[Ada] Add the System.Bitfield_Utils runtime unit

2019-08-21  Bob Duff  <duff@adacore.com>

gcc/ada/

	* Makefile.rtl (GNATRTL_NONTASKING_OBJS): Add s-bitutil.o and
	s-biutin.o.
	* exp_ch5.adb (Expand_Assign_Array_Bitfield): New function to
	generate a call to Copy_Bitfield. This is disabled for now.
	(Expand_Assign_Array_Loop_Or_Bitfield): New function to decide
	whether to call Expand_Assign_Array_Bitfield.
	(Expand_Assign_Array): Call Expand_Assign_Array_Loop_Or_Bitfield
	instead of Expand_Assign_Array_Loop.
	* libgnat/s-bitfie.ads, libgnat/s-bituti.adb,
	libgnat/s-bituti.ads: New units.
	* rtsfind.ads: Add enum literals for accessing Copy_Bitfield.

From-SVN: r274785

gcc/ada/ChangeLog

+2019-08-21  Bob Duff  <duff@adacore.com>
+
+	* Makefile.rtl (GNATRTL_NONTASKING_OBJS): Add s-bitutil.o and
+	s-biutin.o.
+	* exp_ch5.adb (Expand_Assign_Array_Bitfield): New function to
+	generate a call to Copy_Bitfield. This is disabled for now.
+	(Expand_Assign_Array_Loop_Or_Bitfield): New function to decide
+	whether to call Expand_Assign_Array_Bitfield.
+	(Expand_Assign_Array): Call Expand_Assign_Array_Loop_Or_Bitfield
+	instead of Expand_Assign_Array_Loop.
+	* libgnat/s-bitfie.ads, libgnat/s-bituti.adb,
+	libgnat/s-bituti.ads: New units.
+	* rtsfind.ads: Add enum literals for accessing Copy_Bitfield.
+
 2019-08-21  Piotr Trojanek  <trojanek@adacore.com>
 
 	* bindo-graphs.ads (Iterate_Edges_To_Successors): Fix typo in

gcc/ada/Makefile.rtl

@@ -502,7 +502,9 @@ GNATRTL_NONTASKING_OBJS= \
   s-atopri$(objext) \
   s-auxdec$(objext) \
   s-bignum$(objext) \
+  s-bitfie$(objext) \
   s-bitops$(objext) \
+  s-bituti$(objext) \
   s-boarop$(objext) \
   s-boustr$(objext) \
   s-bytswa$(objext) \

gcc/ada/exp_ch5.adb

@@ -114,6 +114,28 @@ package body Exp_Ch5 is
    --  Auxiliary declarations are inserted before node N using the standard
    --  Insert_Actions mechanism.
 
+   function Expand_Assign_Array_Bitfield
+     (N      : Node_Id;
+      Larray : Entity_Id;
+      Rarray : Entity_Id;
+      L_Type : Entity_Id;
+      R_Type : Entity_Id;
+      Rev    : Boolean) return Node_Id;
+   --  Alternative to Expand_Assign_Array_Loop for packed bitfields. Generates
+   --  a call to the System.Bitfields.Copy_Bitfield, which is more efficient
+   --  than copying component-by-component.
+
+   function Expand_Assign_Array_Loop_Or_Bitfield
+     (N      : Node_Id;
+      Larray : Entity_Id;
+      Rarray : Entity_Id;
+      L_Type : Entity_Id;
+      R_Type : Entity_Id;
+      Ndim   : Pos;
+      Rev    : Boolean) return Node_Id;
+   --  Calls either Expand_Assign_Array_Loop or Expand_Assign_Array_Bitfield as
+   --  appropriate.
+
    procedure Expand_Assign_Record (N : Node_Id);
    --  N is an assignment of an untagged record value. This routine handles
    --  the case where the assignment must be made component by component,
@@ -314,6 +336,10 @@ package body Exp_Ch5 is
 
