Re: RFC: GIMPLE tuples. Design and implementation proposal

[Andrew MacLeod <amacleod at redhat dot com>]

On Tue, 2007-04-10 at 19:54 +0200, J.C. Pizarro wrote:
> Hi Diego Novillo
> 
> Your "Tuple representation" of the GIMPLE instructions was:
> HEADER:
>   code        16 bits
>   subcode     16bits
>   next        word
>   prev        word
>   bb          word
>   locus       word
>   block       word
> BODY:
>   OP0         word
>   ..
>   OPN         word
> 
> I've a little idea,
> 
> Can i remove the word "prev"?
> Thanks to "bb", i can traverse the short list of
> the small basic block getted from its hashtable.

Do you mean implement this as a single linked list and then to find the
previous instruction, start at the beginning of the block and traverse
forward? Back in the early days of tree-ssa we did such a thing with the
tree iterators. It was too slow. there are many LARGE basic blocks which
make the computation too expensive for any pass that goes backwards
through a block.

Andrew