Index: ELF/Driver.cpp
===================================================================
--- ELF/Driver.cpp
+++ ELF/Driver.cpp
@@ -1119,6 +1119,21 @@
     Symtab->fetchLazy<ELFT>(Sym);
 }
 
+// If all references to a DSO happen to be weak, the DSO is not added
+// to DT_NEEDED. If that happens, we need to eliminate shared symbols
+// created from the DSO. Otherwise, they become dangling references
+// that point to a non-existent DSO.
+template <class ELFT> static void demoteSharedSymbols() {
+  for (Symbol *Sym : Symtab->getSymbols())
+    if (auto *S = dyn_cast<SharedSymbol>(Sym))
+      if (!S->getFile<ELFT>().IsNeeded) {
+        bool Used = S->Used;
+        replaceSymbol<Undefined>(S, nullptr, S->getName(), STB_WEAK, S->StOther,
+                                 S->Type);
+        S->Used = Used;
+      }
+}
+
 // Do actual linking. Note that when this function is called,
 // all linker scripts have already been parsed.
 template <class ELFT> void LinkerDriver::link(opt::InputArgList &Args) {
@@ -1279,6 +1294,7 @@
   // Do size optimizations: garbage collection, merging of SHF_MERGE sections
   // and identical code folding.
   markLive<ELFT>();
+  demoteSharedSymbols<ELFT>();
   decompressSections();
   mergeSections();
   if (Config->ICF)
Index: test/ELF/as-needed-weak.s
===================================================================
--- /dev/null
+++ test/ELF/as-needed-weak.s
@@ -0,0 +1,22 @@
+# REQUIRES: x86
+
+# RUN: echo '.globl foo; .type foo, @function; foo:' | \
+# RUN:   llvm-mc -filetype=obj -triple=x86_64-unknown-linux - -o %t1.o
+# RUN: ld.lld -shared -o %t1.so -soname libfoo %t1.o
+
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t2.o
+# RUN: ld.lld -o %t.exe %t2.o --as-needed %t1.so
+# RUN: llvm-readelf -dynamic-table -dyn-symbols %t.exe | FileCheck %s
+
+# CHECK-NOT: libfoo
+
+# CHECK:      Symbol table of .hash for image:
+# CHECK-NEXT: Num Buc:    Value          Size   Type   Bind Vis      Ndx Name
+# CHECK-NEXT:   1   1: 0000000000000000     0 FUNC    WEAK   DEFAULT UND foo@
+
+.globl _start
+.weak foo
+
+_start:
+  mov $foo, %eax
+  callq foo
Index: test/ELF/gc-sections-shared.s
===================================================================
--- test/ELF/gc-sections-shared.s
+++ test/ELF/gc-sections-shared.s
@@ -25,6 +25,15 @@
 # CHECK-NEXT:     Section: Undefined (0x0)
 # CHECK-NEXT:   }
 # CHECK-NEXT:   Symbol {
+# CHECK-NEXT:     Name: qux
+# CHECK-NEXT:     Value:
+# CHECK-NEXT:     Size:
+# CHECK-NEXT:     Binding: Weak
+# CHECK-NEXT:     Type:
+# CHECK-NEXT:     Other:
+# CHECK-NEXT:     Section: Undefined
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Symbol {
 # CHECK-NEXT:     Name: bar
 # CHECK-NEXT:     Value:
 # CHECK-NEXT:     Size:
@@ -51,15 +60,6 @@
 # CHECK-NEXT:     Other:
 # CHECK-NEXT:     Section: .text
 # CHECK-NEXT:   }
-# CHECK-NEXT:   Symbol {
-# CHECK-NEXT:     Name: qux
-# CHECK-NEXT:     Value:
-# CHECK-NEXT:     Size:
-# CHECK-NEXT:     Binding: Weak
-# CHECK-NEXT:     Type:
-# CHECK-NEXT:     Other:
-# CHECK-NEXT:     Section: Undefined
-# CHECK-NEXT:   }
 # CHECK-NEXT: ]
 
 # CHECK-NOT: NEEDED
@@ -68,59 +68,7 @@
 
 # Test with %t.o at the end too.
 # RUN: ld.lld --gc-sections --export-dynamic-symbol foo -o %t --as-needed %t2.so %t3.so %t4.so %t.o
-# RUN: llvm-readobj --dynamic-table --dyn-symbols %t | FileCheck --check-prefix=CHECK2 %s
-
-# CHECK2:      DynamicSymbols [
-# CHECK2-NEXT:   Symbol {
-# CHECK2-NEXT:     Name:
-# CHECK2-NEXT:     Value:
-# CHECK2-NEXT:     Size:
-# CHECK2-NEXT:     Binding: Local
-# CHECK2-NEXT:     Type:
-# CHECK2-NEXT:     Other:
-# CHECK2-NEXT:     Section: Undefined (0x0)
-# CHECK2-NEXT:   }
-# CHECK2-NEXT:   Symbol {
-# CHECK2-NEXT:     Name: bar
-# CHECK2-NEXT:     Value:
-# CHECK2-NEXT:     Size:
-# CHECK2-NEXT:     Binding: Global
-# CHECK2-NEXT:     Type:
-# CHECK2-NEXT:     Other:
-# CHECK2-NEXT:     Section: .text
-# CHECK2-NEXT:   }
-# CHECK2-NEXT:   Symbol {
-# CHECK2-NEXT:     Name: baz
-# CHECK2-NEXT:     Value:
-# CHECK2-NEXT:     Size:
-# CHECK2-NEXT:     Binding: Global
-# CHECK2-NEXT:     Type:
-# CHECK2-NEXT:     Other:
-# CHECK2-NEXT:     Section: Undefined
-# CHECK2-NEXT:   }
-# CHECK2-NEXT:   Symbol {
-# CHECK2-NEXT:     Name: qux
-# CHECK2-NEXT:     Value:
-# CHECK2-NEXT:     Size:
-# CHECK2-NEXT:     Binding: Weak
-# CHECK2-NEXT:     Type:
-# CHECK2-NEXT:     Other:
-# CHECK2-NEXT:     Section: Undefined
-# CHECK2-NEXT:   }
-# CHECK2-NEXT:   Symbol {
-# CHECK2-NEXT:     Name: foo
-# CHECK2-NEXT:     Value:
-# CHECK2-NEXT:     Size:
-# CHECK2-NEXT:     Binding: Global
-# CHECK2-NEXT:     Type:
-# CHECK2-NEXT:     Other:
-# CHECK2-NEXT:     Section: .text
-# CHECK2-NEXT:   }
-# CHECK2-NEXT: ]
-
-# CHECK2-NOT: NEEDED
-# CHECK2:     NEEDED Shared library: [{{.*}}3.so]
-# CHECK2-NOT: NEEDED
+# RUN: llvm-readobj --dynamic-table --dyn-symbols %t | FileCheck --check-prefix=CHECK %s
 
 .section .text.foo, "ax"
 .globl foo