Add llc integration for LLVM IR (#979)

Check LLVM IR with llc

ale_linters/llvm/llc.vim

@@ -0,0 +1,35 @@
+" Author: rhysd <https://rhysd.github.io>
+" Description: Support for checking LLVM IR with llc
+
+call ale#Set('llvm_llc_executable', 'llc')
+
+function! ale_linters#llvm#llc#GetExecutable(buffer) abort
+    return ale#Var(a:buffer, 'llvm_llc_executable')
+endfunction
+
+function! ale_linters#llvm#llc#GetCommand(buffer) abort
+    return ale#Escape(ale_linters#llvm#llc#GetExecutable(a:buffer))
+    \   . ' -filetype=null -o='
+    \   . ale#Escape(g:ale#util#nul_file)
+endfunction
+
+function! ale_linters#llvm#llc#HandleErrors(buffer, lines) abort
+    " Handle '{path}: {file}:{line}:{col}: error: {message}' format
+    let l:pattern = '\v^[a-zA-Z]?:?[^:]+: [^:]+:(\d+):(\d+): (.+)$'
+    let l:matches = ale#util#GetMatches(a:lines, l:pattern)
+
+    return map(l:matches, "{
+    \   'lnum': str2nr(v:val[1]),
+    \   'col': str2nr(v:val[2]),
+    \   'text': v:val[3],
+    \   'type': 'E',
+    \}")
+endfunction
+
+call ale#linter#Define('llvm', {
+\   'name': 'llc',
+\   'executable_callback': 'ale_linters#llvm#llc#GetExecutable',
+\   'output_stream': 'stderr',
+\   'command_callback': 'ale_linters#llvm#llc#GetCommand',
+\   'callback': 'ale_linters#llvm#llc#HandleErrors',
+\})