Bug for fclass instr ????

[IC-Dream]

Hi,

The definition of NAN from IEEE 754-2008 standard:
The value NaN (Not a Number) is used to represent a value that does not represent a real number. NaNs are represented by a bit pattern with an exponent of all ones and a non-zero mantissa. The sign bit can be 0 or 1 – it has no bearing.

There are two categories of NaNs:
QNaN (Quiet NaN) – arising when the result of an arithmetic operation is mathematically undefined. The MSB of the mantissa is '1' for this type of NaN.
SNaN (Signaling NaN) – used to signal an exception when an invalid operation is performed. The MSB of the mantissa is '0' for this type of NaN.

But the implement of fpu_core may exist some problem in riscv_alu.sv:

it seems that the RTL violates the definition of NAN.

Thanks
Dream

[FrancescoConti]

I think you're correct - however I transferred the issue to the riscy core repository, which is more appropriate.

[IC-Dream]

@FrancescoConti Thanks a lot

[stmach]

See #52