[turbofan] Introduce dedicated NumberToBoolean operator.

src/compiler/operation-typer.cc

 // Copyright 2016 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/operation-typer.h"
 
 #include "src/compiler/common-operator.h"
 #include "src/compiler/type-cache.h"
 #include "src/compiler/types.h"
 #include "src/factory.h"
@@ skipping 442 matching lines @@
   return Type::Number();
 }
 
 Type* OperationTyper::NumberTrunc(Type* type) {
   DCHECK(type->Is(Type::Number()));
   if (type->Is(cache_.kIntegerOrMinusZeroOrNaN)) return type;
   // TODO(bmeurer): We could infer a more precise type here.
   return cache_.kIntegerOrMinusZeroOrNaN;
 }
 
+Type* OperationTyper::NumberToBoolean(Type* type) {
+  DCHECK(type->Is(Type::Number()));
+  if (!type->IsInhabited()) return Type::None();
+  if (type->Is(cache_.kZeroish)) return singleton_false_;
+  if (type->Is(Type::PlainNumber()) && (type->Max() < 0 || 0 < type->Min())) {
+    return singleton_true_;  // Ruled out nan, -0 and +0.
+  }
+  return Type::Boolean();
+}
+
 Type* OperationTyper::NumberToInt32(Type* type) {
   DCHECK(type->Is(Type::Number()));
 
   if (type->Is(Type::Signed32())) return type;
   if (type->Is(cache_.kZeroish)) return cache_.kSingletonZero;
   if (type->Is(signed32ish_)) {
     return Type::Intersect(Type::Union(type, cache_.kSingletonZero, zone()),
                            Type::Signed32(), zone());
   }
   return Type::Signed32();
@@ skipping 486 matching lines @@
   return singleton_true();
 }
 
 Type* OperationTyper::TypeTypeGuard(const Operator* sigma_op, Type* input) {
   return Type::Intersect(input, TypeGuardTypeOf(sigma_op), zone());
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8