Fix error reporting in the PNaCl bitcode reader.

lib/IRReader/IRReader.cpp

 //===---- IRReader.cpp - Reader for LLVM IR files -------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/IRReader/IRReader.h"
@@ skipping 90 matching lines @@
 // @LOCALMOD-BEGIN
 Module *llvm::NaClParseIR(MemoryBuffer *Buffer,
                           NaClFileFormat Format,
                           SMDiagnostic &Err,
                           LLVMContext &Context) {
   NamedRegionTimer T(TimeIRParsingName, TimeIRParsingGroupName,
                      TimePassesIsEnabled);
   if ((Format == PNaClFormat) &&
       isNaClBitcode((const unsigned char *)Buffer->getBufferStart(),
                     (const unsigned char *)Buffer->getBufferEnd())) {
-    std::string ErrMsg;
-    Module *M = NaClParseBitcodeFile(Buffer, Context, &ErrMsg);
-    if (M == 0)
+    ErrorOr<Module *> MOrErr =

[jvoung (off chromium), 2014/12/01 23:23:50]

"ModuleOrError" to be consistent with ParseIR() ?

[JF, 2014/12/02 00:49:04]

Upstream uses MOrErr, so I'd keep that.

[Karl, 2014/12/03 18:32:10]

Since our local version uses ModuleOrError, will make consistent with that.

+        NaClParseBitcodeFile(Buffer, Context, /*VerboseErrors=*/false);

[jvoung (off chromium), 2014/12/01 23:23:50]

how do you decide between setting VerboseErrors to true or false?

[Karl, 2014/12/03 18:32:10]

Good point. Adding as argument so that calling tool can decide.

+    if (std::error_code EC = MOrErr.getError())
       Err = SMDiagnostic(Buffer->getBufferIdentifier(), SourceMgr::DK_Error,
-                         ErrMsg);
+                         EC.message());
     // ParseBitcodeFile does not take ownership of the Buffer.
-    return M;
+    return MOrErr.get();
   } else if (Format == LLVMFormat) {
     if (isBitcode((const unsigned char *)Buffer->getBufferStart(),
                   (const unsigned char *)Buffer->getBufferEnd())) {
       ErrorOr<Module *> MOrErr = parseBitcodeFile(Buffer, Context);
       if (std::error_code EC = MOrErr.getError())
         Err = SMDiagnostic(Buffer->getBufferIdentifier(), SourceMgr::DK_Error,
                            EC.message());
       // ParseBitcodeFile does not take ownership of the Buffer.
       return MOrErr.get();
     }
@@ skipping 43 matching lines @@
       Diag.print(nullptr, os, false);
       os.flush();
 
       *OutMessage = strdup(buf.c_str());
     }
     return 1;
   }
 
   return 0;
 }