[LLVM-C] Add accessor to retrieve DINode's tag

[CodaFi]

Summary

Add LLVMDIMetadataGetTag to retrieve any DINode's DWARF tag.

[aprantl]

What's the actual use-case for this? I'm afraid that this might expose something that is more an implementation detail and would make the C API more brittle.

[CodaFi]

I've only seen it used to discriminate between different kinds of DIScopes. If it's really an implementation detail, I can abandon this patch.

[whitequark]

I think it's worth asking on llvm-dev as to what kind of API is this.

[whitequark]

Resigning to get out of my queue--retag me if there's any progress.

[CodaFi]

Abandoning this revision to keep it out of the review queue.

include/llvm-c/DebugInfo.h

  * \param Flags           Flags.
  */
 LLVMMetadataRef LLVMDIBuilderCreateParameterVariable(
     LLVMDIBuilderRef Builder, LLVMMetadataRef Scope, const char *Name,
     size_t NameLen, unsigned ArgNo, LLVMMetadataRef File, unsigned LineNo,
     LLVMMetadataRef Ty, LLVMBool AlwaysPreserve, LLVMDIFlags Flags);
 
 /**
+ * Retrieve the DWARF tag associated with a given metadata node.
+ * \param Node    The DINode.
+ */
+unsigned LLVMDIMetadataGetTag(LLVMMetadataRef Node);
+
+/**
  * Get the metadata of the subprogram attached to a function.
  *
  * @see llvm::Function::getSubprogram()
  */
 LLVMMetadataRef LLVMGetSubprogram(LLVMValueRef Func);
 
 /**
  * Set the subprogram attached to a function.

lib/IR/DebugInfo.cpp

 
 LLVMMetadataRef LLVMDIBuilderGetOrCreateArray(LLVMDIBuilderRef Builder,
                                               LLVMMetadataRef *Data,
                                               size_t Length) {
   Metadata **DataValue = unwrap(Data);
   return wrap(unwrap(Builder)->getOrCreateArray({DataValue, Length}).get());
 }
 
+unsigned LLVMDIMetadataGetTag(LLVMMetadataRef Node) {
+  return unwrapDI<DINode>(Node)->getTag();
+}
+
 LLVMMetadataRef LLVMGetSubprogram(LLVMValueRef Func) {
   return wrap(unwrap<Function>(Func)->getSubprogram());
 }
 
 void LLVMSetSubprogram(LLVMValueRef Func, LLVMMetadataRef SP) {
   unwrap<Function>(Func)->setSubprogram(unwrap<DISubprogram>(SP));
 }