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[Ada] Computation of Shift_Left and large signed values

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gcc/ada/

	* sem_eval.adb (Fold_Shift): Fix computation of Shift_Left
	resulting in negative signed values.
This commit is contained in:
Arnaud Charlet 2021-01-29 10:57:39 -05:00 • committed by Pierre-Marie de Rodat
parent f3a8f939ba
commit fde5868f36
1 changed files with 19 additions and 17 deletions
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36
gcc/ada/sem_eval.adb
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@ -4983,7 +4983,7 @@ package body Sem_Eval is
end if;
end Check_Elab_Call;
Modulus : Uint;
Modulus, Val : Uint;
begin
if Compile_Time_Known_Value (Left)
@ -4994,23 +4994,25 @@ package body Sem_Eval is
if Op = N_Op_Shift_Left then
Check_Elab_Call;
declare
Modulus : Uint;
begin
if Is_Modular_Integer_Type (Typ) then
Modulus := Einfo.Modulus (Typ);
else
Modulus := Uint_2 ** RM_Size (Typ);
end if;
if Is_Modular_Integer_Type (Typ) then
Modulus := Einfo.Modulus (Typ);
else
Modulus := Uint_2 ** RM_Size (Typ);
end if;
-- Fold Shift_Left (X, Y) by computing (X * 2**Y) rem modulus
-- Fold Shift_Left (X, Y) by computing
-- (X * 2**Y) rem modulus [- Modulus]
Fold_Uint
(N,
(Expr_Value (Left) * (Uint_2 ** Expr_Value (Right)))
rem Modulus,
Static => Static);
end;
Val := (Expr_Value (Left) * (Uint_2 ** Expr_Value (Right)))
rem Modulus;
if Is_Modular_Integer_Type (Typ)
or else Val < Modulus / Uint_2
then
Fold_Uint (N, Val, Static => Static);
else
Fold_Uint (N, Val - Modulus, Static => Static);
end if;
elsif Op = N_Op_Shift_Right then
Check_Elab_Call;
@ -5042,7 +5044,7 @@ package body Sem_Eval is
Check_Elab_Call;
declare
Two_Y : constant Uint := Uint_2 ** Expr_Value (Right);
Two_Y : constant Uint := Uint_2 ** Expr_Value (Right);
begin
if Is_Modular_Integer_Type (Typ) then
Modulus := Einfo.Modulus (Typ);