Re: [Qemu-devel] [RFC] alpha qemu arithmetic exceptions

[Richard Henderson]

On 06/24/2014 01:32 PM, Al Viro wrote:
> If you have any ideas for testing, I do have working hw (the box that is
> currently alive is ev45, though; I _can_ try to boot a UP1000 one, but
> I make no promises regarding its fans, both in PSU and in CPU module ;-/)

Ah.  Gotta be careful with ev4/45... half of the fpu is unimplemented, and so
if you're not careful all you're testing is the kernel emulation behaviour.

> Um?  No, I mean having gen_fp_exc_raise() generate a call of one of the 8
> helpers; gen_ieee_arith3() and friends would remain as-is.  It's just that
> instead of generating load to exc, andi, call of helper_fp_exc_raise_s or
> call of helper_fp_exc_raise we would generate a call of one of the
> helper_fp_exc_raise{,_u,_v,_s,_su,_sui,_sv,_svi} and let that sucker deal
> with loading exc, updating ->fpcr_exc_status and generating traps.

Ah, I getcha.  Yes, that makes sense.

>>> Another thing: shouldn't arithmetics on denorms without /S raise EXC_M_INV,
>>> rather than EXC_M_UNF?
>>
>> No idea.  Should they?
> 
> They seem to - both from the arch.manual and from direct experiment...  And
> they do set FPCR.INV at the same time, not just trigger the trap.

Ok.  I'll try to make time to fix up some of this stuff this weekend.


r~