[gcc r12-6225] [Ada] Fix lemma in generic unit System.Arith_Double

[Pierre-Marie de Rodat]

https://gcc.gnu.org/g:50d8b1066a46cc134c1accc270c9be1b1cae8bc2

commit r12-6225-g50d8b1066a46cc134c1accc270c9be1b1cae8bc2
Author: Yannick Moy <moy@adacore.com>
Date:   Mon Nov 29 16:15:32 2021 +0100

    [Ada] Fix lemma in generic unit System.Arith_Double
    
    gcc/ada/
    
            * libgnat/s-aridou.adb (Lemma_Word_Commutation): Fix for
            instances with other values of Single_Size.

Diff:
---
 gcc/ada/libgnat/s-aridou.adb | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/gcc/ada/libgnat/s-aridou.adb b/gcc/ada/libgnat/s-aridou.adb
index 0a75f08fcb9..57d427b147e 100644
--- a/gcc/ada/libgnat/s-aridou.adb
+++ b/gcc/ada/libgnat/s-aridou.adb
@@ -541,7 +541,8 @@ is
    procedure Lemma_Word_Commutation (X : Single_Uns)
    with
      Ghost,
-     Post => Big_2xx32 * Big (Double_Uns (X)) = Big (2**32 * Double_Uns (X));
+     Post => Big_2xx32 * Big (Double_Uns (X))
+       = Big (2**Single_Size * Double_Uns (X));
 
    -----------------------------
    -- Local lemma null bodies --