DebugInfo: Drop fake DW_TAG_expression

Break MDExpression off of DebugNode (inherit directly from `MDNode`) and
drop the fake `DW_TAG_expression` tag in the process.

AFAICT, there's no real functionality change here.  The tag was
originally used by `DIDescriptor::isExpression()` to discriminate
between `MDNode`s, but in the new hierarchy we don't need that.

Fixes PR22780.

llvm-svn: 232550

4 files changed, 3 insertions, 7 deletions

diff --git a/llvm/include/llvm/IR/DebugInfoMetadata.h b/llvm/include/llvm/IR/DebugInfoMetadata.h
index c09b7d0477d..5bf1d01a8dd 100644
--- a/llvm/include/llvm/IR/DebugInfoMetadata.h
+++ b/llvm/include/llvm/IR/DebugInfoMetadata.h
@@ -146,7 +146,6 @@ public:
     case MDTemplateValueParameterKind:
     case MDGlobalVariableKind:
     case MDLocalVariableKind:
-    case MDExpressionKind:
     case MDObjCPropertyKind:
     case MDImportedEntityKind:
       return true;
@@ -1447,17 +1446,16 @@ public:
 /// \brief DWARF expression.
 ///
 /// TODO: Co-allocate the expression elements.
-/// TODO: Drop fake DW_TAG_expression and separate from DebugNode.
 /// TODO: Separate from MDNode, or otherwise drop Distinct and Temporary
 /// storage types.
-class MDExpression : public DebugNode {
+class MDExpression : public MDNode {
   friend class LLVMContextImpl;
   friend class MDNode;
 
   std::vector<uint64_t> Elements;
 
   MDExpression(LLVMContext &C, StorageType Storage, ArrayRef<uint64_t> Elements)
-      : DebugNode(C, MDExpressionKind, Storage, dwarf::DW_TAG_expression, None),
+      : MDNode(C, MDExpressionKind, Storage, None),
         Elements(Elements.begin(), Elements.end()) {}
   ~MDExpression() {}
 
diff --git a/llvm/include/llvm/IR/Metadata.def b/llvm/include/llvm/IR/Metadata.def
index 66589e0a709..fa4274b1631 100644
--- a/llvm/include/llvm/IR/Metadata.def
+++ b/llvm/include/llvm/IR/Metadata.def
@@ -61,6 +61,7 @@ HANDLE_METADATA_LEAF(LocalAsMetadata)
 HANDLE_MDNODE_BRANCH(MDNode)
 HANDLE_MDNODE_LEAF(MDTuple)
 HANDLE_SPECIALIZED_MDNODE_LEAF(MDLocation)
+HANDLE_SPECIALIZED_MDNODE_LEAF(MDExpression)
 HANDLE_SPECIALIZED_MDNODE_BRANCH(DebugNode)
 HANDLE_SPECIALIZED_MDNODE_LEAF(GenericDebugNode)
 HANDLE_SPECIALIZED_MDNODE_LEAF(MDSubrange)
@@ -86,7 +87,6 @@ HANDLE_SPECIALIZED_MDNODE_LEAF(MDTemplateValueParameter)
 HANDLE_SPECIALIZED_MDNODE_BRANCH(MDVariable)
 HANDLE_SPECIALIZED_MDNODE_LEAF(MDGlobalVariable)
 HANDLE_SPECIALIZED_MDNODE_LEAF(MDLocalVariable)
-HANDLE_SPECIALIZED_MDNODE_LEAF(MDExpression)
 HANDLE_SPECIALIZED_MDNODE_LEAF(MDObjCProperty)
 HANDLE_SPECIALIZED_MDNODE_LEAF(MDImportedEntity)
 
diff --git a/llvm/include/llvm/Support/Dwarf.def b/llvm/include/llvm/Support/Dwarf.def
index c663af94472..4b923b897e6 100644
--- a/llvm/include/llvm/Support/Dwarf.def
+++ b/llvm/include/llvm/Support/Dwarf.def
@@ -102,7 +102,6 @@ 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.
-HANDLE_DW_TAG(0x0102, expression)    // Tag for complex address expressions.
 
 // New in DWARF v5.
 HANDLE_DW_TAG(0x0044, coarray_type)
diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
index b2711a439b6..219a7aa16a4 100644
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -754,7 +754,6 @@ void Verifier::visitMDLocalVariable(const MDLocalVariable &N) {
 }
 
 void Verifier::visitMDExpression(const MDExpression &N) {
-  Assert(N.getTag() == dwarf::DW_TAG_expression, "invalid tag", &N);
   Assert(N.isValid(), "invalid expression", &N);
 }