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2024-04-01 15:19:46 +00:00
------------------------------------------------------------------------------
-- --
-- GNAT COMPILER COMPONENTS --
-- --
-- E X P _ P A K D --
-- --
-- B o d y --
-- --
-- Copyright (C) 1992-2020, 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. --
-- --
------------------------------------------------------------------------------
with Atree; use Atree;
with Checks; use Checks;
with Einfo; use Einfo;
with Errout; use Errout;
with Exp_Dbug; use Exp_Dbug;
with Exp_Util; use Exp_Util;
with Layout; use Layout;
with Lib.Xref; use Lib.Xref;
with Namet; use Namet;
with Nlists; use Nlists;
with Nmake; use Nmake;
with Opt; use Opt;
with Sem; use Sem;
with Sem_Aux; use Sem_Aux;
with Sem_Ch3; use Sem_Ch3;
with Sem_Ch8; use Sem_Ch8;
with Sem_Ch13; use Sem_Ch13;
with Sem_Eval; use Sem_Eval;
with Sem_Res; use Sem_Res;
with Sem_Util; use Sem_Util;
with Sinfo; use Sinfo;
with Snames; use Snames;
with Stand; use Stand;
with Targparm; use Targparm;
with Tbuild; use Tbuild;
with Ttypes; use Ttypes;
with Uintp; use Uintp;
package body Exp_Pakd is
---------------------------
-- Endian Considerations --
---------------------------
-- As described in the specification, bit numbering in a packed array
-- is consistent with bit numbering in a record representation clause,
-- and hence dependent on the endianness of the machine:
-- For little-endian machines, element zero is at the right hand end
-- (low order end) of a bit field.
-- For big-endian machines, element zero is at the left hand end
-- (high order end) of a bit field.
-- The shifts that are used to right justify a field therefore differ in
-- the two cases. For the little-endian case, we can simply use the bit
-- number (i.e. the element number * element size) as the count for a right
-- shift. For the big-endian case, we have to subtract the shift count from
-- an appropriate constant to use in the right shift. We use rotates
-- instead of shifts (which is necessary in the store case to preserve
-- other fields), and we expect that the backend will be able to change the
-- right rotate into a left rotate, avoiding the subtract, if the machine
-- architecture provides such an instruction.
-----------------------
-- Local Subprograms --
-----------------------
procedure Compute_Linear_Subscript
(Atyp : Entity_Id;
N : Node_Id;
Subscr : out Node_Id);
-- Given a constrained array type Atyp, and an indexed component node N
-- referencing an array object of this type, build an expression of type
-- Standard.Integer representing the zero-based linear subscript value.
-- This expression includes any required range checks.
function Compute_Number_Components
(N : Node_Id;
Typ : Entity_Id) return Node_Id;
-- Build an expression that multiplies the length of the dimensions of the
-- array, used to control array equality checks.
procedure Convert_To_PAT_Type (Aexp : Node_Id);
-- Given an expression of a packed array type, builds a corresponding
-- expression whose type is the implementation type used to represent
-- the packed array. Aexp is analyzed and resolved on entry and on exit.
procedure Get_Base_And_Bit_Offset
(N : Node_Id;
Base : out Node_Id;
Offset : out Node_Id);
-- Given a node N for a name which involves a packed array reference,
-- return the base object of the reference and build an expression of
-- type Standard.Integer representing the zero-based offset in bits
-- from Base'Address to the first bit of the reference.
function Known_Aligned_Enough (Obj : Node_Id; Csiz : Nat) return Boolean;
-- There are two versions of the Set routines, the ones used when the
-- object is known to be sufficiently well aligned given the number of
-- bits, and the ones used when the object is not known to be aligned.
-- This routine is used to determine which set to use. Obj is a reference
-- to the object, and Csiz is the component size of the packed array.
-- True is returned if the alignment of object is known to be sufficient,
-- defined as 1 for odd bit sizes, 4 for bit sizes divisible by 4, and
-- 2 otherwise.
function Make_Shift_Left (N : Node_Id; S : Node_Id) return Node_Id;
-- Build a left shift node, checking for the case of a shift count of zero
function Make_Shift_Right (N : Node_Id; S : Node_Id) return Node_Id;
-- Build a right shift node, checking for the case of a shift count of zero
function RJ_Unchecked_Convert_To
(Typ : Entity_Id;
Expr : Node_Id) return Node_Id;
-- The packed array code does unchecked conversions which in some cases
-- may involve non-discrete types with differing sizes. The semantics of
-- such conversions is potentially endianness dependent, and the effect
-- we want here for such a conversion is to do the conversion in size as
-- though numeric items are involved, and we extend or truncate on the
-- left side. This happens naturally in the little-endian case, but in
-- the big endian case we can get left justification, when what we want
-- is right justification. This routine does the unchecked conversion in
-- a stepwise manner to ensure that it gives the expected result. Hence
-- the name (RJ = Right justified). The parameters Typ and Expr are as
-- for the case of a normal Unchecked_Convert_To call.
procedure Setup_Enumeration_Packed_Array_Reference (N : Node_Id);
-- This routine is called in the Get and Set case for arrays that are
-- packed but not bit-packed, meaning that they have at least one
-- subscript that is of an enumeration type with a non-standard
-- representation. This routine modifies the given node to properly
-- reference the corresponding packed array type.
procedure Setup_Inline_Packed_Array_Reference
(N : Node_Id;
Atyp : Entity_Id;
Obj : in out Node_Id;
Cmask : out Uint;
Shift : out Node_Id);
-- This procedure performs common processing on the N_Indexed_Component
-- parameter given as N, whose prefix is a reference to a packed array.
-- This is used for the get and set when the component size is 1, 2, 4,
-- or for other component sizes when the packed array type is a modular
-- type (i.e. the cases that are handled with inline code).
--
-- On entry:
--
-- N is the N_Indexed_Component node for the packed array reference
--
-- Atyp is the constrained array type (the actual subtype has been
-- computed if necessary to obtain the constraints, but this is still
-- the original array type, not the Packed_Array_Impl_Type value).
--
-- Obj is the object which is to be indexed. It is always of type Atyp.
--
-- On return:
--
-- Obj is the object containing the desired bit field. It is of type
-- Unsigned, Long_Unsigned, or Long_Long_Unsigned, and is either the
-- entire value, for the small static case, or the proper selected byte
-- from the array in the large or dynamic case. This node is analyzed
-- and resolved on return.
--
-- Shift is a node representing the shift count to be used in the
-- rotate right instruction that positions the field for access.
-- This node is analyzed and resolved on return.
--
-- Cmask is a mask corresponding to the width of the component field.
-- Its value is 2 ** Csize - 1 (e.g. 2#1111# for component size of 4).
--
-- Note: in some cases the call to this routine may generate actions
-- (for handling multi-use references and the generation of the packed
-- array type on the fly). Such actions are inserted into the tree
-- directly using Insert_Action.
function Revert_Storage_Order (N : Node_Id) return Node_Id;
-- Perform appropriate justification and byte ordering adjustments for N,
-- an element of a packed array type, when both the component type and
-- the enclosing packed array type have reverse scalar storage order.
-- On little-endian targets, the value is left justified before byte
-- swapping. The Etype of the returned expression is an integer type of
-- an appropriate power-of-2 size.
--------------------------
-- Revert_Storage_Order --
--------------------------
function Revert_Storage_Order (N : Node_Id) return Node_Id is
Loc : constant Source_Ptr := Sloc (N);
T : constant Entity_Id := Etype (N);
T_Size : constant Uint := RM_Size (T);
Swap_RE : RE_Id;
Swap_F : Entity_Id;
Swap_T : Entity_Id;
-- Swapping function
Arg : Node_Id;
Adjusted : Node_Id;
Shift : Uint;
begin
if T_Size <= 8 then
-- Array component size is less than a byte: no swapping needed
Swap_F := Empty;
Swap_T := RTE (RE_Unsigned_8);
else
-- Select byte swapping function depending on array component size
if T_Size <= 16 then
Swap_RE := RE_Bswap_16;
elsif T_Size <= 32 then
Swap_RE := RE_Bswap_32;
elsif T_Size <= 64 then
Swap_RE := RE_Bswap_64;
else pragma Assert (T_Size <= 128);
Swap_RE := RE_Bswap_128;
end if;
Swap_F := RTE (Swap_RE);
Swap_T := Etype (Swap_F);
end if;
Shift := Esize (Swap_T) - T_Size;
Arg := RJ_Unchecked_Convert_To (Swap_T, N);
if not Bytes_Big_Endian and then Shift > Uint_0 then
Arg :=
Make_Op_Shift_Left (Loc,
Left_Opnd => Arg,
Right_Opnd => Make_Integer_Literal (Loc, Shift));
end if;
if Present (Swap_F) then
Adjusted :=
Make_Function_Call (Loc,
Name => New_Occurrence_Of (Swap_F, Loc),
Parameter_Associations => New_List (Arg));
else
Adjusted := Arg;
end if;
Set_Etype (Adjusted, Swap_T);
return Adjusted;
end Revert_Storage_Order;
------------------------------
-- Compute_Linear_Subscript --
------------------------------
procedure Compute_Linear_Subscript
(Atyp : Entity_Id;
N : Node_Id;
Subscr : out Node_Id)
is
Loc : constant Source_Ptr := Sloc (N);
Oldsub : Node_Id;
Newsub : Node_Id;
Indx : Node_Id;
Styp : Entity_Id;
begin
Subscr := Empty;
-- Loop through dimensions
Indx := First_Index (Atyp);
Oldsub := First (Expressions (N));
while Present (Indx) loop
Styp := Etype (Indx);
Newsub := Relocate_Node (Oldsub);
-- Get expression for the subscript value. First, if Do_Range_Check
-- is set on a subscript, then we must do a range check against the
-- original bounds (not the bounds of the packed array type). We do
-- this by introducing a subtype conversion.
if Do_Range_Check (Newsub)
and then Etype (Newsub) /= Styp
then
Newsub := Convert_To (Styp, Newsub);
end if;
-- Now evolve the expression for the subscript. First convert
-- the subscript to be zero based and of an integer type.
