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* eval_fat.adb: Revert previous change.

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From-SVN: r91880
This commit is contained in:
Arnaud Charlet 2004-12-08 12:26:32 +01:00
parent 0da07eae29
commit e913f03bad
1 changed files with 91 additions and 34 deletions
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125
gcc/ada/eval_fat.adb
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@ -38,14 +38,14 @@ package body Eval_Fat is
-- case of anyone ever having to adjust this code for another value,
-- and for documentation purposes.
-- Another assumption is that the range of the floating-point type
-- is symmetric around zero.
type Radix_Power_Table is array (Int range 1 .. 4) of Int;
Radix_Powers : constant Radix_Power_Table :=
(Radix ** 1, Radix ** 2, Radix ** 3, Radix ** 4);
function Float_Radix return T renames Ureal_2;
-- Radix expressed in real form
-----------------------
-- Local Subprograms --
-----------------------
@ -74,6 +74,12 @@ package body Eval_Fat is
-- even, a floor operation or a ceiling operation depending on the setting
-- of Mode (see corresponding descriptions in Urealp).
function Eps_Model (RT : R) return T;
-- Return the smallest model number of R.
function Eps_Denorm (RT : R) return T;
-- Return the smallest denormal of type R.
function Machine_Emin (RT : R) return Int;
-- Return value of the Machine_Emin attribute
@ -85,8 +91,10 @@ package body Eval_Fat is
begin
if Towards = X then
return X;
elsif Towards > X then
return Succ (RT, X);
else
return Pred (RT, X);
end if;
@ -98,11 +106,14 @@ package body Eval_Fat is
function Ceiling (RT : R; X : T) return T is
XT : constant T := Truncation (RT, X);
begin
if UR_Is_Negative (X) then
return XT;
elsif X = XT then
return X;
else
return XT + Ureal_1;
end if;
@ -371,10 +382,10 @@ package body Eval_Fat is
Calculate_Fraction_And_Exponent : begin
Uintp_Mark := Mark;
-- Determine correct rounding based on the remainder which is in
-- N and the divisor D. The rounding is performed on the absolute
-- value of X, so Ceiling and Floor need to check for the sign of
-- X explicitly.
-- Determine correct rounding based on the remainder
-- which is in N and the divisor D. The rounding is
-- performed on the absolute value of X, so Ceiling
-- and Floor need to check for the sign of X explicitly.
case Mode is
when Round_Even =>
@ -429,6 +440,25 @@ package body Eval_Fat is
end Calculate_Fraction_And_Exponent;
end Decompose_Int;
----------------
-- Eps_Denorm --
----------------
function Eps_Denorm (RT : R) return T is
begin
return Float_Radix ** UI_From_Int
(Machine_Emin (RT) - Machine_Mantissa (RT));
end Eps_Denorm;
---------------
-- Eps_Model --
---------------
function Eps_Model (RT : R) return T is
begin
return Float_Radix ** UI_From_Int (Machine_Emin (RT));
end Eps_Model;
--------------
-- Exponent --
--------------
@ -705,8 +735,37 @@ package body Eval_Fat is
----------
function Pred (RT : R; X : T) return T is
Result_F : UI;
Result_X : UI;
begin
return -Succ (RT, -X);
if abs X < Eps_Model (RT) then
if Denorm_On_Target then
return X - Eps_Denorm (RT);
elsif X > Ureal_0 then
-- Target does not support denorms, so predecessor is 0.0
return Ureal_0;
else
-- Target does not support denorms, and X is 0.0
-- or at least bigger than -Eps_Model (RT)
return -Eps_Model (RT);
end if;
else
Decompose_Int (RT, X, Result_F, Result_X, Ceiling);
return UR_From_Components
(Num => Result_F - 1,
Den => Machine_Mantissa (RT) - Result_X,
Rbase => Radix,
Negative => False);
-- Result_F may be false, but this is OK as UR_From_Components
-- handles that situation.
end if;
end Pred;
---------------
@ -833,38 +892,35 @@ package body Eval_Fat is
----------
function Succ (RT : R; X : T) return T is
Emin : constant UI := UI_From_Int (Machine_Emin (RT));
Mantissa : constant UI := UI_From_Int (Machine_Mantissa (RT));
Exp : UI := UI_Max (Emin, Exponent (RT, X));
Frac : T;
New_Frac : T;
Result_F : UI;
Result_X : UI;
begin
if UR_Is_Zero (X) then
Exp := Emin;
end if;
if abs X < Eps_Model (RT) then
if Denorm_On_Target then
return X + Eps_Denorm (RT);
-- Set exponent such that the radix point will be directly
-- following the mantissa after scaling
elsif X < Ureal_0 then
-- Target does not support denorms, so successor is 0.0
return Ureal_0;
if Denorm_On_Target or Exp /= Emin then
Exp := Exp - Mantissa;
else
Exp := Exp - 1;
end if;
Frac := Scaling (RT, X, -Exp);
New_Frac := Ceiling (RT, Frac);
if New_Frac = Frac then
if New_Frac = Scaling (RT, -Ureal_1, Mantissa - 1) then
New_Frac := New_Frac + Scaling (RT, Ureal_1, Uint_Minus_1);
else
New_Frac := New_Frac + Ureal_1;
end if;
end if;
-- Target does not support denorms, and X is 0.0
-- or at least smaller than Eps_Model (RT)
return Scaling (RT, New_Frac, Exp);
return Eps_Model (RT);
end if;
else
Decompose_Int (RT, X, Result_F, Result_X, Floor);
return UR_From_Components
(Num => Result_F + 1,
Den => Machine_Mantissa (RT) - Result_X,
Rbase => Radix,
Negative => False);
-- Result_F may be false, but this is OK as UR_From_Components
-- handles that situation.
end if;
end Succ;
----------------
@ -873,6 +929,7 @@ package body Eval_Fat is
function Truncation (RT : R; X : T) return T is
pragma Warnings (Off, RT);
begin
return UR_From_Uint (UR_Trunc (X));
end Truncation;