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From: Thomas Koenig <tkoenig@netcologne.de>
Newsgroups: comp.arch
Subject: Re: Reverse engineering of Intel branch predictors
Date: Mon, 11 Nov 2024 09:03:36 -0000 (UTC)
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MitchAlsup1 <mitchalsup@aol.com> schrieb:

> For example: The classical way to do dense switches is a LD of the
> target
> address and a jump to the target. This requires verifying the address of
> the target. Whereas if you predict as JTT does, you verify by matching
> the index number (which is known earlier and since the table is
> read-only
> you don't need to verify the target address.
>
> So, it is not that you don't predict, it is that the data used to
> verify the prediction is more precise and available earlier.

Hmm... just wondering.

How does this handle

  switch(a)
    {
       case 1:
       case 3:
       case 4:
       case 7:
         /* Do something */
       break;
       case 2:
       case 5:
       case 11:
         /* Do something else */
       break;
       default:
         /* Something else entirely  */
    }

Would the values 1,3,4 and 7 be considered different for
prediciton purposes?