-- Case of integer type, where we just subtract to get lower bound
if Is_Integer_Type (Styp) then
-- If length of integer type is smaller than standard integer,
-- then we convert to integer first, then do the subtract
-- Integer (subscript) - Integer (Styp'First)
if Esize (Styp) < Standard_Integer_Size then
Newsub :=
Make_Op_Subtract (Loc,
Left_Opnd => Convert_To (Standard_Integer, Newsub),
Right_Opnd =>
Convert_To (Standard_Integer,
Make_Attribute_Reference (Loc,
Prefix => New_Occurrence_Of (Styp, Loc),
Attribute_Name => Name_First)));
-- For larger integer types, subtract first, then convert to
-- integer, this deals with strange long long integer bounds.
-- Integer (subscript - Styp'First)
else
Newsub :=
Convert_To (Standard_Integer,
Make_Op_Subtract (Loc,
Left_Opnd => Newsub,
Right_Opnd =>
Make_Attribute_Reference (Loc,
Prefix => New_Occurrence_Of (Styp, Loc),
Attribute_Name => Name_First)));
end if;
-- For the enumeration case, we have to use 'Pos to get the value
-- to work with before subtracting the lower bound.
-- Integer (Styp'Pos (subscr)) - Integer (Styp'Pos (Styp'First));
-- This is not quite right for bizarre cases where the size of the
-- enumeration type is > Integer'Size bits due to rep clause ???
else
pragma Assert (Is_Enumeration_Type (Styp));
Newsub :=
Make_Op_Subtract (Loc,
Left_Opnd => Convert_To (Standard_Integer,
Make_Attribute_Reference (Loc,
Prefix => New_Occurrence_Of (Styp, Loc),
Attribute_Name => Name_Pos,
Expressions => New_List (Newsub))),
Right_Opnd =>
Convert_To (Standard_Integer,
Make_Attribute_Reference (Loc,
Prefix => New_Occurrence_Of (Styp, Loc),
Attribute_Name => Name_Pos,
Expressions => New_List (
Make_Attribute_Reference (Loc,
Prefix => New_Occurrence_Of (Styp, Loc),
Attribute_Name => Name_First)))));
end if;
Set_Paren_Count (Newsub, 1);
-- For the first subscript, we just copy that subscript value
if No (Subscr) then
Subscr := Newsub;
-- Otherwise, we must multiply what we already have by the current
-- stride and then add in the new value to the evolving subscript.
else
Subscr :=
Make_Op_Add (Loc,
Left_Opnd =>
Make_Op_Multiply (Loc,
Left_Opnd => Subscr,
Right_Opnd =>
Make_Attribute_Reference (Loc,
Attribute_Name => Name_Range_Length,
Prefix => New_Occurrence_Of (Styp, Loc))),
Right_Opnd => Newsub);
end if;
-- Move to next subscript
Next_Index (Indx);
Next (Oldsub);
end loop;
end Compute_Linear_Subscript;
-------------------------------
-- Compute_Number_Components --
-------------------------------
function Compute_Number_Components
(N : Node_Id;
Typ : Entity_Id) return Node_Id
is
Loc : constant Source_Ptr := Sloc (N);
Len_Expr : Node_Id;
begin
Len_Expr :=
Make_Attribute_Reference (Loc,
Attribute_Name => Name_Length,
Prefix => New_Occurrence_Of (Typ, Loc),
Expressions => New_List (Make_Integer_Literal (Loc, 1)));
for J in 2 .. Number_Dimensions (Typ) loop
Len_Expr :=
Make_Op_Multiply (Loc,
Left_Opnd => Len_Expr,
Right_Opnd =>
Make_Attribute_Reference (Loc,
Attribute_Name => Name_Length,
Prefix => New_Occurrence_Of (Typ, Loc),
Expressions => New_List (Make_Integer_Literal (Loc, J))));
end loop;
return Len_Expr;
end Compute_Number_Components;
-------------------------
-- Convert_To_PAT_Type --
-------------------------
-- The PAT is always obtained from the actual subtype
procedure Convert_To_PAT_Type (Aexp : Node_Id) is
Act_ST : Entity_Id;
begin
Convert_To_Actual_Subtype (Aexp);
Act_ST := Underlying_Type (Etype (Aexp));
Create_Packed_Array_Impl_Type (Act_ST);
-- Just replace the etype with the packed array type. This works because
-- the expression will not be further analyzed, and Gigi considers the
-- two types equivalent in any case.
-- This is not strictly the case ??? If the reference is an actual in
-- call, the expansion of the prefix is delayed, and must be reanalyzed,
-- see Reset_Packed_Prefix. On the other hand, if the prefix is a simple
-- array reference, reanalysis can produce spurious type errors when the
-- PAT type is replaced again with the original type of the array. Same
-- for the case of a dereference. Ditto for function calls: expansion
-- may introduce additional actuals which will trigger errors if call is
-- reanalyzed. The following is correct and minimal, but the handling of
-- more complex packed expressions in actuals is confused. Probably the
-- problem only remains for actuals in calls.
Set_Etype (Aexp, Packed_Array_Impl_Type (Act_ST));
if Is_Entity_Name (Aexp)
or else
(Nkind (Aexp) = N_Indexed_Component
and then Is_Entity_Name (Prefix (Aexp)))
or else Nkind (Aexp) in N_Explicit_Dereference | N_Function_Call
then
Set_Analyzed (Aexp);
end if;
end Convert_To_PAT_Type;
-----------------------------------
-- Create_Packed_Array_Impl_Type --
-----------------------------------
procedure Create_Packed_Array_Impl_Type (Typ : Entity_Id) is
Loc : constant Source_Ptr := Sloc (Typ);
Ctyp : constant Entity_Id := Component_Type (Typ);
Csize : constant Uint := Component_Size (Typ);
Ancest : Entity_Id;
PB_Type : Entity_Id;
PASize : Uint;
Decl : Node_Id;
PAT : Entity_Id;
Len_Expr : Node_Id;
Len_Bits : Uint;
Bits_U1 : Node_Id;
PAT_High : Node_Id;
Btyp : Entity_Id;
Lit : Node_Id;
procedure Install_PAT;
-- This procedure is called with Decl set to the declaration for the
-- packed array type. It creates the type and installs it as required.
procedure Set_PB_Type;
-- Set PB_Type to [Rev_]Packed_Bytes{1,2,4} as required by the alignment
-- and the scalar storage order requirements (see documentation in the
-- spec of this package).
-----------------
-- Install_PAT --
-----------------
procedure Install_PAT is
Pushed_Scope : Boolean := False;
begin
-- We do not want to put the declaration we have created in the tree
-- since it is often hard, and sometimes impossible to find a proper
-- place for it (the impossible case arises for a packed array type
-- with bounds depending on the discriminant, a declaration cannot
-- be put inside the record, and the reference to the discriminant
-- cannot be outside the record).
-- The solution is to analyze the declaration while temporarily
-- attached to the tree at an appropriate point, and then we install
-- the resulting type as an Itype in the packed array type field of
-- the original type, so that no explicit declaration is required.
-- Note: the packed type is created in the scope of its parent type.
-- There are at least some cases where the current scope is deeper,
-- and so when this is the case, we temporarily reset the scope
-- for the definition. This is clearly safe, since the first use
-- of the packed array type will be the implicit reference from
-- the corresponding unpacked type when it is elaborated.
if Is_Itype (Typ) then
Set_Parent (Decl, Associated_Node_For_Itype (Typ));
else
Set_Parent (Decl, Declaration_Node (Typ));
end if;
if Scope (Typ) /= Current_Scope then
Push_Scope (Scope (Typ));
Pushed_Scope := True;
end if;
Set_Is_Itype (PAT, True);
Set_Is_Packed_Array_Impl_Type (PAT, True);
Set_Packed_Array_Impl_Type (Typ, PAT);
Analyze (Decl, Suppress => All_Checks);
if Pushed_Scope then
Pop_Scope;
end if;
-- Set Esize and RM_Size to the actual size of the packed object
-- Do not reset RM_Size if already set, as happens in the case of
-- a modular type.
if Unknown_Esize (PAT) then
Set_Esize (PAT, PASize);
end if;
if Unknown_RM_Size (PAT) then
Set_RM_Size (PAT, PASize);
end if;
Adjust_Esize_Alignment (PAT);
-- Set remaining fields of packed array type
Init_Alignment (PAT);
Set_Parent (PAT, Empty);
Set_Associated_Node_For_Itype (PAT, Typ);
Set_Original_Array_Type (PAT, Typ);
-- Propagate representation aspects
Set_Is_Atomic (PAT, Is_Atomic (Typ));
Set_Is_Independent (PAT, Is_Independent (Typ));
Set_Is_Volatile (PAT, Is_Volatile (Typ));
Set_Is_Volatile_Full_Access (PAT, Is_Volatile_Full_Access (Typ));
Set_Treat_As_Volatile (PAT, Treat_As_Volatile (Typ));
-- We definitely do not want to delay freezing for packed array
-- types. This is of particular importance for the itypes that are
-- generated for record components depending on discriminants where
-- there is no place to put the freeze node.
Set_Has_Delayed_Freeze (PAT, False);
Set_Has_Delayed_Freeze (Etype (PAT), False);
-- If we did allocate a freeze node, then clear out the reference
-- since it is obsolete (should we delete the freeze node???)
