[MERGE #5207 @MikeHolman] add NaN check for simple Sets

Merge pull request #5207 from MikeHolman:setnan

It is possible for sign bit to be set on NaNs (e.g. when they are the result of some math operations), so canonicalize them when adding to simple set in order to avoid duplicating entries.

We can do this because the sign bit on NaN is not observable to JS code.

OS: 17498790

Author: MikeHolman

lib/Runtime/Language/JavascriptConversion.inl

@@ -292,9 +292,15 @@ namespace Js {
            {
                return taggedInt;
            }
-
 #if FLOATVAR
-           return value;
+           if (typeId == TypeIds_Number)
+           {
+               // NaN could have sign bit set, but that isn't observable so canonicalize to positive NaN
+               double numberValue = JavascriptNumber::GetValue(value);
+               return JavascriptNumber::IsNan(numberValue)
+                   ? JavascriptNumber::ToVar(JavascriptNumber::NaN)
+                   : value;
+           }
 #else
            return nullptr;
 #endif