[LLVM-C] Add an accessor for the kind of a Metadata Node

[CodaFi]

Summary

Allows for retrieving the type of a metadata node. Has the added benefit of ensuring that the C and C++ kind APIs stay in sync as a failure to add a corresponding LLVMMetadataKind will result in the switch in the accessor being semantically malformed.

[whitequark]

include/llvm-c/DebugInfo.h

1198

C enums don't have a defined ABI and should never be used in function signatures, because this makes FFI impossible to do correctly without going through something libclang.

[CodaFi]

include/llvm-c/DebugInfo.h

1198

So what's the workaround here? I recognize the ABI concerns given LLVM's stated policy on the C API, but I'm curious to know how this hasn't come up before considering Core.h and DebugInfo.h define and use over 20 different enumerations across their signatures.

[whitequark]

include/llvm-c/DebugInfo.h

1198

Cast to an integer. I think to unsigned. All other uses of enumerations are a mistake as well; I'm not sure why they were introduced, but ideally they should be fixed.

[CodaFi]

@whitequark Done.

[whitequark]

LGTM, thanks!

include/llvm-c/DebugInfo.h

  */
 typedef enum {
     LLVMDWARFEmissionNone = 0,
     LLVMDWARFEmissionFull,
     LLVMDWARFEmissionLineTablesOnly
 } LLVMDWARFEmissionKind;
 
 /**
+ * The kind of metadata nodes.
+ */
+typedef enum {
+  LLVMMDStringMetadataKind,
+  LLVMConstantAsMetadataMetadataKind,
+  LLVMLocalAsMetadataMetadataKind,
+  LLVMDistinctMDOperandPlaceholderMetadataKind,
+  LLVMMDTupleMetadataKind,
+  LLVMDILocationMetadataKind,
+  LLVMDIExpressionMetadataKind,
+  LLVMDIGlobalVariableExpressionMetadataKind,
+  LLVMGenericDINodeMetadataKind,
+  LLVMDISubrangeMetadataKind,
+  LLVMDIEnumeratorMetadataKind,
+  LLVMDIBasicTypeMetadataKind,
+  LLVMDIDerivedTypeMetadataKind,
+  LLVMDICompositeTypeMetadataKind,
+  LLVMDISubroutineTypeMetadataKind,
+  LLVMDIFileMetadataKind,
+  LLVMDICompileUnitMetadataKind,
+  LLVMDISubprogramMetadataKind,
+  LLVMDILexicalBlockMetadataKind,
+  LLVMDILexicalBlockFileMetadataKind,
+  LLVMDINamespaceMetadataKind,
+  LLVMDIModuleMetadataKind,
+  LLVMDITemplateTypeParameterMetadataKind,
+  LLVMDITemplateValueParameterMetadataKind,
+  LLVMDIGlobalVariableMetadataKind,
+  LLVMDILocalVariableMetadataKind,
+  LLVMDILabelMetadataKind,
+  LLVMDIObjCPropertyMetadataKind,
+  LLVMDIImportedEntityMetadataKind,
+  LLVMDIMacroMetadataKind,
+  LLVMDIMacroFileMetadataKind
+} LLVMMetadataKind;
+
+/**
  * An LLVM DWARF type encoding.
  */
 typedef unsigned LLVMDWARFTypeEncoding;
 
 /**
  * The current debug metadata version number.
  */
 unsigned LLVMDebugMetadataVersion(void);

 
 /**
  * Set the subprogram attached to a function.
  *
  * @see llvm::Function::setSubprogram()
  */
 void LLVMSetSubprogram(LLVMValueRef Func, LLVMMetadataRef SP);
 
+/**
+ * Obtain the enumerated type of a Metadata instance.
+ *
+ * @see llvm::Metadata::getMetadataID()
+ */
+LLVMMetadataKind LLVMGetMetadataKind(LLVMMetadataRef Metadata);
+
 #ifdef __cplusplus
 } /* end extern "C" */
 #endif
 
 #endif

lib/IR/DebugInfo.cpp

 
 LLVMMetadataRef LLVMGetSubprogram(LLVMValueRef Func) {
   return wrap(unwrap<Function>(Func)->getSubprogram());
 }
 
 void LLVMSetSubprogram(LLVMValueRef Func, LLVMMetadataRef SP) {
   unwrap<Function>(Func)->setSubprogram(unwrap<DISubprogram>(SP));
 }
+
+LLVMMetadataKind LLVMGetMetadataKind(LLVMMetadataRef Metadata) {
+  switch(unwrap(Metadata)->getMetadataID()) {
+#define HANDLE_METADATA_LEAF(CLASS) \
+  case Metadata::CLASS##Kind: \
+    return LLVM##CLASS##MetadataKind;
+#include "llvm/IR/Metadata.def"
+  default:
+    return LLVMGenericDINodeMetadataKind;
+  }
+}