Set_Freeze_Node (PAT, Empty);
Set_Freeze_Node (Etype (PAT), Empty);
end Install_PAT;
-----------------
-- Set_PB_Type --
-----------------
procedure Set_PB_Type is
begin
-- If the user has specified an explicit alignment for the
-- type or component, take it into account.
if Csize <= 2 or else Csize = 4 or else Csize mod 2 /= 0
or else Alignment (Typ) = 1
or else Component_Alignment (Typ) = Calign_Storage_Unit
then
if Reverse_Storage_Order (Typ) then
PB_Type := RTE (RE_Rev_Packed_Bytes1);
else
PB_Type := RTE (RE_Packed_Bytes1);
end if;
elsif Csize mod 4 /= 0
or else Alignment (Typ) = 2
then
if Reverse_Storage_Order (Typ) then
PB_Type := RTE (RE_Rev_Packed_Bytes2);
else
PB_Type := RTE (RE_Packed_Bytes2);
end if;
else
if Reverse_Storage_Order (Typ) then
PB_Type := RTE (RE_Rev_Packed_Bytes4);
else
PB_Type := RTE (RE_Packed_Bytes4);
end if;
end if;
-- The Rev_Packed_Bytes{1,2,4} types cannot be directly declared with
-- the reverse scalar storage order in System.Unsigned_Types because
-- their component type is aliased and the combination would then be
-- flagged as illegal by the compiler. Moreover changing the compiler
-- would not address the bootstrap path issue with earlier versions.
Set_Reverse_Storage_Order (PB_Type, Reverse_Storage_Order (Typ));
end Set_PB_Type;
-- Start of processing for Create_Packed_Array_Impl_Type
begin
-- If we already have a packed array type, nothing to do
if Present (Packed_Array_Impl_Type (Typ)) then
return;
end if;
-- If our immediate ancestor subtype is constrained, and it already
-- has a packed array type, then just share the same type, since the
-- bounds must be the same. If the ancestor is not an array type but
-- a private type, as can happen with multiple instantiations, create
-- a new packed type, to avoid privacy issues.
if Ekind (Typ) = E_Array_Subtype then
Ancest := Ancestor_Subtype (Typ);
if Present (Ancest)
and then Is_Array_Type (Ancest)
and then Is_Constrained (Ancest)
and then Present (Packed_Array_Impl_Type (Ancest))
then
Set_Packed_Array_Impl_Type (Typ, Packed_Array_Impl_Type (Ancest));
return;
end if;
end if;
-- We preset the result type size from the size of the original array
-- type, since this size clearly belongs to the packed array type. The
-- size of the conceptual unpacked type is always set to unknown.
PASize := RM_Size (Typ);
-- Case of an array where at least one index is of an enumeration
-- type with a non-standard representation, but the component size
-- is not appropriate for bit packing. This is the case where we
-- have Is_Packed set (we would never be in this unit otherwise),
-- but Is_Bit_Packed_Array is false.
-- Note that if the component size is appropriate for bit packing,
-- then the circuit for the computation of the subscript properly
-- deals with the non-standard enumeration type case by taking the
-- Pos anyway.
if not Is_Bit_Packed_Array (Typ) then
-- Here we build a declaration:
-- type tttP is array (index1, index2, ...) of component_type
-- where index1, index2, are the index types. These are the same
-- as the index types of the original array, except for the non-
-- standard representation enumeration type case, where we have
-- two subcases.
-- For the unconstrained array case, we use
-- Natural range <>
-- For the constrained case, we use
-- Natural range Enum_Type'Pos (Enum_Type'First) ..
-- Enum_Type'Pos (Enum_Type'Last);
-- Note that tttP is created even if no index subtype is a non
-- standard enumeration, because we still need to remove padding
-- normally inserted for component alignment.
PAT :=
Make_Defining_Identifier (Loc,
Chars => New_External_Name (Chars (Typ), 'P'));
declare
Indexes : constant List_Id := New_List;
Indx : Node_Id;
Indx_Typ : Entity_Id;
Enum_Case : Boolean;
Typedef : Node_Id;
begin
Indx := First_Index (Typ);
while Present (Indx) loop
Indx_Typ := Etype (Indx);
Enum_Case := Is_Enumeration_Type (Indx_Typ)
and then Has_Non_Standard_Rep (Indx_Typ);
-- Unconstrained case
if not Is_Constrained (Typ) then
if Enum_Case then
Indx_Typ := Standard_Natural;
end if;
Append_To (Indexes, New_Occurrence_Of (Indx_Typ, Loc));
-- Constrained case
else
if not Enum_Case then
Append_To (Indexes, New_Occurrence_Of (Indx_Typ, Loc));
else
Append_To (Indexes,
Make_Subtype_Indication (Loc,
Subtype_Mark =>
New_Occurrence_Of (Standard_Natural, Loc),
Constraint =>
Make_Range_Constraint (Loc,
Range_Expression =>
Make_Range (Loc,
Low_Bound =>
Make_Attribute_Reference (Loc,
Prefix =>
New_Occurrence_Of (Indx_Typ, Loc),
Attribute_Name => Name_Pos,
Expressions => New_List (
Make_Attribute_Reference (Loc,
Prefix =>
New_Occurrence_Of (Indx_Typ, Loc),
Attribute_Name => Name_First))),
High_Bound =>
Make_Attribute_Reference (Loc,
Prefix =>
New_Occurrence_Of (Indx_Typ, Loc),
Attribute_Name => Name_Pos,
Expressions => New_List (
Make_Attribute_Reference (Loc,
Prefix =>
New_Occurrence_Of (Indx_Typ, Loc),
Attribute_Name => Name_Last)))))));
end if;
end if;
Next_Index (Indx);
end loop;
if not Is_Constrained (Typ) then
Typedef :=
Make_Unconstrained_Array_Definition (Loc,
Subtype_Marks => Indexes,
Component_Definition =>
Make_Component_Definition (Loc,
Aliased_Present => False,
Subtype_Indication =>
New_Occurrence_Of (Ctyp, Loc)));
else
Typedef :=
Make_Constrained_Array_Definition (Loc,
Discrete_Subtype_Definitions => Indexes,
Component_Definition =>
Make_Component_Definition (Loc,
Aliased_Present => False,
Subtype_Indication =>
New_Occurrence_Of (Ctyp, Loc)));
end if;
Decl :=
Make_Full_Type_Declaration (Loc,
Defining_Identifier => PAT,
Type_Definition => Typedef);
end;
Install_PAT;
-- Propagate the reverse storage order flag to the base type
Set_Reverse_Storage_Order (Etype (PAT), Reverse_Storage_Order (Typ));
return;
-- Case of bit-packing required for unconstrained array. We create
-- a subtype that is equivalent to use Packed_Bytes{1,2,4} as needed.
elsif not Is_Constrained (Typ) then
-- When generating standard DWARF (i.e when GNAT_Encodings is
-- DWARF_GNAT_Encodings_Minimal), the ___XP suffix will be stripped
-- by the back-end but generate it anyway to ease compiler debugging.
-- This will help to distinguish implementation types from original
-- packed arrays.
PAT :=
Make_Defining_Identifier (Loc,
Chars => Make_Packed_Array_Impl_Type_Name (Typ, Csize));
Set_PB_Type;
Decl :=
Make_Subtype_Declaration (Loc,
Defining_Identifier => PAT,
Subtype_Indication => New_Occurrence_Of (PB_Type, Loc));
Install_PAT;
return;
-- Remaining code is for the case of bit-packing for constrained array
-- The name of the packed array subtype is
-- ttt___XPsss
-- where sss is the component size in bits and ttt is the name of
-- the parent packed type.
else
PAT :=
Make_Defining_Identifier (Loc,
Chars => Make_Packed_Array_Impl_Type_Name (Typ, Csize));
-- Build an expression for the length of the array in bits.
-- This is the product of the length of each of the dimensions
Len_Expr := Compute_Number_Components (Typ, Typ);
-- Temporarily attach the length expression to the tree and analyze
-- and resolve it, so that we can test its value. We assume that the
-- total length fits in type Integer. This expression may involve
-- discriminants, so we treat it as a default/per-object expression.
Set_Parent (Len_Expr, Typ);
Preanalyze_Spec_Expression (Len_Expr, Standard_Long_Long_Integer);
-- Use a modular type if possible. We can do this if we have
-- static bounds, and the length is small enough, and the length
-- is not zero. We exclude the zero length case because the size
-- of things is always at least one, and the zero length object
-- would have an anomalous size.
if Compile_Time_Known_Value (Len_Expr) then
Len_Bits := Expr_Value (Len_Expr) * Csize;
-- Check for size known to be too large
if Len_Bits >
Uint_2 ** (Standard_Integer_Size - 1) * System_Storage_Unit
then
if System_Storage_Unit = 8 then
Error_Msg_N
("packed array size cannot exceed " &
"Integer''Last bytes", Typ);
else
Error_Msg_N
("packed array size cannot exceed " &
"Integer''Last storage units", Typ);
end if;
-- Reset length to arbitrary not too high value to continue
Len_Expr := Make_Integer_Literal (Loc, 65535);
Analyze_And_Resolve (Len_Expr, Standard_Long_Long_Integer);
end if;
-- We normally consider small enough to mean no larger than the
-- value of System_Max_Binary_Modulus_Power, checking that in the
-- case of values longer than word size, we have long shifts.
if Len_Bits > 0
and then
(Len_Bits <= System_Word_Size
or else (Len_Bits <= System_Max_Binary_Modulus_Power
and then Support_Long_Shifts_On_Target))
then
-- We can use the modular type, it has the form:
-- subtype tttPn is btyp
-- range 0 .. 2 ** ((Typ'Length (1)
-- * ... * Typ'Length (n)) * Csize) - 1;
-- The bounds are statically known, and btyp is one of the
-- unsigned types, depending on the length.
