From: Ralf Baechle <ralf@oss.sgi.com>
To: "Zajerko-McKee, Nick" <nmckee@telogy.com>
Cc: "Linux-Mips (E-mail)" <linux-mips@oss.sgi.com>
Subject: Re: GAS 4kc question...
Date: Wed, 31 Jul 2002 02:31:40 +0200 [thread overview]
Message-ID: <20020731023140.B2142@dea.linux-mips.net> (raw)
In-Reply-To: <37A3C2F21006D611995100B0D0F9B73CBFE213@tnint11.telogy.design.ti.com>; from nmckee@telogy.com on Tue, Jul 30, 2002 at 06:28:32PM -0400
On Tue, Jul 30, 2002 at 06:28:32PM -0400, Zajerko-McKee, Nick wrote:
> I'm trying to write some inline assembler code that needs the madd and mulu
> op codes found on the 4KC processor. I've tried setting the cpu to 4650,
> but it failed to recognize the mulu instruction. Can someone give me the
> magic incantation? I'm running right now GCC 2.95.3 from Montavista. I
> guess one way I can attack it for now is to build the op code by hand, but
> that is quite dirty, IMHO...
That's an inconsistence in the MIPS instruction set. The old two operand
multiply instruction exists as both signed and unsigned (mult / multu)
but the new-style signed multiply only in an unsigned flavour. In other
words, there is no mulu instruction.
I guess the reason was that this instruction is mainly used for DSP-style
stuff which need signed arithmetics while burning valuable space in the
instruction set for a mulu instruction wasn't considered worth the
instruction space.
Ralf
next prev parent reply other threads:[~2002-07-31 0:30 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-07-30 22:28 GAS 4kc question Zajerko-McKee, Nick
2002-07-30 23:08 ` Thiemo Seufer
2002-07-31 0:31 ` Ralf Baechle [this message]
2002-07-31 6:03 ` Carsten Langgaard
2002-07-31 7:04 ` Kevin D. Kissell
2002-07-31 7:04 ` Kevin D. Kissell
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