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------------------------------------------------------------------------------
--                                                                          --
--                         GNAT COMPILER COMPONENTS                         --
--                                                                          --
--           S Y S T E M . V A X _ F L O A T _ O P E R A T I O N S          --
--                                                                          --
--                                 B o d y                                  --
--                                                                          --
--          Copyright (C) 1997-2009, Free Software Foundation, Inc.         --
--                       (Version for Alpha OpenVMS)                        --
--                                                                          --
-- 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.IO;
with System.Machine_Code; use System.Machine_Code;
 
package body System.Vax_Float_Operations is
 
   --  Ensure this gets compiled with -O to avoid extra (and possibly
   --  improper) memory stores.
 
   pragma Optimize (Time);
 
   --  Declare the functions that do the conversions between floating-point
   --  formats.  Call the operands IEEE float so they get passed in
   --  FP registers.
 
   function Cvt_G_T (X : T) return T;
   function Cvt_T_G (X : T) return T;
   function Cvt_T_F (X : T) return S;
 
   pragma Import (C, Cvt_G_T, "OTS$CVT_FLOAT_G_T");
   pragma Import (C, Cvt_T_G, "OTS$CVT_FLOAT_T_G");
   pragma Import (C, Cvt_T_F, "OTS$CVT_FLOAT_T_F");
 
   --  In each of the conversion routines that are done with OTS calls,
   --  we define variables of the corresponding IEEE type so that they are
   --  passed and kept in the proper register class.
 
   Debug_String_Buffer : String (1 .. 32);
   --  Buffer used by all Debug_String_x routines for returning result
 
   ------------
   -- D_To_G --
   ------------
 
   function D_To_G (X : D) return G is
      A, B : T;
      C    : G;
   begin
      Asm ("ldg %0,%1", T'Asm_Output ("=f", A), D'Asm_Input ("m", X),
           Volatile => True);
      Asm ("cvtdg %1,%0", T'Asm_Output ("=f", B), T'Asm_Input ("f", A),
           Volatile => True);
      Asm ("stg %1,%0", G'Asm_Output ("=m", C), T'Asm_Input ("f", B),
           Volatile => True);
      return C;
   end D_To_G;
 
   ------------
   -- F_To_G --
   ------------
 
   function F_To_G (X : F) return G is
      A : T;
      B : G;
   begin
      Asm ("ldf %0,%1", T'Asm_Output ("=f", A), F'Asm_Input ("m", X),
           Volatile => True);
      Asm ("stg %1,%0", G'Asm_Output ("=m", B), T'Asm_Input ("f", A),
           Volatile => True);
      return B;
   end F_To_G;
 
   ------------
   -- F_To_S --
   ------------
 
   function F_To_S (X : F) return S is
      A : T;
      B : S;
 
   begin
      --  Because converting to a wider FP format is a no-op, we say
      --  A is 64-bit even though we are loading 32 bits into it.
 
      Asm ("ldf %0,%1", T'Asm_Output ("=f", A), F'Asm_Input ("m", X),
           Volatile => True);
 
      B := S (Cvt_G_T (A));
      return B;
   end F_To_S;
 
   ------------
   -- G_To_D --
   ------------
 
   function G_To_D (X : G) return D is
      A, B : T;
      C    : D;
   begin
      Asm ("ldg %0,%1", T'Asm_Output ("=f", A), G'Asm_Input ("m", X),
           Volatile => True);
      Asm ("cvtgd %1,%0", T'Asm_Output ("=f", B), T'Asm_Input ("f", A),
           Volatile => True);
      Asm ("stg %1,%0", D'Asm_Output ("=m", C), T'Asm_Input ("f", B),
           Volatile => True);
      return C;
   end G_To_D;
 
   ------------
   -- G_To_F --
   ------------
 
   function G_To_F (X : G) return F is
      A : T;
      B : S;
      C : F;
   begin
      Asm ("ldg %0,%1", T'Asm_Output ("=f", A), G'Asm_Input ("m", X),
           Volatile => True);
      Asm ("cvtgf %1,%0", S'Asm_Output ("=f", B), T'Asm_Input ("f", A),
           Volatile => True);
      Asm ("stf %1,%0", F'Asm_Output ("=m", C), S'Asm_Input ("f", B),
           Volatile => True);
      return C;
   end G_To_F;
 
