[TableGen] Detect multiple Processors with the same name.

[craig.topper]

Summary

Due to a bad merge we ended up with duplicate entries in our
downstream repo. I was surprised that nothing caught it. I wrote
this check so I could fix our downstream repo and figured I might
as well share it.

[spatel]

LGTM

[RKSimon]

LGTM

llvm/utils/TableGen/CodeGenSchedule.cpp

 //===- CodeGenSchedule.cpp - Scheduling MachineModels ---------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
void CodeGenSchedModels::collectOptionalProcessorInfo() {
   checkCompleteness();
 }
 
 /// Gather all processor models.
 void CodeGenSchedModels::collectProcModels() {
   RecVec ProcRecords = Records.getAllDerivedDefinitions("Processor");
   llvm::sort(ProcRecords, LessRecordFieldName());
 
+  // Check for duplicated names.
+  auto I = std::adjacent_find(ProcRecords.begin(), ProcRecords.end(),
+                              [](const Record *Rec1, const Record *Rec2) {
+    return Rec1->getValueAsString("Name") == Rec2->getValueAsString("Name");
+  });
+  if (I != ProcRecords.end())
+    PrintFatalError((*I)->getLoc(), "Duplicate processor name " +
+                    (*I)->getValueAsString("Name"));
+
   // Reserve space because we can. Reallocation would be ok.
   ProcModels.reserve(ProcRecords.size()+1);
 
   // Use idx=0 for NoModel/NoItineraries.
   Record *NoModelDef = Records.getDef("NoSchedModel");
   Record *NoItinsDef = Records.getDef("NoItineraries");
   ProcModels.emplace_back(0, "NoSchedModel", NoModelDef, NoItinsDef);
   ProcModelMap[NoModelDef] = 0;