[gcc r17-2450] Fix typo in comment of invert_mod2n

https://gcc.gnu.org/g:6ba996c6580cc443ceb9a0848d905431d972ca45

commit r17-2450-g6ba996c6580cc443ceb9a0848d905431d972ca45
Author: Eric Botcazou <[email protected]>
Date:   Thu Jul 16 13:02:52 2026 +0200

    Fix typo in comment of invert_mod2n
    
    The typo is just one letter 'Z' -> 'X', but a 1-character change is a waste
    of resources so I have beefed up the comment with a few references.
    
    gcc/
            * expmed.cc (invert_mod2n): Fix typo in comment and add references.

Diff:
---
 gcc/expmed.cc | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/gcc/expmed.cc b/gcc/expmed.cc
index 4285c846bf2d..b87d06bc9a43 100644
--- a/gcc/expmed.cc
+++ b/gcc/expmed.cc
@@ -3838,9 +3838,9 @@ invert_mod2n (unsigned HOST_WIDE_INT x, int n)
 {
   gcc_assert ((x & 1) == 1);
 
-  /* The algorithm notes that the choice Y = Z satisfies X*Y == 1 mod 2^3,
-     since X is odd.  Then each iteration doubles the number of bits of
-     significance in Y.  */
+  /* The algorithm notes that the choice Y = X satisfies X*Y == 1 mod 2^3,
+     since X is odd.  Then each Newton-Raphson iteration doubles the number
+     of bits of significance in Y (Hensel's lemma).  */
 
   const unsigned HOST_WIDE_INT mask
     = (n == HOST_BITS_PER_WIDE_INT