uintp.adb (Most_Sig_2_Digits): In case Direct (Right)...

2017-04-25  Bob Duff  <duff@adacore.com>

	* uintp.adb (Most_Sig_2_Digits): In case Direct (Right), fetch
	Direct_Val (Right), instead of the incorrect Direct_Val (Left).
	(UI_GCD): Remove ??? comment involving possible efficiency
	improvements. This just isn't important after all these years.
	Also minor cleanup.
	* uintp.ads: Minor cleanup.

From-SVN: r247144

gcc/ada/ChangeLog

+2017-04-25  Bob Duff  <duff@adacore.com>
+
+	* uintp.adb (Most_Sig_2_Digits): In case Direct (Right), fetch
+	Direct_Val (Right), instead of the incorrect Direct_Val (Left).
+	(UI_GCD): Remove ??? comment involving possible efficiency
+	improvements. This just isn't important after all these years.
+	Also minor cleanup.
+	* uintp.ads: Minor cleanup.
+
 2017-04-25  Hristian Kirtchev  <kirtchev@adacore.com>
 
 	* exp_util.adb, exp_util.ads, sem_ch7.adb, sem_prag.adb, exp_ch3.adb:

gcc/ada/uintp.adb

@@ -52,7 +52,7 @@ package body Uintp is
 
    UI_Power_2 : array (Int range 0 .. 64) of Uint;
    --  This table is used to memoize exponentiations by powers of 2. The Nth
-   --  entry, if set, contains the Uint value 2 ** N. Initially UI_Power_2_Set
+   --  entry, if set, contains the Uint value 2**N. Initially UI_Power_2_Set
    --  is zero and only the 0'th entry is set, the invariant being that all
    --  entries in the range 0 .. UI_Power_2_Set are initialized.
 
@@ -149,9 +149,9 @@ package body Uintp is
       Left_Hat  : out Int;
       Right_Hat : out Int);
    --  Returns leading two significant digits from the given pair of Uint's.
-   --  Mathematically: returns Left / (Base ** K) and Right / (Base ** K) where
+   --  Mathematically: returns Left / (Base**K) and Right / (Base**K) where
    --  K is as small as possible S.T. Right_Hat < Base * Base. It is required
-   --  that Left > Right for the algorithm to work.
+   --  that Left >= Right for the algorithm to work.
 
    function N_Digits (Input : Uint) return Int;
    pragma Inline (N_Digits);
@@ -264,7 +264,7 @@ package body Uintp is
       -------------------
 
       function Better_In_Hex return Boolean is
-         T16 : constant Uint := Uint_2 ** Int'(16);
+         T16 : constant Uint := Uint_2**Int'(16);
          A   : Uint;
 
       begin
@@ -506,6 +506,7 @@ package body Uintp is
       pragma Assert (Left >= Right);
 
       if Direct (Left) then
+         pragma Assert (Direct (Right));
          Left_Hat  := Direct_Val (Left);
          Right_Hat := Direct_Val (Right);
          return;
@@ -533,7 +534,7 @@ package body Uintp is
 
       begin
          if Direct (Right) then
-            T := Direct_Val (Left);
+            T := Direct_Val (Right);
             R1 := abs (T / Base);
             R2 := T rem Base;
             Length_R := 2;
@@ -1370,7 +1371,7 @@ package body Uintp is
 
       elsif Right <= Uint_64 then
 
-         --  2 ** N for N in 2 .. 64
+         --  2**N for N in 2 .. 64
 
          if Left = Uint_2 then
             declare
@@ -1390,7 +1391,7 @@ package body Uintp is
                return UI_Power_2 (Right_Int);
             end;
 
-         --  10 ** N for N in 2 .. 64
+         --  10**N for N in 2 .. 64
 
          elsif Left = Uint_10 then
             declare
@@ -1585,20 +1586,6 @@ package body Uintp is
          else
             --  Use prior single precision steps to compute this Euclid step
 
-            --  For constructs such as:
-            --  sqrt_2: constant := 1.41421_35623_73095_04880_16887_24209_698;
-            --  sqrt_eps: constant long_float := long_float( 1.0 / sqrt_2)
-            --    ** long_float'machine_mantissa;
-            --
-            --  we spend 80% of our time working on this step. Perhaps we need
-            --  a special case Int / Uint dot product to speed things up. ???
-
-            --  Alternatively we could increase the single precision iterations
-            --  to handle Uint's of some small size ( <5 digits?). Then we
-            --  would have more iterations on small Uint. On the code above, we
-            --  only get 5 (on average) single precision iterations per large
-            --  iteration. ???
-
             Tmp_UI := (UI_From_Int (A) * U) + (UI_From_Int (B) * V);
             V := (UI_From_Int (C) * U) + (UI_From_Int (D) * V);
             U := Tmp_UI;

gcc/ada/uintp.ads

@@ -238,7 +238,7 @@ package Uintp is
      (B      : Uint;
       E      : Uint;
       Modulo : Uint) return Uint;
-   --  Efficiently compute (B ** E) rem Modulo
+   --  Efficiently compute (B**E) rem Modulo
 
    function UI_Modular_Inverse (N : Uint; Modulo : Uint) return Uint;
    --  Compute the multiplicative inverse of N in modular arithmetics with the
@@ -438,7 +438,7 @@ private
    Base_Bits : constant := 15;
    --  Number of bits in base value
 
-   Base : constant Int := 2 ** Base_Bits;
+   Base : constant Int := 2**Base_Bits;
 
    --  Values in the range -(Base-1) .. Max_Direct are encoded directly as
    --  Uint values by adding a bias value. The value of Max_Direct is chosen
@@ -454,13 +454,13 @@ private
    --  avoid accidental use of Uint arithmetic on these values, which is never
    --  correct.
 
-   type Ctrl is range Int'First .. Int'Last;
+   type Ctrl is new Int;
 
    Uint_Direct_Bias  : constant Ctrl := Ctrl (Uint_Low_Bound) + Ctrl (Base);
    Uint_Direct_First : constant Ctrl := Uint_Direct_Bias + Ctrl (Min_Direct);
    Uint_Direct_Last  : constant Ctrl := Uint_Direct_Bias + Ctrl (Max_Direct);
 
-   Uint_0   : constant Uint := Uint (Uint_Direct_Bias);
+   Uint_0   : constant Uint := Uint (Uint_Direct_Bias + 0);
    Uint_1   : constant Uint := Uint (Uint_Direct_Bias + 1);
    Uint_2   : constant Uint := Uint (Uint_Direct_Bias + 2);
    Uint_3   : constant Uint := Uint (Uint_Direct_Bias + 3);
@@ -499,7 +499,7 @@ private
    Uint_Minus_80  : constant Uint := Uint (Uint_Direct_Bias - 80);
    Uint_Minus_128 : constant Uint := Uint (Uint_Direct_Bias - 128);
 
-   Uint_Max_Simple_Mul : constant := Uint_Direct_Bias + 2 ** 15;
+   Uint_Max_Simple_Mul : constant := Uint_Direct_Bias + 2**15;
    --  If two values are directly represented and less than or equal to this
    --  value, then we know the product fits in a 32-bit integer. This allows
    --  UI_Mul to efficiently compute the product in this case.