Re: [f-cpu] New snapshot for EU_INC and EU_CMP

[Michael Riepe <michael@stud.uni-hannover.de>]

On Wed, Jul 31, 2002 at 06:31:04PM +0200, Etienne LABARRE wrote:
> On Wed, Jul 31, 2002 at 01:33:18AM +0200, Michael Riepe wrote:
> > 
> > CMP is supposed to be either 0 or -1: cmp(a, b) = a < b ? -1 : 0.
> > 
> > MSB1 is supposed to return the *number* of the most significant `1'
> > bit: msb1(0xffffffff) = 64, msb1(0) = 0. Currently it returns some
> > strange bit mask. Likewise for MSB0.
> 
> Idon't agree with you. The criteria for CMP unit for me is :
> If A = B, then result is null, else result not null.

We have XOR for that, don't we?

The instruction we need is `cmpl', aka `CoMPare Less' (A < B).

> I think that is more simple, and permit to win one or more level
> latency.
> 
> But, my unit is not compliant to the manual. What must we correct :
> manual or code ?

Since the semantics of scan/lsb/msb seem to have changed behind my
back, we will have to discuss that here. CMP/MIN/MAX/SORT is wrong,
however.

-- 
 Michael "Tired" Riepe <Michael.Riepe@stud.uni-hannover.de>
 "All I wanna do is have a little fun before I die"
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