Subject: Re: [stella] Stella conditional breakpoint support RFC From: "B. Watson" <atari@xxxxxxxxxxxxxx> Date: Mon, 11 Jul 2005 22:22:52 -0400 |
On Mon, 11 Jul 2005, Eric Ball wrote: > Hmmm, is all that really necessary? I'd think all you'd need to do is > preprocess the conditional breakpoints into a set of simple comparisons, > e.g. > PC = val > A op val > X op val > Y op val > etc > where op is > = < or don't care, maybe with some special ops for BIT style > operations and combinations with an address watch. Each emulated CPU cycle > you check PC first, then test the rest of the conditions. Well, the thing that turns expressions into this set of comparisons... that's a compiler :) How would you express (a==1 || x==2), as opposed to (a==1 && x==2), in your scheme? How about ((a==10 || a==20 || a==30) && (x==1 || y==1))? OK, they're fairly contrived examples (especially the last one)... but you really might want to use (@address+y & 0x80). @address means "16-bit word pointed to by address", and +y of course adds Y... so that simulates (indirect),y addressing. We'd be telling it to break when an indirect address is about to load a negative number (well, assuming we're in a loop where Y changes.) But your scheme is a good idea, and could be made to work, I just dunno how yet (my fault, that is). Everything I just said sounds like I'm trying to poke holes in it, but I'm really not (well, if I am, not in a negative way). My #1 biggest question though, was: should I even try to support conditions that aren't tied to a PC-based breakpoint or address-based trap? Your answer implies that I shouldn't ("check PC first..."), so I guess that counts as one vote against arbitrary conditions...? -- B. Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://stella.biglist.com
Current Thread |
---|
|
<- Previous | Index | Next -> |
---|---|---|
Re: [stella] Stella conditional bre, Eric Ball | Thread | Re: [stella] Stella conditional bre, Eric Ball |
Re: [stella] Stella conditional bre, Eric Ball | Date | Re: [stella] Stella conditional bre, Jeremy Penner |
Month |