Fix a bug that would cause subzero to fail when --threads=0.

src/IceCompiler.cpp

 //===- subzero/src/IceCompiler.cpp - Driver for bitcode translation -------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file defines a driver for translating PNaCl bitcode into native code.
@@ skipping 123 matching lines @@
     std::unique_ptr<Converter> Converter(new class Converter(Mod.get(), &Ctx));
     Converter->convertToIce();
     Translator.reset(Converter.release());
   } else {
     Ctx.getStrDump() << "Error: Build doesn't allow LLVM IR, "
                      << "--build-on-read=0 not allowed\n";
     return Ctx.getErrorStatus()->assign(EC_Args);
   }
 
   Ctx.waitForWorkerThreads();
-  Translator->transferErrorCode();
-  Translator->emitConstants();
+  if (Translator->getErrorStatus()) {
+    Ctx.getErrorStatus()->assign(Translator->getErrorStatus().value());
+  } else {
+    Ctx.lowerGlobals("last");
+    Ctx.lowerProfileData();
+    Ctx.lowerConstants();
 
-  if (Ctx.getFlags().getOutFileType() == FT_Elf) {
-    TimerMarker T1(Ice::TimerStack::TT_emit, &Ctx);
-    Ctx.getObjectWriter()->setUndefinedSyms(Ctx.getConstantExternSyms());
-    Ctx.getObjectWriter()->writeNonUserSections();
+    if (Ctx.getFlags().getOutFileType() == FT_Elf) {
+      TimerMarker T1(Ice::TimerStack::TT_emit, &Ctx);
+      Ctx.getObjectWriter()->setUndefinedSyms(Ctx.getConstantExternSyms());
+      Ctx.getObjectWriter()->writeNonUserSections();
+    }
   }
+
   if (Ctx.getFlags().getSubzeroTimingEnabled())
     Ctx.dumpTimers();
+
   if (Ctx.getFlags().getTimeEachFunction()) {
     const bool DumpCumulative = false;
     Ctx.dumpTimers(GlobalContext::TSK_Funcs, DumpCumulative);
   }
-  const bool FinalStats = true;
+  constexpr bool FinalStats = true;
   Ctx.dumpStats("_FINAL_", FinalStats);
 }
 
 } // end of namespace Ice