Re: Signed multiplication

From: Nate Lawson <>
Date: Thu, 05 Nov 2009 15:11:08 -0800
Message-ID: <>
Ullrich von Bassewitz wrote:
> On Thu, Nov 05, 2009 at 09:38:54AM -0800, Nate Lawson wrote:
>> By "signed" do you mean simply that "result is negative if sign bits are
>> different, else positive"? Or are you trying to account for overflow
>> somehow?

[description of multiplication snipped]

> What I need is a multiplication that gets a correct value for the high 16 bit
> (the result should be $FFFFFFFC instead of $1FFFC). Currently, I'm using an
> unsigned 16x16=>32 multiplication with the absolute values of the operands,
> and adjust the sign of the result. The question is, if there is a faster
> method than this.

No, you should just adjust the sign manually.


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Received on 2009-11-06 00:00:02

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