[turbofan] Introduce dedicated NumberToBoolean operator.

src/compiler/typer.cc

 // Copyright 2014 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/typer.h"
 
 #include <iomanip>
 
 #include "src/base/flags.h"
 #include "src/bootstrapper.h"
@@ skipping 405 matching lines @@
     return type;
   }
   return Type::Primitive();
 }
 
 
 Type* Typer::Visitor::ToBoolean(Type* type, Typer* t) {
   if (type->Is(Type::Boolean())) return type;
   if (type->Is(t->falsish_)) return t->singleton_false_;
   if (type->Is(t->truish_)) return t->singleton_true_;
-  if (type->Is(Type::PlainNumber()) && (type->Max() < 0 || 0 < type->Min())) {
-    return t->singleton_true_;  // Ruled out nan, -0 and +0.
+  if (type->Is(Type::Number())) {
+    return t->operation_typer()->NumberToBoolean(type);
   }
   return Type::Boolean();
 }
 
 
 // static
 Type* Typer::Visitor::ToInteger(Type* type, Typer* t) {
   // ES6 section 7.1.4 ToInteger ( argument )
   type = ToNumber(type, t);
   if (type->Is(t->cache_.kIntegerOrMinusZero)) return type;
@@ skipping 1265 matching lines @@
 Type* Typer::Visitor::TypeConstant(Handle<Object> value) {
   if (Type::IsInteger(*value)) {
     return Type::Range(value->Number(), value->Number(), zone());
   }
   return Type::Constant(value, zone());
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8