Re: [hatari-devel] Re: FPU update

[Andreas Grabher <andreas.grabher@xxxxxxxxxxxx>]

Am 21.01.2017 um 17:47 schrieb Toni Wilen <twilen@xxxxxxxxxx>:

>> Attached is screenshot that shows errors, what do they mean? (Is it
>> correct or incorrect value or something else?)
> 
> FSGLMUL and FSGLDIV error cause most likely is this (which is not
> handled yet):
> 
> "The input operand mantissas truncate to single precision before the
> multiply operation" (from M68000PRM.pdf)
> 
> (How to emulate this correctly?)
> 
These SGL functions are quite weird. I wrote some special functions assuming this:
- The input values are truncated (not rounded) to single precision mantissa (after normalization, if necessary)
- The output value is rounded to single precision mantissa with these exceptions:
	- Output overflows: Infinity or biggest normal number with extended mantissa
	- Output severely underflows: Zero or smallest denormalized number with extended mantissa

Please try the appended patch, but be aware this is highly experimental. I'll have a look at FNEG and FABS tomorrow. But on first view this can only be caused by missing NaN handling in those functions. Other than this these functions are quite simple.

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