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

Author: dexonsmith

llvm/docs/LangRef.rst

@@ -3900,22 +3900,18 @@ mandatory, and points at an :ref:`DILexicalBlockFile`, an
 DILocalVariable
 """""""""""""""
 
-``DILocalVariable`` nodes represent local variables in the source language.
-Instead of ``DW_TAG_variable``, they use LLVM-specific fake tags to
-discriminate between local variables (``DW_TAG_auto_variable``) and subprogram
-arguments (``DW_TAG_arg_variable``).  In the latter case, the ``arg:`` field
-specifies the argument position, and this variable will be included in the
-``variables:`` field of its :ref:`DISubprogram`.
-
-.. code-block:: llvm
-
-    !0 = !DILocalVariable(tag: DW_TAG_arg_variable, name: "this", arg: 1,
-                          scope: !3, file: !2, line: 7, type: !3,
-                          flags: DIFlagArtificial)
-    !1 = !DILocalVariable(tag: DW_TAG_arg_variable, name: "x", arg: 2,
-                          scope: !4, file: !2, line: 7, type: !3)
-    !2 = !DILocalVariable(tag: DW_TAG_auto_variable, name: "y",
-                          scope: !5, file: !2, line: 7, type: !3)
+``DILocalVariable`` nodes represent local variables in the source language.  If
+the ``arg:`` field is set to non-zero, then this variable is a subprogram
+parameter, and it will be included in the ``variables:`` field of its
+:ref:`DISubprogram`.
+
+.. code-block:: llvm
+
+    !0 = !DILocalVariable(name: "this", arg: 1, scope: !3, file: !2, line: 7,
+                          type: !3, flags: DIFlagArtificial)
+    !1 = !DILocalVariable(name: "x", arg: 2, scope: !4, file: !2, line: 7,
+                          type: !3)
+    !2 = !DILocalVariable(name: "y", scope: !5, file: !2, line: 7, type: !3)
 
 DIExpression
 """"""""""""

llvm/docs/SourceLevelDebugging.rst

@@ -270,13 +270,13 @@ Compiled to LLVM, this function would be represented like this:
   !8 = !{i32 2, !"Debug Info Version", i32 3}
   !9 = !{i32 1, !"PIC Level", i32 2}
   !10 = !{!"clang version 3.7.0 (trunk 231150) (llvm/trunk 231154)"}
-  !11 = !DILocalVariable(tag: DW_TAG_auto_variable, name: "X", scope: !4, file: !1, line: 2, type: !12)
+  !11 = !DILocalVariable(name: "X", scope: !4, file: !1, line: 2, type: !12)
   !12 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
   !13 = !DIExpression()
   !14 = !DILocation(line: 2, column: 9, scope: !4)
-  !15 = !DILocalVariable(tag: DW_TAG_auto_variable, name: "Y", scope: !4, file: !1, line: 3, type: !12)
+  !15 = !DILocalVariable(name: "Y", scope: !4, file: !1, line: 3, type: !12)
   !16 = !DILocation(line: 3, column: 9, scope: !4)
-  !17 = !DILocalVariable(tag: DW_TAG_auto_variable, name: "Z", scope: !18, file: !1, line: 5, type: !12)
+  !17 = !DILocalVariable(name: "Z", scope: !18, file: !1, line: 5, type: !12)
   !18 = distinct !DILexicalBlock(scope: !4, file: !1, line: 4, column: 5)
   !19 = !DILocation(line: 5, column: 11, scope: !18)
   !20 = !DILocation(line: 6, column: 11, scope: !18)