Add a funciton to get the segment name of a section.

On MachO, sections also have segment names. When a tool looking at a .o file
prints a segment name, this is what they mean. In reality, a .o has only one,
anonymous, segment.

This patch adds a MachO only function to fetch that segment name. I named it
getSectionFinalSegmentName since the main use for the name seems to be informing
the linker with segment this section should go to.

The patch also changes MachOObjectFile::getSectionName to return just the
section name instead of computing SegmentName,SectionName.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@170095 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/llvm-objdump/MachODump.cpp b/tools/llvm-objdump/MachODump.cpp
index 3a35038..c324ff1 100644
--- a/tools/llvm-objdump/MachODump.cpp
+++ b/tools/llvm-objdump/MachODump.cpp
@@ -334,9 +334,15 @@
   for (unsigned SectIdx = 0; SectIdx != Sections.size(); SectIdx++) {
     StringRef SectName;
     if (Sections[SectIdx].getName(SectName) ||
-        SectName.compare("__TEXT,__text"))
+        SectName != "__text")
       continue; // Skip non-text sections
 
+    StringRef SegmentName;
+    DataRefImpl DR = Sections[SectIdx].getRawDataRefImpl();
+    if (MachOOF->getSectionFinalSegmentName(DR, SegmentName) ||
+        SegmentName != "__TEXT")
+      continue;
+
     // Insert the functions from the function starts segment into our map.
     uint64_t VMAddr;
     Sections[SectIdx].getAddress(VMAddr);