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
diff --git a/llvm/test/CodeGen/Hexagon/hwloop-dbg.ll b/llvm/test/CodeGen/Hexagon/hwloop-dbg.ll
index 66c6662..bf2f5a3 100644
--- a/llvm/test/CodeGen/Hexagon/hwloop-dbg.ll
+++ b/llvm/test/CodeGen/Hexagon/hwloop-dbg.ll
@@ -47,9 +47,9 @@
 !9 = !DIDerivedType(tag: DW_TAG_pointer_type, size: 32, align: 32, baseType: !10)
 !10 = !DIBasicType(tag: DW_TAG_base_type, name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
 !11 = !{!13, !14, !15}
-!13 = !DILocalVariable(tag: DW_TAG_arg_variable, name: "a", line: 1, arg: 1, scope: !5, file: !6, type: !9)
-!14 = !DILocalVariable(tag: DW_TAG_arg_variable, name: "b", line: 1, arg: 2, scope: !5, file: !6, type: !9)
-!15 = !DILocalVariable(tag: DW_TAG_auto_variable, name: "i", line: 2, scope: !16, file: !6, type: !10)
+!13 = !DILocalVariable(name: "a", line: 1, arg: 1, scope: !5, file: !6, type: !9)
+!14 = !DILocalVariable(name: "b", line: 1, arg: 2, scope: !5, file: !6, type: !9)
+!15 = !DILocalVariable(name: "i", line: 2, scope: !16, file: !6, type: !10)
 !16 = distinct !DILexicalBlock(line: 1, column: 26, file: !28, scope: !5)
 !17 = !DILocation(line: 1, column: 15, scope: !5)
 !18 = !DILocation(line: 1, column: 23, scope: !5)