[m-rev.] diff: fix deforestation bug

[Simon Taylor]

On 29-Apr-2002, Fergus Henderson <fjh at cs.mu.OZ.AU> wrote:
> On 29-Apr-2002, Simon Taylor <stayl at cs.mu.OZ.AU> wrote:
> > compiler/deforest.m:
> > 	Don't attempt to improve the determinism of procedures
> > 	with determinism cc_multi or cc_nondet -- those determinisms
> > 	can't be inferred, and attempting to do so would cause
> > 	errors in determinism analysis.
> 
> The comment here is wrong -- the compiler *can* infer determinism
> `cc_multi' or `cc_nondet'.

>From det_analysis.m:

                % Work out whether the procedure occurs in a single-solution
                % context or not.  Currently we only assume so if
                % the predicate has an explicit determinism declaration
                % that says so.
        proc_info_declared_determinism(Proc0, MaybeDeclaredDetism),
        ( MaybeDeclaredDetism = yes(DeclaredDetism) ->
                det_get_soln_context(DeclaredDetism, SolnContext)
        ;
                SolnContext = all_solns
        ),

To infer a cc_multi or cc_nondet determinism for a procedure the compiler
would need to check that the procedure is only ever called in a single
solution context. 

Simon.
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