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)

llvm/include/llvm/IR/DebugInfoMetadata.h

@@ -1750,15 +1750,13 @@ class DITemplateValueParameter : public DITemplateParameter {
 };
 
 /// \brief Base class for variables.
-///
-/// TODO: Hardcode to DW_TAG_variable.
 class DIVariable : public DINode {
   unsigned Line;
 
 protected:
-  DIVariable(LLVMContext &C, unsigned ID, StorageType Storage, unsigned Tag,
-             unsigned Line, ArrayRef<Metadata *> Ops)
-      : DINode(C, ID, Storage, Tag, Ops), Line(Line) {}
+  DIVariable(LLVMContext &C, unsigned ID, StorageType Storage, unsigned Line,
+             ArrayRef<Metadata *> Ops)
+      : DINode(C, ID, Storage, dwarf::DW_TAG_variable, Ops), Line(Line) {}
   ~DIVariable() = default;
 
 public:
@@ -1803,8 +1801,7 @@ class DIGlobalVariable : public DIVariable {
   DIGlobalVariable(LLVMContext &C, StorageType Storage, unsigned Line,
                    bool IsLocalToUnit, bool IsDefinition,
                    ArrayRef<Metadata *> Ops)
-      : DIVariable(C, DIGlobalVariableKind, Storage, dwarf::DW_TAG_variable,
-                   Line, Ops),
+      : DIVariable(C, DIGlobalVariableKind, Storage, Line, Ops),
         IsLocalToUnit(IsLocalToUnit), IsDefinition(IsDefinition) {}
   ~DIGlobalVariable() = default;
 
@@ -1876,8 +1873,6 @@ class DIGlobalVariable : public DIVariable {
 
 /// \brief Local variable.
 ///
-/// TODO: Split between arguments and otherwise.
-/// TODO: Use \c DW_TAG_variable instead of fake tags.
 /// TODO: Split up flags.
 class DILocalVariable : public DIVariable {
   friend class LLVMContextImpl;
@@ -1886,42 +1881,42 @@ class DILocalVariable : public DIVariable {
   unsigned Arg;
   unsigned Flags;
 
-  DILocalVariable(LLVMContext &C, StorageType Storage, unsigned Tag,
-                  unsigned Line, unsigned Arg, unsigned Flags,
-                  ArrayRef<Metadata *> Ops)
-      : DIVariable(C, DILocalVariableKind, Storage, Tag, Line, Ops), Arg(Arg),
+  DILocalVariable(LLVMContext &C, StorageType Storage, unsigned Line,
+                  unsigned Arg, unsigned Flags, ArrayRef<Metadata *> Ops)
+      : DIVariable(C, DILocalVariableKind, Storage, Line, Ops), Arg(Arg),
         Flags(Flags) {}
   ~DILocalVariable() = default;
 
-  static DILocalVariable *getImpl(LLVMContext &Context, unsigned Tag,
-                                  DIScope *Scope, StringRef Name, DIFile *File,
-                                  unsigned Line, DITypeRef Type, unsigned Arg,
-                                  unsigned Flags, StorageType Storage,
+  static DILocalVariable *getImpl(LLVMContext &Context, DIScope *Scope,
+                                  StringRef Name, DIFile *File, unsigned Line,
+                                  DITypeRef Type, unsigned Arg, unsigned Flags,
+                                  StorageType Storage,
                                   bool ShouldCreate = true) {
-    return getImpl(Context, Tag, Scope, getCanonicalMDString(Context, Name),
-                   File, Line, Type, Arg, Flags, Storage, ShouldCreate);
+    return getImpl(Context, Scope, getCanonicalMDString(Context, Name), File,
+                   Line, Type, Arg, Flags, Storage, ShouldCreate);
   }
-  static DILocalVariable *
-  getImpl(LLVMContext &Context, unsigned Tag, Metadata *Scope, MDString *Name,
-          Metadata *File, unsigned Line, Metadata *Type, unsigned Arg,
-          unsigned Flags, StorageType Storage, bool ShouldCreate = true);
+  static DILocalVariable *getImpl(LLVMContext &Context, Metadata *Scope,
+                                  MDString *Name, Metadata *File, unsigned Line,
+                                  Metadata *Type, unsigned Arg, unsigned Flags,
+                                  StorageType Storage,
+                                  bool ShouldCreate = true);
 
