patch 9.1.1466: filetype: not all lex files are recognized

Problem:  filetype: not all lex files are recognized
Solution: detect *.ll as lex, llvm or lifelines filetype, depending on
          the content (Eisuke Kawashima)

closes: #17560

Signed-off-by: Eisuke Kawashima <e-kwsm@users.noreply.github.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/autoload/dist/ft.vim b/runtime/autoload/dist/ft.vim
index 95135c8..5014e75 100644
--- a/runtime/autoload/dist/ft.vim
+++ b/runtime/autoload/dist/ft.vim
@@ -3,7 +3,7 @@
 # Vim functions for file type detection
 #
 # Maintainer:		The Vim Project <https://github.com/vim/vim>
-# Last Change:		2025 Apr 21
+# Last Change:		2025 Jun 17
 # Former Maintainer:	Bram Moolenaar <Bram@vim.org>
 
 # These functions are moved here from runtime/filetype.vim to make startup
@@ -184,9 +184,18 @@
 export def FTll()
   if getline(1) =~ ';\|\<source_filename\>\|\<target\>'
     setf llvm
-  else
-    setf lifelines
+    return
   endif
+  var n = 1
+  while n < 100 && n <= line("$")
+    var line = getline(n)
+    if line =~ '^\s*%'
+      setf lex
+      return
+    endif
+    n += 1
+  endwhile
+  setf lifelines
 enddef
 
 export def FTlpc()
diff --git a/runtime/filetype.vim b/runtime/filetype.vim
index 76229ed..f90c6f8 100644
--- a/runtime/filetype.vim
+++ b/runtime/filetype.vim
@@ -1420,7 +1420,7 @@
 " LFTP
 au BufNewFile,BufRead lftp.conf,.lftprc,*lftp/rc	setf lftp
 
-" Lifelines (or Lex for C++!)
+" Lifelines, LLVM, or Lex for C++
 au BufNewFile,BufRead *.ll			call dist#ft#FTll()
 
 " Lilo: Linux loader
diff --git a/src/testdir/test_filetype.vim b/src/testdir/test_filetype.vim
index c2ea8f1..3ae16e4 100644
--- a/src/testdir/test_filetype.vim
+++ b/src/testdir/test_filetype.vim
@@ -2634,6 +2634,12 @@
   call assert_equal('llvm', &filetype)
   bwipe!
 
+  " lex (C++)
+  call writefile(['%{', '#include <iostream>', '%}'], 'Xfile.ll', 'D')
+  split Xfile.ll
+  call assert_equal('lex', &filetype)
+  bwipe!
+
   " lifelines
   call writefile(['proc main() {}'], 'Xfile.ll', 'D')
   split Xfile.ll
diff --git a/src/version.c b/src/version.c
index fc2abd8..0b6a3b0 100644
--- a/src/version.c
+++ b/src/version.c
@@ -710,6 +710,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1466,
+/**/
     1465,
 /**/
     1464,