From: Yannick Moy <moy@adacore.com>
Date: Tue, 4 Jan 2022 09:37:53 +0000 (+0100)
Subject: [Ada] Adapt ghost code to maintain proof
X-Git-Tag: basepoints/gcc-13~1861
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=371b4ad7c423891d13f9b855f5fdd469a82f7160;p=thirdparty%2Fgcc.git

[Ada] Adapt ghost code to maintain proof

gcc/ada/

	* libgnat/s-expmod.adb (Exp_Modular): Add assertions.
---

diff --git a/gcc/ada/libgnat/s-expmod.adb b/gcc/ada/libgnat/s-expmod.adb
index 61faed16b256..60d86e505b8a 100644
--- a/gcc/ada/libgnat/s-expmod.adb
+++ b/gcc/ada/libgnat/s-expmod.adb
@@ -278,6 +278,7 @@ is
                  (Big (Result) * Big (Factor) ** (Exp - 1),
                   Big (Left) ** Right));
                Lemma_Exp_Expand (Big (Factor), Exp - 1);
+               pragma Assert (Exp / 2 = (Exp - 1) / 2);
             end if;
 
             Lemma_Exp_Expand (Big (Factor), Exp);
@@ -286,6 +287,8 @@ is
             exit when Exp = 0;
 
             Rest := Big (Factor) ** Exp;
+            pragma Assert (Equal_Modulo
+              (Big (Result) * (Rest * Rest), Big (Left) ** Right));
             Lemma_Exp_Mod (Big (Factor) * Big (Factor), Exp, Big (Modulus));
             pragma Assert
               ((Big (Factor) * Big (Factor)) ** Exp = Rest * Rest);