   TempDILocalVariable cloneImpl() const {
-    return getTemporary(getContext(), getTag(), getScope(), getName(),
-                        getFile(), getLine(), getType(), getArg(), getFlags());
+    return getTemporary(getContext(), getScope(), getName(), getFile(),
+                        getLine(), getType(), getArg(), getFlags());
   }
 
 public:
   DEFINE_MDNODE_GET(DILocalVariable,
-                    (unsigned Tag, DILocalScope *Scope, StringRef Name,
-                     DIFile *File, unsigned Line, DITypeRef Type, unsigned Arg,
+                    (DILocalScope * Scope, StringRef Name, DIFile *File,
+                     unsigned Line, DITypeRef Type, unsigned Arg,
                      unsigned Flags),
-                    (Tag, Scope, Name, File, Line, Type, Arg, Flags))
+                    (Scope, Name, File, Line, Type, Arg, Flags))
   DEFINE_MDNODE_GET(DILocalVariable,
-                    (unsigned Tag, Metadata *Scope, MDString *Name,
-                     Metadata *File, unsigned Line, Metadata *Type,
-                     unsigned Arg, unsigned Flags),
-                    (Tag, Scope, Name, File, Line, Type, Arg, Flags))
+                    (Metadata * Scope, MDString *Name, Metadata *File,
+                     unsigned Line, Metadata *Type, unsigned Arg,
+                     unsigned Flags),
+                    (Scope, Name, File, Line, Type, Arg, Flags))
 
   TempDILocalVariable clone() const { return cloneImpl(); }
 
@@ -1932,6 +1927,7 @@ class DILocalVariable : public DIVariable {
     return cast<DILocalScope>(DIVariable::getScope());
   }
 
+  bool isParameter() const { return Arg; }
   unsigned getArg() const { return Arg; }
   unsigned getFlags() const { return Flags; }
 

llvm/include/llvm/Support/Dwarf.def

@@ -99,10 +99,6 @@ HANDLE_DW_TAG(0x0041, type_unit)
 HANDLE_DW_TAG(0x0042, rvalue_reference_type)
 HANDLE_DW_TAG(0x0043, template_alias)
 
-// Mock tags we use as discriminators.
-HANDLE_DW_TAG(0x0100, auto_variable) // Tag for local (auto) variables.
-HANDLE_DW_TAG(0x0101, arg_variable)  // Tag for argument variables.
-
 // New in DWARF v5.
 HANDLE_DW_TAG(0x0044, coarray_type)
 HANDLE_DW_TAG(0x0045, generic_subrange)

llvm/lib/AsmParser/LLParser.cpp

@@ -3773,24 +3773,25 @@ bool LLParser::ParseDIGlobalVariable(MDNode *&Result, bool IsDistinct) {
 }
 
 /// ParseDILocalVariable:
-///   ::= !DILocalVariable(tag: DW_TAG_arg_variable, scope: !0, name: "foo",
+///   ::= !DILocalVariable(arg: 7, scope: !0, name: "foo",
+///                        file: !1, line: 7, type: !2, arg: 2, flags: 7)
+///   ::= !DILocalVariable(scope: !0, name: "foo",
 ///                        file: !1, line: 7, type: !2, arg: 2, flags: 7)
 bool LLParser::ParseDILocalVariable(MDNode *&Result, bool IsDistinct) {
 #define VISIT_MD_FIELDS(OPTIONAL, REQUIRED)                                    \
-  REQUIRED(tag, DwarfTagField, );                                              \
   REQUIRED(scope, MDField, (/* AllowNull */ false));                           \
   OPTIONAL(name, MDStringField, );                                             \
+  OPTIONAL(arg, MDUnsignedField, (0, UINT16_MAX));                             \
   OPTIONAL(file, MDField, );                                                   \
   OPTIONAL(line, LineField, );                                                 \
   OPTIONAL(type, MDField, );                                                   \
-  OPTIONAL(arg, MDUnsignedField, (0, UINT16_MAX));                             \
   OPTIONAL(flags, DIFlagField, );
   PARSE_MD_FIELDS();
 #undef VISIT_MD_FIELDS
 
