[m-dev.] diff: fix aborts during deforestation

[Fergus Henderson]

On 01-Sep-2000, Simon Taylor <stayl at cs.mu.OZ.AU> wrote:
> 
> 
> Estimated hours taken: 2
> 
> Fix bugs which caused compilation of Tom Conway's XML parser
> to fail during deforestation.
> 
> compiler/inlining.m:
> 	If some of the output variables of an inlined call are not
> 	used by the caller, run quantification on the goal
> 	to push that information into the inlined goal.

That one is not a bug as such, because it is OK for the
non-locals field to be a superset of the true non-locals.
That should just be an optimization issue.

If you leave that change out, does anything break?
(If so, that other thing should be fixed.)

> Index: compiler/inlining.m
> @@ -558,7 +587,7 @@
>  
>  %-----------------------------------------------------------------------------%
>  
> -inlining__do_inline_call(HeadTypeParams, ArgVars, PredInfo, ProcInfo, 
> +inlining__do_inline_call(_, ArgVars, PredInfo, ProcInfo, 
>  		VarSet0, VarSet, VarTypes0, VarTypes, TypeVarSet0, TypeVarSet, 
>  		TypeInfoVarMap0, TypeInfoVarMap, Goal) :-
>  
> @@ -610,6 +639,12 @@
>  	map__apply_to_list(ArgVars, VarTypes0, ArgTypes),
>  
>  	pred_info_get_exist_quant_tvars(PredInfo, CalleeExistQVars),
> +
> +	% Typechecking has already succeeded, so we don't need
> +	% to check for binding of head type parameters.
> +	% Also, existentially-typed head type parameters
> +	% may be bound by inlining.
> +	HeadTypeParams = [],
>  	inlining__get_type_substitution(HeadTypes, ArgTypes, HeadTypeParams,
>  		CalleeExistQVars, TypeSubn),
>  

The log message didn't mention that change.

> Index: compiler/modes.m
> +compute_goal_instmap_delta(InstMap0, Goal,
> +		GoalInfo0, GoalInfo, ModeInfo0, ModeInfo) :-
> +	( Goal = conj([]) ->
> +		instmap_delta_init_reachable(DeltaInstMap),
> +		mode_info_set_instmap(InstMap0, ModeInfo0, ModeInfo)
> +	;
> +		mode_info_get_completed_nonlocals(GoalInfo0, NonLocals,
> +			ModeInfo0, ModeInfo),
> +		mode_info_get_instmap(ModeInfo, InstMap),
> +		compute_instmap_delta(InstMap0, InstMap,
> +			NonLocals, DeltaInstMap)
> +	),
>  	goal_info_set_instmap_delta(GoalInfo0, DeltaInstMap, GoalInfo).

It would be helpful to have a comment here explaining why `conj([])'
needs to be treated specially.

-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh>  |  of excellence is a lethal habit"
PGP: finger fjh at 128.250.37.3        |     -- the last words of T. S. Garp.
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