Add support for subsections to the ELF assembler. Fixes PR8717.

Differential Revision: http://llvm-reviews.chandlerc.com/D598

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179725 91177308-0d34-0410-b5e6-96231b3b80d8

8 files changed, 64 insertions, 33 deletions

diff --git a/include/llvm/MC/MCAssembler.h b/include/llvm/MC/MCAssembler.h
index 32df38b..38a70f0 100644
--- a/include/llvm/MC/MCAssembler.h
+++ b/include/llvm/MC/MCAssembler.h
@@ -82,7 +82,7 @@ private:
   /// @}
 
 protected:
-  MCFragment(FragmentType _Kind, MCSectionData *_Parent);
+  MCFragment(FragmentType _Kind, MCSectionData *_Parent = 0);
 
 public:
   // Only for sentinel.
@@ -92,6 +92,7 @@ public:
   FragmentType getKind() const { return Kind; }
 
   MCSectionData *getParent() const { return Parent; }
+  void setParent(MCSectionData *Value) { Parent = Value; }
 
   MCSymbolData *getAtom() const { return Atom; }
   void setAtom(MCSymbolData *Value) { Atom = Value; }
@@ -132,7 +133,7 @@ class MCEncodedFragment : public MCFragment {
 
   uint8_t BundlePadding;
 public:
-  MCEncodedFragment(MCFragment::FragmentType FType, MCSectionData *SD)
+  MCEncodedFragment(MCFragment::FragmentType FType, MCSectionData *SD = 0)
     : MCFragment(FType, SD), BundlePadding(0)
   {
   }
@@ -347,7 +348,7 @@ class MCAlignFragment : public MCFragment {
 
 public:
   MCAlignFragment(unsigned _Alignment, int64_t _Value, unsigned _ValueSize,
-                  unsigned _MaxBytesToEmit, MCSectionData *SD)
+                  unsigned _MaxBytesToEmit, MCSectionData *SD = 0)
     : MCFragment(FT_Align, SD), Alignment(_Alignment),
       Value(_Value),ValueSize(_ValueSize),
       MaxBytesToEmit(_MaxBytesToEmit), EmitNops(false) {}
@@ -388,7 +389,7 @@ class MCFillFragment : public MCFragment {
 
 public:
   MCFillFragment(int64_t _Value, unsigned _ValueSize, uint64_t _Size,
-                 MCSectionData *SD)
+                 MCSectionData *SD = 0)
     : MCFragment(FT_Fill, SD),
       Value(_Value), ValueSize(_ValueSize), Size(_Size) {
     assert((!ValueSize || (Size % ValueSize) == 0) &&
@@ -421,7 +422,7 @@ class MCOrgFragment : public MCFragment {
   int8_t Value;
 
 public:
-  MCOrgFragment(const MCExpr &_Offset, int8_t _Value, MCSectionData *SD)
+  MCOrgFragment(const MCExpr &_Offset, int8_t _Value, MCSectionData *SD = 0)
     : MCFragment(FT_Org, SD),
       Offset(&_Offset), Value(_Value) {}
 
@@ -450,7 +451,7 @@ class MCLEBFragment : public MCFragment {
 
   SmallString<8> Contents;
 public:
-  MCLEBFragment(const MCExpr &Value_, bool IsSigned_, MCSectionData *SD)
+  MCLEBFragment(const MCExpr &Value_, bool IsSigned_, MCSectionData *SD = 0)
     : MCFragment(FT_LEB, SD),
       Value(&Value_), IsSigned(IsSigned_) { Contents.push_back(0); }
 
@@ -486,7 +487,7 @@ class MCDwarfLineAddrFragment : public MCFragment {
 
 public:
   MCDwarfLineAddrFragment(int64_t _LineDelta, const MCExpr &_AddrDelta,
-                      MCSectionData *SD)
+                      MCSectionData *SD = 0)
     : MCFragment(FT_Dwarf, SD),
       LineDelta(_LineDelta), AddrDelta(&_AddrDelta) { Contents.push_back(0); }
 
@@ -517,7 +518,7 @@ class MCDwarfCallFrameFragment : public MCFragment {
   SmallString<8> Contents;
 
 public:
-  MCDwarfCallFrameFragment(const MCExpr &_AddrDelta,  MCSectionData *SD)
+  MCDwarfCallFrameFragment(const MCExpr &_AddrDelta,  MCSectionData *SD = 0)
     : MCFragment(FT_DwarfFrame, SD),
       AddrDelta(&_AddrDelta) { Contents.push_back(0); }
 
@@ -589,6 +590,10 @@ private:
   /// it.
   unsigned HasInstructions : 1;
 
