Signed multiplication

From: Ullrich von Bassewitz <*uz_at_musoftware.de*> Date: Wed, 4 Nov 2009 14:42:37 +0100 Message-ID: <20091104134237.GA16028@trixie.musoftware.de> · uz_at_musoftware.de

I'm looking for a signed 16x16 => 32 multiplication routine. Currently I'm
using the 16x16 => 32 unsigned routine with the absolute values of the
operands, and adjust the sign of the result if necessary. But this quite some
overhead. 

Is there a fast way to do it, for example by accounting for the sign in the
shift-and-add loop? I've tried to find a solution myself, but all I came up
with was extending the addition to 32 bits to keep the information about
signedness, and this is at least as slow as using absolute values and negating
the result.

Regards

        Uz

-- 
Ullrich von Bassewitz                                  uz@musoftware.de

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