   ------------
   -- G_To_Q --
   ------------
 
   function G_To_Q (X : G) return Q is
      A : T;
      B : Q;
   begin
      Asm ("ldg %0,%1", T'Asm_Output ("=f", A), G'Asm_Input ("m", X),
           Volatile => True);
      Asm ("cvtgq %1,%0", Q'Asm_Output ("=f", B), T'Asm_Input ("f", A),
           Volatile => True);
      return B;
   end G_To_Q;
 
   ------------
   -- G_To_T --
   ------------
 
   function G_To_T (X : G) return T is
      A, B : T;
   begin
      Asm ("ldg %0,%1", T'Asm_Output ("=f", A), G'Asm_Input ("m", X),
           Volatile => True);
      B := Cvt_G_T (A);
      return B;
   end G_To_T;
 
   ------------
   -- F_To_Q --
   ------------
 
   function F_To_Q (X : F) return Q is
   begin
      return G_To_Q (F_To_G (X));
   end F_To_Q;
 
   ------------
   -- Q_To_F --
   ------------
 
   function Q_To_F (X : Q) return F is
      A : S;
      B : F;
   begin
      Asm ("cvtqf %1,%0", S'Asm_Output ("=f", A), Q'Asm_Input ("f", X),
           Volatile => True);
      Asm ("stf %1,%0", F'Asm_Output ("=m", B), S'Asm_Input ("f", A),
           Volatile => True);
      return B;
   end Q_To_F;
 
   ------------
   -- Q_To_G --
   ------------
 
   function Q_To_G (X : Q) return G is
      A : T;
      B : G;
   begin
      Asm ("cvtqg %1,%0", T'Asm_Output ("=f", A), Q'Asm_Input ("f", X),
           Volatile => True);
      Asm ("stg %1,%0", G'Asm_Output ("=m", B), T'Asm_Input ("f", A),
           Volatile => True);
      return B;
   end Q_To_G;
 
   ------------
   -- S_To_F --
   ------------
 
   function S_To_F (X : S) return F is
      A : S;
      B : F;
   begin
      A := Cvt_T_F (T (X));
      Asm ("stf %1,%0", F'Asm_Output ("=m", B), S'Asm_Input ("f", A),
           Volatile => True);
      return B;
   end S_To_F;
 
   ------------
   -- T_To_D --
   ------------
 
   function T_To_D (X : T) return D is
   begin
      return G_To_D (T_To_G (X));
   end T_To_D;
 
   ------------
   -- T_To_G --
   ------------
 
   function T_To_G (X : T) return G is
      A : T;
      B : G;
   begin
      A := Cvt_T_G (X);
      Asm ("stg %1,%0", G'Asm_Output ("=m", B), T'Asm_Input ("f", A),
           Volatile => True);
      return B;
   end T_To_G;
 
   -----------
   -- Abs_F --
   -----------
 
   function Abs_F (X : F) return F is
      A, B : S;
      C    : F;
   begin
      Asm ("ldf %0,%1", S'Asm_Output ("=f", A), F'Asm_Input ("m", X),
           Volatile => True);
      Asm ("cpys $f31,%1,%0", S'Asm_Output ("=f", B), S'Asm_Input ("f", A),
           Volatile => True);
      Asm ("stf %1,%0", F'Asm_Output ("=m", C), S'Asm_Input ("f", B),
           Volatile => True);
      return C;
   end Abs_F;
 
   -----------
   -- Abs_G --
   -----------
 
   function Abs_G (X : G) return G is
      A, B : T;
      C    : G;
   begin
      Asm ("ldg %0,%1", T'Asm_Output ("=f", A), G'Asm_Input ("m", X));
      Asm ("cpys $f31,%1,%0", T'Asm_Output ("=f", B), T'Asm_Input ("f", A),
           Volatile => True);
      Asm ("stg %1,%0", G'Asm_Output ("=m", C), T'Asm_Input ("f", B),
           Volatile => True);
      return C;
   end Abs_G;
 