       Crep : constant Boolean := Change_Of_Representation (N);
 
+      pragma Assert
+        (Crep
+          or else Is_Bit_Packed_Array (L_Type) = Is_Bit_Packed_Array (R_Type));
+
       Larray  : Node_Id;
       Rarray  : Node_Id;
 
@@ -939,7 +965,7 @@ package body Exp_Ch5 is
 
             else
                Rewrite (N,
-                 Expand_Assign_Array_Loop
+                 Expand_Assign_Array_Loop_Or_Bitfield
                    (N, Larray, Rarray, L_Type, R_Type, Ndim,
                     Rev => not Forwards_OK (N)));
             end if;
@@ -1092,12 +1118,12 @@ package body Exp_Ch5 is
                    Condition => Condition,
 
                    Then_Statements => New_List (
-                     Expand_Assign_Array_Loop
+                     Expand_Assign_Array_Loop_Or_Bitfield
                       (N, Larray, Rarray, L_Type, R_Type, Ndim,
                        Rev => False)),
 
                    Else_Statements => New_List (
-                     Expand_Assign_Array_Loop
+                     Expand_Assign_Array_Loop_Or_Bitfield
                       (N, Larray, Rarray, L_Type, R_Type, Ndim,
                        Rev => True))));
             end if;
@@ -1320,6 +1346,134 @@ package body Exp_Ch5 is
       return Assign;
    end Expand_Assign_Array_Loop;
 
