Index: include/llvm/LTO/LTO.h
===================================================================
--- include/llvm/LTO/LTO.h
+++ include/llvm/LTO/LTO.h
@@ -126,6 +126,7 @@
     using irsymtab::Symbol::getCommonSize;
     using irsymtab::Symbol::getCommonAlignment;
     using irsymtab::Symbol::getCOFFWeakExternalFallback;
+    using irsymtab::Symbol::hasELFCIdentifierSectionName;
     using irsymtab::Symbol::isExecutable;
   };
 
Index: include/llvm/Object/IRSymtab.h
===================================================================
--- include/llvm/Object/IRSymtab.h
+++ include/llvm/Object/IRSymtab.h
@@ -121,6 +121,13 @@
   /// COFF-specific: the name of the symbol that a weak external resolves to
   /// if not defined.
   Str COFFWeakExternFallbackName;
+
+  /// ELF-specific: ELF linkers generate __start_<secname> and __stop_<secname>
+  /// symbols when there is a value in a section <secname> where the name is a
+  /// valid C identifier. Track symbols in such a section, so that we can
+  /// ensure that they aren't internalized and eliminated, which would
+  /// suppress the generation of the special __start_ and __end_ symbols.
+  bool HasELFCIdentifierSectionName;
 };
 
 struct Header {
@@ -128,7 +135,7 @@
   /// when the format changes, but it does not need to be incremented if a
   /// change to LLVM would cause it to create a different symbol table.
   Word Version;
-  enum { kCurrentVersion = 0 };
+  enum { kCurrentVersion = 1 };
 
   /// The producer's version string (LLVM_VERSION_STRING " " LLVM_REVISION).
   /// Consumers should rebuild the symbol table from IR if the producer's
@@ -165,6 +172,7 @@
   // Copied from storage::Uncommon.
   uint32_t CommonSize, CommonAlign;
   StringRef COFFWeakExternFallbackName;
+  bool HasELFCIdentifierSectionName;
 
   /// Returns the mangled symbol name.
   StringRef getName() const { return Name; }
@@ -215,6 +223,15 @@
     assert(isWeak() && isIndirect());
     return COFFWeakExternFallbackName;
   }
+
+  /// ELF-specific: ELF linkers generate __start_<secname> and __stop_<secname>
+  /// symbols when there is a value in a section <secname> where the name is a
+  /// valid C identifier. Track symbols in such a section, so that we can
+  /// ensure that they aren't internalized and eliminated, which would
+  /// suppress the generation of the special __start_ and __end_ symbols.
+  bool hasELFCIdentifierSectionName() const {
+    return HasELFCIdentifierSectionName;
+  }
 };
 
 /// This class can be used to read a Symtab and Strtab produced by
@@ -300,6 +317,7 @@
       CommonSize = UncI->CommonSize;
       CommonAlign = UncI->CommonAlign;
       COFFWeakExternFallbackName = R->str(UncI->COFFWeakExternFallbackName);
+      HasELFCIdentifierSectionName = UncI->HasELFCIdentifierSectionName;
     }
   }
 
Index: lib/LTO/LTO.cpp
===================================================================
--- lib/LTO/LTO.cpp
+++ lib/LTO/LTO.cpp
@@ -384,8 +384,13 @@
     // Set the partition to external if we know it is re-defined by the linker
     // with -defsym or -wrap options, used elsewhere, e.g. it is visible to a
     // regular object, is referenced from llvm.compiler_used, or was already
-    // recorded as being referenced from a different partition.
+    // recorded as being referenced from a different partition. Also,
+    // if this is ELF and the symbol has a C identifier section name, we
+    // need to keep it around to ensure the linker generates special
+    // __start_<secname> and __end_<secname> symbols which may be used
+    // elsewhere.
     if (Res.LinkerRedefined || Res.VisibleToRegularObj || Sym.isUsed() ||
+        Sym.hasELFCIdentifierSectionName() ||
         (GlobalRes.Partition != GlobalResolution::Unknown &&
          GlobalRes.Partition != Partition)) {
       GlobalRes.Partition = GlobalResolution::External;
@@ -396,7 +401,8 @@
     // Flag as visible outside of summary if visible from a regular object or
     // from a module that does not have a summary.
     GlobalRes.VisibleOutsideSummary |=
-        (Res.VisibleToRegularObj || Sym.isUsed() || !InSummary);
+        (Res.VisibleToRegularObj || Sym.isUsed() || !InSummary ||
+         Sym.hasELFCIdentifierSectionName());
   }
 }
 
