On 13/11/16 22:31, Eric Botcazou wrote:
> Similarly to x86, PowerPC and SPARC, this enables the use of custom run-time
> descriptors in Ada, thus eliminating the need for trampolines and executable
> stack in presence of pointers to nested functions.
>
> This still uses bit 1 for the run-time identification scheme because bumping
> the function alignment to 64 bits seems undesirable in Thumb mode.
>
> Tested on ARM/Linux, OK for the mainline?
>
>
> 2016-11-13 Eric Botcazou <ebotca...@adacore.com>
>
> PR ada/67205
> * config/arm/arm.c (TARGET_CUSTOM_FUNCTION_DESCRIPTORS): Define.
> (arm_function_ok_for_sibcall): Return false for an indirect call by
> descriptor if all the argument registers are used.
> (arm_relayout_function): Use FUNCTION_ALIGNMENT macro to adjust the
> alignment of the function.
>
Is this ABI, or private to a release of the compiler? If the latter,
then OK. Otherwise, I don't think we should presume that the reserved
bits won't get used.
R.
>
> p.diff
>
>
> Index: config/arm/arm.c
> ===================================================================
> --- config/arm/arm.c (revision 242334)
> +++ config/arm/arm.c (working copy)
> @@ -738,6 +738,11 @@ static const struct attribute_spec arm_a
> #undef TARGET_EXPAND_DIVMOD_LIBFUNC
> #define TARGET_EXPAND_DIVMOD_LIBFUNC arm_expand_divmod_libfunc
>
> +/* Although the architecture reserves bits 0 and 1, only the former is
> + used for ARM/Thumb ISA selection in v7 and earlier versions. */
> +#undef TARGET_CUSTOM_FUNCTION_DESCRIPTORS
> +#define TARGET_CUSTOM_FUNCTION_DESCRIPTORS 2
> +
> struct gcc_target targetm = TARGET_INITIALIZER;
>
> /* Obstack for minipool constant handling. */
> @@ -6810,6 +6815,29 @@ arm_function_ok_for_sibcall (tree decl,
> && DECL_WEAK (decl))
> return false;
>
> + /* We cannot do a tailcall for an indirect call by descriptor if all the
> + argument registers are used because the only register left to load the
> + address is IP and it will already contain the static chain. */
> + if (!decl && CALL_EXPR_BY_DESCRIPTOR (exp) && !flag_trampolines)
> + {
> + tree fntype = TREE_TYPE (TREE_TYPE (CALL_EXPR_FN (exp)));
> + CUMULATIVE_ARGS cum;
> + cumulative_args_t cum_v;
> +
> + arm_init_cumulative_args (&cum, fntype, NULL_RTX, NULL_TREE);
> + cum_v = pack_cumulative_args (&cum);
> +
> + for (tree t = TYPE_ARG_TYPES (fntype); t; t = TREE_CHAIN (t))
> + {
> + tree type = TREE_VALUE (t);
> + if (!VOID_TYPE_P (type))
> + arm_function_arg_advance (cum_v, TYPE_MODE (type), type, true);
> + }
> +
> + if (!arm_function_arg (cum_v, SImode, integer_type_node, true))
> + return false;
> + }
> +
> /* Everything else is ok. */
> return true;
> }
> @@ -29101,7 +29129,9 @@ arm_relayout_function (tree fndecl)
> callee_tree = target_option_default_node;
>
> struct cl_target_option *opts = TREE_TARGET_OPTION (callee_tree);
> - SET_DECL_ALIGN (fndecl, FUNCTION_BOUNDARY_P (opts->x_target_flags));
> + SET_DECL_ALIGN
> + (fndecl,
> + FUNCTION_ALIGNMENT (FUNCTION_BOUNDARY_P (opts->x_target_flags)));
> }
>
> /* Inner function to process the attribute((target(...))), take an argument
> and
>
