[m-rev.] for review: deleting code_exprn

[Zoltan Somogyi]

On 14-Oct-2002, Fergus Henderson <fjh at cs.mu.OZ.AU> wrote:
> Ah, now I remember which features of the lazy LLDS code generator are not
> supported in the new LLDS code generator:
> 	(1) --no-static-ground-terms
> 	(2) the `jump' and `fast' grades.
> 
> Do we really want to get rid of those?
> 
> Note that (1) is currently needed for structure reuse,
> e.g. the tests in tests/general/structure_reuse.

About (1):

Although I see that tests/general/structure_reuse/Mmakefile specifies
--no-static-ground-terms, it doesn't specify --lazy-code, so handle_options.m
would have turned --static-ground-terms back on again. After my change,
--lazy-code isn't mentioned anywhere except in a couple of comments,
which I have now deleted.

var_locn.m already has a predicate for creating a cell dynamically.
Exporting it to code_info and making code_info export it to other modules
would take about five minutes; I can do it in this diff. If we had a pass
that marked unifications as must_be_dynamic, it would be trivial to modify
unify_gen.m to use that version of the predicate instead of the one that
checks for groundness first.

About (2), I don't know of anything that would make code_exprn and var_locn
differ in their support for the jump and fast grades. All the magic for
initializing the globals associated with labels is done behind a layer of
abstraction provided by macros; the code generators don't look behind
the curtain.

In short, this diff doesn't lose functionality on either point.

Zoltan.
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