   Result = GET_OR_DISTINCT(DILocalVariable,
-                           (Context, tag.Val, scope.Val, name.Val, file.Val,
-                            line.Val, type.Val, arg.Val, flags.Val));
+                           (Context, scope.Val, name.Val, file.Val, line.Val,
+                            type.Val, arg.Val, flags.Val));
   return false;
 }
 

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

@@ -1972,15 +1972,19 @@ std::error_code BitcodeReader::parseMetadata() {
     }
     case bitc::METADATA_LOCAL_VAR: {
       // 10th field is for the obseleted 'inlinedAt:' field.
-      if (Record.size() != 9 && Record.size() != 10)
+      if (Record.size() < 8 || Record.size() > 10)
         return error("Invalid record");
 
+      // 2nd field used to be an artificial tag, either DW_TAG_auto_variable or
+      // DW_TAG_arg_variable.
+      bool HasTag = Record.size() > 8;
       MDValueList.assignValue(
           GET_OR_DISTINCT(DILocalVariable, Record[0],
-                          (Context, Record[1], getMDOrNull(Record[2]),
-                           getMDString(Record[3]), getMDOrNull(Record[4]),
-                           Record[5], getMDOrNull(Record[6]), Record[7],
-                           Record[8])),
+                          (Context, getMDOrNull(Record[1 + HasTag]),
+                           getMDString(Record[2 + HasTag]),
+                           getMDOrNull(Record[3 + HasTag]), Record[4 + HasTag],
+                           getMDOrNull(Record[5 + HasTag]), Record[6 + HasTag],
+                           Record[7 + HasTag])),
           NextMDValueNo++);
       break;
     }

llvm/lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -1100,7 +1100,6 @@ static void WriteDILocalVariable(const DILocalVariable *N,
                                  SmallVectorImpl<uint64_t> &Record,
                                  unsigned Abbrev) {
   Record.push_back(N->isDistinct());
-  Record.push_back(N->getTag());
   Record.push_back(VE.getMetadataOrNullID(N->getScope()));
   Record.push_back(VE.getMetadataOrNullID(N->getRawName()));
   Record.push_back(VE.getMetadataOrNullID(N->getFile()));

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

@@ -1156,7 +1156,7 @@ void DwarfDebug::beginFunction(const MachineFunction *MF) {
     // The first mention of a function argument gets the CurrentFnBegin
     // label, so arguments are visible when breaking at function entry.
     const DILocalVariable *DIVar = Ranges.front().first->getDebugVariable();
-    if (DIVar->getTag() == dwarf::DW_TAG_arg_variable &&
+    if (DIVar->isParameter() &&
         getDISubprogram(DIVar->getScope())->describes(MF->getFunction())) {
       LabelsBeforeInsn[Ranges.front().first] = Asm->getFunctionBegin();
       if (Ranges.front().first->getDebugExpression()->isBitPiece()) {

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h

@@ -156,7 +156,8 @@ class DbgVariable {
 
   // Translate tag to proper Dwarf tag.
   dwarf::Tag getTag() const {
-    if (Var->getTag() == dwarf::DW_TAG_arg_variable)
+    // FIXME: Why don't we just infer this tag and store it all along?
+    if (Var->isParameter())
       return dwarf::DW_TAG_formal_parameter;
 
     return dwarf::DW_TAG_variable;

llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp

@@ -299,8 +299,6 @@ void DwarfUnit::addDIEEntry(DIE &Die, dwarf::Attribute Attribute,
 }
 
 DIE &DwarfUnit::createAndAddDIE(unsigned Tag, DIE &Parent, const DINode *N) {
-  assert(Tag != dwarf::DW_TAG_auto_variable &&
-         Tag != dwarf::DW_TAG_arg_variable);
   DIE &Die = Parent.addChild(DIE::get(DIEValueAllocator, (dwarf::Tag)Tag));
   if (N)
     insertDIE(N, &Die);