   -----------
   -- Add_F --
   -----------
 
   function Add_F (X, Y : F) return F is
      X1, Y1, R : S;
      R1        : F;
   begin
      Asm ("ldf %0,%1", S'Asm_Output ("=f", X1), F'Asm_Input ("m", X));
      Asm ("ldf %0,%1", S'Asm_Output ("=f", Y1), F'Asm_Input ("m", Y),
           Volatile => True);
      Asm ("addf %1,%2,%0", S'Asm_Output ("=f", R),
           (S'Asm_Input ("f", X1), S'Asm_Input ("f", Y1)),
           Volatile => True);
      Asm ("stf %1,%0", F'Asm_Output ("=m", R1), S'Asm_Input ("f", R),
           Volatile => True);
      return R1;
   end Add_F;
 
   -----------
   -- Add_G --
   -----------
 
   function Add_G (X, Y : G) return G is
      X1, Y1, R : T;
      R1        : G;
   begin
      Asm ("ldg %0,%1", T'Asm_Output ("=f", X1), G'Asm_Input ("m", X));
      Asm ("ldg %0,%1", T'Asm_Output ("=f", Y1), G'Asm_Input ("m", Y),
           Volatile => True);
      Asm ("addg %1,%2,%0", T'Asm_Output ("=f", R),
           (T'Asm_Input ("f", X1), T'Asm_Input ("f", Y1)),
           Volatile => True);
      Asm ("stg %1,%0", G'Asm_Output ("=m", R1), T'Asm_Input ("f", R),
           Volatile => True);
      return R1;
   end Add_G;
 
   --------------------
   -- Debug_Output_D --
   --------------------
 
   procedure Debug_Output_D (Arg : D) is
   begin
      System.IO.Put (D'Image (Arg));
   end Debug_Output_D;
 
   --------------------
   -- Debug_Output_F --
   --------------------
 
   procedure Debug_Output_F (Arg : F) is
   begin
      System.IO.Put (F'Image (Arg));
   end Debug_Output_F;
 
   --------------------
   -- Debug_Output_G --
   --------------------
 
   procedure Debug_Output_G (Arg : G) is
   begin
      System.IO.Put (G'Image (Arg));
   end Debug_Output_G;
 
   --------------------
   -- Debug_String_D --
   --------------------
 
   function Debug_String_D (Arg : D) return System.Address is
      Image_String : constant String  := D'Image (Arg) & ASCII.NUL;
      Image_Size   : constant Integer := Image_String'Length;
   begin
      Debug_String_Buffer (1 .. Image_Size) := Image_String;
      return Debug_String_Buffer (1)'Address;
   end Debug_String_D;
 
   --------------------
   -- Debug_String_F --
   --------------------
 
   function Debug_String_F (Arg : F) return System.Address is
      Image_String : constant String  := F'Image (Arg) & ASCII.NUL;
      Image_Size   : constant Integer := Image_String'Length;
   begin
      Debug_String_Buffer (1 .. Image_Size) := Image_String;
      return Debug_String_Buffer (1)'Address;
   end Debug_String_F;
 
   --------------------
   -- Debug_String_G --
   --------------------
 
   function Debug_String_G (Arg : G) return System.Address is
      Image_String : constant String  := G'Image (Arg) & ASCII.NUL;
      Image_Size   : constant Integer := Image_String'Length;
   begin
      Debug_String_Buffer (1 .. Image_Size) := Image_String;
      return Debug_String_Buffer (1)'Address;
   end Debug_String_G;
 
   -----------
   -- Div_F --
   -----------
 
   function Div_F (X, Y : F) return F is
      X1, Y1, R : S;
      R1        : F;
   begin
      Asm ("ldf %0,%1", S'Asm_Output ("=f", X1), F'Asm_Input ("m", X));
      Asm ("ldf %0,%1", S'Asm_Output ("=f", Y1), F'Asm_Input ("m", Y),
           Volatile => True);
      Asm ("divf %1,%2,%0", S'Asm_Output ("=f", R),
           (S'Asm_Input ("f", X1), S'Asm_Input ("f", Y1)),
           Volatile => True);
      Asm ("stf %1,%0", F'Asm_Output ("=m", R1), S'Asm_Input ("f", R),
           Volatile => True);
      return R1;
   end Div_F;
 
   -----------
   -- Div_G --
   -----------
 
   function Div_G (X, Y : G) return G is
      X1, Y1, R : T;
      R1        : G;
   begin
      Asm ("ldg %0,%1", T'Asm_Output ("=f", X1), G'Asm_Input ("m", X));
      Asm ("ldg %0,%1", T'Asm_Output ("=f", Y1), G'Asm_Input ("m", Y),
           Volatile => True);
      Asm ("divg %1,%2,%0", T'Asm_Output ("=f", R),
           (T'Asm_Input ("f", X1), T'Asm_Input ("f", Y1)),
           Volatile => True);
      Asm ("stg %1,%0", G'Asm_Output ("=m", R1), T'Asm_Input ("f", R),
           Volatile => True);
      return R1;
   end Div_G;
 