+   ----------------------------------
+   -- Expand_Assign_Array_Bitfield --
+   ----------------------------------
+
+   function Expand_Assign_Array_Bitfield
+     (N      : Node_Id;
+      Larray : Entity_Id;
+      Rarray : Entity_Id;
+      L_Type : Entity_Id;
+      R_Type : Entity_Id;
+      Rev    : Boolean) return Node_Id
+   is
+      pragma Assert (not Rev);
+      --  Reverse copying is not yet supported by Copy_Bitfield.
+
+      pragma Assert (not Change_Of_Representation (N));
+      --  This won't work, for example, to copy a packed array to an unpacked
+      --  array.
+
+      Loc  : constant Source_Ptr := Sloc (N);
+
+      L_Index_Typ : constant Node_Id := Etype (First_Index (L_Type));
+      R_Index_Typ : constant Node_Id := Etype (First_Index (R_Type));
+      Left_Lo  : constant Node_Id := Type_Low_Bound  (L_Index_Typ);
+      Right_Lo : constant Node_Id := Type_Low_Bound  (R_Index_Typ);
+
+      L_Addr : constant Node_Id :=
+        Make_Attribute_Reference (Loc,
+          Prefix =>
+            Make_Indexed_Component (Loc,
+              Prefix =>
+                Duplicate_Subexpr (Larray, True),
+              Expressions => New_List (New_Copy_Tree (Left_Lo))),
+          Attribute_Name => Name_Address);
+
+      L_Bit : constant Node_Id :=
+        Make_Attribute_Reference (Loc,
+          Prefix =>
+            Make_Indexed_Component (Loc,
+              Prefix =>
+                Duplicate_Subexpr (Larray, True),
+              Expressions => New_List (New_Copy_Tree (Left_Lo))),
+          Attribute_Name => Name_Bit);
+
+      R_Addr : constant Node_Id :=
+        Make_Attribute_Reference (Loc,
+          Prefix =>
+            Make_Indexed_Component (Loc,
+              Prefix =>
+                Duplicate_Subexpr (Rarray, True),
+              Expressions => New_List (New_Copy_Tree (Right_Lo))),
+          Attribute_Name => Name_Address);
+
+      R_Bit : constant Node_Id :=
+        Make_Attribute_Reference (Loc,
+          Prefix =>
+            Make_Indexed_Component (Loc,
+              Prefix =>
+                Duplicate_Subexpr (Rarray, True),
+              Expressions => New_List (New_Copy_Tree (Right_Lo))),
+          Attribute_Name => Name_Bit);
+
+      --  Compute the Size of the bitfield. ???We can't use Size here, because
+      --  it doesn't work properly for slices of packed arrays, so we compute
+      --  the L'Size as L'Length*L'Component_Size.
+      --
+      --  Note that the length check has already been done, so we can use the
+      --  size of either L or R.
+
+      Size : constant Node_Id :=
+        Make_Op_Multiply (Loc,
+          Make_Attribute_Reference (Loc,
+            Prefix =>
+              Duplicate_Subexpr (Name (N), True),
+            Attribute_Name => Name_Length),
+          Make_Attribute_Reference (Loc,
+            Prefix =>
+              Duplicate_Subexpr (Name (N), True),
+            Attribute_Name => Name_Component_Size));
+
+   begin
+      return Make_Procedure_Call_Statement (Loc,
+        Name => New_Occurrence_Of (RTE (RE_Copy_Bitfield), Loc),
+        Parameter_Associations => New_List (
+          R_Addr, R_Bit, L_Addr, L_Bit, Size));
+   end Expand_Assign_Array_Bitfield;
+
+   ------------------------------------------
+   -- Expand_Assign_Array_Loop_Or_Bitfield --
+   ------------------------------------------
+
+   function Expand_Assign_Array_Loop_Or_Bitfield
+     (N      : Node_Id;
+      Larray : Entity_Id;
+      Rarray : Entity_Id;
+      L_Type : Entity_Id;
+      R_Type : Entity_Id;
+      Ndim   : Pos;
+      Rev    : Boolean) return Node_Id
+   is
+      Slices : constant Boolean :=
+        Nkind (Name (N)) = N_Slice or else Nkind (Expression (N)) = N_Slice;
+   begin
+      --  Determine whether Copy_Bitfield is appropriate (will work, and will
+      --  be more efficient than component-by-component copy). Copy_Bitfield
+      --  doesn't work for reversed storage orders. It is efficient only for
+      --  slices of bit-packed arrays.
+
+      --  Note that Expand_Assign_Array_Bitfield is disabled for now
+
+      if False -- ???
+        and then Is_Bit_Packed_Array (L_Type)
+        and then Is_Bit_Packed_Array (R_Type)
+        and then RTE_Available (RE_Copy_Bitfield)
+        and then not Reverse_Storage_Order (L_Type)
+        and then not Reverse_Storage_Order (R_Type)
+        and then Ndim = 1
+        and then not Rev
+        and then Slices
+      then
+         return Expand_Assign_Array_Bitfield
+           (N, Larray, Rarray, L_Type, R_Type, Rev);
+      else
+         return Expand_Assign_Array_Loop
+           (N, Larray, Rarray, L_Type, R_Type, Ndim, Rev);
+      end if;
+   end Expand_Assign_Array_Loop_Or_Bitfield;
+
    --------------------------
    -- Expand_Assign_Record --
    --------------------------

