ensure that every error return sets a message (and goes through Error, for

easy breakpointing).

Fix bugs reading constantexpr geps.  We now can disassemble kc++ global
initializers.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@36398 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Bitcode/Reader/ReaderWrappers.cpp

@@ -51,6 +51,7 @@ bool BitcodeFileReader::Read(std::string *ErrMsg) {
   unsigned char *Buffer = reinterpret_cast<unsigned char*>(File.base());
   if (!ParseBitcode(Buffer, File.size(), Filename))
     return false;
+  assert(getErrorString() && "Didn't set an error string?");
   if (ErrMsg) *ErrMsg = getErrorString();
   return true;
 }