   ----------
   -- Eq_F --
   ----------
 
   function Eq_F (X, Y : F) return Boolean is
      X1, Y1, R : S;
   begin
      Asm ("ldf %0,%1", S'Asm_Output ("=f", X1), F'Asm_Input ("m", X));
      Asm ("ldf %0,%1", S'Asm_Output ("=f", Y1), F'Asm_Input ("m", Y),
           Volatile => True);
      Asm ("cmpgeq %1,%2,%0", S'Asm_Output ("=f", R),
           (S'Asm_Input ("f", X1), S'Asm_Input ("f", Y1)),
           Volatile => True);
      return R /= 0.0;
   end Eq_F;
 
   ----------
   -- Eq_G --
   ----------
 
   function Eq_G (X, Y : G) return Boolean is
      X1, Y1, R : T;
   begin
      Asm ("ldg %0,%1", T'Asm_Output ("=f", X1), G'Asm_Input ("m", X));
      Asm ("ldg %0,%1", T'Asm_Output ("=f", Y1), G'Asm_Input ("m", Y),
           Volatile => True);
      Asm ("cmpgeq %1,%2,%0", T'Asm_Output ("=f", R),
           (T'Asm_Input ("f", X1), T'Asm_Input ("f", Y1)),
           Volatile => True);
      return R /= 0.0;
   end Eq_G;
 
   ----------
   -- Le_F --
   ----------
 
   function Le_F (X, Y : F) return Boolean is
      X1, Y1, R : S;
   begin
      Asm ("ldf %0,%1", S'Asm_Output ("=f", X1), F'Asm_Input ("m", X));
      Asm ("ldf %0,%1", S'Asm_Output ("=f", Y1), F'Asm_Input ("m", Y),
           Volatile => True);
      Asm ("cmpgle %1,%2,%0", S'Asm_Output ("=f", R),
           (S'Asm_Input ("f", X1), S'Asm_Input ("f", Y1)),
           Volatile => True);
      return R /= 0.0;
   end Le_F;
 
   ----------
   -- Le_G --
   ----------
 
   function Le_G (X, Y : G) return Boolean is
      X1, Y1, R : T;
   begin
      Asm ("ldg %0,%1", T'Asm_Output ("=f", X1), G'Asm_Input ("m", X));
      Asm ("ldg %0,%1", T'Asm_Output ("=f", Y1), G'Asm_Input ("m", Y),
           Volatile => True);
      Asm ("cmpgle %1,%2,%0", T'Asm_Output ("=f", R),
           (T'Asm_Input ("f", X1), T'Asm_Input ("f", Y1)),
           Volatile => True);
      return R /= 0.0;
   end Le_G;
 
   ----------
   -- Lt_F --
   ----------
 
   function Lt_F (X, Y : F) return Boolean is
      X1, Y1, R : S;
   begin
      Asm ("ldf %0,%1", S'Asm_Output ("=f", X1), F'Asm_Input ("m", X));
      Asm ("ldf %0,%1", S'Asm_Output ("=f", Y1), F'Asm_Input ("m", Y),
           Volatile => True);
      Asm ("cmpglt %1,%2,%0", S'Asm_Output ("=f", R),
           (S'Asm_Input ("f", X1), S'Asm_Input ("f", Y1)),
           Volatile => True);
      return R /= 0.0;
   end Lt_F;
 
   ----------
   -- Lt_G --
   ----------
 
   function Lt_G (X, Y : G) return Boolean is
      X1, Y1, R : T;
   begin
      Asm ("ldg %0,%1", T'Asm_Output ("=f", X1), G'Asm_Input ("m", X));
      Asm ("ldg %0,%1", T'Asm_Output ("=f", Y1), G'Asm_Input ("m", Y),
           Volatile => True);
      Asm ("cmpglt %1,%2,%0", T'Asm_Output ("=f", R),
           (T'Asm_Input ("f", X1), T'Asm_Input ("f", Y1)),
           Volatile => True);
      return R /= 0.0;
   end Lt_G;
 
