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This eliminates the use of the secondary stack to return specific tagged types from functions in calls that are not dispatching on result, which comprises returning controlled types, by introducing thunks whose only purpose is to move the result from the primary to the secondary stack for primitive functions that are controlling on result, and referencing them in the dispatch table in lieu of the primitive functions. The implementation reuses the existing machinery of interface thunks and thus creates another kind of thunks, secondary stack thunks, which only perform a call to the primitive function and return the result. gcc/ada/ * einfo.ads (Has_Controlling_Result): Document new usage. (Is_Thunk): Document secondary stack thunks. (Returns_By_Ref): Adjust. * exp_ch6.adb (Caller_Known_Size): Return true for tagged types. (Expand_N_Extended_Return_Statement): Do not call Set_By_Ref. (Expand_Simple_Function_Return): For a BIP return with an Alloc_Form parameter, mark the node as returning on the secondary stack. Replace call to Is_Limited_Interface with Is_Limited_View. Deal wit secondary stack thunks. Do not call Set_By_Ref. Optimize the case of a call to a function whose type also needs finalization. (Needs_BIP_Task_Actuals): Replace Thunk_Entity with Thunk_Target. (Needs_BIP_Finalization_Master): Cosmetic fixes. (Needs_BIP_Alloc_Form): Check No_Secondary_Stack restriction and return true for tagged types. * exp_ch7.adb (Transient Scope Management): Update description. * exp_disp.adb (Expand_Dispatching_Call): Always set Returns_By_Ref on designated type if the call is dispatching on result. Tidy up. (Expand_Interface_Thunk): Change type of Thunk_Code from Node_Id to List_Id. Change type of local variables from Node_Id to Entity_Id. Propagate Aliased_Present flag to create the formals and explicitly set Has_Controlling_Result to False. Build a secondary stack thunk if necessary in the function case. (Expand_Secondary_Stack_Thunk): New function. (Make_Secondary_DT): Build secondary stack thunks if necessary. (Make_DT): Likewise. (Register_Predefined_Primitive): Likewise. (Register_Primitive): Likewise. * exp_util.ads (Is_Secondary_Stack_Thunk): Declare. (Thunk_Target): Likewise. * exp_util.adb (Is_Secondary_Stack_Thunk): New function. (Thunk_Target): Likewise. * fe.h (Is_Secondary_Stack_Thunk): Declare. (Thunk_Target): Likewise. * gen_il-fields.ads (Opt_Field_Enum): Remove By_Ref. * gen_il-gen-gen_nodes.adb (N_Simple_Return_Statement): Likewise. (N_Extended_Return_Statement): Likewise. * sem_ch6.adb (Analyze_Subprogram_Specification): Skip check for abstract return type in the thunk case. (Create_Extra_Formals): Replace Thunk_Entity with Thunk_Target. * sem_disp.adb (Check_Controlling_Formals): Skip in the thunk case. * sem_util.adb: Add use and with clauses for Exp_Ch6. (Compute_Returns_By_Ref): Do not process procedures and only set the flag for direct return by reference. (Needs_Secondary_Stack): Do not return true for specific tagged types and adjust comments accordingly. * sinfo.ads (By_Ref): Delete. (N_Simple_Return_Statement): Remove By_Ref. (N_Extended_Return_Statement): Likewise. * gcc-interface/ada-tree.h (TYPE_RETURN_UNCONSTRAINED_P): Delete. * gcc-interface/decl.cc (gnat_to_gnu_subprog_type): Do not use it. Return by direct reference if the return type needs the secondary stack as well as for secondary stack thunks. * gcc-interface/gigi.h (fntype_same_flags_p): Remove parameter. * gcc-interface/misc.cc (gnat_type_hash_eq): Adjust to above change. * gcc-interface/trans.cc (finalize_nrv): Replace test on TYPE_RETURN_UNCONSTRAINED_P with TYPE_RETURN_BY_DIRECT_REF_P. (Subprogram_Body_to_gnu): Do not call maybe_make_gnu_thunk for secondary stack thunks. (Call_to_gnu): Do not test TYPE_RETURN_UNCONSTRAINED_P. (gnat_to_gnu) <N_Simple_Return_Statement>: In the return by direct reference case, test for the presence of Storage_Pool on the node to build an allocator. (maybe_make_gnu_thunk): Deal with Thunk_Entity and Thunk_Target. * gcc-interface/utils.cc (fntype_same_flags_p): Remove parameter. |
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This directory contains the GNU Compiler Collection (GCC). The GNU Compiler Collection is free software. See the files whose names start with COPYING for copying permission. The manuals, and some of the runtime libraries, are under different terms; see the individual source files for details. The directory INSTALL contains copies of the installation information as HTML and plain text. The source of this information is gcc/doc/install.texi. The installation information includes details of what is included in the GCC sources and what files GCC installs. See the file gcc/doc/gcc.texi (together with other files that it includes) for usage and porting information. An online readable version of the manual is in the files gcc/doc/gcc.info*. See http://gcc.gnu.org/bugs/ for how to report bugs usefully. Copyright years on GCC source files may be listed using range notation, e.g., 1987-2012, indicating that every year in the range, inclusive, is a copyrightable year that could otherwise be listed individually.