OpenE2K/gcc
2
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

[Ada] Adapt proof of double arithmetic runtime unit

Browse Source 
After changes in Why3 and generation of VCs, ghost code needs to be
adapted for proofs to remain automatic.

gcc/ada/

	* libgnat/s-aridou.adb (Big3): Change return type.
	(Lemma_Mult_Non_Negative, Lemma_Mult_Non_Positive): Reorder
	alphabetically.
	(Lemma_Concat_Definition, Lemma_Double_Big_2xxsingle): New
	lemmas.
	(Double_Divide, Scaled_Divide): Add assertions.
This commit is contained in:
Yannick Moy 2022-04-08 15:24:49 +00:00 committed by Pierre-Marie de Rodat
parent 6f8f9d1bcf
commit c6c9b82bc1
1 changed files with 67 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

83
gcc/ada/libgnat/s-aridou.adb
View File

@ -133,7 +133,7 @@ is
Post => Big_2xx'Result > 0;
-- 2**N as a big integer
function Big3 (X1, X2, X3 : Single_Uns) return Big_Integer is
function Big3 (X1, X2, X3 : Single_Uns) return Big_Natural is
(Big_2xxSingle * Big_2xxSingle * Big (Double_Uns (X1))
+ Big_2xxSingle * Big (Double_Uns (X2))
+ Big (Double_Uns (X3)))
@ -208,20 +208,6 @@ is
Ghost,
Post => abs (X * Y) = abs X * abs Y;
procedure Lemma_Mult_Non_Negative (X, Y : Big_Integer)
with
Ghost,
Pre => (X >= Big_0 and then Y >= Big_0)
or else (X <= Big_0 and then Y <= Big_0),
Post => X * Y >= Big_0;
procedure Lemma_Mult_Non_Positive (X, Y : Big_Integer)
with
Ghost,
Pre => (X <= Big_0 and then Y >= Big_0)
or else (X >= Big_0 and then Y <= Big_0),
Post => X * Y <= Big_0;
procedure Lemma_Abs_Rem_Commutation (X, Y : Big_Integer)
with
Ghost,
@ -246,6 +232,12 @@ is
Pre => M < N and then N < Double_Size,
Post => Double_Uns'(2)**M < Double_Uns'(2)**N;
procedure Lemma_Concat_Definition (X, Y : Single_Uns)
with
Ghost,
Post => Big (X & Y) = Big_2xxSingle * Big (Double_Uns (X))
+ Big (Double_Uns (Y));
procedure Lemma_Deep_Mult_Commutation
(Factor : Big_Integer;
X, Y : Single_Uns)
@ -289,6 +281,11 @@ is
Pre => A * S = B * S + R and then S /= 0,
Post => A = B + R / S;
procedure Lemma_Double_Big_2xxSingle
with
Ghost,
Post => Big_2xxSingle * Big_2xxSingle = Big_2xxDouble;
procedure Lemma_Double_Shift (X : Double_Uns; S, S1 : Double_Uns)
with
Ghost,
@ -419,6 +416,20 @@ is
Ghost,
Post => X * (Y + Z) = X * Y + X * Z;
procedure Lemma_Mult_Non_Negative (X, Y : Big_Integer)
with
Ghost,
Pre => (X >= Big_0 and then Y >= Big_0)
or else (X <= Big_0 and then Y <= Big_0),
Post => X * Y >= Big_0;
procedure Lemma_Mult_Non_Positive (X, Y : Big_Integer)
with
Ghost,
Pre => (X <= Big_0 and then Y >= Big_0)
or else (X >= Big_0 and then Y <= Big_0),
Post => X * Y <= Big_0;
procedure Lemma_Neg_Div (X, Y : Big_Integer)
with
Ghost,
@ -552,6 +563,7 @@ is
procedure Lemma_Add_Commutation (X : Double_Uns; Y : Single_Uns) is null;
procedure Lemma_Add_One (X : Double_Uns) is null;
procedure Lemma_Bounded_Powers_Of_2_Increasing (M, N : Natural) is null;
procedure Lemma_Concat_Definition (X, Y : Single_Uns) is null;
procedure Lemma_Deep_Mult_Commutation
(Factor : Big_Integer;
X, Y : Single_Uns)
@ -566,6 +578,7 @@ is
procedure Lemma_Div_Ge (X, Y, Z : Big_Integer) is null;
procedure Lemma_Div_Lt (X, Y, Z : Big_Natural) is null;
procedure Lemma_Div_Eq (A, B, S, R : Big_Integer) is null;
procedure Lemma_Double_Big_2xxSingle is null;
procedure Lemma_Double_Shift (X : Double_Uns; S, S1 : Double_Uns) is null;
procedure Lemma_Double_Shift (X : Single_Uns; S, S1 : Natural) is null;