+  /// Mapping from subsection number to insertion point for subsection numbers
+  /// below that number.
+  SmallVector<std::pair<unsigned, MCFragment *>, 1> SubsectionFragmentMap;
+
   /// @}
 
 public:
@@ -632,6 +637,8 @@ public:
 
   bool empty() const { return Fragments.empty(); }
 
+  iterator getSubsectionInsertionPoint(unsigned Subsection);
+
   bool isBundleLocked() const {
     return BundleLockState != NotBundleLocked;
   }
diff --git a/include/llvm/MC/MCELFStreamer.h b/include/llvm/MC/MCELFStreamer.h
index 6fb2d22..55c05b0 100644
--- a/include/llvm/MC/MCELFStreamer.h
+++ b/include/llvm/MC/MCELFStreamer.h
@@ -50,7 +50,8 @@ public:
 
   virtual void InitSections();
   virtual void InitToTextSection();
-  virtual void ChangeSection(const MCSection *Section);
+  virtual void ChangeSection(const MCSection *Section,
+                             const MCExpr *Subsection);
   virtual void EmitLabel(MCSymbol *Symbol);
   virtual void EmitDebugLabel(MCSymbol *Symbol);
   virtual void EmitAssemblerFlag(MCAssemblerFlag Flag);
diff --git a/include/llvm/MC/MCObjectStreamer.h b/include/llvm/MC/MCObjectStreamer.h
index f06c49f..22a2839 100644
--- a/include/llvm/MC/MCObjectStreamer.h
+++ b/include/llvm/MC/MCObjectStreamer.h
@@ -10,6 +10,7 @@
 #ifndef LLVM_MC_MCOBJECTSTREAMER_H
 #define LLVM_MC_MCOBJECTSTREAMER_H
 
+#include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCStreamer.h"
 
 namespace llvm {
@@ -32,6 +33,7 @@ class raw_ostream;
 class MCObjectStreamer : public MCStreamer {
   MCAssembler *Assembler;
   MCSectionData *CurSectionData;
+  MCSectionData::iterator CurInsertionPoint;
 
   virtual void EmitInstToData(const MCInst &Inst) = 0;
   virtual void EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame);
@@ -56,6 +58,11 @@ protected:
 
   MCFragment *getCurrentFragment() const;
 
+  void insert(MCFragment *F) const {
+    CurSectionData->getFragmentList().insert(CurInsertionPoint, F);
+    F->setParent(CurSectionData);
+  }
+
   /// Get a data fragment to write into, creating a new one if the current
   /// fragment is not a data fragment.
   MCDataFragment *getOrCreateDataFragment() const;
@@ -76,7 +83,8 @@ public:
   virtual void EmitULEB128Value(const MCExpr *Value);
   virtual void EmitSLEB128Value(const MCExpr *Value);
   virtual void EmitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol);
-  virtual void ChangeSection(const MCSection *Section);
+  virtual void ChangeSection(const MCSection *Section,
+                             const MCExpr *Subsection);
   virtual void EmitInstruction(const MCInst &Inst);
 
   /// \brief Emit an instruction to a special fragment, because this instruction
diff --git a/include/llvm/MC/MCSection.h b/include/llvm/MC/MCSection.h
index e575424..de2678a 100644
--- a/include/llvm/MC/MCSection.h
+++ b/include/llvm/MC/MCSection.h
@@ -20,6 +20,7 @@
 
 namespace llvm {
   class MCAsmInfo;
+  class MCExpr;
   class raw_ostream;
 
   /// MCSection - Instances of this class represent a uniqued identifier for a
@@ -48,7 +49,8 @@ namespace llvm {
     SectionVariant getVariant() const { return Variant; }
 
     virtual void PrintSwitchToSection(const MCAsmInfo &MAI,
-                                      raw_ostream &OS) const = 0;
+                                      raw_ostream &OS,
+                                      const MCExpr *Subsection) const = 0;
 
     // Convenience routines to get label names for the beginning/end of a
     // section.
diff --git a/include/llvm/MC/MCSectionCOFF.h b/include/llvm/MC/MCSectionCOFF.h
index 07c4714..50e33a5 100644
--- a/include/llvm/MC/MCSectionCOFF.h
+++ b/include/llvm/MC/MCSectionCOFF.h
@@ -60,7 +60,8 @@ namespace llvm {
     int getSelection () const { return Selection; }
 
     virtual void PrintSwitchToSection(const MCAsmInfo &MAI,
-                                      raw_ostream &OS) const;
+                                      raw_ostream &OS,
+                                      const MCExpr *Subsection) const;
     virtual bool UseCodeAlign() const;
     virtual bool isVirtualSection() const;
 
diff --git a/include/llvm/MC/MCSectionELF.h b/include/llvm/MC/MCSectionELF.h
index 4b8b849..5979915 100644
--- a/include/llvm/MC/MCSectionELF.h
+++ b/include/llvm/MC/MCSectionELF.h
@@ -70,7 +70,8 @@ public:
   const MCSymbol *getGroup() const { return Group; }
 
   void PrintSwitchToSection(const MCAsmInfo &MAI,
-                            raw_ostream &OS) const;
+                            raw_ostream &OS,
+                            const MCExpr *Subsection) const;
   virtual bool UseCodeAlign() const;
   virtual bool isVirtualSection() const;
 
diff --git a/include/llvm/MC/MCSectionMachO.h b/include/llvm/MC/MCSectionMachO.h
index 898f571..b68bd85 100644
--- a/include/llvm/MC/MCSectionMachO.h
+++ b/include/llvm/MC/MCSectionMachO.h
@@ -175,7 +175,8 @@ public:
                                            unsigned  &StubSize); // Out.
 