Index: lib/Object/IRSymtab.cpp
===================================================================
--- lib/Object/IRSymtab.cpp
+++ lib/Object/IRSymtab.cpp
@@ -140,6 +140,18 @@
   return Error::success();
 }
 
+static bool isAlpha(char C) {
+  return ('a' <= C && C <= 'z') || ('A' <= C && C <= 'Z') || C == '_';
+}
+
+static bool isAlnum(char C) { return isAlpha(C) || ('0' <= C && C <= '9'); }
+
+// Returns true if S is valid as a C language identifier.
+static bool isValidCIdentifier(StringRef S) {
+  return !S.empty() && isAlpha(S[0]) &&
+         std::all_of(S.begin() + 1, S.end(), isAlnum);
+}
+
 Error Builder::addSymbol(const ModuleSymbolTable &Msymtab,
                          const SmallPtrSet<GlobalValue *, 8> &Used,
                          ModuleSymbolTable::Symbol Msym) {
@@ -240,6 +252,10 @@
     }
   }
 
+  if (TT.isOSBinFormatELF())
+    Uncommon().HasELFCIdentifierSectionName =
+        isValidCIdentifier(Base->getSection());
+
   return Error::success();
 }
 
Index: test/Object/X86/irsymtab.ll
===================================================================
--- test/Object/X86/irsymtab.ll
+++ test/Object/X86/irsymtab.ll
@@ -9,13 +9,13 @@
 
 ; BCA:      <SYMTAB_BLOCK
 ; Version stored at offset 0.
-; BCA-NEXT:   <BLOB abbrevid=4/> blob data = '\x00\x00\x00\x00\x06\x00\x00\x00\x08\x00\x00\x00D\x00\x00\x00\x01\x00\x00\x00P\x00\x00\x00\x00\x00\x00\x00P\x00\x00\x00\x02\x00\x00\x00\x80\x00\x00\x00\x00\x00\x00\x00\x0E\x00\x00\x00\x18\x00\x00\x00&\x00\x00\x00\x0B\x00\x00\x001\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x03\x00\x00\x00\x00\x00\x00\x00\x03\x00\x00\x00\xFF\xFF\xFF\xFF\x00$\x00\x00\x03\x00\x00\x00\x03\x00\x00\x00\x03\x00\x00\x00\x03\x00\x00\x00\xFF\xFF\xFF\xFF\x08$\x00\x00'
+; BCA-NEXT:   <BLOB abbrevid=4/> blob data = '\x01\x00\x00\x00\x06\x00\x00\x00\x08\x00\x00\x00D\x00\x00\x00\x01\x00\x00\x00P\x00\x00\x00\x00\x00\x00\x00P\x00\x00\x00\x02\x00\x00\x00\x80\x00\x00\x00\x02\x00\x00\x00\x0E\x00\x00\x00\x18\x00\x00\x00&\x00\x00\x00\x0B\x00\x00\x001\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x03\x00\x00\x00\x00\x00\x00\x00\x03\x00\x00\x00\xFF\xFF\xFF\xFF\x04$\x00\x00\x03\x00\x00\x00\x03\x00\x00\x00\x03\x00\x00\x00\x03\x00\x00\x00\xFF\xFF\xFF\xFF\x0C$\x00\x00\x00\x00\x00\x00\x00\x00\x00\x001\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x001\x00\x00\x00\x00\x00\x00\x00\x00'
 ; BCA-NEXT: </SYMTAB_BLOCK>
 ; BCA-NEXT: <STRTAB_BLOCK
 ; BCA-NEXT:   <BLOB abbrevid=4/> blob data = 'foobarproducerx86_64-unknown-linux-gnuirsymtab.ll'
 ; BCA-NEXT: </STRTAB_BLOCK>
 
