5 files changed, 45 insertions, 5 deletions

diff --git a/lld/ELF/InputFiles.cpp b/lld/ELF/InputFiles.cpp
index 71d7a585583..bccbddf5058 100644
--- a/lld/ELF/InputFiles.cpp
+++ b/lld/ELF/InputFiles.cpp
@@ -12,6 +12,7 @@
 #include "InputSection.h"
 #include "Symbols.h"
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/CodeGen/Analysis.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Object/IRObjectFile.h"
@@ -498,8 +499,11 @@ BitcodeFile::createSymbolBody(const DenseSet<const Comdat *> &KeptComdats,
     Body = new (Alloc) DefinedBitcode(NameRef, IsWeak, Visibility);
   }
   // FIXME: Expose a thread-local flag for module asm symbols.
-  if (GV && GV->isThreadLocal())
-    Body->Type = STT_TLS;
+  if (GV) {
+    if (GV->isThreadLocal())
+      Body->Type = STT_TLS;
+    Body->CanOmitFromDynSym = canBeOmittedFromSymbolTable(GV);
+  }
   return Body;
 }
 
diff --git a/lld/ELF/Symbols.cpp b/lld/ELF/Symbols.cpp
index 747161efe8b..e6f8842b80d 100644
--- a/lld/ELF/Symbols.cpp
+++ b/lld/ELF/Symbols.cpp
@@ -109,6 +109,7 @@ void SymbolBody::init() {
                        K == DefinedSyntheticKind || K == UndefinedElfKind;
   CanKeepUndefined = false;
   MustBeInDynSym = false;
+  CanOmitFromDynSym = false;
   NeedsCopyOrPltAddr = false;
 }
 
@@ -241,6 +242,9 @@ int SymbolBody::compare(SymbolBody *Other) {
   if (IsUsedInRegularObj || Other->IsUsedInRegularObj)
     IsUsedInRegularObj = Other->IsUsedInRegularObj = true;
 
+  if (!CanOmitFromDynSym || !Other->CanOmitFromDynSym)
+    CanOmitFromDynSym = Other->CanOmitFromDynSym = false;
+
   if (L != R)
     return -1;
   if (!isDefined() || isShared() || isWeak())
@@ -360,7 +364,9 @@ bool SymbolBody::includeInDynsym() const {
   uint8_t V = getVisibility();
   if (V != STV_DEFAULT && V != STV_PROTECTED)
     return false;
-  return Config->ExportDynamic || Config->Shared;
+  if (!Config->ExportDynamic && !Config->Shared)
+    return false;
+  return !CanOmitFromDynSym;
 }
 
 template uint32_t SymbolBody::template getVA<ELF32LE>(uint32_t) const;
diff --git a/lld/ELF/Symbols.h b/lld/ELF/Symbols.h
index 11fcdcb5a45..da2ab59a72c 100644
--- a/lld/ELF/Symbols.h
+++ b/lld/ELF/Symbols.h
@@ -147,6 +147,12 @@ protected:
   unsigned IsUsedInRegularObj : 1;
 
 public:
+  // True if this symbol can be omitted from the symbol table if nothing else
+  // requires it to be there. Right now this is only used for linkonce_odr in
+  // LTO, but we could add the feature to ELF. It would be similar to
+  // MachO's .weak_def_can_be_hidden.
+  unsigned CanOmitFromDynSym : 1;
+
   // If true, the symbol is added to .dynsym symbol table.
   unsigned MustBeInDynSym : 1;
 
diff --git a/lld/test/ELF/lto/Inputs/internalize-exportdyn.ll b/lld/test/ELF/lto/Inputs/internalize-exportdyn.ll
new file mode 100644
index 00000000000..21ac3580762
--- /dev/null
+++ b/lld/test/ELF/lto/Inputs/internalize-exportdyn.ll
@@ -0,0 +1,6 @@
+target triple = "x86_64-unknown-linux-gnu"
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+define weak_odr void @bah() {
+  ret void
+}
diff --git a/lld/test/ELF/lto/internalize-exportdyn.ll b/lld/test/ELF/lto/internalize-exportdyn.ll
index fd70812fef7..4a71289c68f 100644
--- a/lld/test/ELF/lto/internalize-exportdyn.ll
+++ b/lld/test/ELF/lto/internalize-exportdyn.ll
@@ -1,6 +1,7 @@
 ; REQUIRES: x86
 ; RUN: llvm-as %s -o %t.o
-; RUN: ld.lld -m elf_x86_64 %t.o -o %t2 --export-dynamic -save-temps
+; RUN: llvm-as %p/Inputs/internalize-exportdyn.ll -o %t2.o
+; RUN: ld.lld -m elf_x86_64 %t.o %t2.o -o %t2 --export-dynamic -save-temps
 ; RUN: llvm-dis < %t2.lto.bc | FileCheck %s
 
 target triple = "x86_64-unknown-linux-gnu"
@@ -18,7 +19,24 @@ define hidden void @bar() {
   ret void
 }
 
-; Check that _start and foo are not internalized, but bar is.
+define linkonce_odr void @zed() unnamed_addr {
+  ret void
+}
+
+define linkonce_odr void @bah() {
+  ret void
+}
+
+define linkonce_odr void @baz() {
+  ret void
+}
+
+@use_baz = global void ()* @baz
+
+; Check what gets internalized.
 ; CHECK: define void @_start()
 ; CHECK: define void @foo()
 ; CHECK: define internal void @bar()
+; CHECK: define internal void @zed()
+; CHECK: define weak_odr void @bah()
+; CHECK: define weak_odr void @baz()