   virtual void PrintSwitchToSection(const MCAsmInfo &MAI,
-                                    raw_ostream &OS) const;
+                                    raw_ostream &OS,
+                                    const MCExpr *Subsection) const;
   virtual bool UseCodeAlign() const;
   virtual bool isVirtualSection() const;
 
diff --git a/include/llvm/MC/MCStreamer.h b/include/llvm/MC/MCStreamer.h
index a069a2b..2cab481 100644
--- a/include/llvm/MC/MCStreamer.h
+++ b/include/llvm/MC/MCStreamer.h
@@ -37,6 +37,8 @@ namespace llvm {
   class raw_ostream;
   class formatted_raw_ostream;
 
+  typedef std::pair<const MCSection *, const MCExpr *> MCSectionSubPair;
+
   /// MCStreamer - Streaming machine code generation interface.  This interface
   /// is intended to provide a programatic interface that is very similar to the
   /// level that an assembler .s file provides.  It has callbacks to emit bytes,
@@ -86,8 +88,7 @@ namespace llvm {
 
     /// SectionStack - This is stack of current and previous section
     /// values saved by PushSection.
-    SmallVector<std::pair<const MCSection *,
-                const MCSection *>, 4> SectionStack;
+    SmallVector<std::pair<MCSectionSubPair, MCSectionSubPair>, 4> SectionStack;
 
     bool AutoInitSections;
 
@@ -174,25 +175,25 @@ namespace llvm {
 
     /// getCurrentSection - Return the current section that the streamer is
     /// emitting code to.
-    const MCSection *getCurrentSection() const {
+    MCSectionSubPair getCurrentSection() const {
       if (!SectionStack.empty())
         return SectionStack.back().first;
-      return NULL;
+      return MCSectionSubPair();
     }
 
     /// getPreviousSection - Return the previous section that the streamer is
     /// emitting code to.
-    const MCSection *getPreviousSection() const {
+    MCSectionSubPair getPreviousSection() const {
       if (!SectionStack.empty())
         return SectionStack.back().second;
-      return NULL;
+      return MCSectionSubPair();
     }
 
     /// ChangeSection - Update streamer for a new active section.
     ///
     /// This is called by PopSection and SwitchSection, if the current
     /// section changes.
-    virtual void ChangeSection(const MCSection *) = 0;
+    virtual void ChangeSection(const MCSection *, const MCExpr *) = 0;
 
     /// pushSection - Save the current and previous section on the
     /// section stack.
@@ -208,11 +209,19 @@ namespace llvm {
     bool PopSection() {
       if (SectionStack.size() <= 1)
         return false;
-      const MCSection *oldSection = SectionStack.pop_back_val().first;
-      const MCSection *curSection = SectionStack.back().first;
+      MCSectionSubPair oldSection = SectionStack.pop_back_val().first;
+      MCSectionSubPair curSection = SectionStack.back().first;
 
       if (oldSection != curSection)
-        ChangeSection(curSection);
+        ChangeSection(curSection.first, curSection.second);
+      return true;
+    }
+
+    bool SubSection(const MCExpr *Subsection) {
+      if (SectionStack.empty())
+        return false;
+
+      SwitchSection(SectionStack.back().first.first, Subsection);
       return true;
     }
 
@@ -220,25 +229,26 @@ namespace llvm {
     /// @p Section.  This is required to update CurSection.
     ///
     /// This corresponds to assembler directives like .section, .text, etc.
-    void SwitchSection(const MCSection *Section) {
+    void SwitchSection(const MCSection *Section, const MCExpr *Subsection = 0) {
       assert(Section && "Cannot switch to a null section!");
-      const MCSection *curSection = SectionStack.back().first;
+      MCSectionSubPair curSection = SectionStack.back().first;
       SectionStack.back().second = curSection;
-      if (Section != curSection) {
-        SectionStack.back().first = Section;
-        ChangeSection(Section);
+      if (MCSectionSubPair(Section, Subsection) != curSection) {
+        SectionStack.back().first = MCSectionSubPair(Section, Subsection);
+        ChangeSection(Section, Subsection);
       }
     }
 
     /// SwitchSectionNoChange - Set the current section where code is being
     /// emitted to @p Section.  This is required to update CurSection. This
     /// version does not call ChangeSection.
-    void SwitchSectionNoChange(const MCSection *Section) {
+    void SwitchSectionNoChange(const MCSection *Section,
+                               const MCExpr *Subsection = 0) {
       assert(Section && "Cannot switch to a null section!");
-      const MCSection *curSection = SectionStack.back().first;
+      MCSectionSubPair curSection = SectionStack.back().first;
       SectionStack.back().second = curSection;
-      if (Section != curSection)
-        SectionStack.back().first = Section;
+      if (MCSectionSubPair(Section, Subsection) != curSection)
+        SectionStack.back().first = MCSectionSubPair(Section, Subsection);
     }
 
     /// Initialize the streamer.