FPU rounding issues

phx · 10 November 2014, 12:10

I'm sorry if that problem has already been fixed, but I often see FPU rounding issues with the UAE core in E-UAE and Hatari.

For reproduction, shouldn't the following program return -1 in d0? It returns 0. The rounding mode in FPCR is ignored.

Code:

    fmove.l    fpcr,d1
    and.w      #$ffcf,d1
    or.w       #$0020,d1
    fmove.l    d1,fpcr
    fmove.d    #-0.01,fp0
    fmove.l    fp0,d0
    rts

Toni Wilen · 10 November 2014, 18:29

It returns -1 here. E-UAE is too ancient.

phx · 11 November 2014, 09:58

Indeed. Now I had a chance to get access to a recent WinUAE version. It works as expected. Sorry for the noise.

alexh · 11 November 2014, 17:03

Hatari developers are currently looking to replace their age old WinUAE 680x0 emulator core with the 2.8.1 WinUAE 680x0 core.

http://atari-forum.com/viewtopic.php...260414#p260414

phx · 12 November 2014, 09:34

In fact I was contacted by an Atari developer who suspected a bug in vasm first. But it turned out to be a problem in Hatari.

alexh · 12 November 2014, 09:58

That wouldnt be DML aka Doug? Who is writing a Quake port for Falcon's which heavily uses the FPU?

phx · 12 November 2014, 10:03

Exactly!
Our Amiga and Atari worlds are just too small...

10 November 2014, 12:10	#1
phx Natteravn Join Date: Nov 2009 Location: Herford / Germany Posts: 2,537	FPU rounding issues I'm sorry if that problem has already been fixed, but I often see FPU rounding issues with the UAE core in E-UAE and Hatari. For reproduction, shouldn't the following program return -1 in d0? It returns 0. The rounding mode in FPCR is ignored. Code: fmove.l fpcr,d1 and.w #$ffcf,d1 or.w #$0020,d1 fmove.l d1,fpcr fmove.d #-0.01,fp0 fmove.l fp0,d0 rts

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10 November 2014, 18:29	#2
Toni Wilen WinUAE developer Join Date: Aug 2001 Location: Hämeenlinna/Finland Age: 49 Posts: 26,553	It returns -1 here. E-UAE is too ancient.

11 November 2014, 09:58	#3
phx Natteravn Join Date: Nov 2009 Location: Herford / Germany Posts: 2,537	Indeed. Now I had a chance to get access to a recent WinUAE version. It works as expected. Sorry for the noise.

11 November 2014, 17:03	#4
alexh Thalion Webshrine Join Date: Jan 2004 Location: Oxford Posts: 14,448	Hatari developers are currently looking to replace their age old WinUAE 680x0 emulator core with the 2.8.1 WinUAE 680x0 core. http://atari-forum.com/viewtopic.php...260414#p260414

12 November 2014, 09:34	#5
phx Natteravn Join Date: Nov 2009 Location: Herford / Germany Posts: 2,537	In fact I was contacted by an Atari developer who suspected a bug in vasm first. But it turned out to be a problem in Hatari.

12 November 2014, 09:58	#6
alexh Thalion Webshrine Join Date: Jan 2004 Location: Oxford Posts: 14,448	That wouldnt be DML aka Doug? Who is writing a Quake port for Falcon's which heavily uses the FPU?

12 November 2014, 10:03	#7
phx Natteravn Join Date: Nov 2009 Location: Herford / Germany Posts: 2,537	Exactly! Our Amiga and Atari worlds are just too small...

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