[tree-ssa] Block merging (updated)

[Richard Henderson]

On Tue, Jan 13, 2004 at 10:57:47AM -0700, law@redhat.com wrote:
> No.  We do not delete user labels.  If something is deleting a user label,
> then that code is buggy.

I'm less and less interested in preserving user labels these days.

> Err, no.  We have turned them into DELETED_LABELs, but that is not the
> same as removing them since they will end up in the debug information.

As DELETED_LABELs, they float around a *lot*.  Quite often to 
the beginning of the function.  We have bug reports about this.

My personal thought is that it would actually be more useful
for the user if the label was completely removed so that we
could not emit the address in the debug info so that the
debugger could say "label has been optimized away".

That's not to say we shouldn't make efforts to preserve the user's
label when that's an alternative.  E.g. don't accidentally let an
artificial label at the same block get used instead.



r~