Wrong ILogB result for subnormal values

[huoyaoyuan]

Math.ILogB incorrectly uses TZCNT instead of LZCNT for subnormal values:

runtime/src/libraries/System.Private.CoreLib/src/System/Math.cs

Line 898 in 8234fe3

return double.MinExponent - (BitOperations.TrailingZeroCount(x.TrailingSignificand) - double.BiasedExponentLength);

Math.ILogB(1e-308) returns -1024 on .NET 8, and -1012 on .NET 9. The correct result is -1024.

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[hez2010]

The correct result is -1012.

Did you mean -1024?