[BOLT] Ignore duplicate global symbols

[rafauler]

Summary

We noticed some binaries with duplicated global symbol
entries (same name, address and size). Ignore them as it is possibly a
bug in the linker, and continue processing, unless the symbol has a
different size or address.

[maksfb]

Since the erroneous condition could be triggered by a bad input, we should replace the assertion with an error.

[rafauler]

Convert assertion into error

[maksfb]

LGTM

bolt/lib/Rewrite/RewriteInstance.cpp

for (auto ISym = SortedFileSymbols.begin(); ISym != SortedSymbolsEnd;
     //
     // NOTE: the naming convention for local symbols should match
     //       the one we use for profile data.
     std::string UniqueName;
     std::string AlternativeName;
     if (Name.empty()) {
       UniqueName = "ANONYMOUS." + std::to_string(AnonymousId++);
     } else if (cantFail(Symbol.getFlags()) & SymbolRef::SF_Global) {
-      assert(!BC->getBinaryDataByName(Name) && "global name not unique");
+      if (const BinaryData *BD = BC->getBinaryDataByName(Name)) {
+        if (BD->getSize() == ELFSymbolRef(Symbol).getSize() &&
+            BD->getAddress() == Address) {
+          if (opts::Verbosity > 1)
+            errs() << "BOLT-WARNING: ignoring duplicate global symbol " << Name
+                   << "\n";
+          // Ignore duplicate entry - possibly a bug in the linker
+          continue;
+        }
+        errs() << "BOLT-ERROR: bad input binary, global symbol \"" << Name
+               << "\" is not unique\n";
+        exit(1);
+      }
       UniqueName = Name;
     } else {
       // If we have a local file name, we should create 2 variants for the
       // function name. The reason is that perf profile might have been
       // collected on a binary that did not have the local file name (e.g. as
       // a side effect of stripping debug info from the binary):
       //
       //   primary:     <function>/<id>