> Date: Tue, 24 Aug 1999 18:04:45 -0700
> From: "David S. Miller" <davem@redhat.com>
> To: nanook@eskimo.com
> Cc: linux-kernel@vger.rutgers.edu
> Subject: Re: Sparc CFLAGS question relating to 2.2.x
>
> Date: Tue, 24 Aug 1999 17:32:36 -0700 (PDT)
> From: Robert Dinse <nanook@eskimo.com>
>
> In arch/sparc/Makefile, CFLAGS has amoung other things
> -mno-fpu.
>
> It was my understanding that no floating point math was
> allowed in the kernel anyway, so I fail to understand the need for
> that flag.
>
> The compiler can emit floating point load/stores during high register
> pressure to move variables around if you don't tell it otherwise.
Thank you, wasn't aware of that. But now am curious how this breaks
things if no actual floating point operations are performed?
> On the other hand, there seems to be no detection for version
> 8 Sparc and the inclusion of -mv8. It would seem to make sense to
> use hardware to do interger multiply/divides if it exists?
>
> The single 32-bit Sparc kernel image runs on sun4/sun4c/sun4m systems,
> so adding this compiler option is not allowed.
>
> However, the only real gain from -mv8 is that hardware divide,
> remainer, and multiply instructions are used. And if you check the
> kernel bootup sequence we patch the ".umul", ".udiv" etc. routines to
> use the instructions on sun4m systems which have it.
Wouldn't this be less effecient though since you have to go to this
routine instead of using a hardware divide instruction inline?
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