(i386-linux x sh-elf) More weak stack addressing

[Clinton Popetz]

On Thu, Jul 20, 2000 at 03:06:35PM -0700, Toshiyasu Morita wrote:
 
> Maybe I'm missing something, but it seems peeking beyond labels is 
> extremely important for the Hitachi SH. Forgive me for overexplaining
> a bit - I'm basically explaining my assumptions to see if people
> can spot any glaring oversights.
> 
> Consider:
> 
> The SH uses pc-relative addressing to load large constants, 
> therefore it generates literal pools in the .text segment. These 
> literal pools must be "jumped around" to continue execution.
> 
> >From a code analysis perspective, these jumps aren't really jumps
> since they jump to a label accessed by only a single jump. Therefore
> the jump destination can be considered in the same block as the jump
> source.
> 
> If an optimization pass assumes a jump ends a basic block, it will miss 
> many potential optimiations.

Essentially you want the various optimization passes to operate on EBB
(extended basic blocks) where possible.  This is a worthwhile goal,
but it will take a lot of work to get there.

				-Clint