[llvm] Implement the DWARF 6 language and version attributes. (PR #89980)

[David Blaikie via llvm-commits]

================
@@ -209,6 +209,282 @@ enum SourceLanguage {
   DW_LANG_hi_user = 0xffff
 };
 
+enum SourceLanguageName : uint16_t {
+#define HANDLE_DW_LNAME(ID, NAME, DESC, LOWER_BOUND) DW_LNAME_##NAME = ID,
+#include "llvm/BinaryFormat/Dwarf.def"
+};
+
+/// Convert a DWARF 6 pair of language name and version to a DWARF 5 DW_LANG.
+inline std::optional<SourceLanguage> toDW_LANG(SourceLanguageName name,
+                                               uint32_t version) {
+  switch (name) {
+  case DW_LNAME_Ada: // YYYY
+    if (version <= 1983)
+      return DW_LANG_Ada83;
+    if (version <= 1995)
+      return DW_LANG_Ada95;
+    if (version <= 2005)
+      return DW_LANG_Ada2005;
+    if (version <= 2012)
+      return DW_LANG_Ada2012;
+    return {};
+  case DW_LNAME_BLISS:
+    return DW_LANG_BLISS;
+  case DW_LNAME_C: // YYYYMM, K&R 000000
+    if (version == 0)
+      return DW_LANG_C;
+    if (version <= 198912)
+      return DW_LANG_C89;
+    if (version <= 199901)
+      return DW_LANG_C99;
+    if (version <= 201112)
+      return DW_LANG_C11;
+    if (version <= 201710)
+      return DW_LANG_C17;
+    return {};
+  case DW_LNAME_C_plus_plus: // YYYYMM
+    if (version == 0)
+      return DW_LANG_C_plus_plus;
+    if (version <= 199711)
+      return DW_LANG_C_plus_plus;
+    if (version <= 200310)
+      return DW_LANG_C_plus_plus_03;
+    if (version <= 201103)
+      return DW_LANG_C_plus_plus_11;
+    if (version <= 201402)
+      return DW_LANG_C_plus_plus_14;
+    if (version <= 201703)
+      return DW_LANG_C_plus_plus_17;
+    if (version <= 202002)
----------------
dwblaikie wrote:

It's not immediately obvious that the correct thing to do is to round up partial implementations to their nearest standard (or round down... ) - if there's a partial implementation that ends up being incompatible with the final standard... 

But, yeah, on balance, for DWARF consumers, rounding up is probably right-enough. But might be worth a comment explaining that.

https://github.com/llvm/llvm-project/pull/89980