MC: Support multiple sections with the same name in the same comdat group

Code review by Eric Christopher and Rafael Espindola.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193209 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/MC/ELFObjectWriter.cpp b/lib/MC/ELFObjectWriter.cpp
index c5f7287..eb197f2 100644
--- a/lib/MC/ELFObjectWriter.cpp
+++ b/lib/MC/ELFObjectWriter.cpp
@@ -1298,10 +1298,12 @@
     // Remove ".rel" and ".rela" prefixes.
     unsigned SecNameLen = (Section.getType() == ELF::SHT_REL) ? 4 : 5;
     StringRef SectionName = Section.getSectionName().substr(SecNameLen);
+    StringRef GroupName =
+        Section.getGroup() ? Section.getGroup()->getName() : "";
 
-    InfoSection = Asm.getContext().getELFSection(SectionName,
-                                                 ELF::SHT_PROGBITS, 0,
-                                                 SectionKind::getReadOnly());
+    InfoSection = Asm.getContext().getELFSection(SectionName, ELF::SHT_PROGBITS,
+                                                 0, SectionKind::getReadOnly(),
+                                                 0, GroupName);
     sh_info = SectionIndexMap.lookup(InfoSection);
     break;
   }
@@ -1351,11 +1353,12 @@
                                        ELF::SHF_EXECINSTR | ELF::SHF_ALLOC,
                                        SectionKind::getText()));
     } else if (SecName.startswith(".ARM.exidx")) {
-      sh_link = SectionIndexMap.lookup(
-        Asm.getContext().getELFSection(SecName.substr(sizeof(".ARM.exidx") - 1),
-                                       ELF::SHT_PROGBITS,
-                                       ELF::SHF_EXECINSTR | ELF::SHF_ALLOC,
-                                       SectionKind::getText()));
+      StringRef GroupName =
+          Section.getGroup() ? Section.getGroup()->getName() : "";
+      sh_link = SectionIndexMap.lookup(Asm.getContext().getELFSection(
+          SecName.substr(sizeof(".ARM.exidx") - 1), ELF::SHT_PROGBITS,
+          ELF::SHF_EXECINSTR | ELF::SHF_ALLOC, SectionKind::getText(), 0,
+          GroupName));
     }
   }