Btyp := Small_Integer_Type_For (Len_Bits, Uns => True);
Lit := Make_Integer_Literal (Loc, 2 ** Len_Bits - 1);
Set_Print_In_Hex (Lit);
Decl :=
Make_Subtype_Declaration (Loc,
Defining_Identifier => PAT,
Subtype_Indication =>
Make_Subtype_Indication (Loc,
Subtype_Mark => New_Occurrence_Of (Btyp, Loc),
Constraint =>
Make_Range_Constraint (Loc,
Range_Expression =>
Make_Range (Loc,
Low_Bound =>
Make_Integer_Literal (Loc, 0),
High_Bound => Lit))));
if PASize = Uint_0 then
PASize := Len_Bits;
end if;
Install_PAT;
-- Propagate a given alignment to the modular type. This can
-- cause it to be under-aligned, but that's OK.
if Present (Alignment_Clause (Typ)) then
Set_Alignment (PAT, Alignment (Typ));
end if;
return;
end if;
end if;
-- Could not use a modular type, for all other cases, we build
-- a packed array subtype:
-- subtype tttPn is
-- System.Packed_Bytes{1,2,4} (0 .. (Bits + 7) / 8 - 1);
-- Bits is the length of the array in bits
Set_PB_Type;
Bits_U1 :=
Make_Op_Add (Loc,
Left_Opnd =>
Make_Op_Multiply (Loc,
Left_Opnd =>
Make_Integer_Literal (Loc, Csize),
Right_Opnd => Len_Expr),
Right_Opnd =>
Make_Integer_Literal (Loc, 7));
Set_Paren_Count (Bits_U1, 1);
PAT_High :=
Make_Op_Subtract (Loc,
Left_Opnd =>
Make_Op_Divide (Loc,
Left_Opnd => Bits_U1,
Right_Opnd => Make_Integer_Literal (Loc, 8)),
Right_Opnd => Make_Integer_Literal (Loc, 1));
Decl :=
Make_Subtype_Declaration (Loc,
Defining_Identifier => PAT,
Subtype_Indication =>
Make_Subtype_Indication (Loc,
Subtype_Mark => New_Occurrence_Of (PB_Type, Loc),
Constraint =>
Make_Index_Or_Discriminant_Constraint (Loc,
Constraints => New_List (
Make_Range (Loc,
Low_Bound =>
Make_Integer_Literal (Loc, 0),
High_Bound =>
Convert_To (Standard_Integer, PAT_High))))));
Install_PAT;
-- Currently the code in this unit requires that packed arrays
-- represented by non-modular arrays of bytes be on a byte
-- boundary for bit sizes handled by System.Pack_nn units.
-- That's because these units assume the array being accessed
-- starts on a byte boundary.
if Get_Id (UI_To_Int (Csize)) /= RE_Null then
Set_Must_Be_On_Byte_Boundary (Typ);
end if;
end if;
end Create_Packed_Array_Impl_Type;
-----------------------------------
-- Expand_Bit_Packed_Element_Set --
-----------------------------------
procedure Expand_Bit_Packed_Element_Set (N : Node_Id) is
Loc : constant Source_Ptr := Sloc (N);
Lhs : constant Node_Id := Name (N);
Ass_OK : constant Boolean := Assignment_OK (Lhs);
-- Used to preserve assignment OK status when assignment is rewritten
Expr : Node_Id;
Rhs : Node_Id := Expression (N);
-- Initially Rhs is the right hand side value, it will be replaced
-- later by an appropriate unchecked conversion for the assignment.
Obj : Node_Id;
Atyp : Entity_Id;
PAT : Entity_Id;
Ctyp : Entity_Id;
Csiz : Int;
Cmask : Uint;
Shift : Node_Id;
-- The expression for the shift value that is required
Shift_Used : Boolean := False;
-- Set True if Shift has been used in the generated code at least once,
-- so that it must be duplicated if used again.
New_Lhs : Node_Id;
New_Rhs : Node_Id;
Rhs_Val_Known : Boolean;
Rhs_Val : Uint;
-- If the value of the right hand side as an integer constant is
-- known at compile time, Rhs_Val_Known is set True, and Rhs_Val
-- contains the value. Otherwise Rhs_Val_Known is set False, and
-- the Rhs_Val is undefined.
function Get_Shift return Node_Id;
-- Function used to get the value of Shift, making sure that it
-- gets duplicated if the function is called more than once.
---------------
-- Get_Shift --
---------------
function Get_Shift return Node_Id is
begin
-- If we used the shift value already, then duplicate it. We
-- set a temporary parent in case actions have to be inserted.
if Shift_Used then
Set_Parent (Shift, N);
return Duplicate_Subexpr_No_Checks (Shift);
-- If first time, use Shift unchanged, and set flag for first use
else
Shift_Used := True;
return Shift;
end if;
end Get_Shift;
-- Start of processing for Expand_Bit_Packed_Element_Set
begin
pragma Assert (Is_Bit_Packed_Array (Etype (Prefix (Lhs))));
Obj := Relocate_Node (Prefix (Lhs));
Convert_To_Actual_Subtype (Obj);
Atyp := Etype (Obj);
PAT := Packed_Array_Impl_Type (Atyp);
Ctyp := Component_Type (Atyp);
Csiz := UI_To_Int (Component_Size (Atyp));
-- We remove side effects, in case the rhs modifies the lhs, because we
-- are about to transform the rhs into an expression that first READS
-- the lhs, so we can do the necessary shifting and masking. Example:
-- "X(2) := F(...);" where F modifies X(3). Otherwise, the side effect
-- will be lost.
Remove_Side_Effects (Rhs);
-- We convert the right hand side to the proper subtype to ensure
-- that an appropriate range check is made (since the normal range
-- check from assignment will be lost in the transformations). This
-- conversion is analyzed immediately so that subsequent processing
-- can work with an analyzed Rhs (and e.g. look at its Etype)
-- If the right-hand side is a string literal, create a temporary for
-- it, constant-folding is not ready to wrap the bit representation
-- of a string literal.
if Nkind (Rhs) = N_String_Literal then
declare
Decl : Node_Id;
begin
Decl :=
Make_Object_Declaration (Loc,
Defining_Identifier => Make_Temporary (Loc, 'T', Rhs),
Object_Definition => New_Occurrence_Of (Ctyp, Loc),
Expression => New_Copy_Tree (Rhs));
Insert_Actions (N, New_List (Decl));
Rhs := New_Occurrence_Of (Defining_Identifier (Decl), Loc);
end;
end if;
Rhs := Convert_To (Ctyp, Rhs);
Set_Parent (Rhs, N);
-- If we are building the initialization procedure for a packed array,
-- and Initialize_Scalars is enabled, each component assignment is an
-- out-of-range value by design. Compile this value without checks,
-- because a call to the array init_proc must not raise an exception.
-- Condition is not consistent with description above, Within_Init_Proc
-- is True also when we are building the IP for a record or protected
-- type that has a packed array component???
if Within_Init_Proc
and then Initialize_Scalars
then
Analyze_And_Resolve (Rhs, Ctyp, Suppress => All_Checks);
else
Analyze_And_Resolve (Rhs, Ctyp);
end if;
-- If any of the indices has a nonstandard representation, introduce
-- the proper Rep_To_Pos conversion, which in turn will generate index
-- checks when needed. We do this on a copy of the index expression,
-- rather that rewriting the LHS altogether.
Expr := First (Expressions (Lhs));
while Present (Expr) loop
declare
Expr_Typ : constant Entity_Id := Etype (Expr);
Loc : constant Source_Ptr := Sloc (Expr);
Expr_Copy : Node_Id;
begin
if Is_Enumeration_Type (Expr_Typ)
and then Has_Non_Standard_Rep (Expr_Typ)
then
Expr_Copy :=
Make_Attribute_Reference (Loc,
Prefix => New_Occurrence_Of (Expr_Typ, Loc),
Attribute_Name => Name_Pos,
Expressions => New_List (Relocate_Node (Expr)));
Set_Parent (Expr_Copy, N);
Analyze_And_Resolve (Expr_Copy, Standard_Natural);
end if;
end;
Next (Expr);
end loop;
-- Case of component size 1,2,4 or any component size for the modular
-- case. These are the cases for which we can inline the code.
if Csiz = 1 or else Csiz = 2 or else Csiz = 4
or else (Present (PAT) and then Is_Modular_Integer_Type (PAT))
then
Setup_Inline_Packed_Array_Reference (Lhs, Atyp, Obj, Cmask, Shift);
-- The statement to be generated is:
-- Obj := atyp!((Obj and Mask1) or (shift_left (rhs, Shift)))
-- or in the case of a freestanding Reverse_Storage_Order object,
-- Obj := Swap (atyp!((Swap (Obj) and Mask1)
-- or (shift_left (rhs, Shift))))
-- where Mask1 is obtained by shifting Cmask left Shift bits
-- and then complementing the result.
-- the "and Mask1" is omitted if rhs is constant and all 1 bits
-- the "or ..." is omitted if rhs is constant and all 0 bits
-- rhs is converted to the appropriate type
-- The result is converted back to the array type, since
-- otherwise we lose knowledge of the packed nature.
