Index: test/tools/llvm-objcopy/weaken.test
===================================================================
--- /dev/null
+++ test/tools/llvm-objcopy/weaken.test
@@ -0,0 +1,75 @@
+# RUN: yaml2obj %s > %t
+# RUN: llvm-objcopy --weaken-symbol Global -W Local -W Weak %t %t2
+# RUN: llvm-readobj -symbols %t2 | FileCheck %s
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_X86_64
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Address:         0x1000
+    AddressAlign:    0x0000000000000010
+    Size:            64
+Symbols:
+  Local:
+    - Name:     Local
+      Type:     STT_FUNC
+      Section:  .text
+      Value:    0x1000
+      Size:     8
+  Weak:
+    - Name:     Weak
+      Type:     STT_FUNC
+      Size:     8
+      Section:  .text
+      Value:    0x1008
+  Global:
+    - Name:     Global
+      Type:     STT_FUNC
+      Size:     8
+      Section:  .text
+      Value:    0x1010
+
+#CHECK: Symbols [
+#CHECK-NEXT:  Symbol {
+#CHECK-NEXT:    Name:
+#CHECK-NEXT:    Value: 0x0
+#CHECK-NEXT:    Size: 0
+#CHECK-NEXT:    Binding: Local
+#CHECK-NEXT:    Type: None
+#CHECK-NEXT:    Other: 0
+#CHECK-NEXT:    Section: Undefined
+#CHECK-NEXT:  }
+#CHECK-NEXT:  Symbol {
+#CHECK-NEXT:    Name: Local
+#CHECK-NEXT:    Value: 0x1000
+#CHECK-NEXT:    Size: 8
+#CHECK-NEXT:    Binding: Local
+#CHECK-NEXT:    Type: Function
+#CHECK-NEXT:    Other: 0
+#CHECK-NEXT:    Section: .text
+#CHECK-NEXT:  }
+#CHECK-NEXT:  Symbol {
+#CHECK-NEXT:    Name: Global
+#CHECK-NEXT:    Value: 0x1010
+#CHECK-NEXT:    Size: 8
+#CHECK-NEXT:    Binding: Weak
+#CHECK-NEXT:    Type: Function
+#CHECK-NEXT:    Other: 0
+#CHECK-NEXT:    Section: .text
+#CHECK-NEXT:  }
+#CHECK-NEXT:  Symbol {
+#CHECK-NEXT:    Name: Weak
+#CHECK-NEXT:    Value: 0x1008
+#CHECK-NEXT:    Size: 8
+#CHECK-NEXT:    Binding: Weak
+#CHECK-NEXT:    Type: Function
+#CHECK-NEXT:    Other: 0
+#CHECK-NEXT:    Section: .text
+#CHECK-NEXT:  }
+#CHECK-NEXT:]
Index: tools/llvm-objcopy/Opts.td
===================================================================
--- tools/llvm-objcopy/Opts.td
+++ tools/llvm-objcopy/Opts.td
@@ -67,3 +67,8 @@
 defm globalize_symbol : Eq<"globalize-symbol">,
                        MetaVarName<"symbol">,
                        HelpText<"Mark <symbol> as global">;
+defm weaken_symbol : Eq<"weaken-symbol">,
+                       MetaVarName<"symbol">,
+                       HelpText<"Mark <symbol> as weak">;
+def W : JoinedOrSeparate<["-"], "W">,
+        Alias<weaken_symbol>;
Index: tools/llvm-objcopy/llvm-objcopy.cpp
===================================================================
--- tools/llvm-objcopy/llvm-objcopy.cpp
+++ tools/llvm-objcopy/llvm-objcopy.cpp
@@ -120,6 +120,7 @@
   std::vector<StringRef> AddSection;
   std::vector<StringRef> SymbolsToLocalize;
   std::vector<StringRef> SymbolsToGlobalize;
+  std::vector<StringRef> SymbolsToWeaken;
   StringMap<StringRef> SymbolsToRename;
   bool StripAll;
   bool StripAllGNU;
@@ -328,6 +329,11 @@
           is_contained(Config.SymbolsToGlobalize, Sym.Name))
         Sym.Binding = STB_GLOBAL;
 
+      if (!Config.SymbolsToWeaken.empty() &&
+          is_contained(Config.SymbolsToWeaken, Sym.Name) &&
+          Sym.Binding == STB_GLOBAL)
+        Sym.Binding = STB_WEAK;
+
       const auto I = Config.SymbolsToRename.find(Sym.Name);
       if (I != Config.SymbolsToRename.end())
         Sym.Name = I->getValue();
@@ -421,6 +427,8 @@
     Config.SymbolsToLocalize.push_back(Arg->getValue());
   for (auto Arg : InputArgs.filtered(OBJCOPY_globalize_symbol))
     Config.SymbolsToGlobalize.push_back(Arg->getValue());
+  for (auto Arg : InputArgs.filtered(OBJCOPY_weaken_symbol))
+    Config.SymbolsToWeaken.push_back(Arg->getValue());
 
   return Config;
 }