[m-rev.] For review: Fix dummy type handling in the IL backend

[Julien Fischer]

Pete, could you please take a look at this one.
(That's Peter Ross - not any of the other Peters).

Cheers,
Julien.

On Wed, 27 Sep 2006, Jonathan Morgan wrote:

> With the below patch mercury-0.13 handles the IL backend correctly (as
> well as it ever did).  I cannot test the patch on main, as
> foreign_export does not yet work properly with the IL backend, but it
> should work without change.
>
> Jon
> ================================================================
> Branches: release, main
>
> Previously in the IL backend dummy variables were assigned to
> private_builtin.dummy_var, which did not work when values were
> assigned to it using the high-level data representation, as their type
> was not the low-level object[].  This change changes the
> representation of dummy variables from object[] (the low-level
> representation) to object (suitable for high-level data), and causes
> the IL backend to detect assignments to dummy_var and cast them to
> type object before assigning to them.
>
> compiler/mlds_to_il.m:
>   Detect when an object is constructed and assigned to
> private_builtin.dummy_var, and cast to il_generic_type (object) before
> assigning the constructed object.
>
> library/private_builtin.m:
>   Change dummy_var's type from object[] to object.
>
> Index: compiler/mlds_to_il.m
> ===================================================================
> RCS file: /home/mercury1/repository/mercury/compiler/mlds_to_il.m,v
> retrieving revision 1.161
> diff -u -u -r1.161 mlds_to_il.m
> --- compiler/mlds_to_il.m	29 Mar 2006 08:07:05 -0000	1.161
> +++ compiler/mlds_to_il.m	27 Sep 2006 11:06:28 -0000
> @@ -2056,7 +2056,23 @@
>        ILArgTypes = list.map(mlds_type_to_ilds_type(DataRep), ArgTypes),
>        list.map_foldl(load, Args, ArgsLoadInstrsTrees, !Info),
>        ArgsLoadInstrs = tree_list(ArgsLoadInstrsTrees),
> -        get_load_store_lval_instrs(Target, LoadMemRefInstrs,
> +        % check if it's assigning to private_builtin.dummy_var
> +        % If so, then it needs to be cast to il_generic_type.
> +        (
> +            Target = var(qual(MLDS_Module, QualKind, VarName), _),
> +            VarName = mlds_var_name("dummy_var", _),
> +            mercury_private_builtin_module(PrivateBuiltin),
> +            MLDS_PrivateBuiltin = 
> mercury_module_name_to_mlds(PrivateBuiltin),
> +            mlds_append_wrapper_class(MLDS_PrivateBuiltin) = MLDS_Module
> +        ->
> +            MaybeCastInstrs = node([castclass(il_generic_type)]),
> +            Target1 = var(qual(MLDS_Module, QualKind, VarName),
> +                mlds_generic_type)
> +        ;
> +            MaybeCastInstrs = empty,
> +            Target1 = Target
> +        ),
> +        get_load_store_lval_instrs(Target1, LoadMemRefInstrs,
>            StoreLvalInstrs, !Info),
>        CallCtor = newobj_constructor(ClassName, ILArgTypes),
>        Instrs = tree_list([
> @@ -2064,6 +2080,7 @@
>            comment_node("new object (call constructor)"),
>            ArgsLoadInstrs,
>            instr_node(CallCtor),
> +            MaybeCastInstrs,
>            StoreLvalInstrs
>        ])
>    ;
> @@ -3112,7 +3129,7 @@
>    il_object_array_type.
> mlds_mercury_type_to_ilds_type(_, _, type_cat_tuple) = il_object_array_type.
> mlds_mercury_type_to_ilds_type(_, _, type_cat_enum) =  il_object_array_type.
> -mlds_mercury_type_to_ilds_type(_, _, type_cat_dummy) = 
> il_object_array_type.
> +mlds_mercury_type_to_ilds_type(_, _, type_cat_dummy) =  il_generic_type.
> mlds_mercury_type_to_ilds_type(_, _, type_cat_variable) = il_generic_type.
> mlds_mercury_type_to_ilds_type(DataRep, MercuryType, type_cat_type_info) =
>    mlds_mercury_type_to_ilds_type(DataRep, MercuryType, type_cat_user_ctor).
> Index: library/private_builtin.m
> ===================================================================
> RCS file: /home/mercury1/repository/mercury/library/private_builtin.m,v
> retrieving revision 1.154.2.3
> diff -u -u -r1.154.2.3 private_builtin.m
> --- library/private_builtin.m	21 Aug 2006 05:37:25 -0000	1.154.2.3
> +++ library/private_builtin.m	27 Sep 2006 11:07:54 -0000
> @@ -124,7 +124,7 @@
> // will be used by the code generator as an lval, so we use
> // private_builtin:dummy_var as that lval.
>
> -public static object[] dummy_var;
> +public static object dummy_var;
>
> ").
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