[m-rev.] diff: increase from_ground_term_threshold to 1000000 to avoid regressions

[Peter Wang]

2009/4/27 Zoltan Somogyi <zs at csse.unimelb.edu.au>:
> On 27-Apr-2009, Peter Ross <pro at missioncriticalit.com> wrote:
>> Increase from_ground_term_threshold from 5 to 1000000 to avoid
>> the two regressions reported in bugs 93 and 94 in the bug database.
>
> Bug 93 is not so much as a bug as an issue that arises because we have not
> (yet) resolved the tension between two competing optimizations. Opt1 is
> replacing code that constructs ground terms at runtime with references
> to static ground terms; opt2 is compile time garbage collection.

The immediate problem is during mode checking.  As I understand it, the
from-ground-term optimisation assigns terms a non-unique inst, which may
conflict with a mode that the user has declared.

> I think all ground terms should be non-unique, and ctgc should introduce
> code that makes unique copies of ground terms whenever it needs them.

What does it mean for terms appearing in `uo' argument positions?
And `di' arguments might not actually be destroyable?

Peter
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