DI: Remove DW_TAG_arg_variable and DW_TAG_auto_variable

Remove the fake `DW_TAG_auto_variable` and `DW_TAG_arg_variable` tags,
using `DW_TAG_variable` in their place Stop exposing the `tag:` field at
all in the assembly format for `DILocalVariable`.

Most of the testcase updates were generated by the following sed script:

    find test/ -name "*.ll" -o -name "*.mir" |
    xargs grep -l 'DILocalVariable' |
    xargs sed -i '' \
      -e 's/tag: DW_TAG_arg_variable, //' \
      -e 's/tag: DW_TAG_auto_variable, //'

There were only a handful of tests in `test/Assembly` that I needed to
update by hand.

(Note: a follow-up could change `DILocalVariable::DILocalVariable()` to
set the tag to `DW_TAG_formal_parameter` instead of `DW_TAG_variable`
(as appropriate), instead of having that logic magically in the backend
in `DbgVariable`.  I've added a FIXME to that effect.)

llvm-svn: 243774

llvm/lib/IR/DIBuilder.cpp

@@ -613,10 +613,9 @@ static DILocalVariable *createLocalVariable(
   // the only valid scopes)?
   DIScope *Context = getNonCompileUnitScope(Scope);
 
-  dwarf::Tag Tag = ArgNo ? dwarf::DW_TAG_arg_variable : dwarf::DW_TAG_auto_variable;
-  auto *Node = DILocalVariable::get(
-      VMContext, Tag, cast_or_null<DILocalScope>(Context), Name, File, LineNo,
-      DITypeRef::get(Ty), ArgNo, Flags);
+  auto *Node =
+      DILocalVariable::get(VMContext, cast_or_null<DILocalScope>(Context), Name,
+                           File, LineNo, DITypeRef::get(Ty), ArgNo, Flags);
   if (AlwaysPreserve) {
     // The optimizer may remove local variables. If there is an interest
     // to preserve variable info in such situation then stash it in a