gcc/ada/libgnat/s-bitfie.ads

+------------------------------------------------------------------------------
+--                                                                          --
+--                         GNAT RUN-TIME COMPONENTS                         --
+--                                                                          --
+--                 S Y S T E M . B I T F I E L D _ U T I L S                --
+--                                                                          --
+--                                 S p e c                                  --
+--                                                                          --
+--               Copyright (C) 2019, 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.                                     --
+--                                                                          --
+-- As a special exception under Section 7 of GPL version 3, you are granted --
+-- additional permissions described in the GCC Runtime Library Exception,   --
+-- version 3.1, as published by the Free Software Foundation.               --
+--                                                                          --
+-- You should have received a copy of the GNU General Public License and    --
+-- a copy of the GCC Runtime Library Exception along with this program;     --
+-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
+-- <http://www.gnu.org/licenses/>.                                          --
+--                                                                          --
+-- GNAT was originally developed  by the GNAT team at  New York University. --
+-- Extensive contributions were provided by Ada Core Technologies Inc.      --
+--                                                                          --
+------------------------------------------------------------------------------
+
+with System.Bitfield_Utils;
+
+package System.Bitfields is
+
+   --  Instances of the generic package in System.Bitfield_Utils. So far
+   --  we have just one, which defaults to the natural endianness of the
+   --  machine. We might someday want to support Scalar_Storage_Order.
+
+   Val_Bytes : constant := 4;
+   Val_Bits : constant := Val_Bytes * System.Storage_Unit;
+   type Val_2 is mod 2**(Val_Bits * 2) with Alignment => Val_Bytes;
+   pragma Provide_Shift_Operators (Val_2);
+   type Val is mod 2**Val_Bits with Alignment => Val_Bytes;
+
+   package Utils is new System.Bitfield_Utils.G (Val, Val_2);
+
+   procedure Copy_Bitfield
+     (Src_Address  : Address;
+      Src_Offset   : Utils.Bit_Offset_In_Byte;
+      Dest_Address : Address;
+      Dest_Offset  : Utils.Bit_Offset_In_Byte;
+      Size         : Utils.Bit_Size)
+     renames Utils.Copy_Bitfield;
+
+end System.Bitfields;

