[llvm][Dwarf] Add DW_LNAME_ string/enum getters (llvm#162434)

These are going to be used in a follow-up patch. And they are generally
useful for consumers (we have these for most other attributes).

(cherry picked from commit 9ac8cd6)

Author: Michael137

llvm/include/llvm/BinaryFormat/Dwarf.h

@@ -997,6 +997,7 @@ LLVM_ABI StringRef VisibilityString(unsigned Visibility);
 LLVM_ABI StringRef VirtualityString(unsigned Virtuality);
 LLVM_ABI StringRef EnumKindString(unsigned EnumKind);
 LLVM_ABI StringRef LanguageString(unsigned Language);
+LLVM_ABI StringRef SourceLanguageNameString(SourceLanguageName Lang);
 LLVM_ABI StringRef CaseString(unsigned Case);
 LLVM_ABI StringRef ConventionString(unsigned Convention);
 LLVM_ABI StringRef InlineCodeString(unsigned Code);
@@ -1037,6 +1038,7 @@ LLVM_ABI unsigned getSubOperationEncoding(unsigned OpEncoding,
 LLVM_ABI unsigned getVirtuality(StringRef VirtualityString);
 LLVM_ABI unsigned getEnumKind(StringRef EnumKindString);
 LLVM_ABI unsigned getLanguage(StringRef LanguageString);
+LLVM_ABI unsigned getSourceLanguageName(StringRef SourceLanguageNameString);
 LLVM_ABI unsigned getCallingConvention(StringRef LanguageString);
 LLVM_ABI unsigned getAttributeEncoding(StringRef EncodingString);
 LLVM_ABI unsigned getMacinfo(StringRef MacinfoString);

llvm/lib/BinaryFormat/Dwarf.cpp

@@ -583,6 +583,26 @@ StringRef llvm::dwarf::LanguageDescription(dwarf::SourceLanguageName Name,
   return LanguageDescription(Name);
 }
 
+llvm::StringRef llvm::dwarf::SourceLanguageNameString(SourceLanguageName Lang) {
+  switch (Lang) {
+#define HANDLE_DW_LNAME(ID, NAME, DESC, LOWER_BOUND)                           \
+  case DW_LNAME_##NAME:                                                        \
+    return "DW_LNAME_" #NAME;
+#include "llvm/BinaryFormat/Dwarf.def"
+  }
+
+  return {};
+}
+
+unsigned
+llvm::dwarf::getSourceLanguageName(StringRef SourceLanguageNameString) {
+  return StringSwitch<unsigned>(SourceLanguageNameString)
+#define HANDLE_DW_LNAME(ID, NAME, DESC, LOWER_BOUND)                           \
+  .Case("DW_LNAME_" #NAME, DW_LNAME_##NAME)
+#include "llvm/BinaryFormat/Dwarf.def"
+      .Default(0);
+}
+
 StringRef llvm::dwarf::CaseString(unsigned Case) {
   switch (Case) {
   case DW_ID_case_sensitive: