Index: include/lld/Core/LinkingContext.h
===================================================================
--- include/lld/Core/LinkingContext.h
+++ include/lld/Core/LinkingContext.h
@@ -234,9 +234,7 @@
   /// but that can be changed by the LinkingContext.  This is also an
   /// opportunity for flavor specific processing.
   virtual void notifySymbolTableCoalesce(const Atom *existingAtom,
-                                         const Atom *newAtom,
-                                         bool &useNew) const {
-  }
+                                         const Atom *newAtom, bool &useNew) {}
 
   /// This method adds undefined symbols specified by the -u option to the to
   /// the list of undefined symbols known to the linker. This option essentially
Index: include/lld/Core/SymbolTable.h
===================================================================
--- include/lld/Core/SymbolTable.h
+++ include/lld/Core/SymbolTable.h
@@ -36,7 +36,7 @@
 /// if an atom has been coalesced away.
 class SymbolTable {
 public:
-  explicit SymbolTable(const LinkingContext &);
+  explicit SymbolTable(LinkingContext &);
 
   /// @brief add atom to symbol table
   bool add(const DefinedAtom &);
@@ -108,7 +108,7 @@
   bool addByName(const Atom &);
   bool addByContent(const DefinedAtom &);
 
-  const LinkingContext &_context;
+  LinkingContext &_context;
   AtomToAtom _replacedAtoms;
   NameToAtom _nameTable;
   NameToAtom _groupTable;
Index: include/lld/ReaderWriter/ELFLinkingContext.h
===================================================================
--- include/lld/ReaderWriter/ELFLinkingContext.h
+++ include/lld/ReaderWriter/ELFLinkingContext.h
@@ -19,6 +19,7 @@
 #include "lld/ReaderWriter/Reader.h"
 #include "lld/ReaderWriter/Writer.h"
 
+#include "llvm/ADT/StringSet.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/Object/ELF.h"
 #include "llvm/Support/ELF.h"
@@ -69,6 +70,9 @@
   bool mergeCommonStrings() const { return _mergeCommonStrings; }
   virtual uint64_t getBaseAddress() const { return _baseAddress; }
 
+  void notifySymbolTableCoalesce(const Atom *existingAtom, const Atom *newAtom,
+                                 bool &useNew) override;
+
   /// This controls if undefined atoms need to be created for undefines that are
   /// present in a SharedLibrary. If this option is set, undefined atoms are
   /// created for every undefined symbol that are present in the dynamic table
@@ -251,6 +255,10 @@
     return true;
   }
 
+  bool hasCoalescedWeakPair(StringRef name) const {
+    return _weakCoalescedSymbols.count(name) != 0;
+  }
+
 private:
   ELFLinkingContext() LLVM_DELETED_FUNCTION;
 
@@ -284,6 +292,7 @@
   StringRefVector _rpathList;
   StringRefVector _rpathLinkList;
   std::map<std::string, uint64_t> _absoluteSymbols;
+  llvm::StringSet<> _weakCoalescedSymbols;
 };
 } // end namespace lld
 
Index: lib/Core/SymbolTable.cpp
===================================================================
--- lib/Core/SymbolTable.cpp
+++ lib/Core/SymbolTable.cpp
@@ -30,7 +30,7 @@
 #include <vector>
 
 namespace lld {
-SymbolTable::SymbolTable(const LinkingContext &context) : _context(context) {}
+SymbolTable::SymbolTable(LinkingContext &context) : _context(context) {}
 
 bool SymbolTable::add(const UndefinedAtom &atom) { return addByName(atom); }
 
Index: lib/ReaderWriter/ELF/ELFLinkingContext.cpp
===================================================================
--- lib/ReaderWriter/ELF/ELFLinkingContext.cpp
+++ lib/ReaderWriter/ELF/ELFLinkingContext.cpp
@@ -241,4 +241,29 @@
   return std::move(undefinedSymFile);
 }
 
+static bool isSharedWeakAtom(const UndefinedAtom *ua) {
+  return ua->canBeNull() != UndefinedAtom::canBeNullNever &&
+         isa<SharedLibraryFile>(ua->file());
+}
+
+void ELFLinkingContext::notifySymbolTableCoalesce(const Atom *existingAtom,
+                                                  const Atom *newAtom,
+                                                  bool &useNew) {
+  // First suppose that the `existingAtom` is defined
+  // and the `newAtom` is undefined.
+  auto *da = dyn_cast<DefinedAtom>(existingAtom);
+  auto *ua = dyn_cast<UndefinedAtom>(newAtom);
+  if (!da && !ua) {
+    // Then try to reverse the assumption.
+    da = dyn_cast<DefinedAtom>(newAtom);
+    ua = dyn_cast<UndefinedAtom>(existingAtom);
+  }
+
+  if (da && ua && da->scope() == Atom::scopeGlobal && isSharedWeakAtom(ua))
+    // If strong defined atom coalesces away weak atom declared
+    // in the shared object the strong atom needs to be dynamicaly exported.
+    // Save its name.
+    _weakCoalescedSymbols.insert(ua->name());
+}
+
 } // end namespace lld
Index: lib/ReaderWriter/ELF/OutputELFWriter.h
===================================================================
--- lib/ReaderWriter/ELF/OutputELFWriter.h
+++ lib/ReaderWriter/ELF/OutputELFWriter.h
@@ -182,7 +182,8 @@
     if (auto section = dyn_cast<AtomSection<ELFT>>(sec))
       for (const auto &atom : section->atoms()) {
         const DefinedAtom *da = dyn_cast<const DefinedAtom>(atom->_atom);
-        if (da && da->dynamicExport() == DefinedAtom::dynamicExportAlways)
+        if (da && (da->dynamicExport() == DefinedAtom::dynamicExportAlways ||
+                   _context.hasCoalescedWeakPair(da->name())))
           _dynamicSymbolTable->addSymbol(atom->_atom, section->ordinal(),
                                          atom->_virtualAddr, atom);
       }
Index: test/elf/X86_64/dynsym-weak.test
===================================================================
--- /dev/null
+++ test/elf/X86_64/dynsym-weak.test
@@ -0,0 +1,118 @@
+# Check that a symbol declared as a week in a shared library gets a dynamic
+# symbol table record in an executable file if this executabe file declares the
+# symbol as strong.
+
+# RUN: yaml2obj -format=elf -docnum 1 %s > %t.foo.o
+# RUN: lld -flavor gnu -target x86_64 -shared -o %t.so %t.foo.o
+# RUN: yaml2obj -format=elf -docnum 2 %s > %t.main.o
+#
+# Link executable file with strong symbol. Weak symbol is in the shared lib.
+# RUN: lld -flavor gnu -target x86_64 -e main -o %t1.exe %t.main.o %t.so
+# RUN: llvm-readobj -dyn-symbols %t1.exe | FileCheck -check-prefix=EXE %s
+#
+# Link executable file. Strong and weak symbol come from different object files.
+# RUN: lld -flavor gnu -target x86_64 -e main -o %t2.exe %t.main.o %t.foo.o
+# RUN: llvm-readobj -dyn-symbols %t2.exe | FileCheck -check-prefix=OBJ %s
+#
+# Link shared library. Weak symbol is in the another shared lib.
+# RUN: lld -flavor gnu -target x86_64 -shared -o %t.res.so %t.main.o %t.so
+# RUN: llvm-readobj -dyn-symbols %t.res.so | FileCheck -check-prefix=SO %s
+
+# EXE:      Symbol {
+# EXE:        Name: flag@ ({{[0-9]+}})
+# EXE-NEXT:   Value: 0x{{[0-9A-F]+}}
+# EXE-NEXT:   Size: 4
+# EXE-NEXT:   Binding: Global (0x1)
+# EXE-NEXT:   Type: Object (0x1)
+# EXE-NEXT:   Other: 0
+# EXE-NEXT:   Section: .data (0x{{[0-9A-F]+}})
+# EXE-NEXT: }
+
+# OBJ-NOT:  Name: flag@ ({{[0-9]+}})
+
+# SO:      Symbol {
+# SO:        Name: flag@ ({{[0-9]+}})
+# SO-NEXT:   Value: 0x{{[0-9A-F]+}}
+# SO-NEXT:   Size: 4
+# SO-NEXT:   Binding: Global (0x1)
+# SO-NEXT:   Type: Object (0x1)
+# SO-NEXT:   Other: 0
+# SO-NEXT:   Section: .data (0x{{[0-9A-F]+}})
+# SO-NEXT: }
+
+# foo.o
+---
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_X86_64
+
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    AddressAlign:    0x04
+    Size:            0x08
+  - Name:            .rela.text
+    Type:            SHT_RELA
+    Link:            .symtab
+    AddressAlign:    0x08
+    Info:            .text
+    Relocations:
+      - Offset:          0x00
+        Symbol:          flag
+        Type:            R_X86_64_GOTPCREL
+        Addend:          -4
+
+Symbols:
+  Global:
+    - Name:            foo
+      Type:            STT_FUNC
+      Section:         .text
+      Size:            0x08
+  Weak:
+    - Name:            flag
+
+# main.o
+---
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_X86_64
+
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    AddressAlign:    0x04
+    Size:            0x08
+  - Name:            .rela.text
+    Type:            SHT_RELA
+    Link:            .symtab
+    AddressAlign:    0x08
+    Info:            .text
+    Relocations:
+      - Offset:          0x00
+        Symbol:          foo
+        Type:            R_X86_64_PLT32
+        Addend:          -4
+  - Name:            .data
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_WRITE, SHF_ALLOC ]
+    AddressAlign:    0x04
+    Size:            0x04
+
+Symbols:
+  Global:
+    - Name:            flag
+      Type:            STT_OBJECT
+      Section:         .data
+      Size:            0x04
+    - Name:            main
+      Type:            STT_FUNC
+      Section:         .text
+      Size:            0x08
+    - Name:            foo
+...