-- Determine if right side is all 0 bits or all 1 bits
if Compile_Time_Known_Value (Rhs) then
Rhs_Val := Expr_Rep_Value (Rhs);
Rhs_Val_Known := True;
-- The following test catches the case of an unchecked conversion of
-- an integer literal. This results from optimizing aggregates of
-- packed types.
elsif Nkind (Rhs) = N_Unchecked_Type_Conversion
and then Compile_Time_Known_Value (Expression (Rhs))
then
Rhs_Val := Expr_Rep_Value (Expression (Rhs));
Rhs_Val_Known := True;
else
Rhs_Val := No_Uint;
Rhs_Val_Known := False;
end if;
-- Some special checks for the case where the right hand value is
-- known at compile time. Basically we have to take care of the
-- implicit conversion to the subtype of the component object.
if Rhs_Val_Known then
-- If we have a biased component type then we must manually do the
-- biasing, since we are taking responsibility in this case for
-- constructing the exact bit pattern to be used.
if Has_Biased_Representation (Ctyp) then
Rhs_Val := Rhs_Val - Expr_Rep_Value (Type_Low_Bound (Ctyp));
end if;
-- For a negative value, we manually convert the two's complement
-- value to a corresponding unsigned value, so that the proper
-- field width is maintained. If we did not do this, we would
-- get too many leading sign bits later on.
if Rhs_Val < 0 then
Rhs_Val := 2 ** UI_From_Int (Csiz) + Rhs_Val;
end if;
end if;
-- Now create copies removing side effects. Note that in some complex
-- cases, this may cause the fact that we have already set a packed
-- array type on Obj to get lost. So we save the type of Obj, and
-- make sure it is reset properly.
declare
T : constant Entity_Id := Etype (Obj);
begin
New_Lhs := Duplicate_Subexpr (Obj, Name_Req => True);
New_Rhs := Duplicate_Subexpr_No_Checks (Obj);
Set_Etype (Obj, T);
Set_Etype (New_Lhs, T);
Set_Etype (New_Rhs, T);
end;
-- First we deal with the "and"
if not Rhs_Val_Known or else Rhs_Val /= Cmask then
declare
Mask1 : Node_Id;
Lit : Node_Id;
begin
if Compile_Time_Known_Value (Shift) then
Mask1 :=
Make_Integer_Literal (Loc,
Modulus (Etype (Obj)) - 1 -
(Cmask * (2 ** Expr_Value (Get_Shift))));
Set_Print_In_Hex (Mask1);
else
Lit := Make_Integer_Literal (Loc, Cmask);
Set_Print_In_Hex (Lit);
Mask1 :=
Make_Op_Not (Loc,
Right_Opnd => Make_Shift_Left (Lit, Get_Shift));
end if;
New_Rhs :=
Make_Op_And (Loc,
Left_Opnd => New_Rhs,
Right_Opnd => Mask1);
end;
end if;
-- Then deal with the "or"
if not Rhs_Val_Known or else Rhs_Val /= 0 then
declare
Or_Rhs : Node_Id;
procedure Fixup_Rhs;
-- Adjust Rhs by bias if biased representation for components
-- or remove extraneous high order sign bits if signed.
procedure Fixup_Rhs is
Etyp : constant Entity_Id := Etype (Rhs);
begin
-- For biased case, do the required biasing by simply
-- converting to the biased subtype (the conversion
-- will generate the required bias).
if Has_Biased_Representation (Ctyp) then
Rhs := Convert_To (Ctyp, Rhs);
-- For a signed integer type that is not biased, generate
-- a conversion to unsigned to strip high order sign bits.
elsif Is_Signed_Integer_Type (Ctyp) then
Rhs := Unchecked_Convert_To (RTE (Bits_Id (Csiz)), Rhs);
end if;
-- Set Etype, since it can be referenced before the node is
-- completely analyzed.
Set_Etype (Rhs, Etyp);
-- We now need to do an unchecked conversion of the
-- result to the target type, but it is important that
-- this conversion be a right justified conversion and
-- not a left justified conversion.
Rhs := RJ_Unchecked_Convert_To (Etype (Obj), Rhs);
end Fixup_Rhs;
begin
if Rhs_Val_Known
and then Compile_Time_Known_Value (Get_Shift)
then
Or_Rhs :=
Make_Integer_Literal (Loc,
Rhs_Val * (2 ** Expr_Value (Get_Shift)));
Set_Print_In_Hex (Or_Rhs);
else
-- We have to convert the right hand side to Etype (Obj).
-- A special case arises if what we have now is a Val
-- attribute reference whose expression type is Etype (Obj).
-- This happens for assignments of fields from the same
-- array. In this case we get the required right hand side
-- by simply removing the inner attribute reference.
if Nkind (Rhs) = N_Attribute_Reference
and then Attribute_Name (Rhs) = Name_Val
and then Etype (First (Expressions (Rhs))) = Etype (Obj)
then
Rhs := Relocate_Node (First (Expressions (Rhs)));
Fixup_Rhs;
-- If the value of the right hand side is a known integer
-- value, then just replace it by an untyped constant,
-- which will be properly retyped when we analyze and
-- resolve the expression.
elsif Rhs_Val_Known then
-- Note that Rhs_Val has already been normalized to
-- be an unsigned value with the proper number of bits.
Rhs := Make_Integer_Literal (Loc, Rhs_Val);
-- Otherwise we need an unchecked conversion
else
Fixup_Rhs;
end if;
Or_Rhs := Make_Shift_Left (Rhs, Get_Shift);
end if;
if Nkind (New_Rhs) = N_Op_And then
Set_Paren_Count (New_Rhs, 1);
Set_Etype (New_Rhs, Etype (Left_Opnd (New_Rhs)));
end if;
New_Rhs :=
Make_Op_Or (Loc,
Left_Opnd => New_Rhs,
Right_Opnd => Or_Rhs);
end;
end if;
-- Now do the rewrite
Rewrite (N,
Make_Assignment_Statement (Loc,
Name => New_Lhs,
Expression =>
Unchecked_Convert_To (Etype (New_Lhs), New_Rhs)));
Set_Assignment_OK (Name (N), Ass_OK);
-- All other component sizes for non-modular case
else
-- We generate
-- Set_nn (Arr'address, Subscr, Bits_nn!(Rhs))
-- where Subscr is the computed linear subscript
declare
Bits_nn : constant Entity_Id := RTE (Bits_Id (Csiz));
Set_nn : Entity_Id;
Subscr : Node_Id;
Atyp : Entity_Id;
Rev_SSO : Node_Id;
begin
if No (Bits_nn) then
-- Error, most likely High_Integrity_Mode restriction
return;
end if;
-- Acquire proper Set entity. We use the aligned or unaligned
-- case as appropriate.
if Known_Aligned_Enough (Obj, Csiz) then
Set_nn := RTE (Set_Id (Csiz));
else
Set_nn := RTE (SetU_Id (Csiz));
end if;
-- Now generate the set reference
Obj := Relocate_Node (Prefix (Lhs));
Convert_To_Actual_Subtype (Obj);
Atyp := Etype (Obj);
Compute_Linear_Subscript (Atyp, Lhs, Subscr);
-- Set indication of whether the packed array has reverse SSO
Rev_SSO :=
New_Occurrence_Of
(Boolean_Literals (Reverse_Storage_Order (Atyp)), Loc);
-- Below we must make the assumption that Obj is
-- at least byte aligned, since otherwise its address
-- cannot be taken. The assumption holds since the
-- only arrays that can be misaligned are small packed
-- arrays which are implemented as a modular type, and
-- that is not the case here.
Rewrite (N,
Make_Procedure_Call_Statement (Loc,
Name => New_Occurrence_Of (Set_nn, Loc),
Parameter_Associations => New_List (
Make_Attribute_Reference (Loc,
Prefix => Obj,
Attribute_Name => Name_Address),
Subscr,
Unchecked_Convert_To (Bits_nn, Convert_To (Ctyp, Rhs)),
Rev_SSO)));
end;
end if;
Analyze (N, Suppress => All_Checks);
end Expand_Bit_Packed_Element_Set;
-------------------------------------
-- Expand_Packed_Address_Reference --
-------------------------------------
procedure Expand_Packed_Address_Reference (N : Node_Id) is
Loc : constant Source_Ptr := Sloc (N);
Base : Node_Id;
Offset : Node_Id;
begin
-- We build an expression that has the form
-- outer_object'Address
-- + (linear-subscript * component_size for each array reference
-- + field'Bit_Position for each record field
-- + ...
-- + ...) / Storage_Unit;
Get_Base_And_Bit_Offset (Prefix (N), Base, Offset);
Rewrite (N,
Unchecked_Convert_To (RTE (RE_Address),
Make_Op_Add (Loc,
Left_Opnd =>
Unchecked_Convert_To (RTE (RE_Integer_Address),
Make_Attribute_Reference (Loc,
Prefix => Base,
Attribute_Name => Name_Address)),
Right_Opnd =>
Unchecked_Convert_To (RTE (RE_Integer_Address),
Make_Op_Divide (Loc,
Left_Opnd => Offset,
Right_Opnd =>
Make_Integer_Literal (Loc, System_Storage_Unit))))));
Analyze_And_Resolve (N, RTE (RE_Address));
end Expand_Packed_Address_Reference;
---------------------------------
-- Expand_Packed_Bit_Reference --
---------------------------------
procedure Expand_Packed_Bit_Reference (N : Node_Id) is
Loc : constant Source_Ptr := Sloc (N);
Base : Node_Id;
Offset : Node_Id;
begin
-- We build an expression that has the form
-- (linear-subscript * component_size for each array reference
-- + field'Bit_Position for each record field
-- + ...
-- + ...) mod Storage_Unit;
Get_Base_And_Bit_Offset (Prefix (N), Base, Offset);
Rewrite (N,
Unchecked_Convert_To (Standard_Natural,
Make_Op_Mod (Loc,
Left_Opnd => Offset,
Right_Opnd => Make_Integer_Literal (Loc, System_Storage_Unit))));
Analyze_And_Resolve (N, Standard_Natural);
end Expand_Packed_Bit_Reference;
------------------------------------
-- Expand_Packed_Boolean_Operator --
------------------------------------
-- This routine expands "a op b" for the packed cases
procedure Expand_Packed_Boolean_Operator (N : Node_Id) is
Loc : constant Source_Ptr := Sloc (N);
Typ : constant Entity_Id := Etype (N);
L : constant Node_Id := Relocate_Node (Left_Opnd (N));
R : Node_Id := Relocate_Node (Right_Opnd (N));
Ltyp : Entity_Id;
Rtyp : Entity_Id;
PAT : Entity_Id;
begin
Convert_To_Actual_Subtype (L);
Convert_To_Actual_Subtype (R);
Ensure_Defined (Etype (L), N);
Ensure_Defined (Etype (R), N);
Apply_Length_Check (R, Etype (L));
Ltyp := Etype (L);
Rtyp := Etype (R);
-- Deal with silly case of XOR where the subcomponent has a range
-- True .. True where an exception must be raised.
if Nkind (N) = N_Op_Xor then
R := Duplicate_Subexpr (R);
Silly_Boolean_Array_Xor_Test (N, R, Rtyp);
end if;
-- Now that silliness is taken care of, get packed array type
Convert_To_PAT_Type (L);
Convert_To_PAT_Type (R);
PAT := Etype (L);
-- For the modular case, we expand a op b into
-- rtyp!(pat!(a) op pat!(b))
-- where rtyp is the Etype of the left operand. Note that we do not
-- convert to the base type, since this would be unconstrained, and
-- hence not have a corresponding packed array type set.