-; SYMTAB:      version: 0
+; SYMTAB:      version: 1
 ; SYMTAB-NEXT: producer: producer
 ; SYMTAB-NEXT: target triple: x86_64-unknown-linux-gnu
 ; SYMTAB-NEXT: source filename: irsymtab.ll
Index: test/tools/gold/X86/Inputs/global_with_section.ll
===================================================================
--- /dev/null
+++ test/tools/gold/X86/Inputs/global_with_section.ll
@@ -0,0 +1,6 @@
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @deadfunc2() {
+  ret void
+}
Index: test/tools/gold/X86/global_with_section.ll
===================================================================
--- /dev/null
+++ test/tools/gold/X86/global_with_section.ll
@@ -0,0 +1,59 @@
+; Test to ensure we don't internalize or treat as dead a global value
+; with a section. Otherwise, ELF linker generation of __start_"sectionname"
+; and __stop_"sectionname" symbols would not occur and we can end up
+; with undefined references at link time.
+
+; RUN: opt %s -o %t.o
+; RUN: llvm-lto2 dump-symtab %t.o | FileCheck %s --check-prefix=SYMTAB
+; RUN: opt %p/Inputs/global_with_section.ll -o %t2.o
+; RUN: %gold -m elf_x86_64 -plugin %llvmshlibdir/LLVMgold.so \
+; RUN:     -u foo \
+; RUN:     --plugin-opt=save-temps \
+; RUN:     -o %t3.o %t.o %t2.o
+; Check results of internalization
+; RUN: llvm-dis %t3.o.0.2.internalize.bc -o - | FileCheck %s --check-prefix=CHECK2-REGULARLTO
+
+; Do setup work for all below tests: generate bitcode
+; RUN: opt -module-summary %s -o %t.o
+; RUN: llvm-lto2 dump-symtab %t.o | FileCheck %s --check-prefix=SYMTAB
+; RUN: opt -module-summary %p/Inputs/global_with_section.ll -o %t2.o
+
+; RUN: %gold -m elf_x86_64 -plugin %llvmshlibdir/LLVMgold.so \
+; RUN:     -u foo \
+; RUN:     --plugin-opt=thinlto \
+; RUN:     --plugin-opt=save-temps \
+; RUN:     -o %t3.o %t.o %t2.o
+; Check results of internalization
+; RUN: llvm-dis %t.o.2.internalize.bc -o - | FileCheck %s
+; RUN: llvm-dis %t2.o.2.internalize.bc -o - | FileCheck %s --check-prefix=CHECK2-THINLTO
+
+; SYMTAB: deadfunc
+; SYMTAB-NEXT: has C idenfier section name
+; SYMTAB-NEXT: deadfunc2
+; SYMTAB-NEXT: var_with_section
+; SYMTAB-NEXT: has C idenfier section name
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; We should not internalize @var_with_section due to section
+; CHECK-DAG: @var_with_section = global i32 0, section "some_section"
+@var_with_section = global i32 0, section "some_section"
+
+; We should not internalize @deadfunc due to section
+; CHECK-DAG: define void @deadfunc() section "some_other_section"
+define void @deadfunc() section "some_other_section" {
+  call void @deadfunc2()
+  ret void
+}
+
+; In RegularLTO mode, where we have combined all the IR, @deadfunc2
+; should still exist but would be internalized.
+; CHECK2-REGULARLTO: define internal void @deadfunc2
+; In ThinLTO mode, we can't internalize it as it needs to be preserved
+; (due to the access from @deadfunc which must be preserved), and
+; can't be internalized since the reference is from a different module.
+; CHECK2-THINLTO: define void @deadfunc2
+declare void @deadfunc2()
+
+@foo = global i32 0
Index: tools/llvm-lto2/llvm-lto2.cpp
===================================================================
--- tools/llvm-lto2/llvm-lto2.cpp
+++ tools/llvm-lto2/llvm-lto2.cpp
@@ -355,6 +355,9 @@
 
       if (TT.isOSBinFormatCOFF() && Sym.isWeak() && Sym.isIndirect())
         outs() << "         fallback " << Sym.getCOFFWeakExternalFallback() << '\n';
+
+      if (TT.isOSBinFormatELF() && Sym.hasELFCIdentifierSectionName())
+        outs() << "         has C idenfier section name\n";
     }
 
     outs() << '\n';