   -----------
   -- Mul_F --
   -----------
 
   function Mul_F (X, Y : F) return F is
      X1, Y1, R : S;
      R1        : F;
   begin
      Asm ("ldf %0,%1", S'Asm_Output ("=f", X1), F'Asm_Input ("m", X));
      Asm ("ldf %0,%1", S'Asm_Output ("=f", Y1), F'Asm_Input ("m", Y),
           Volatile => True);
      Asm ("mulf %1,%2,%0", S'Asm_Output ("=f", R),
           (S'Asm_Input ("f", X1), S'Asm_Input ("f", Y1)),
           Volatile => True);
      Asm ("stf %1,%0", F'Asm_Output ("=m", R1), S'Asm_Input ("f", R),
           Volatile => True);
      return R1;
   end Mul_F;
 
   -----------
   -- Mul_G --
   -----------
 
   function Mul_G (X, Y : G) return G is
      X1, Y1, R : T;
      R1        : G;
   begin
      Asm ("ldg %0,%1", T'Asm_Output ("=f", X1), G'Asm_Input ("m", X));
      Asm ("ldg %0,%1", T'Asm_Output ("=f", Y1), G'Asm_Input ("m", Y),
           Volatile => True);
      Asm ("mulg %1,%2,%0", T'Asm_Output ("=f", R),
           (T'Asm_Input ("f", X1), T'Asm_Input ("f", Y1)),
           Volatile => True);
      Asm ("stg %1,%0", G'Asm_Output ("=m", R1), T'Asm_Input ("f", R),
           Volatile => True);
      return R1;
   end Mul_G;
 
   ----------
   -- Ne_F --
   ----------
 
   function Ne_F (X, Y : F) return Boolean is
      X1, Y1, R : S;
   begin
      Asm ("ldf %0,%1", S'Asm_Output ("=f", X1), F'Asm_Input ("m", X));
      Asm ("ldf %0,%1", S'Asm_Output ("=f", Y1), F'Asm_Input ("m", Y),
           Volatile => True);
      Asm ("cmpgeq %1,%2,%0", S'Asm_Output ("=f", R),
           (S'Asm_Input ("f", X1), S'Asm_Input ("f", Y1)),
           Volatile => True);
      return R = 0.0;
   end Ne_F;
 
   ----------
   -- Ne_G --
   ----------
 
   function Ne_G (X, Y : G) return Boolean is
      X1, Y1, R : T;
   begin
      Asm ("ldg %0,%1", T'Asm_Output ("=f", X1), G'Asm_Input ("m", X));
      Asm ("ldg %0,%1", T'Asm_Output ("=f", Y1), G'Asm_Input ("m", Y),
           Volatile => True);
      Asm ("cmpgeq %1,%2,%0", T'Asm_Output ("=f", R),
           (T'Asm_Input ("f", X1), T'Asm_Input ("f", Y1)),
           Volatile => True);
      return R = 0.0;
   end Ne_G;
 
   -----------
   -- Neg_F --
   -----------
 
   function Neg_F (X : F) return F is
      A, B : S;
      C    : F;
   begin
      Asm ("ldf %0,%1", S'Asm_Output ("=f", A), F'Asm_Input ("m", X));
      Asm ("cpysn %1,%1,%0", S'Asm_Output ("=f", B), S'Asm_Input ("f", A),
           Volatile => True);
      Asm ("stf %1,%0", F'Asm_Output ("=m", C), S'Asm_Input ("f", B),
           Volatile => True);
      return C;
   end Neg_F;
 
   -----------
   -- Neg_G --
   -----------
 
   function Neg_G (X : G) return G is
      A, B : T;
      C    : G;
   begin
      Asm ("ldg %0,%1", T'Asm_Output ("=f", A), G'Asm_Input ("m", X));
      Asm ("cpysn %1,%1,%0", T'Asm_Output ("=f", B), T'Asm_Input ("f", A),
           Volatile => True);
      Asm ("stg %1,%0", G'Asm_Output ("=m", C), T'Asm_Input ("f", B),
           Volatile => True);
      return C;
   end Neg_G;
 
   --------
   -- pd --
   --------
 
   procedure pd (Arg : D) is
   begin
      System.IO.Put_Line (D'Image (Arg));
   end pd;
 
   --------
   -- pf --
   --------
 
   procedure pf (Arg : F) is
   begin
      System.IO.Put_Line (F'Image (Arg));
   end pf;
 
   --------
   -- pg --
   --------
 
   procedure pg (Arg : G) is
   begin
      System.IO.Put_Line (G'Image (Arg));
   end pg;
 
   --------------
   -- Return_D --
   --------------
 
   function Return_D (X : D) return D is
      R : D;
 
   begin
      --  The return value is already in $f0 so we need to trick the compiler
      --  into thinking that we're moving X to $f0.
 