gcc/ada/libgnat/s-bituti.ads

+------------------------------------------------------------------------------
+--                                                                          --
+--                         GNAT RUN-TIME COMPONENTS                         --
+--                                                                          --
+--                 S Y S T E M . B I T F I E L D _ U T I L S                --
+--                                                                          --
+--                                 S p e c                                  --
+--                                                                          --
+--               Copyright (C) 2019, 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.                                     --
+--                                                                          --
+-- As a special exception under Section 7 of GPL version 3, you are granted --
+-- additional permissions described in the GCC Runtime Library Exception,   --
+-- version 3.1, as published by the Free Software Foundation.               --
+--                                                                          --
+-- You should have received a copy of the GNU General Public License and    --
+-- a copy of the GCC Runtime Library Exception along with this program;     --
+-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
+-- <http://www.gnu.org/licenses/>.                                          --
+--                                                                          --
+-- GNAT was originally developed  by the GNAT team at  New York University. --
+-- Extensive contributions were provided by Ada Core Technologies Inc.      --
+--                                                                          --
+------------------------------------------------------------------------------
+
+package System.Bitfield_Utils is
+
+   --  This package provides a procedure for copying arbitrarily large and
+   --  arbitrarily bit-aligned bit fields.
+
+   --  Type Val is used to represent small bit fields. Val_2 represents a
+   --  contiguous pair of Vals. Val_2'Alignment is half of its size in bytes,
+   --  which is likely not the natural alignment. This is done to ensure that
+   --  any bit field that fits in a Val can fit in an aligned Val_2, starting
+   --  somewhere in the first half, and possibly crossing over into the second
+   --  half. This allows us to isolate a Val value by shifting and masking the
+   --  Val_2.
+   --
+   --  Val can be 8, 16, or 32 bits; larger values are more efficient. It can't
+   --  be 64 bits, because we need Val_2 to be a double-wide shiftable type,
+   --  and 128 bits is not supported. Instantiating with an 8-bit Val is useful
+   --  for testing and debugging; 32 bits should be used for production.
+   --
+   --  We use modular types here, not because we want modular arithmetic, but
+   --  so we can do shifting and masking. The actual for Val_2 should have
+   --  pragma Provide_Shift_Operators, so that the Shift_Left and Shift_Right
+   --  intrinsics can be passed in. It is impossible to put that pragma on a
+   --  generic formal, or on a type derived from a generic formal, so they have
+   --  to be passed in.
+   --
+   --  Endian indicates whether we're on little-endian or big-endian machine.
+
+   pragma Elaborate_Body;
+
+   Little : constant Bit_Order := Low_Order_First;
+   Big : constant Bit_Order := High_Order_First;
+
+   generic
+      type Val is mod <>;
+      type Val_2 is mod <>;
+
+     with function Shift_Left
+       (Value  : Val_2;
+        Amount : Natural) return Val_2 is <>;
+
+     with function Shift_Right
+       (Value  : Val_2;
+        Amount : Natural) return Val_2 is <>;
+
+      Endian : Bit_Order := Default_Bit_Order;
+
+   package G is
+      --  Assert that Val has one of the allowed sizes, and that Val_2 is twice
+      --  that.
+
+      pragma Assert (Val'Size in 8 | 16 | 32);
+      pragma Assert (Val_2'Size = Val'Size * 2);
+
+      --  Assert that both are aligned the same, to the size in bytes of Val
+      --  (not Val_2).
+
+      pragma Assert (Val'Alignment = Val'Size / Storage_Unit);
+      pragma Assert (Val_2'Alignment = Val'Alignment);
+
+      type Val_Array is array (Positive range <>) of Val;
+
+      --  It might make more sense to have:
+      --    subtype Val is Val_2 range 0 .. 2**Val'Size - 1;
+      --  But then GNAT gets the component size of Val_Array wrong.
+
+      pragma Assert (Val_Array'Alignment = Val'Alignment);
+      pragma Assert (Val_Array'Component_Size = Val'Size);
+
+      subtype Bit_Size is Natural; -- Size in bits of a bit field
+      subtype Small_Size is Bit_Size range 0 .. Val'Size;
+      --  Size of a small one
+      subtype Bit_Offset is Small_Size range 0 .. Val'Size - 1;
+      --  Starting offset
+      subtype Bit_Offset_In_Byte is Bit_Offset range 0 .. Storage_Unit - 1;
+
+      procedure Copy_Bitfield
+        (Src_Address  : Address;
+         Src_Offset   : Bit_Offset_In_Byte;
+         Dest_Address : Address;
+         Dest_Offset  : Bit_Offset_In_Byte;
+         Size         : Bit_Size);
+      --  An Address and a Bit_Offset together form a "bit address". This
+      --  copies the source bit field to the destination. Size is the size in
+      --  bits of the bit field. The bit fields can be arbitrarily large, but
+      --  the starting offsets must be within the first byte that the Addresses
+      --  point to. The Address values need not be aligned.
+      --
+      --  For example, a slice assignment of a packed bit field:
+      --
+      --     D (D_First .. D_Last) := S (S_First .. S_Last);
+      --
+      --  can be implemented using:
+      --
+      --     Copy_Bitfield
+      --       (S (S_First)'Address, S (S_First)'Bit,
+      --        D (D_First)'Address, D (D_First)'Bit,
+      --        Size);
+
+   end G;
+
+end System.Bitfield_Utils;

gcc/ada/rtsfind.ads

@@ -220,6 +220,7 @@ package Rtsfind is
       System_Atomic_Primitives,
       System_Aux_DEC,
       System_Bignums,
+      System_Bitfields,
       System_Bit_Ops,
       System_Boolean_Array_Operations,
       System_Byte_Swapping,
@@ -809,6 +810,8 @@ package Rtsfind is
      RE_To_Bignum,                       -- System.Bignums
      RE_From_Bignum,                     -- System.Bignums
 
+     RE_Copy_Bitfield,                   -- System.Bitfields
+
      RE_Bit_And,                         -- System.Bit_Ops
      RE_Bit_Eq,                          -- System.Bit_Ops
      RE_Bit_Not,                         -- System.Bit_Ops
@@ -2051,6 +2054,8 @@ package Rtsfind is
      RE_To_Bignum                        => System_Bignums,
      RE_From_Bignum                      => System_Bignums,
 
+     RE_Copy_Bitfield                    => System_Bitfields,
+
      RE_Bit_And                          => System_Bit_Ops,
      RE_Bit_Eq                           => System_Bit_Ops,
      RE_Bit_Not                          => System_Bit_Ops,