Date: Thu, 09 Nov 1995 11:02:52 +0100 From: Poul-Henning Kamp <phk@critter.tfs.com> To: "Amancio Hasty Jr." <hasty@rah.star-gate.com> Cc: Luigi Rizzo <luigi@labinfo.iet.unipi.it>, koshy@blr.novell.com, freebsd-hackers@freebsd.org Subject: Re: Load/Store using FPU regs ... Message-ID: <6539.815911372@critter.tfs.com> In-Reply-To: Your message of "Thu, 09 Nov 1995 02:59:42 PST." <199511091059.CAA03746@rah.star-gate.com>
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> >>> Luigi Rizzo said: > > > > Now, I'm not sure if this approach can be used across all processors. > > > > Some FPU's could raise exceptions if illegal bit-patterns are loaded > > > > into its registers. The x86 FPU in particular has very few registers > > > > and a LIFO access pattern for loads and stores so I don't know if the > > > > same trick would work well for it. > > > > > > Not to mention that you might not have a FPU. > > > > So what ? You still have the FPU emulator :) > > Just ignore Pohl's comment we can probably figure out a clever way > to find out if we have a FPU . sure, there's a flag in the kernel, and it's a sysctl var too. > What would be nice to see is if there is indeed a performance gain > by using the floating point instructions if there is for sure I will > use it. The place to use it would be in the Copy-On-Write and Demand-Zero parts of the VM system. -- Poul-Henning Kamp | phk@FreeBSD.ORG FreeBSD Core-team. http://www.freebsd.org/~phk | phk@login.dknet.dk Private mailbox. whois: [PHK] | phk@ref.tfs.com TRW Financial Systems, Inc. Future will arrive by its own means, progress not so.
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