      Asm ("cvtdg $f0,$f0", Inputs => D'Asm_Input ("g", X), Clobber => "$f0",
           Volatile => True);
      Asm ("stg $f0,%0", D'Asm_Output ("=m", R), Volatile => True);
      return R;
   end Return_D;
 
   --------------
   -- Return_F --
   --------------
 
   function Return_F (X : F) return F is
      R : F;
 
   begin
      --  The return value is already in $f0 so we need to trick the compiler
      --  into thinking that we're moving X to $f0.
 
      Asm ("stf $f0,%0", F'Asm_Output ("=m", R), F'Asm_Input ("g", X),
           Clobber => "$f0", Volatile => True);
      return R;
   end Return_F;
 
   --------------
   -- Return_G --
   --------------
 
   function Return_G (X : G) return G is
      R : G;
 
   begin
      --  The return value is already in $f0 so we need to trick the compiler
      --  into thinking that we're moving X to $f0.
 
      Asm ("stg $f0,%0", G'Asm_Output ("=m", R), G'Asm_Input ("g", X),
           Clobber => "$f0", Volatile => True);
      return R;
   end Return_G;
 
   -----------
   -- Sub_F --
   -----------
 
   function Sub_F (X, Y : F) return F is
      X1, Y1, R : S;
      R1        : F;
 
   begin
      Asm ("ldf %0,%1", S'Asm_Output ("=f", X1), F'Asm_Input ("m", X));
      Asm ("ldf %0,%1", S'Asm_Output ("=f", Y1), F'Asm_Input ("m", Y),
           Volatile => True);
      Asm ("subf %1,%2,%0", S'Asm_Output ("=f", R),
           (S'Asm_Input ("f", X1), S'Asm_Input ("f", Y1)),
           Volatile => True);
      Asm ("stf %1,%0", F'Asm_Output ("=m", R1), S'Asm_Input ("f", R),
           Volatile => True);
      return R1;
   end Sub_F;
 
   -----------
   -- Sub_G --
   -----------
 
   function Sub_G (X, Y : G) return G is
      X1, Y1, R : T;
      R1        : G;
   begin
      Asm ("ldg %0,%1", T'Asm_Output ("=f", X1), G'Asm_Input ("m", X));
      Asm ("ldg %0,%1", T'Asm_Output ("=f", Y1), G'Asm_Input ("m", Y),
           Volatile => True);
      Asm ("subg %1,%2,%0", T'Asm_Output ("=f", R),
           (T'Asm_Input ("f", X1), T'Asm_Input ("f", Y1)),
           Volatile => True);
      Asm ("stg %1,%0", G'Asm_Output ("=m", R1), T'Asm_Input ("f", R),
           Volatile => True);
      return R1;
   end Sub_G;
 
   -------------
   -- Valid_D --
   -------------
 
   --  For now, convert to IEEE and do Valid test on result. This is not quite
   --  accurate, but is good enough in practice.
 
   function Valid_D (Arg : D) return Boolean is
      Val : constant T := G_To_T (D_To_G (Arg));
   begin
      return Val'Valid;
   end Valid_D;
 
   -------------
   -- Valid_F --
   -------------
 
   --  For now, convert to IEEE and do Valid test on result. This is not quite
   --  accurate, but is good enough in practice.
 
   function Valid_F (Arg : F) return Boolean is
      Val : constant S := F_To_S (Arg);
   begin
      return Val'Valid;
   end Valid_F;
 
   -------------
   -- Valid_G --
   -------------
 
   --  For now, convert to IEEE and do Valid test on result. This is not quite
   --  accurate, but is good enough in practice.
 
   function Valid_G (Arg : G) return Boolean is
      Val : constant T := G_To_T (Arg);
   begin
      return Val'Valid;
   end Valid_G;
 
end System.Vax_Float_Operations;