[turbofan] Fix typing rule for Math.sign.

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 1306 matching lines @@
         case kMathFround:
         case kMathLog:
         case kMathLog1p:
         case kMathLog10:
         case kMathLog2:
         case kMathSin:
         case kMathSqrt:
         case kMathTan:
           return Type::Number();
         case kMathSign:
-          return t->cache_.kMinusOneToOne;
+          return t->cache_.kMinusOneToOneOrMinusZeroOrNaN;
         // Binary math functions.
         case kMathAtan2:
         case kMathPow:
         case kMathMax:
         case kMathMin:
           return Type::Number();
         case kMathImul:
           return Type::Signed32();
         case kMathClz32:
           return t->cache_.kZeroToThirtyTwo;
@@ skipping 381 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