Update

syntax/mir.vim

@@ -0,0 +1,52 @@
+if polyglot#init#is_disabled(expand('<sfile>:p'), 'llvm', 'syntax/mir.vim')
+  finish
+endif
+
+" Vim syntax file
+" Language:   mir
+" Maintainer: The LLVM team, http://llvm.org/
+" Version:      $Revision$
+
+if version < 600
+  syntax clear
+elseif exists("b:current_syntax")
+  finish
+endif
+
+syn case match
+
+" MIR is embedded in a yaml container, so we load all of the yaml syntax.
+runtime! syntax/yaml.vim
+unlet b:current_syntax
+
+" The first document of a file is allowed to contain an LLVM IR module inside
+" a top-level yaml block string.
+syntax include @LLVM syntax/llvm.vim
+" FIXME: This should only be allowed for the first document of the file
+syntax region llvm start=/\(^---\s*|\)\@<=/ end=/\(^\.\.\.\)\@=/ contains=@LLVM
+
+" The `body:` field of a document contains the MIR dump of the function
+syntax include @MIR syntax/machine-ir.vim
+syntax region mir start=/\(^body:\s*|\)\@<=/ end=/\(^[^[:space:]]\)\@=/ contains=@MIR
+
+" Syntax-highlight lit test commands and bug numbers.
+syn match  mirSpecialComment /#\s*PR\d*\s*$/
+syn match  mirSpecialComment /#\s*REQUIRES:.*$/
+syn match  mirSpecialComment /#\s*RUN:.*$/
+syn match  mirSpecialComment /#\s*ALLOW_RETRIES:.*$/
+syn match  mirSpecialComment /#\s*CHECK:.*$/
+syn match  mirSpecialComment "\v#\s*CHECK-(NEXT|NOT|DAG|SAME|LABEL):.*$"
+syn match  mirSpecialComment /#\s*XFAIL:.*$/
+
+if version >= 508 || !exists("did_c_syn_inits")
+  if version < 508
+    let did_c_syn_inits = 1
+    command -nargs=+ HiLink hi link <args>
+  else
+    command -nargs=+ HiLink hi def link <args>
+  endif
+
+  HiLink mirSpecialComment SpecialComment
+endif
+
+let b:current_syntax = "mir"