Mercurial > hg > CbC > CbC_gcc
diff gcc/ada/sem_mech.ads @ 111:04ced10e8804
gcc 7
author | kono |
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date | Fri, 27 Oct 2017 22:46:09 +0900 |
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children | 84e7813d76e9 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/gcc/ada/sem_mech.ads Fri Oct 27 22:46:09 2017 +0900 @@ -0,0 +1,144 @@ +------------------------------------------------------------------------------ +-- -- +-- GNAT COMPILER COMPONENTS -- +-- -- +-- S E M _ M E C H -- +-- -- +-- S p e c -- +-- -- +-- Copyright (C) 1996-2014, Free Software Foundation, Inc. -- +-- -- +-- GNAT is free software; you can redistribute it and/or modify it under -- +-- terms of the GNU General Public License as published by the Free Soft- -- +-- ware Foundation; either version 3, or (at your option) any later ver- -- +-- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- +-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- +-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License -- +-- for more details. You should have received a copy of the GNU General -- +-- Public License distributed with GNAT; see file COPYING3. If not, go to -- +-- http://www.gnu.org/licenses for a complete copy of the license. -- +-- -- +-- GNAT was originally developed by the GNAT team at New York University. -- +-- Extensive contributions were provided by Ada Core Technologies Inc. -- +-- -- +------------------------------------------------------------------------------ + +-- This package contains the routine used to establish calling mechanisms +-- The reason we separate this off into its own package is that it is +-- entirely possible that it may need some target specific specialization. + +with Types; use Types; + +package Sem_Mech is + + ------------------------------------------------- + -- Definitions for Parameter Mechanism Control -- + ------------------------------------------------- + + -- For parameters passed to subprograms, and for function return values, + -- a passing mechanism is defined. The entity attribute Mechanism returns + -- an indication of the mechanism, and Set_Mechanism can be used to set + -- the mechanism. At the program level, there are three ways to explicitly + -- set the mechanism: + + -- An Import_xxx or Export_xxx pragma (where xxx is Function, Procedure, + -- or Valued_Procedure) can explicitly set the mechanism for either a + -- parameter or a function return value. A mechanism explicitly set by + -- such a pragma overrides the effect of C_Pass_By_Copy described below. + + -- If convention C_Pass_By_Copy is set for a record, and the record type + -- is used as the formal type of a subprogram with a foreign convention, + -- then the mechanism is set to By_Copy. + + -- If a pragma C_Pass_By_Copy applies, and a record type has Convention + -- C, and the record type is used as the formal type of a subprogram + -- with a foreign convention, then the mechanism is set to use By_Copy + -- if the size of the record is sufficiently small (as determined by + -- the value of the parameter to pragma C_Pass_By_Copy). + + -- The subtype Mechanism_Type (declared in Types) is used to describe + -- the mechanism to be used. The following special values of this type + -- specify the mechanism, as follows. + + Default_Mechanism : constant Mechanism_Type := 0; + -- The default setting indicates that the backend will choose the proper + -- default mechanism. This depends on the convention of the subprogram + -- involved, and is generally target dependent. In the compiler, the + -- backend chooses the mechanism in this case in accordance with any + -- requirements imposed by the ABI. Note that Default is never used for + -- record types on foreign convention subprograms, since By_Reference + -- is forced for such types unless one of the above described approaches + -- is used to explicitly force By_Copy. + + By_Copy : constant Mechanism_Type := -1; + -- Passing by copy is forced. The exact meaning of By_Copy (e.g. whether + -- at a low level the value is passed in registers, or the value is copied + -- and a pointer is passed), is determined by the backend in accordance + -- with requirements imposed by the ABI. Note that in the extended import + -- and export pragma mechanisms, this is called Value, rather than Copy. + + By_Reference : constant Mechanism_Type := -2; + -- Passing by reference is forced. This is always equivalent to passing + -- a simple pointer in the case of subprograms with a foreign convention. + -- For unconstrained arrays passed to foreign convention subprograms, the + -- address of the first element of the array is passed. For convention + -- Ada, the result is logically to pass a reference, but the precise + -- mechanism (e.g. to pass bounds of unconstrained types and other needed + -- special information) is determined by the backend in accordance with + -- requirements imposed by the ABI as interpreted for Ada. + + pragma Assert (Mechanism_Type'First = -2); + -- Check definition in types is right! + + -- All the above special values are non-positive. Positive values for + -- Mechanism_Type values have a special meaning. They are used only in + -- the case of records, as a result of the use of the C_Pass_By_Copy + -- pragma, and the meaning is that if the size of the record is known + -- at compile time and does not exceed the mechanism type value, then + -- By_Copy passing is forced, otherwise By_Reference is forced. + + ---------------------- + -- Global Variables -- + ---------------------- + + Default_C_Record_Mechanism : Mechanism_Type := By_Reference; + -- This value is the default mechanism used for C convention records + -- in foreign-convention subprograms if no mechanism is otherwise + -- specified. This value is modified appropriately by the occurrence + -- of a C_Pass_By_Copy configuration pragma. + + ----------------- + -- Subprograms -- + ----------------- + + procedure Set_Mechanisms (E : Entity_Id); + -- E is a subprogram or subprogram type that has been frozen, so the + -- convention of the subprogram and all its formal types and result + -- type in the case of a function are established. The function of + -- this call is to set mechanism values for formals and for the + -- function return if they have not already been explicitly set by + -- a use of an extended Import or Export pragma. The idea is to set + -- mechanism values wherever the semantics is dictated by either + -- requirements or implementation advice in the RM, and to leave + -- the mechanism set to Default if there is no requirement, so that + -- the back-end is free to choose the most efficient method. + + procedure Set_Mechanism_Value (Ent : Entity_Id; Mech_Name : Node_Id); + -- Mech is a parameter passing mechanism (see Import_Function syntax + -- for MECHANISM_NAME). This routine checks that the mechanism argument + -- has the right form, and if not issues an error message. If the + -- argument has the right form then the Mechanism field of Ent is + -- set appropriately. It also performs some error checks. Note that + -- the mechanism name has not been analyzed (and cannot indeed be + -- analyzed, since it is semantic nonsense), so we get it in the + -- exact form created by the parser. + + procedure Set_Mechanism_With_Checks + (Ent : Entity_Id; + Mech : Mechanism_Type; + Enod : Node_Id); + -- Sets the mechanism of Ent to the given Mech value, after first checking + -- that the request makes sense. If it does not make sense, a warning is + -- posted on node Enod, and the Mechanism of Ent is unchanged. + +end Sem_Mech;