Fix FPRF handling of denormal singles #9811
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Sintendo
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The interpreter was wrong after all. Hardware verified.
Performance optimization, along with making the code a little neater. Saves us from performing a single -> double -> single conversion when calling UpdateFPRFSingle.
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Tilka
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phire
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We were classifying denormal singles as if they were normals (because we converted singles to doubles and then classified them using the same code as for doubles), but this behavior has been confirmed incorrect by dolphin-emu/hwtests#41.
When fixing this, I went with an approach of performing classification on 32-bit floats in all CPU emulation cores (i.e. classification is performed after forcing the result to single but before converting it back to double). It would be possible to perform classification after converting to double, but that would require us to check if the exponent is in a certain range instead of just checking if it is zero, so I think the approach I went with is better.