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

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

llvm-svn: 179725

1 files changed, 32 insertions, 1 deletions

diff --git a/llvm/lib/MC/MCAssembler.cpp b/llvm/lib/MC/MCAssembler.cpp
index 8970e18a2ce..fb5ab28bcf5 100644
--- a/llvm/lib/MC/MCAssembler.cpp
+++ b/llvm/lib/MC/MCAssembler.cpp
@@ -214,7 +214,8 @@ MCFragment::~MCFragment() {
 MCFragment::MCFragment(FragmentType _Kind, MCSectionData *_Parent)
   : Kind(_Kind), Parent(_Parent), Atom(0), Offset(~UINT64_C(0))
 {
-  Parent->getFragmentList().push_back(this);
+  if (Parent)
+    Parent->getFragmentList().push_back(this);
 }
 
 /* *** */
@@ -242,6 +243,36 @@ MCSectionData::MCSectionData(const MCSection &_Section, MCAssembler *A)
     A->getSectionList().push_back(this);
 }
 
+MCSectionData::iterator
+MCSectionData::getSubsectionInsertionPoint(unsigned Subsection) {
+  if (Subsection == 0 && SubsectionFragmentMap.empty())
+    return end();
+
+  SmallVectorImpl<std::pair<unsigned, MCFragment *> >::iterator MI =
+    std::lower_bound(SubsectionFragmentMap.begin(), SubsectionFragmentMap.end(),
+                     std::make_pair(Subsection, (MCFragment *)0));
+  bool ExactMatch = false;
+  if (MI != SubsectionFragmentMap.end()) {
+    ExactMatch = MI->first == Subsection;
+    if (ExactMatch)
+      ++MI;
+  }
+  iterator IP;
+  if (MI == SubsectionFragmentMap.end())
+    IP = end();
+  else
+    IP = MI->second;
+  if (!ExactMatch && Subsection != 0) {
+    // The GNU as documentation claims that subsections have an alignment of 4,
+    // although this appears not to be the case.
+    MCFragment *F = new MCDataFragment();
+    SubsectionFragmentMap.insert(MI, std::make_pair(Subsection, F));
+    getFragmentList().insert(IP, F);
+    F->setParent(this);
+  }
+  return IP;
+}
+
 /* *** */
 
 MCSymbolData::MCSymbolData() : Symbol(0) {}