistered() const { return IsRegistered; }
   void setIsRegistered(bool Value) { IsRegistered = Value; }
 

llvm/lib/MC/MCObjectStreamer.cpp

@@ -569,12 +569,6 @@ void MCObjectStreamer::EmitBytes(StringRef Data) {
   MCDataFragment *DF = getOrCreateDataFragment();
   flushPendingLabels(DF, DF->getContents().size());
   DF->getContents().append(Data.begin(), Data.end());
-
-  // EmitBytes might not cover all possible ways we emit data (or could be used
-  // to emit executable code in some cases), but is the best method we have
-  // right now for checking this.
-  MCSection *Sec = getCurrentSectionOnly();
-  Sec->setHasData(true);
 }
 
 void MCObjectStreamer::EmitValueToAlignment(unsigned ByteAlignment,

llvm/lib/MC/MCSection.cpp

@@ -22,8 +22,7 @@ using namespace llvm;
 
 MCSection::MCSection(SectionVariant V, SectionKind K, MCSymbol *Begin)
     : Begin(Begin), BundleGroupBeforeFirstInst(false), HasInstructions(false),
-      HasData(false), IsRegistered(false), DummyFragment(this), Variant(V),
-      Kind(K) {}
+      IsRegistered(false), DummyFragment(this), Variant(V), Kind(K) {}
 
 MCSymbol *MCSection::getEndSymbol(MCContext &Ctx) {
   if (!End)

llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp

@@ -255,8 +255,11 @@ void ARMELFObjectWriter::addTargetSectionFlags(MCContext &Ctx,
   // execute-only section in the object.
   MCSectionELF *TextSection =
       static_cast<MCSectionELF *>(Ctx.getObjectFileInfo()->getTextSection());
-  if (Sec.getKind().isExecuteOnly() && !TextSection->hasInstructions() &&
-      !TextSection->hasData()) {
+  if (Sec.getKind().isExecuteOnly() && !TextSection->hasInstructions()) {
+    for (auto &F : TextSection->getFragmentList())
+      if (auto *DF = dyn_cast<MCDataFragment>(&F))
+        if (!DF->getContents().empty())
+          return;
     TextSection->setFlags(TextSection->getFlags() | ELF::SHF_ARM_PURECODE);
   }
 }