-- --
-- B o d y --
-- --
--- Copyright (C) 1992-2005 Free Software Foundation, Inc. --
+-- Copyright (C) 1992-2006, 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- --
-- value, since the issue is host representation of integer values.
Uint_Int_Last : Uint;
- -- Uint value containing Int'Last value set by Initialize.
+ -- Uint value containing Int'Last value set by Initialize
UI_Power_2 : array (Int range 0 .. 64) of Uint;
-- This table is used to memoize exponentiations by powers of 2. The Nth
-- digit of Vec contains the sign, all other digits are always non-
-- negative. Note that the input may be directly represented, and in
-- this case Vec will contain the corresponding one or two digit value.
+ -- The low bound of Vec is always 1.
function Least_Sig_Digit (Arg : Uint) return Int;
pragma Inline (Least_Sig_Digit);
procedure Init_Operand (UI : Uint; Vec : out UI_Vector) is
Loc : Int;
+ pragma Assert (Vec'First = Int'(1));
+
begin
if Direct (UI) then
Vec (1) := Direct_Val (UI);
Num : Nat;
begin
- if UI_Is_In_Int_Range (Input) then
+ -- Largest negative number has to be handled specially, since it is in
+ -- Int_Range, but we cannot take the absolute value.
+
+ if Input = Uint_Int_First then
+ return Int'Size;
+
+ -- For any other number in Int_Range, get absolute value of number
+
+ elsif UI_Is_In_Int_Range (Input) then
Num := abs (UI_To_Int (Input));
Bits := 0;
+ -- If not in Int_Range then initialize bit count for all low order
+ -- words, and set number to high order digit.
+
else
Bits := Base_Bits * (Uints.Table (Input).Length - 1);
Num := abs (Udigits.Table (Uints.Table (Input).Loc));
end if;
+ -- Increase bit count for remaining value in Num
+
while Types.">" (Num, 0) loop
Num := Num / 2;
Bits := Bits + 1;
-- Mathematically: assume base congruent to 1 and compute an equivelent
-- integer to Left.
- -- If Sign = -1 return the alternating sum of the "digits".
+ -- If Sign = -1 return the alternating sum of the "digits"
- -- D1 - D2 + D3 - D4 + D5 . . .
+ -- D1 - D2 + D3 - D4 + D5 ...
-- (where D1 is Least Significant Digit)
if Tmp_Int >= Base then
- -- Sign must be 1.
+ -- Sign must be 1
Tmp_Int := (Tmp_Int / Base) + 1;
Carry := Tmp_Int / Base;
end loop;
- -- Multiply Divisor by d.
+ -- Multiply Divisor by d
Carry := 0;
for J in reverse Divisor'Range loop
end loop;
end if;
- -- Main loop of long division algorithm.
+ -- Main loop of long division algorithm
Divisor_Dig1 := Divisor (1);
Divisor_Dig2 := Divisor (2);
for J in Quotient'Range loop
- -- [ CALCULATE Q (hat) ] (step D3 in the algorithm).
+ -- [ CALCULATE Q (hat) ] (step D3 in the algorithm)
Tmp_Int := Dividend (J) * Base + Dividend (J + 1);
if Right = Uint_0 then
return Uint_1;
- -- 0 to any positive power is 0.
+ -- 0 to any positive power is 0
elsif Left = Uint_0 then
return Uint_0;
-- UI_GCD --
------------
- -- Lehmer's algorithm for GCD.
+ -- Lehmer's algorithm for GCD
-- The idea is to avoid using multiple precision arithmetic wherever
-- possible, substituting Int arithmetic instead. See Knuth volume II,
loop
-- We might overflow and get division by zero here. This just
- -- means we can not take the single precision step
+ -- means we cannot take the single precision step
Den1 := V_Hat + C;
Den2 := V_Hat + D;
if B = Int_0 then
- -- No single precision steps take a regular Euclid step.
+ -- No single precision steps take a regular Euclid step
Tmp_UI := U rem V;
U := V;
V := Tmp_UI;
else
- -- Use prior single precision steps to compute this Euclid step.
+ -- Use prior single precision steps to compute this Euclid step
-- Fixed bug 1415-008 spends 80% of its time working on this
-- step. Perhaps we need a special case Int / Uint dot
-- and replace the rem with simpler operations where
-- possible.
- -- Least_Sig_Digit might return Negative numbers.
+ -- Least_Sig_Digit might return Negative numbers
when 2 =>
return UI_From_Int (
end if;
- -- Else fall through to general case.
+ -- Else fall through to general case
-- ???This needs to be improved. We have the Rem when we do the
-- Div. Div throws it away!
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