[gcc r13-609] [Ada] Fix proof of runtime unit s-valeu

[Pierre-Marie de Rodat <pmderodat@gcc.gnu.org>]

https://gcc.gnu.org/g:6f8f9d1bcf55187cb81ef7b0ef1e23db1bc0d440

commit r13-609-g6f8f9d1bcf55187cb81ef7b0ef1e23db1bc0d440
Author: Claire Dross <dross@adacore.com>
Date:   Fri Apr 8 16:38:47 2022 +0200

    [Ada] Fix proof of runtime unit s-valeu
    
    Update to provers caused some proof regressions.  Fix the proof by
    changing ghost code.
    
    gcc/ada/
    
            * libgnat/s-valueu.adb (Scan_Raw_Unsigned): Add assertions.

Diff:
---
 gcc/ada/libgnat/s-valueu.adb | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/gcc/ada/libgnat/s-valueu.adb b/gcc/ada/libgnat/s-valueu.adb
index b8bfd447237..f5a6881dbc5 100644
--- a/gcc/ada/libgnat/s-valueu.adb
+++ b/gcc/ada/libgnat/s-valueu.adb
@@ -522,6 +522,9 @@ package body System.Value_U is
                   Uval := Base;
                   Base := 10;
                   pragma Assert (Ptr.all = Last_Num_Init + 1);
+                  pragma Assert
+                    (if Starts_As_Based then P = Last_Num_Based + 1);
+                  pragma Assert (not Is_Based);
                   pragma Assert (if not Overflow then Uval = Init_Val.Value);
                   exit;
                end if;
@@ -569,10 +572,6 @@ package body System.Value_U is
                   end if;
                end if;
 
-               Lemma_Scan_Digit
-                 (Str, P, Last_Num_Based, Digit, Base, Old_Uval, Uval,
-                  Based_Val, Old_Overflow, Overflow);
-
                --  If at end of string with no base char, not a based number
                --  but we signal Constraint_Error and set the pointer past
                --  the end of the field, since this is what the ACVC tests
@@ -580,6 +579,10 @@ package body System.Value_U is
 
                P := P + 1;
 
+               Lemma_Scan_Digit
+                 (Str, P - 1, Last_Num_Based, Digit, Base, Old_Uval, Uval,
+                  Based_Val, Old_Overflow, Overflow);
+
                if P > Max then
                   Ptr.all := P;
                   Bad_Value (Str);
@@ -590,6 +593,7 @@ package body System.Value_U is
                if Str (P) = Base_Char then
                   Ptr.all := P + 1;
                   pragma Assert (Ptr.all = Last_Num_Based + 2);
+                  pragma Assert (Is_Based);
                   pragma Assert
                     (if not Overflow then
                        Based_Val = Scan_Based_Number_Ghost