Messages in this thread | | | Subject | Re: [PATCH] ppc32 use simplified mmenonics | From | Albert Cahalan <> | Date | 22 Aug 2004 08:40:22 -0400 |
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On Sun, 2004-08-22 at 10:45, Vincent Hanquez wrote: > On Sun, Aug 22, 2004 at 06:41:32AM -0400, Albert Cahalan wrote:
> > This is a slightly better example, but still, it's > > lots easier to look up "bc" to see the selection of > > options that are available. > > > > Plus, yeah, "what the hell is 4,2", but those numbers > > replace a _lot_ of other things you'd need to remember. > > There are 456 of these "simplified" branch instructions. > > If you use those, you'll tend to restrict your code to > > those few common ones you remember. There's bdnzltrl, > > bdnzfla, bunla... That's madness. > > So you writing assembly ppc code with your book on your side ? > because I don't see any reason to associate easily '4,2' with 'not equal'
As I said, it's a slightly better example. (it's also NOT what the patch was changing)
> bdnzltrl kinds of mmenonics are actually not fair, they are not really used :). > But even that I would prefer bdnztlrl which I would have to lookup, > than bclr with cryptics numbers which I would had to lookup too.
See, that's a problem. You're limiting yourself to just 96 of the 456 listed operations, which are only 1/5 of the 2304 available operations.
I do admit to using bne at times. The bit manipulation stuff is different though. It's not so cryptic in the raw form. The same goes for using "or" to copy a register.
If you don't use the full bit manipulation notation all the time, you might forget what it can do. Then you'll end up using 2 instructions where one would do.
> > That's 114 opcodes to 1. > > There's not 1 opcode for conditional branching. There are more on ppc basis: > > bc, bca, bclr, bcctr, bcl, bcla, bclrl, bcctrl
OK, that's 8. Dividing 456 by that, I still see a 57:1 ratio.
There's also that matter of the 1848 operations you can't access via the "simplified" instruction names.
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