Subzero: Improve the usability of UnimplementedError during lowering.

src/IceTargetLowering.cpp

 //===- subzero/src/IceTargetLowering.cpp - Basic lowering implementation --===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 441 matching lines @@
       continue;
     FOREACH_VAR_IN_INST(Var, *Inst) {
       if (Var == Dest) {
         Inst->setDestRedefined();
         break;
       }
     }
   }
 }
 
+void TargetLowering::addFakeDefUses(const Inst *Instr) {
+  FOREACH_VAR_IN_INST(Var, *Instr) {
+    if (auto *Var64 = llvm::dyn_cast<Variable64On32>(Var)) {
+      Context.insert<InstFakeUse>(Var64->getLo());
+      Context.insert<InstFakeUse>(Var64->getHi());
+    } else {
+      Context.insert<InstFakeUse>(Var);
+    }
+  }
+  Variable *Dest = Instr->getDest();
+  if (Dest == nullptr)
+    return;
+  if (auto *Var64 = llvm::dyn_cast<Variable64On32>(Dest)) {
+    Context.insert<InstFakeDef>(Var64->getLo());
+    Context.insert<InstFakeDef>(Var64->getHi());
+  } else {
+    Context.insert<InstFakeDef>(Dest);
+  }
+}
+
 void TargetLowering::sortVarsByAlignment(VarList &Dest,
                                          const VarList &Source) const {
   Dest = Source;
   // Instead of std::sort, we could do a bucket sort with log2(alignment) as
   // the buckets, if performance is an issue.
   std::sort(Dest.begin(), Dest.end(),
             [this](const Variable *V1, const Variable *V2) {
               return typeWidthInBytesOnStack(V1->getType()) >
                      typeWidthInBytesOnStack(V2->getType());
             });
@@ skipping 325 matching lines @@
   case Target_##X:                                                             \
     return ::X::createTargetHeaderLowering(Ctx);
 #include "llvm/Config/SZTargets.def"
 #undef SUBZERO_TARGET
   }
 }
 
 TargetHeaderLowering::~TargetHeaderLowering() = default;
 
 } // end of namespace Ice