Index: llvm/trunk/test/tools/llvm-objdump/X86/warn-missing-disasm-func.test
===================================================================
--- llvm/trunk/test/tools/llvm-objdump/X86/warn-missing-disasm-func.test
+++ llvm/trunk/test/tools/llvm-objdump/X86/warn-missing-disasm-func.test
@@ -0,0 +1,11 @@
+## Warn if --disassemble-functions specifies an unknown symbol.
+# RUN: yaml2obj %s | llvm-objdump - --disassemble-functions=foo 2>&1 | FileCheck %s
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_REL
+  Machine: EM_X86_64
+
+# CHECK: warning: failed to disassemble missing function foo
Index: llvm/trunk/tools/llvm-objdump/llvm-objdump.cpp
===================================================================
--- llvm/trunk/tools/llvm-objdump/llvm-objdump.cpp
+++ llvm/trunk/tools/llvm-objdump/llvm-objdump.cpp
@@ -18,6 +18,7 @@
 #include "llvm-objdump.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SetOperations.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringSet.h"
 #include "llvm/ADT/Triple.h"
@@ -375,6 +376,10 @@
   errs().flush();
 }
 
+void warn(Twine Message) {
+  WithColor::warning(errs(), ToolName) << Message << "\n";
+}
+
 LLVM_ATTRIBUTE_NORETURN void report_error(StringRef File, Twine Message) {
   WithColor::error(errs(), ToolName)
       << "'" << File << "': " << Message << ".\n";
@@ -1091,6 +1096,7 @@
 
   // Sort all the symbols, this allows us to use a simple binary search to find
   // a symbol near an address.
+  StringSet<> FoundDisasmFuncsSet;
   for (std::pair<const SectionRef, SectionSymbolsTy> &SecSyms : AllSymbols)
     array_pod_sort(SecSyms.second.begin(), SecSyms.second.end());
   array_pod_sort(AbsoluteSymbols.begin(), AbsoluteSymbols.end());
@@ -1182,6 +1188,8 @@
       uint64_t Start = std::get<0>(Symbols[SI]);
       if (Start < SectionAddr || StopAddress <= Start)
         continue;
+      else
+        FoundDisasmFuncsSet.insert(std::get<1>(Symbols[SI]));
 
       // The end is the section end, the beginning of the next symbol, or
       // --stop-address.
@@ -1402,6 +1410,10 @@
       }
     }
   }
+  StringSet<> MissingDisasmFuncsSet =
+      set_difference(DisasmFuncsSet, FoundDisasmFuncsSet);
+  for (StringRef MissingDisasmFunc : MissingDisasmFuncsSet.keys())
+    warn("failed to disassemble missing function " + MissingDisasmFunc);
 }
 
 static void disassembleObject(const ObjectFile *Obj, bool InlineRelocs) {