Re: [hatari-devel] Possible bug in 060 exception stack frames

[Toni Wilen <twilen@xxxxxxxxxx>]

>> Documentation says:
>>
>> --
>> 6.6.2.2 TRAP ENABLED RESULTS (FPCR SNAN BIT SET).
>>
>> If the destination is not a floating-point data register (FMOVE OUT
>> instruction), the destination (memory or integer data register) is
>> written with the same data as though the trap were disabled (FPCR SNAN
>> bit clear), and then control is passed to the user SNAN handler as a
>> post-instruction exception. If desired, the user SNAN handler can
>> overwrite the result.
>>
>> For floating-point data register destinations, the source (if
>> register-to-register instruction) and destination floating-point data
>> registers are not modified. Control is passed to the user SNAN handler
>> as a pre-instruction exception when the next floating-point instruction
>> is encountered. In this case, the SNAN user handler should supply the
>> result.
>> --
>>
>> So according to documentation (Test code has FP0 destination), following
>> FPU instruction should trigger the SNAN exception. But test code expects
>> immediate post-instruction exception and gets confused if it gets
>> delayed until next FPU instruction.
> 
> I did some real 68060 tests. As usual, documentation does not want to
> tell the whole truth.
> 
> It mentions many times something like "Since FMOVE to/from the FPCR,
> FPSR, or FPIAR and FMOVEM instructions cannot generate floating-point
> exceptions, you can do blahblahblah" but this only means those
> instructions can't generate exceptions internally and won't modift FPIAR
> (so that FPIAR still points to instruction that caused the exception)
> but they do still cause exception if there is pending FPU exception
> generated by previous FPU instruction. Even FMOVEM.X does this.
> 
> This explains why SNAN, OPERR and DZ tests work.
> 
> Patch coming later..

Done.

Testing 68060 FPSP started:
	Unimplemented <ea>...passed
	Unimplemented data type/format...passed
	Non-maskable overflow...passed
	Non-maskable underflow...passed
Testing 68060 FPSP unimplemented instruction started:
	Unimplemented FP instructions...passed
Testing 68060 FPSP exception enabled started:
	Enabled SNAN...passed
	Enabled OPERR...passed
	Enabled overflow...passed
	Enabled underflow...passed
	Enabled DZ...passed
	Enabled inexact...passed

btw, any idea if 68060 test would work with 68040 FPSP? I guess at least
in theory it should work. (Emulation does not return correct results but
I'd like to have real 68040 results first)