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

src/compiler/ia32/code-generator-ia32.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 51 matching lines @@
             isolate()->factory()->NewNumber(constant.ToFloat32(), TENURED));
       case Constant::kFloat64:
         return Immediate(
             isolate()->factory()->NewNumber(constant.ToFloat64(), TENURED));
       case Constant::kExternalReference:
         return Immediate(constant.ToExternalReference());
       case Constant::kHeapObject:
         return Immediate(constant.ToHeapObject());
       case Constant::kInt64:
         break;
+      case Constant::kRpoNumber:
+        return Immediate::CodeRelativeOffset(ToLabel(operand));
     }
     UNREACHABLE();
     return Immediate(-1);
   }
 
   static int NextOffset(int* offset) {
     int i = *offset;
     (*offset)++;
     return i;
   }
@@ skipping 950 matching lines @@
     }
   }
   MarkLazyDeoptSite();
 }
 
 #undef __
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8