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/ftplugin/llvm.vim

@@ -0,0 +1,12 @@
+" Vim filetype plugin file
+" Language:	LLVM IR
+" Last Change:	2024 Oct 22
+" Maintainer:	Wu, Zhenyu <wuzhenyu@ustc.edu>
+
+if exists("b:did_ftplugin") | finish | endif
+let b:did_ftplugin = 1
+
+setl comments=:;
+setl commentstring=;\ %s
+
+let b:undo_ftplugin = "setl commentstring< comments<"

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

test/old/testdir/test_filetype.vim

@@ -2440,6 +2440,24 @@ func Test_inc_file()
   filetype off
 endfunc
 
+func Test_ll_file()
+  filetype on
+
+  " LLVM IR
+  call writefile(['target triple = "nvptx64-nvidia-cuda"'], 'Xfile.ll', 'D')
+  split Xfile.ll
+  call assert_equal('llvm', &filetype)
+  bwipe!
+
+  " lifelines
+  call writefile(['proc main() {}'], 'Xfile.ll', 'D')
+  split Xfile.ll
+  call assert_equal('lifelines', &filetype)
+  bwipe!
+
+  filetype off
+endfunc
+
 func Test_lsl_file()
   filetype on