procedure Lemma_Double_Shift_Right (X : Double_Uns; S, S1 : Double_Uns)
@ -929,10 +942,18 @@ is
pragma Assert (Big (Double_Uns'(Yhi * Zhi)) >= 1);
if Yhi > 1 or else Zhi > 1 then
pragma Assert (Big (Double_Uns'(Yhi * Zhi)) > 1);
pragma Assert (if X = Double_Int'First and then Round then
Mult > Big_2xxDouble);
elsif Zlo > 0 then
pragma Assert (Big (Double_Uns'(Yhi * Zlo)) > 0);
pragma Assert (if X = Double_Int'First and then Round then
Mult > Big_2xxDouble);
elsif Ylo > 0 then
pragma Assert (Big (Double_Uns'(Ylo * Zhi)) > 0);
pragma Assert (if X = Double_Int'First and then Round then
Mult > Big_2xxDouble);
else
pragma Assert (not (X = Double_Int'First and then Round));
end if;
Prove_Quotient_Zero;
end if;
@ -976,6 +997,7 @@ is
Lemma_Mult_Distribution (Big_2xxSingle,
Big (Double_Uns (Hi (T2))),
Big (Double_Uns (Lo (T2))));
Lemma_Double_Big_2xxSingle;
pragma Assert
(Mult = Big_2xxDouble * Big (Double_Uns (Hi (T2)))
+ Big_2xxSingle * Big (Double_Uns (Lo (T2)))
@ -1890,7 +1912,14 @@ is
Big_2xx (Scale), Big_2xxDouble);
Lemma_Lt_Mult (Big (Double_Uns (D (4))), Big_2xxSingle,
Big_2xx (Scale), Big_2xxDouble);
Lemma_Mult_Commutation (2 ** Scale, D (1) & D (2), T1);
declare
Two_xx_Scale : constant Double_Uns := Double_Uns'(2 ** Scale);
D12 : constant Double_Uns := D (1) & D (2);
begin
pragma Assert (Big_2xx (Scale) * Big (D12) < Big_2xxDouble);
pragma Assert (Big (Two_xx_Scale) * Big (D12) < Big_2xxDouble);
Lemma_Mult_Commutation (Two_xx_Scale, D12, T1);
end;
declare
Big_D12 : constant Big_Integer :=
Big_2xx (Scale) * Big (D (1) & D (2));
@ -1954,6 +1983,10 @@ is
pragma Assert
(Big (Double_Uns (Hi (T3))) + Big (Double_Uns (Hi (T2))) =
Big (Double_Uns (S1)));
pragma Assert
(Big_2xxSingle * Big_2xxSingle * Big (Double_Uns (Hi (T2)))
+ Big_2xxSingle * Big_2xxSingle * Big (Double_Uns (Hi (T3)))
= Big_2xxSingle * Big_2xxSingle * Big (Double_Uns (S1)));
end Prove_Multiplication;
-----------------------------
@ -2092,6 +2125,9 @@ is
Lemma_Div_Lt (Big (T1), Big_2xxSingle, Big (Double_Uns (Zlo)));
Lemma_Div_Commutation (T1, Double_Uns (Zlo));
Lemma_Lo_Is_Ident (T1 / Zlo);
pragma Assert
(Big (T2) <= Big_2xxSingle * (Big (Double_Uns (Zlo)) - 1)
+ Big (Double_Uns (D (4))));
Lemma_Div_Lt (Big (T2), Big_2xxSingle, Big (Double_Uns (Zlo)));
Lemma_Div_Commutation (T2, Double_Uns (Zlo));
Lemma_Lo_Is_Ident (T2 / Zlo);
@ -2304,6 +2340,9 @@ is
-- First normalize the divisor so that it has the leading bit on.
-- We do this by finding the appropriate left shift amount.
Lemma_Lt_Commutation (D (1) & D (2), Zu);
pragma Assert (Mult < Big_2xxDouble * Big (Zu));
Shift := Single_Size;
Mask := Single_Uns'Last;
Scale := 0;
@ -2376,6 +2415,8 @@ is
procedure Prove_Shift_Progress is null;
begin
pragma Assert (Mask = Shift_Left (Single_Uns'Last,
Single_Size - Shift_Prev));
Prove_Power;
Shift := Shift / 2;
@ -2470,6 +2511,16 @@ is
+ Big (Double_Uns (D (3))),
Big3 (D (1), D (2), D (3)),
Big (Double_Uns (D (4))));
Lemma_Concat_Definition (D (1), D (2));
Lemma_Double_Big_2xxSingle;
Lemma_Substitution
(Mult * Big_2xx (Scale), Big_2xxSingle * Big_2xxSingle,
Big_2xxSingle * Big (Double_Uns (D (1)))
+ Big (Double_Uns (D (2))),
Big (D (1) & D (2)),
Big_2xxSingle * Big (Double_Uns (D (3)))
+ Big (Double_Uns (D (4))));
pragma Assert (Big (D (1) & D (2)) < Big (Zu));
-- Loop to compute quotient digits, runs twice for Qd (1) and Qd (2)