Subzero: Track protos + globals w/out initializers as undef too (not just helper funcs)

src/IceConverter.cpp

 //===- subzero/src/IceConverter.cpp - Converts LLVM to Ice  ---------------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the LLVM to ICE converter.
@@ skipping 103 matching lines @@
     Ice::Cfg::setCurrentCfg(nullptr);
     Converter.translateFcn(std::move(Func));
   }
 
   // convertConstant() does not use Func or require it to be a valid
   // Ice::Cfg pointer.  As such, it's suitable for e.g. constructing
   // global initializers.
   Ice::Constant *convertConstant(const Constant *Const) {
     if (const auto GV = dyn_cast<GlobalValue>(Const)) {
       Ice::GlobalDeclaration *Decl = getConverter().getGlobalDeclaration(GV);
-      const Ice::RelocOffsetT Offset = 0;
-      return Ctx->getConstantSym(Offset, Decl->getName(),
-                                 Decl->getSuppressMangling());
+      bool IsUndefined = false;
+      if (const auto *Func = llvm::dyn_cast<Ice::FunctionDeclaration>(Decl))
+        IsUndefined = Func->isProto();
+      else if (const auto *Var = llvm::dyn_cast<Ice::VariableDeclaration>(Decl))
+        IsUndefined = !Var->hasInitializer();
+      else
+        report_fatal_error("Unhandled GlobalDeclaration type");
+      if (IsUndefined)
+        return Ctx->getConstantExternSym(Decl->getName());
+      else {
+        const Ice::RelocOffsetT Offset = 0;
+        return Ctx->getConstantSym(Offset, Decl->getName(),
+                                   Decl->getSuppressMangling());
+      }
     } else if (const auto CI = dyn_cast<ConstantInt>(Const)) {
       Ice::Type Ty = convertToIceType(CI->getType());
       return Ctx->getConstantInt(Ty, CI->getSExtValue());
     } else if (const auto CFP = dyn_cast<ConstantFP>(Const)) {
       Ice::Type Type = convertToIceType(CFP->getType());
       if (Type == Ice::IceType_f32)
         return Ctx->getConstantFloat(CFP->getValueAPF().convertToFloat());
       else if (Type == Ice::IceType_f64)
         return Ctx->getConstantDouble(CFP->getValueAPF().convertToDouble());
       llvm_unreachable("Unexpected floating point type");
@@ skipping 754 matching lines @@
       Ctx->pushTimer(TimerID, StackID);
     }
     LLVM2ICEFunctionConverter FunctionConverter(*this);
     FunctionConverter.convertFunction(&I);
     if (TimeThisFunction)
       Ctx->popTimer(TimerID, StackID);
   }
 }
 
 } // end of namespace Ice