From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (from majordomo@localhost) by oss.sgi.com (8.11.3/8.11.3) id f2GJZq313409 for linux-mips-outgoing; Fri, 16 Mar 2001 11:35:52 -0800 Received: from dea.waldorf-gmbh.de (u-210-18.karlsruhe.ipdial.viaginterkom.de [62.180.18.210]) by oss.sgi.com (8.11.3/8.11.3) with ESMTP id f2GJZlM13406 for ; Fri, 16 Mar 2001 11:35:48 -0800 Received: (from ralf@localhost) by dea.waldorf-gmbh.de (8.11.1/8.11.1) id f2GJZe214975; Fri, 16 Mar 2001 20:35:40 +0100 Date: Fri, 16 Mar 2001 20:35:40 +0100 From: Ralf Baechle To: "Kevin D. Kissell" Cc: Subject: Re: Can't build a CONFIG_CPU_NEVADA kernel Message-ID: <20010316203540.D2857@bacchus.dhis.org> References: <20010314084633.A25674@nevyn.them.org> <20010314195919.A1911@bacchus.dhis.org> <20010314140529.A29525@nevyn.them.org> <20010314202058.B1911@bacchus.dhis.org> <00fc01c0acd3$c881ca80$0deca8c0@Ulysses> <20010316150423.A3529@bacchus.dhis.org> <010201c0ae49$6df089e0$0deca8c0@Ulysses> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: <010201c0ae49$6df089e0$0deca8c0@Ulysses>; from kevink@mips.com on Fri, Mar 16, 2001 at 07:46:23PM +0100 X-Accept-Language: de,en,fr Sender: owner-linux-mips@oss.sgi.com Precedence: bulk On Fri, Mar 16, 2001 at 07:46:23PM +0100, Kevin D. Kissell wrote: > > GCC to schedule instructions for a certain processor xxx. This does not > > enable the full use of it's instruction set. Back in time when I choose > > these options I choose because GCC didn't know -mcpu=r5000 but the R8000 > > was supported and it was the closest fit. Gcc 1.1.2 knows this option > > so I just changed all instances of -mcpu=r8000 into -mcpu=r5000. > > As I understand it, the original intention behind -mcpu was to optimise > instruction scheduling, but it got perverted over time to enable > instructions as well. In any case, the R5000 and R8000 have the > same ISA, but the pipelines are radically different. The R8K is > 4-way superscalar, with a 2-cycle branch penalty and branch > prediction. The R5K is two way supercalar (Int/FP pairs only) > with classic MIPS branch behavior, etc. Gcc's knowledge about MIPS architecture is so limited that an R5000 isn't very much different from an R8000 ... > > Unfortunately true but there is a reason that QED's manual marks it as an > > proprietary extension ... > > Yup. The quesiton is, does gcc's -mmad option actually > select based on -mcpu or some other variable which > semantics to use, or does it assume R4650 semantics If you have a collection which of the CPUs have implemented mmad in what way I'd like to use that to put it into gcc. > (I had the impression that it was the R4650 that drove > the implementation of MIPS madd's into gcc - correct > me if I'm wrong). Guess that's right. Ralf From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 16 Mar 2001 20:35:40 +0100 From: Ralf Baechle Subject: Re: Can't build a CONFIG_CPU_NEVADA kernel Message-ID: <20010316203540.D2857@bacchus.dhis.org> References: <20010314084633.A25674@nevyn.them.org> <20010314195919.A1911@bacchus.dhis.org> <20010314140529.A29525@nevyn.them.org> <20010314202058.B1911@bacchus.dhis.org> <00fc01c0acd3$c881ca80$0deca8c0@Ulysses> <20010316150423.A3529@bacchus.dhis.org> <010201c0ae49$6df089e0$0deca8c0@Ulysses> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <010201c0ae49$6df089e0$0deca8c0@Ulysses>; from kevink@mips.com on Fri, Mar 16, 2001 at 07:46:23PM +0100 Sender: owner-linux-mips@oss.sgi.com To: "Kevin D. Kissell" Cc: linux-mips@oss.sgi.com Message-ID: <20010316193540.HyRswpRtx_43_ionnLzkMr69GNJKDgCtdG3S7VqEtik@z> On Fri, Mar 16, 2001 at 07:46:23PM +0100, Kevin D. Kissell wrote: > > GCC to schedule instructions for a certain processor xxx. This does not > > enable the full use of it's instruction set. Back in time when I choose > > these options I choose because GCC didn't know -mcpu=r5000 but the R8000 > > was supported and it was the closest fit. Gcc 1.1.2 knows this option > > so I just changed all instances of -mcpu=r8000 into -mcpu=r5000. > > As I understand it, the original intention behind -mcpu was to optimise > instruction scheduling, but it got perverted over time to enable > instructions as well. In any case, the R5000 and R8000 have the > same ISA, but the pipelines are radically different. The R8K is > 4-way superscalar, with a 2-cycle branch penalty and branch > prediction. The R5K is two way supercalar (Int/FP pairs only) > with classic MIPS branch behavior, etc. Gcc's knowledge about MIPS architecture is so limited that an R5000 isn't very much different from an R8000 ... > > Unfortunately true but there is a reason that QED's manual marks it as an > > proprietary extension ... > > Yup. The quesiton is, does gcc's -mmad option actually > select based on -mcpu or some other variable which > semantics to use, or does it assume R4650 semantics If you have a collection which of the CPUs have implemented mmad in what way I'd like to use that to put it into gcc. > (I had the impression that it was the R4650 that drove > the implementation of MIPS madd's into gcc - correct > me if I'm wrong). Guess that's right. Ralf