0.0 + 0.0 = 0x7dc00000?

[buloruabutata]

if I run "fadd.s f18, f16, f7" alone, the result of f18 is 0x7dc00000 instead of 0x0000000, I want to know why this is.

[TheThirdOne]

This happens because, before initialization, the floating point registers have a value of double wide 0.0. Trying to access such a register as a float results in getting a NaN because it was not a correctly NaN boxed float.

When I implemented NaN boxing, I didn't give much thought to what the initial values were so maybe there a better solution, but simply initializing the registers you need with values should make it work as you expect.

[radrow]

Why not initialize them to single precision 0.0, so they are usable (and not misleading) for 32bit users? And if they are not meant to be used uninitialized, then I would rather put canonical NaN to make this conspicuous.