[turbofan] false is also falsish.

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 <limits>
 
 #include "src/bootstrapper.h"
 #include "src/compiler/graph-inl.h"
@@ skipping 171 matching lines @@
   undefined_or_number = Type::Union(Type::Undefined(), Type::Number(), zone);
   singleton_false = Type::Constant(f->false_value(), zone);
   singleton_true = Type::Constant(f->true_value(), zone);
   singleton_zero = Type::Range(zero, zero, zone);
   singleton_one = Type::Range(one, one, zone);
   zero_or_one = Type::Union(singleton_zero, singleton_one, zone);
   zeroish = Type::Union(singleton_zero, nan_or_minuszero, zone);
   signed32ish = Type::Union(signed32, truncating_to_zero, zone);
   unsigned32ish = Type::Union(unsigned32, truncating_to_zero, zone);
   falsish = Type::Union(Type::Undetectable(),
-      Type::Union(zeroish, undefined_or_null, zone), zone);
+                        Type::Union(Type::Union(singleton_false, zeroish, zone),
+                                    undefined_or_null, zone),
+                        zone);
   integer = Type::Range(minusinfinity, infinity, zone);
   weakint = Type::Union(integer, nan_or_minuszero, zone);
 
   number_fun0_ = Type::Function(number, zone);
   number_fun1_ = Type::Function(number, number, zone);
   number_fun2_ = Type::Function(number, number, number, zone);
 
   weakint_fun1_ = Type::Function(weakint, number, zone);
   random_fun_ = Type::Function(Type::OrderedNumber(), zone);
 
@@ skipping 1898 matching lines @@
         // TODO(rossberg): Do we want some ClampedArray type to express this?
         break;
     }
   }
   return Type::Constant(value, zone());
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8