vim-patch:9.1.0866: filetype: LLVM IR files are not recognized (#31228)

Problem:  filetype: LLVM IR files are not recognized
Solution: detect '*.ll' files either as lifelines or llvm filetype
          (Wu, Zhenyu)

closes: vim/vim#15824

bc32bbddcf

N/A patch:
vim-patch:7e4b861: runtime(filetype): remove duplicated *.org file pattern

Co-authored-by: Wu, Zhenyu <wuzhenyu@ustc.edu>

runtime/lua/vim/filetype.lua

@@ -682,7 +682,6 @@ local extension = {
   l = 'lex',
   lhs = 'lhaskell',
   lidr = 'lidris2',
-  ll = 'lifelines',
   ly = 'lilypond',
   ily = 'lilypond',
   liquid = 'liquid',
@@ -697,6 +696,7 @@ local extension = {
   lt = 'lite',
   lite = 'lite',
   livemd = 'livebook',
+  ll = detect.ll,
   log = detect.log,
   Log = detect.log,
   LOG = detect.log,

runtime/lua/vim/filetype/detect.lua

@@ -868,6 +868,16 @@ function M.log(path, _)
   end
 end
 
+--- @type vim.filetype.mapfn
+function M.ll(_, bufnr)
+  local first_line = getline(bufnr, 1)
+  if matchregex(first_line, [[;\|\<source_filename\>\|\<target\>]]) then
+    return 'llvm'
+  else
+    return 'lifelines'
+  end
+end
+
 --- @type vim.filetype.mapfn
 function M.lpc(_, bufnr)
   if vim.g.lpc_syntax_for_c then