-- Note that both operands must be modular for this code to be used
if Is_Modular_Integer_Type (PAT)
and then
Is_Modular_Integer_Type (Etype (R))
then
declare
P : Node_Id;
begin
if Nkind (N) = N_Op_And then
P := Make_Op_And (Loc, L, R);
elsif Nkind (N) = N_Op_Or then
P := Make_Op_Or (Loc, L, R);
else -- Nkind (N) = N_Op_Xor
P := Make_Op_Xor (Loc, L, R);
end if;
Rewrite (N, Unchecked_Convert_To (Ltyp, P));
end;
-- For the array case, we insert the actions
-- Result : Ltype;
-- System.Bit_Ops.Bit_And/Or/Xor
-- (Left'Address,
-- Ltype'Length * Ltype'Component_Size;
-- Right'Address,
-- Rtype'Length * Rtype'Component_Size
-- Result'Address);
-- where Left and Right are the Packed_Bytes{1,2,4} operands and
-- the second argument and fourth arguments are the lengths of the
-- operands in bits. Then we replace the expression by a reference
-- to Result.
-- Note that if we are mixing a modular and array operand, everything
-- works fine, since we ensure that the modular representation has the
-- same physical layout as the array representation (that's what the
-- left justified modular stuff in the big-endian case is about).
else
declare
Result_Ent : constant Entity_Id := Make_Temporary (Loc, 'T');
E_Id : RE_Id;
begin
if Nkind (N) = N_Op_And then
E_Id := RE_Bit_And;
elsif Nkind (N) = N_Op_Or then
E_Id := RE_Bit_Or;
else -- Nkind (N) = N_Op_Xor
E_Id := RE_Bit_Xor;
end if;
Insert_Actions (N, New_List (
Make_Object_Declaration (Loc,
Defining_Identifier => Result_Ent,
Object_Definition => New_Occurrence_Of (Ltyp, Loc)),
Make_Procedure_Call_Statement (Loc,
Name => New_Occurrence_Of (RTE (E_Id), Loc),
Parameter_Associations => New_List (
Make_Byte_Aligned_Attribute_Reference (Loc,
Prefix => L,
Attribute_Name => Name_Address),
Make_Op_Multiply (Loc,
Left_Opnd =>
Make_Attribute_Reference (Loc,
Prefix =>
New_Occurrence_Of
(Etype (First_Index (Ltyp)), Loc),
Attribute_Name => Name_Range_Length),
Right_Opnd =>
Make_Integer_Literal (Loc, Component_Size (Ltyp))),
Make_Byte_Aligned_Attribute_Reference (Loc,
Prefix => R,
Attribute_Name => Name_Address),
Make_Op_Multiply (Loc,
Left_Opnd =>
Make_Attribute_Reference (Loc,
Prefix =>
New_Occurrence_Of
(Etype (First_Index (Rtyp)), Loc),
Attribute_Name => Name_Range_Length),
Right_Opnd =>
Make_Integer_Literal (Loc, Component_Size (Rtyp))),
Make_Byte_Aligned_Attribute_Reference (Loc,
Prefix => New_Occurrence_Of (Result_Ent, Loc),
Attribute_Name => Name_Address)))));
Rewrite (N,
New_Occurrence_Of (Result_Ent, Loc));
end;
end if;
Analyze_And_Resolve (N, Typ, Suppress => All_Checks);
end Expand_Packed_Boolean_Operator;
-------------------------------------
-- Expand_Packed_Element_Reference --
-------------------------------------
procedure Expand_Packed_Element_Reference (N : Node_Id) is
Loc : constant Source_Ptr := Sloc (N);
Obj : Node_Id;
Atyp : Entity_Id;
PAT : Entity_Id;
Ctyp : Entity_Id;
Csiz : Int;
Shift : Node_Id;
Cmask : Uint;
Lit : Node_Id;
Arg : Node_Id;
begin
-- If the node is an actual in a call, the prefix has not been fully
-- expanded, to account for the additional expansion for in-out actuals
-- (see expand_actuals for details). If the prefix itself is a packed
-- reference as well, we have to recurse to complete the transformation
-- of the prefix.
if Nkind (Prefix (N)) = N_Indexed_Component
and then not Analyzed (Prefix (N))
and then Is_Bit_Packed_Array (Etype (Prefix (Prefix (N))))
then
Expand_Packed_Element_Reference (Prefix (N));
end if;
-- The prefix may be rewritten below as a conversion. If it is a source
-- entity generate reference to it now, to prevent spurious warnings
-- about unused entities.
if Is_Entity_Name (Prefix (N))
and then Comes_From_Source (Prefix (N))
then
Generate_Reference (Entity (Prefix (N)), Prefix (N), 'r');
end if;
-- If not bit packed, we have the enumeration case, which is easily
-- dealt with (just adjust the subscripts of the indexed component)
-- Note: this leaves the result as an indexed component, which is
-- still a variable, so can be used in the assignment case, as is
-- required in the enumeration case.
if not Is_Bit_Packed_Array (Etype (Prefix (N))) then
Setup_Enumeration_Packed_Array_Reference (N);
return;
end if;
-- Remaining processing is for the bit-packed case
Obj := Relocate_Node (Prefix (N));
Convert_To_Actual_Subtype (Obj);
Atyp := Etype (Obj);
PAT := Packed_Array_Impl_Type (Atyp);
Ctyp := Component_Type (Atyp);
Csiz := UI_To_Int (Component_Size (Atyp));
-- Case of component size 1,2,4 or any component size for the modular
-- case. These are the cases for which we can inline the code.
if Csiz = 1 or else Csiz = 2 or else Csiz = 4
or else (Present (PAT) and then Is_Modular_Integer_Type (PAT))
then
Setup_Inline_Packed_Array_Reference (N, Atyp, Obj, Cmask, Shift);
Lit := Make_Integer_Literal (Loc, Cmask);
Set_Print_In_Hex (Lit);
-- We generate a shift right to position the field, followed by a
-- masking operation to extract the bit field, and we finally do an
-- unchecked conversion to convert the result to the required target.
-- Note that the unchecked conversion automatically deals with the
-- bias if we are dealing with a biased representation. What will
-- happen is that we temporarily generate the biased representation,
-- but almost immediately that will be converted to the original
-- unbiased component type, and the bias will disappear.
Arg :=
Make_Op_And (Loc,
Left_Opnd => Make_Shift_Right (Obj, Shift),
Right_Opnd => Lit);
Set_Etype (Arg, Ctyp);
-- Component extraction is performed on a native endianness scalar
-- value: if Atyp has reverse storage order, then it has been byte
-- swapped, and if the component being extracted is itself of a
-- composite type with reverse storage order, then we need to swap
-- it back to its expected endianness after extraction.
if Reverse_Storage_Order (Atyp)
and then (Is_Record_Type (Ctyp) or else Is_Array_Type (Ctyp))
and then Reverse_Storage_Order (Ctyp)
then
Arg := Revert_Storage_Order (Arg);
end if;
-- We needed to analyze this before we do the unchecked convert
-- below, but we need it temporarily attached to the tree for
-- this analysis (hence the temporary Set_Parent call).
Set_Parent (Arg, Parent (N));
Analyze_And_Resolve (Arg);
Rewrite (N, RJ_Unchecked_Convert_To (Ctyp, Arg));
-- All other component sizes for non-modular case
else
-- We generate
-- Component_Type!(Get_nn (Arr'address, Subscr))
-- where Subscr is the computed linear subscript
declare
Get_nn : Entity_Id;
Subscr : Node_Id;
Rev_SSO : constant Node_Id :=
New_Occurrence_Of
(Boolean_Literals (Reverse_Storage_Order (Atyp)), Loc);
begin
-- Acquire proper Get entity. We use the aligned or unaligned
-- case as appropriate.
if Known_Aligned_Enough (Obj, Csiz) then
Get_nn := RTE (Get_Id (Csiz));
else
Get_nn := RTE (GetU_Id (Csiz));
end if;
-- Now generate the get reference
Compute_Linear_Subscript (Atyp, N, Subscr);
-- Below we make the assumption that Obj is at least byte
-- aligned, since otherwise its address cannot be taken.
-- The assumption holds since the only arrays that can be
-- misaligned are small packed arrays which are implemented
-- as a modular type, and that is not the case here.
Rewrite (N,
Unchecked_Convert_To (Ctyp,
Make_Function_Call (Loc,
Name => New_Occurrence_Of (Get_nn, Loc),
Parameter_Associations => New_List (
Make_Attribute_Reference (Loc,
Prefix => Obj,
Attribute_Name => Name_Address),
Subscr,
Rev_SSO))));
end;
end if;
Analyze_And_Resolve (N, Ctyp, Suppress => All_Checks);
end Expand_Packed_Element_Reference;
----------------------
-- Expand_Packed_Eq --
----------------------
-- Handles expansion of "=" on packed array types
procedure Expand_Packed_Eq (N : Node_Id) is
Loc : constant Source_Ptr := Sloc (N);
L : constant Node_Id := Relocate_Node (Left_Opnd (N));
R : constant Node_Id := Relocate_Node (Right_Opnd (N));
LLexpr : Node_Id;
RLexpr : Node_Id;
Ltyp : Entity_Id;
Rtyp : Entity_Id;
PAT : Entity_Id;
begin
Convert_To_Actual_Subtype (L);
Convert_To_Actual_Subtype (R);
Ltyp := Underlying_Type (Etype (L));
Rtyp := Underlying_Type (Etype (R));
Convert_To_PAT_Type (L);
Convert_To_PAT_Type (R);
PAT := Etype (L);
LLexpr :=
Make_Op_Multiply (Loc,
Left_Opnd => Compute_Number_Components (N, Ltyp),
Right_Opnd => Make_Integer_Literal (Loc, Component_Size (Ltyp)));
RLexpr :=
Make_Op_Multiply (Loc,
Left_Opnd => Compute_Number_Components (N, Rtyp),
Right_Opnd => Make_Integer_Literal (Loc, Component_Size (Rtyp)));
-- For the modular case, we transform the comparison to:
-- Ltyp'Length = Rtyp'Length and then PAT!(L) = PAT!(R)
-- where PAT is the packed array type. This works fine, since in the
-- modular case we guarantee that the unused bits are always zeroes.
