[turbofan] Use special constant type for RPO block number operands.

src/compiler/x64/code-generator-x64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/code-generator.h"
 
 #include "src/compiler/code-generator-impl.h"
 #include "src/compiler/gap-resolver.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties-inl.h"
@@ skipping 901 matching lines @@
         case Constant::kFloat64:
           __ Move(dst,
                   isolate()->factory()->NewNumber(src.ToFloat64(), TENURED));
           break;
         case Constant::kExternalReference:
           __ Move(dst, src.ToExternalReference());
           break;
         case Constant::kHeapObject:
           __ Move(dst, src.ToHeapObject());
           break;
+        case Constant::kRpoNumber:
+          UNREACHABLE();  // TODO(dcarney): load of labels on x64.
+          break;
       }
       if (destination->IsStackSlot()) {
         __ movq(g.ToOperand(destination), kScratchRegister);
       }
     } else if (src.type() == Constant::kFloat32) {
       // TODO(turbofan): Can we do better here?
       uint32_t src_const = bit_cast<uint32_t>(src.ToFloat32());
       if (destination->IsDoubleRegister()) {
         __ Move(g.ToDoubleRegister(destination), src_const);
       } else {
@@ skipping 100 matching lines @@
     }
   }
   MarkLazyDeoptSite();
 }
 
 #undef __
 
 }  // namespace internal
 }  // namespace compiler
 }  // namespace v8