-- We do have to compare the lengths because we could be comparing
-- two different subtypes of the same base type.
if Is_Modular_Integer_Type (PAT) then
Rewrite (N,
Make_And_Then (Loc,
Left_Opnd =>
Make_Op_Eq (Loc,
Left_Opnd => LLexpr,
Right_Opnd => RLexpr),
Right_Opnd =>
Make_Op_Eq (Loc,
Left_Opnd => L,
Right_Opnd => R)));
-- For the non-modular case, we call a runtime routine
-- System.Bit_Ops.Bit_Eq
-- (L'Address, L_Length, R'Address, R_Length)
-- where PAT is the packed array type, and the lengths are the lengths
-- in bits of the original packed arrays. This routine takes care of
-- not comparing the unused bits in the last byte.
else
Rewrite (N,
Make_Function_Call (Loc,
Name => New_Occurrence_Of (RTE (RE_Bit_Eq), Loc),
Parameter_Associations => New_List (
Make_Byte_Aligned_Attribute_Reference (Loc,
Prefix => L,
Attribute_Name => Name_Address),
LLexpr,
Make_Byte_Aligned_Attribute_Reference (Loc,
Prefix => R,
Attribute_Name => Name_Address),
RLexpr)));
end if;
Analyze_And_Resolve (N, Standard_Boolean, Suppress => All_Checks);
end Expand_Packed_Eq;
-----------------------
-- Expand_Packed_Not --
-----------------------
-- Handles expansion of "not" on packed array types
procedure Expand_Packed_Not (N : Node_Id) is
Loc : constant Source_Ptr := Sloc (N);
Typ : constant Entity_Id := Etype (N);
Opnd : constant Node_Id := Relocate_Node (Right_Opnd (N));
Rtyp : Entity_Id;
PAT : Entity_Id;
Lit : Node_Id;
begin
Convert_To_Actual_Subtype (Opnd);
Rtyp := Etype (Opnd);
-- Deal with silly False..False and True..True subtype case
Silly_Boolean_Array_Not_Test (N, Rtyp);
-- Now that the silliness is taken care of, get packed array type
Convert_To_PAT_Type (Opnd);
PAT := Etype (Opnd);
-- For the case where the packed array type is a modular type, "not A"
-- expands simply into:
-- Rtyp!(PAT!(A) xor Mask)
-- where PAT is the packed array type, Mask is a mask of all 1 bits of
-- length equal to the size of this packed type, and Rtyp is the actual
-- actual subtype of the operand.
Lit := Make_Integer_Literal (Loc, 2 ** RM_Size (PAT) - 1);
Set_Print_In_Hex (Lit);
if not Is_Array_Type (PAT) then
Rewrite (N,
Unchecked_Convert_To (Rtyp,
Make_Op_Xor (Loc,
Left_Opnd => Opnd,
Right_Opnd => Lit)));
-- For the array case, we insert the actions
-- Result : Typ;
-- System.Bit_Ops.Bit_Not
-- (Opnd'Address,
-- Typ'Length * Typ'Component_Size,
-- Result'Address);
-- where Opnd is the Packed_Bytes{1,2,4} operand and the second argument
-- is the length of the operand in bits. We then replace the expression
-- with a reference to Result.
else
declare
Result_Ent : constant Entity_Id := Make_Temporary (Loc, 'T');
begin
Insert_Actions (N, New_List (
Make_Object_Declaration (Loc,
Defining_Identifier => Result_Ent,
Object_Definition => New_Occurrence_Of (Rtyp, Loc)),
Make_Procedure_Call_Statement (Loc,
Name => New_Occurrence_Of (RTE (RE_Bit_Not), Loc),
Parameter_Associations => New_List (
Make_Byte_Aligned_Attribute_Reference (Loc,
Prefix => Opnd,
Attribute_Name => Name_Address),
Make_Op_Multiply (Loc,
Left_Opnd =>
Make_Attribute_Reference (Loc,
Prefix =>
New_Occurrence_Of
(Etype (First_Index (Rtyp)), Loc),
Attribute_Name => Name_Range_Length),
Right_Opnd =>
Make_Integer_Literal (Loc, Component_Size (Rtyp))),
Make_Byte_Aligned_Attribute_Reference (Loc,
Prefix => New_Occurrence_Of (Result_Ent, Loc),
Attribute_Name => Name_Address)))));
Rewrite (N, New_Occurrence_Of (Result_Ent, Loc));
end;
end if;
Analyze_And_Resolve (N, Typ, Suppress => All_Checks);
end Expand_Packed_Not;
-----------------------------
-- Get_Base_And_Bit_Offset --
-----------------------------
procedure Get_Base_And_Bit_Offset
(N : Node_Id;
Base : out Node_Id;
Offset : out Node_Id)
is
Loc : Source_Ptr;
Term : Node_Id;
Atyp : Entity_Id;
Subscr : Node_Id;
begin
Base := N;
Offset := Empty;
-- We build up an expression serially that has the form
-- linear-subscript * component_size for each array reference
-- + field'Bit_Position for each record field
-- + ...
loop
Loc := Sloc (Base);
if Nkind (Base) = N_Indexed_Component then
Convert_To_Actual_Subtype (Prefix (Base));
Atyp := Etype (Prefix (Base));
Compute_Linear_Subscript (Atyp, Base, Subscr);
Term :=
Make_Op_Multiply (Loc,
Left_Opnd => Subscr,
Right_Opnd =>
Make_Attribute_Reference (Loc,
Prefix => New_Occurrence_Of (Atyp, Loc),
Attribute_Name => Name_Component_Size));
elsif Nkind (Base) = N_Selected_Component then
Term :=
Make_Attribute_Reference (Loc,
Prefix => Selector_Name (Base),
Attribute_Name => Name_Bit_Position);
else
return;
end if;
if No (Offset) then
Offset := Term;
else
Offset :=
Make_Op_Add (Loc,
Left_Opnd => Offset,
Right_Opnd => Term);
end if;
Base := Prefix (Base);
end loop;
end Get_Base_And_Bit_Offset;
-------------------------------------
-- Involves_Packed_Array_Reference --
-------------------------------------
function Involves_Packed_Array_Reference (N : Node_Id) return Boolean is
begin
if Nkind (N) = N_Indexed_Component
and then Is_Bit_Packed_Array (Etype (Prefix (N)))
then
return True;
elsif Nkind (N) = N_Selected_Component then
return Involves_Packed_Array_Reference (Prefix (N));
else
return False;
end if;
end Involves_Packed_Array_Reference;
--------------------------
-- Known_Aligned_Enough --
--------------------------
function Known_Aligned_Enough (Obj : Node_Id; Csiz : Nat) return Boolean is
Typ : constant Entity_Id := Etype (Obj);
function In_Partially_Packed_Record (Comp : Entity_Id) return Boolean;
-- If the component is in a record that contains previous packed
-- components, consider it unaligned because the back-end might
-- choose to pack the rest of the record. Lead to less efficient code,
-- but safer vis-a-vis of back-end choices.
--------------------------------
-- In_Partially_Packed_Record --
--------------------------------
function In_Partially_Packed_Record (Comp : Entity_Id) return Boolean is
Rec_Type : constant Entity_Id := Scope (Comp);
Prev_Comp : Entity_Id;
begin
Prev_Comp := First_Entity (Rec_Type);
while Present (Prev_Comp) loop
if Is_Packed (Etype (Prev_Comp)) then
return True;
elsif Prev_Comp = Comp then
return False;
end if;
Next_Entity (Prev_Comp);
end loop;
return False;
end In_Partially_Packed_Record;
-- Start of processing for Known_Aligned_Enough
begin
-- Odd bit sizes don't need alignment anyway
if Csiz mod 2 = 1 then
return True;
-- If we have a specified alignment, see if it is sufficient, if not
-- then we can't possibly be aligned enough in any case.
elsif Known_Alignment (Etype (Obj)) then
-- Alignment required is 4 if size is a multiple of 4, and
-- 2 otherwise (e.g. 12 bits requires 4, 10 bits requires 2)
if Alignment (Etype (Obj)) < 4 - (Csiz mod 4) then
return False;
end if;
end if;
-- OK, alignment should be sufficient, if object is aligned
-- If object is strictly aligned, then it is definitely aligned
if Strict_Alignment (Typ) then
return True;
-- Case of subscripted array reference
elsif Nkind (Obj) = N_Indexed_Component then
-- If we have a pointer to an array, then this is definitely
-- aligned, because pointers always point to aligned versions.
if Is_Access_Type (Etype (Prefix (Obj))) then
return True;
-- Otherwise, go look at the prefix
else
return Known_Aligned_Enough (Prefix (Obj), Csiz);
end if;
-- Case of record field
elsif Nkind (Obj) = N_Selected_Component then
-- What is significant here is whether the record type is packed
if Is_Record_Type (Etype (Prefix (Obj)))
and then Is_Packed (Etype (Prefix (Obj)))
then
return False;
-- Or the component has a component clause which might cause
-- the component to become unaligned (we can't tell if the
-- backend is doing alignment computations).
elsif Present (Component_Clause (Entity (Selector_Name (Obj)))) then
return False;
elsif In_Partially_Packed_Record (Entity (Selector_Name (Obj))) then
return False;
-- In all other cases, go look at prefix
else
return Known_Aligned_Enough (Prefix (Obj), Csiz);
end if;
elsif Nkind (Obj) = N_Type_Conversion then
return Known_Aligned_Enough (Expression (Obj), Csiz);
-- For a formal parameter, it is safer to assume that it is not
-- aligned, because the formal may be unconstrained while the actual
-- is constrained. In this situation, a small constrained packed
-- array, represented in modular form, may be unaligned.
elsif Is_Entity_Name (Obj) then
return not Is_Formal (Entity (Obj));
else
-- If none of the above, must be aligned
return True;
end if;
end Known_Aligned_Enough;
---------------------
-- Make_Shift_Left --
---------------------
function Make_Shift_Left (N : Node_Id; S : Node_Id) return Node_Id is
Nod : Node_Id;
begin
if Compile_Time_Known_Value (S) and then Expr_Value (S) = 0 then
return N;
else
Nod :=
Make_Op_Shift_Left (Sloc (N),
Left_Opnd => N,
Right_Opnd => S);
Set_Shift_Count_OK (Nod, True);
return Nod;
end if;
end Make_Shift_Left;
----------------------
-- Make_Shift_Right --
----------------------
function Make_Shift_Right (N : Node_Id; S : Node_Id) return Node_Id is
Nod : Node_Id;
begin
if Compile_Time_Known_Value (S) and then Expr_Value (S) = 0 then
return N;
else
Nod :=
Make_Op_Shift_Right (Sloc (N),
Left_Opnd => N,
Right_Opnd => S);
Set_Shift_Count_OK (Nod, True);
return Nod;
end if;
end Make_Shift_Right;
-----------------------------
-- RJ_Unchecked_Convert_To --
-----------------------------
function RJ_Unchecked_Convert_To
(Typ : Entity_Id;
Expr : Node_Id) return Node_Id
is
Source_Typ : constant Entity_Id := Etype (Expr);
Target_Typ : constant Entity_Id := Typ;
Src : Node_Id := Expr;
Source_Siz : Nat;
Target_Siz : Nat;
begin
Source_Siz := UI_To_Int (RM_Size (Source_Typ));
Target_Siz := UI_To_Int (RM_Size (Target_Typ));
-- For a little-endian target type stored byte-swapped on a
-- big-endian machine, do not mask to Target_Siz bits.
if Bytes_Big_Endian
and then (Is_Record_Type (Target_Typ)
or else
Is_Array_Type (Target_Typ))
and then Reverse_Storage_Order (Target_Typ)
then
Source_Siz := Target_Siz;
end if;
-- First step, if the source type is not a discrete type, then we first
-- convert to a modular type of the source length, since otherwise, on
-- a big-endian machine, we get left-justification. We do it for little-
-- endian machines as well, because there might be junk bits that are
-- not cleared if the type is not numeric. This can be done only if the
-- source siz is different from 0 (i.e. known), otherwise we must trust
-- the type declarations (case of non-discrete components).
if Source_Siz /= 0
and then Source_Siz /= Target_Siz
and then not Is_Discrete_Type (Source_Typ)
then
Src := Unchecked_Convert_To (RTE (Bits_Id (Source_Siz)), Src);
end if;
-- In the big endian case, if the lengths of the two types differ, then
-- we must worry about possible left justification in the conversion,
-- and avoiding that is what this is all about.
if Bytes_Big_Endian and then Source_Siz /= Target_Siz then
-- Next step. If the target is not a discrete type, then we first
-- convert to a modular type of the target length, since otherwise,
-- on a big-endian machine, we get left-justification.
if not Is_Discrete_Type (Target_Typ) then
Src := Unchecked_Convert_To (RTE (Bits_Id (Target_Siz)), Src);
end if;
end if;
-- And now we can do the final conversion to the target type
return Unchecked_Convert_To (Target_Typ, Src);
end RJ_Unchecked_Convert_To;
----------------------------------------------
-- Setup_Enumeration_Packed_Array_Reference --
----------------------------------------------
-- All we have to do here is to find the subscripts that correspond to the
-- index positions that have non-standard enumeration types and insert a
-- Pos attribute to get the proper subscript value.
-- Finally the prefix must be uncheck-converted to the corresponding packed
-- array type.
-- Note that the component type is unchanged, so we do not need to fiddle
-- with the types (Gigi always automatically takes the packed array type if
-- it is set, as it will be in this case).
procedure Setup_Enumeration_Packed_Array_Reference (N : Node_Id) is
Pfx : constant Node_Id := Prefix (N);
Typ : constant Entity_Id := Etype (N);
Exprs : constant List_Id := Expressions (N);
Expr : Node_Id;
begin
-- If the array is unconstrained, then we replace the array reference
-- with its actual subtype. This actual subtype will have a packed array
-- type with appropriate bounds.
if not Is_Constrained (Packed_Array_Impl_Type (Etype (Pfx))) then
Convert_To_Actual_Subtype (Pfx);
end if;
Expr := First (Exprs);
while Present (Expr) loop
declare
Loc : constant Source_Ptr := Sloc (Expr);
Expr_Typ : constant Entity_Id := Etype (Expr);
begin
if Is_Enumeration_Type (Expr_Typ)
and then Has_Non_Standard_Rep (Expr_Typ)
then
Rewrite (Expr,
Make_Attribute_Reference (Loc,
Prefix => New_Occurrence_Of (Expr_Typ, Loc),
Attribute_Name => Name_Pos,
Expressions => New_List (Relocate_Node (Expr))));
Analyze_And_Resolve (Expr, Standard_Natural);
end if;
end;
Next (Expr);
end loop;
Rewrite (N,
Make_Indexed_Component (Sloc (N),
Prefix =>
Unchecked_Convert_To (Packed_Array_Impl_Type (Etype (Pfx)), Pfx),
Expressions => Exprs));
Analyze_And_Resolve (N, Typ);
end Setup_Enumeration_Packed_Array_Reference;
-----------------------------------------
-- Setup_Inline_Packed_Array_Reference --
-----------------------------------------
procedure Setup_Inline_Packed_Array_Reference
(N : Node_Id;
Atyp : Entity_Id;
Obj : in out Node_Id;
Cmask : out Uint;
Shift : out Node_Id)
is
Loc : constant Source_Ptr := Sloc (N);
PAT : Entity_Id;
Otyp : Entity_Id;
Csiz : Uint;
Osiz : Uint;
begin
Csiz := Component_Size (Atyp);
Convert_To_PAT_Type (Obj);
PAT := Etype (Obj);
Cmask := 2 ** Csiz - 1;
if Is_Array_Type (PAT) then
Otyp := Component_Type (PAT);
Osiz := Component_Size (PAT);
else
Otyp := PAT;
-- In the case where the PAT is a modular type, we want the actual
-- size in bits of the modular value we use. This is neither the
-- Object_Size nor the Value_Size, either of which may have been
-- reset to strange values, but rather the minimum size. Note that
-- since this is a modular type with full range, the issue of
-- biased representation does not arise.
Osiz := UI_From_Int (Minimum_Size (Otyp));
end if;
Compute_Linear_Subscript (Atyp, N, Shift);
-- If the component size is not 1, then the subscript must be multiplied
-- by the component size to get the shift count.
if Csiz /= 1 then
Shift :=
Make_Op_Multiply (Loc,
Left_Opnd => Make_Integer_Literal (Loc, Csiz),
Right_Opnd => Shift);
end if;
-- If we have the array case, then this shift count must be broken down
-- into a byte subscript, and a shift within the byte.
if Is_Array_Type (PAT) then
declare
New_Shift : Node_Id;
begin
-- We must analyze shift, since we will duplicate it
Set_Parent (Shift, N);
Analyze_And_Resolve
(Shift, Standard_Integer, Suppress => All_Checks);
-- The shift count within the word is
-- shift mod Osiz
New_Shift :=
Make_Op_Mod (Loc,
Left_Opnd => Duplicate_Subexpr (Shift),
Right_Opnd => Make_Integer_Literal (Loc, Osiz));
-- The subscript to be used on the PAT array is
-- shift / Osiz
Obj :=
Make_Indexed_Component (Loc,
Prefix => Obj,
Expressions => New_List (
Make_Op_Divide (Loc,
Left_Opnd => Duplicate_Subexpr (Shift),
Right_Opnd => Make_Integer_Literal (Loc, Osiz))));
Shift := New_Shift;
end;
-- For the modular integer case, the object to be manipulated is the
-- entire array, so Obj is unchanged. Note that we will reset its type
-- to PAT before returning to the caller.
else
null;
end if;
-- The one remaining step is to modify the shift count for the
-- big-endian case. Consider the following example in a byte:
-- xxxxxxxx bits of byte
-- vvvvvvvv bits of value
-- 33221100 little-endian numbering
-- 00112233 big-endian numbering
-- Here we have the case of 2-bit fields
-- For the little-endian case, we already have the proper shift count
-- set, e.g. for element 2, the shift count is 2*2 = 4.
-- For the big endian case, we have to adjust the shift count, computing
-- it as (N - F) - Shift, where N is the number of bits in an element of
-- the array used to implement the packed array, F is the number of bits
-- in a source array element, and Shift is the count so far computed.
-- We also have to adjust if the storage order is reversed
if Bytes_Big_Endian xor Reverse_Storage_Order (Base_Type (Atyp)) then
Shift :=
Make_Op_Subtract (Loc,
Left_Opnd => Make_Integer_Literal (Loc, Osiz - Csiz),
Right_Opnd => Shift);
end if;
Set_Parent (Shift, N);
Set_Parent (Obj, N);
Analyze_And_Resolve (Obj, Otyp, Suppress => All_Checks);
Analyze_And_Resolve (Shift, Standard_Integer, Suppress => All_Checks);
-- Make sure final type of object is the appropriate packed type
Set_Etype (Obj, Otyp);
end Setup_Inline_Packed_Array_Reference;
end Exp_Pakd;